Food product that is a concentrated solution of a raw material liquid containing sugar, raw material liquid concentration system, and raw material liquid concentration method

Abstract

To provide a sugar-containing raw material liquid concentrated liquid foodstuff that maintains high-quality appearance and flavor, and to provide a raw material liquid concentration system and raw material liquid concentration method that is suitable for producing the concentrated liquid.SOLUTION: Provided is a foodstuff, which is a foodstuff that is a concentrated liquid of a raw material liquid derived from a natural product containing a sugar-containing solute and a liquid medium, and in which the concentrated liquid has a Brix value of 50 or more, the visible light transmittance of the concentrated liquid at a wavelength of 560 nm as measured by an ultraviolet-visible spectrophotometer is 80% or more and 99% or less, and the aroma component collected from the concentrated liquid in 50°C atmosphere contains vanillin.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a food product which is a concentrated liquid obtained by concentrating a raw material liquid containing sugar, and a raw material liquid concentration system and a raw material liquid concentration method capable of suppressing appearance deterioration and flavor degradation due to alteration, reduction, etc. of components in the raw material liquid and efficiently concentrating the raw material liquid when concentrating the raw material liquid containing sugar.

Background Art

[0002] Due to the recent health orientation of consumers, consumers' interest has been drawn to food products harvested, extracted or concentrated from nature. For example, in a food product raw material liquid containing sugar, a concentrated liquid obtained by concentrating the raw material liquid by putting the raw material liquid into an evaporator and heating and evaporating the water is added as a natural sweetener to various dishes and confectioneries. However, when the raw material liquid containing sugar is heated at a high temperature, many components contained in the raw material liquid are altered or disappear, so there has been a problem that appearance deterioration and a significant reduction in flavor of the obtained food product (that is, a food product in the form of a concentrated liquid of the raw material liquid) occur.

[0003] Therefore, as a method capable of concentrating the raw material liquid without requiring heating, the reverse osmosis membrane method is generally performed. For example, Patent Document 1 describes a method of concentrating maple syrup by the reverse osmosis membrane method. Further, Patent Document 2 describes a method of concentrating maple syrup to a relatively high concentration by the reverse osmosis method.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the methods described in Patent Documents 1 and 2, since it is necessary to apply a pressure higher than the osmotic pressure of the concentrated solution, there is a limit to the concentration, and heating is required for concentration to a high concentration. However, due to heating, the useful components contained in the food raw material liquid are deteriorated or lost, and the appearance of the food is deteriorated. Furthermore, since the reverse osmosis membrane method applies a high pressure, there are problems that useful components are adsorbed on the membrane, flavor components are reduced, and long-term operation is not possible.

[0006] An object of the present invention is to solve the above problems and provide a food product which is a concentrated solution containing a high concentration of sugar and which retains the appearance and flavor inherent in a food raw material liquid, as well as a raw material liquid concentration system and a raw material liquid concentration method suitable for producing such a high-quality concentrated solution.

Means for Solving the Problems

[0007] The present invention includes the following aspects. [1] A food product which is a concentrated solution of a raw material liquid derived from a natural product containing a solute containing sugar and a liquid medium, wherein the concentrated solution has a Brix value of 50 or more, the visible light transmittance of the concentrated solution at a wavelength of 560 nm as measured by ultraviolet-visible spectrophotometry is 80% or more and 99% or less, and the aroma components collected from the concentrated solution in an atmosphere of 50 ° C. contain vanillin. [2] The food product according to item 1, wherein the visible light transmittance of the concentrated solution at a wavelength of 560 nm as measured by ultraviolet-visible spectrophotometry is 85% or more and 99% or less. [3] The aroma components collected from the concentrated solution in an atmosphere of 50 ° C. contain vanillin and acetophenone, and when the aroma components are analyzed by gas chromatography, the peak area of vanillin is 1.5 times or more and 10 times or less that of acetophenone. [4] The food product according to any one of items 1 to 3, wherein the change rate of the value of the sugar concentration / magnesium ion concentration of the concentrated solution as compared with the value of the sugar concentration / magnesium ion concentration of the raw material liquid is 5% or less. [5] The food product according to any one of items 1 to 4, wherein the raw material liquid is at least one selected from the group consisting of firefly tree sap, birch tree sap, and coconut liquid endosperm. [6] A raw material liquid concentration system for producing the food product according to any one of items 1 to 5, comprising: A heating unit for heating the raw material liquid to 30°C or higher and 80°C or lower; A vacuum distillation unit for distilling and concentrating the raw material liquid by reducing the pressure of the gas phase in contact with the raw material liquid to -80 kPa or lower; A raw material liquid concentration system having the above components. [7] The raw material liquid concentration system according to item 6, wherein the vacuum distillation unit is a membrane distillation unit having a porous membrane. [8] The raw material liquid concentration system includes a raw material liquid tank for storing the raw material liquid, the heating unit, the membrane distillation unit having a porous membrane, and a circulation pump for circulating the raw material liquid from the raw material liquid tank through the heating unit and the membrane distillation unit in this order and back to the raw material liquid tank. The membrane distillation unit is divided by the porous membrane into a liquid phase part through which the raw material liquid flows and a gas phase part through which the vapor generated from the raw material liquid passes through the porous membrane and diffuses. At the raw material liquid inlet site of the membrane distillation unit, the temperature of the raw material liquid is 30°C or higher and 80°C or lower, and the pressure of the gas phase part inside the membrane distillation unit is reduced to -80 kPa or lower. It is configured as described above. The raw material liquid concentration system according to item 7. [9] The raw material liquid concentration system according to item 7 or 8, wherein the porous membrane is a hollow fiber membrane.

[10] The porous membrane is composed of at least one resin selected from the group consisting of polysulfone, polyethersulfone, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, etc. The raw material liquid concentration system according to any one of items 7 to 9.

[11] A method for producing the food product according to any one of items 1 to 5, using the raw material liquid concentration system according to any one of items 6 to 10. A heating step of heating the raw material liquid in the heating unit, A concentration step of flowing the heated raw material liquid into the vacuum distillation unit and concentrating it by vacuum distillation, A method comprising:

[12] The method according to item 11, wherein the contact part of the heating unit with the raw material liquid is 90 °C or lower.

[13] The method according to item 11 or 12, wherein the heating unit is a heat exchanger that circulates a heat medium that is steam at 50 °C or higher or hot water at 50 °C or higher.

[14] The method according to any one of items 11 to 13, wherein the heating unit utilizes waste heat.

[15] Further comprising an additional concentration step of flowing the concentrated raw material liquid into an evaporator after the concentration step, and the temperature of the raw material liquid in the additional concentration step is equal to or higher than the temperature of the raw material liquid in the concentration step. The method according to any one of items 11 to 14.

[16] The method according to any one of items 11 to 15, further comprising a preliminary concentration step of preliminarily concentrating the raw material liquid with a reverse osmosis membrane.

[17] Further comprising a filtration step of filtering the raw material liquid with a filtration membrane to remove impurities, and supplying the filtered raw material liquid to the concentration step. The method according to any one of items 11 to 16.

[18] The method according to item 17, wherein the pore diameter of the filtration membrane is 20 μm or less.

[19] The method according to item 18, wherein the pore diameter of the filtration membrane is 1.0 μm or less.

[20] The method according to any one of items 17 to 19, wherein the filtration membrane is arranged in a cross-flow configuration.

[21] The method according to any one of items 17 to 20, further comprising a backwashing step of backwashing the filtration membrane.

[22] The method according to any one of items 17 to 21, wherein the concentration step and the filtration step are performed in independent raw material liquid flow paths.

[23] The method according to any one of items 11 to 22, wherein the vacuum distillation unit is a membrane distillation unit having a porous membrane, and a step of removing the raw material liquid adhering to the porous membrane by passing water through the porous membrane is performed more than once a day.

[24] The method according to any one of items 11 to 23, wherein the step of removing the membrane contaminants attached to the porous membrane by passing a chemical solution having a pH of 5 or less or a pH of 9 or more through the porous membrane is performed one or more times per week.

Effect of the Invention

[0008] According to one aspect of the present invention, there can be provided a food product which is a concentrated solution containing a high concentration of sugar and retains the appearance and flavor inherent in the raw material liquid of the food product, as well as a raw material liquid concentration system and a raw material liquid concentration method suitable for producing such a high-quality concentrated solution.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention (hereinafter also referred to as the present embodiments) will be specifically and detailedly described as non-limiting examples. In the drawings of the present disclosure, elements having the same reference numerals are intended to have the same configuration or function as each other.

[0011] "Concentrate of raw material liquid containing sugar" One aspect of the present invention provides a food product that is a concentrate of a raw material liquid derived from a natural product containing a solute containing sugar and a liquid medium. In one aspect, the concentrate has a Brix value of 50 or more. In another aspect, the visible light transmittance of the concentrate at a wavelength of 560 nm measured by ultraviolet-visible spectrophotometry is 80% or more and 99% or less. In another aspect, the aroma components collected from the concentrate in an atmosphere of 50°C contain vanillin.

[0012] In one aspect, the raw material liquid contains a solute containing sugar and a liquid medium. Examples of sugars include monosaccharides (e.g., glucose, fructose, galactose, mannose, ribose, deoxyribose, etc.), disaccharides (e.g., maltose, sucrose, lactose, etc.), sugar chains (e.g., in addition to glucose, galactose, mannose, fucose, xylose, glucuronic acid, iduronic acid, etc.; N-acetylglucosamine, N-acetylgalactosamine, N-acetylneuraminic acid, etc., sugar derivatives, etc.).

[0013] The raw material liquid of the present disclosure may generally be a raw material liquid containing a solute containing sugar and an aqueous medium. Examples of the raw material liquid include highly nutritious and naturally collected water-containing articles, such as maple sap, birch sap, honey, coconut liquid endosperm, sugarcane sugar liquid, and monk fruit juice. In a preferred aspect, the raw material liquid is at least one selected from the group consisting of maple sap, birch sap, and coconut liquid endosperm.

[0014] Maple sap is generally collected from maple trees during the period of the year when the sugar content is highest and the temperature difference between day and night is large (for example, from March to April in the Northern Hemisphere). Since the sap is necessary for the growth of the tree, various strict criteria are provided for its collection, starting from the stage of making holes in the tree. Usually, the sap contains only 2 to 4% by mass of sugar, and about 40 L of sap is required to make 1 L of syrup. The liquid medium dissolves or disperses the solute in the raw material liquid. In a typical embodiment, the liquid medium is water. The raw material liquid may be any fluid, for example, it may be an emulsion or the like.

[0015] In one embodiment, maple sap is used as the raw material liquid and maple syrup is obtained as the concentrated liquid. The quality of maple syrup is graded. Generally, the closer the sap collection time is to the beginning of the season, the lighter the color of the sap, the more delicate the taste of the obtained maple syrup, and the higher the light transmittance. Maple syrup with a high light transmittance is called extra light, while that with a low light transmittance is called dark, and the higher the light transmittance, the higher the quality.

[0016] The Brix value of maple syrup is generally 66.5%, which is comparable to granulated sugar and refined sugar. On the other hand, maple syrup has a lower calorie content compared to, for example, refined sugar and honey, and also tends to have a higher content of minerals such as calcium and potassium than other sweeteners.

[0017] Birch sap is the sap obtained from the trunk of a birch tree and is generally harvested in spring. Birch syrup can be produced in the same way as maple syrup using birch sap as the raw material. Also, birch sap is used as a raw material for the artificial sweetener xylitol. In addition to sugar, the sap contains organic substances such as amino acids, organic acids such as malic acid, polysaccharides, and glycosides. It also contains various minerals including potassium, calcium, and magnesium. Since some of these components have a moisturizing effect on human skin, they are often used in cosmetics. Also in this birch syrup, the higher the light transmittance, the more delicate the taste and the higher the quality.

[0018] Coconut liquid endosperm refers to the translucent liquid endosperm contained in immature coconut fruits. Coconut liquid endosperm is rich in minerals and thus nutritious, and since it has a mineral composition close to body fluids with almost the same osmotic pressure as the human body, it can be a natural moisture replenishing material. Among the minerals abundantly contained in coconut liquid endosperm, magnesium and potassium in particular are known to be effective in relieving swelling and activating metabolic enzymes. Also in coconut liquid endosperm, the higher the light transmittance, the more delicate and high-quality the taste.

[0019] In one aspect, the Brix value (i.e., the sugar content value measured by a Brix meter) of the concentrated liquid is 50 or more. The Brix value of the liquid before concentration (i.e., the raw material liquid) is generally about 1 to 5. When such a raw material liquid is concentrated into a concentrated liquid with a Brix value of 50, the concentration ratio is about 10 times to about 50 times. That is, the fact that the Brix value of the concentrated liquid is 50 or more is an indicator of a concentrated liquid with a high concentration ratio. In one aspect, the concentrated liquid of the present disclosure has a high light transmittance even at a high concentration ratio with a Brix value of 50 or more. This high light transmittance is an indicator that the transmittance of the raw material liquid before concentration is well maintained. From the viewpoint of obtaining a concentrated liquid with a high concentration ratio, the Brix value of the concentrated liquid is preferably 50 or more, or 60 or more. The upper limit of the Brix value of the concentrated liquid is not particularly limited, but from the viewpoint of the ease of manufacturing the concentrated liquid, for example, it may be 75 or less, or 70 or less.

[0020] The concentrated liquid may contain components that are beneficial to health, such as reducing swelling and activating metabolic enzymes. From the perspective of providing a concentrated liquid that contains these components at a high ratio and has few degradation products or impurities, the visible light transmittance of the concentrated liquid at a wavelength of 560 nm measured by ultraviolet-visible spectrophotometry is 80% or more, and preferably may be 85% or more. Further, the above transmittance is 99% or less, and from the perspective of providing a high-quality (especially with a delicate flavor) concentrated liquid, it may preferably be 95% or less. More preferably, the visible light transmittance of the concentrated liquid at a wavelength of 560 nm measured by ultraviolet-visible spectrophotometry is 80% or more and 99% or less, and even more preferably 85% or more and 99% or less.

[0021] In one aspect, the concentrated liquid contains vanillin as an aroma component. In the present disclosure, that the concentrated liquid contains vanillin means that vanillin is detected by gas chromatography analysis of the concentrated liquid (i.e., it is above the detection limit amount). Vanillin is a compound with a sweet smell and is often used in food flavors and perfumes. According to the reference (J.Japan Association on Odor Environment Vol. 36 No. 4 2005), vanillin is classified as having a sweet, soft, and warm aroma. By concentrating the raw material liquid by an appropriate method, the concentrated liquid emits a sweet smell due to vanillin derived from natural products.

[0022] The sweet smell derived from vanillin emitted from the concentrated liquid can be detected by analyzing the aroma components collected from the concentrated liquid in a 50°C atmosphere by gas chromatography. Although the boiling point of vanillin is 285°C, generally, since the quality of food products is judged at room temperature, it is appropriate to set the heating atmosphere of the concentrated liquid during aroma component collection to 50°C or lower. In addition, since the concentration at which the human sense of smell begins to sense the smell of vanillin is sufficiently lower than the detection sensitivity of gas chromatography, if vanillin is detected by gas chromatography, it can prove that humans can sense the smell of vanillin.

[0023] In one aspect, the concentrated liquid contains acetophenone as an aroma component. In the present disclosure, that the concentrated liquid contains acetophenone means that acetophenone is detected by gas chromatography analysis of the concentrated liquid (i.e., it is above the detection limit). Acetophenone is used as a food flavoring in the same way as vanillin. According to the above reference, acetophenone has an aroma reminiscent of vanilla. Acetophenone can be detected in the same way as vanillin.

[0024] Preferably, the aroma components collected from the concentrated liquid in a 50 °C atmosphere contain vanillin and acetophenone. More preferably, vanillin and acetophenone are contained in a predetermined ratio in the aroma components emitted from the concentrated liquid. Specifically, when analyzing the aroma components collected from the concentrated liquid in a 50 °C atmosphere by gas chromatography, the peak area of vanillin is preferably 1.5 times or more and 10 times or less that of acetophenone, more preferably 1.5 times or more and 8.0 times or less, and still more preferably 1.5 times or more and 5.0 times or less. Thereby, the concentrated liquid has a complex and delicate fragrance, and the quality of the concentrated liquid is improved.

[0025] Preferably, the concentrated liquid has magnesium ions as an inorganic ion component in the solution. Since magnesium ions exhibit bitterness, when contained in an appropriate balance, the flavor of the concentrated liquid is improved. Specifically, more preferably, from the viewpoint of providing a concentrated liquid that maintains the flavor derived from natural products and has a balance between sweetness and bitterness, the change rate of the value of the sugar concentration / magnesium ion concentration of the concentrated liquid compared to the value of the sugar concentration / magnesium ion concentration of the raw material liquid is 5% or less, more preferably within 4%, and still more preferably within 3%. Here, the above change rate is represented by the following formula (1):

[0026]

Equation

[0027] According to one aspect of the present invention, a high-quality food product with excellent flavor can be obtained while maintaining the original appearance of the food raw material liquid as described above. Such food products can be produced, for example, by distillation methods, forward osmosis methods, etc. In the manufacturing process, it is advantageous to adjust the heating temperature, heating atmosphere, etc. For example, a method by heating and vacuum distillation can be advantageous for improving the quality of food products such as moderately removing the odor of the raw material liquid and expressing unique and complex aromas and flavors due to the Maillard reaction in the production of maple syrup. Therefore, the present disclosure also refers to vacuum distillation, particularly the procedure of membrane distillation, suitable for the production of food products according to one aspect of the present invention described above.

[0028] 《Porous Membrane》 The porous membrane suitable for manufacturing the food product of the present embodiment by concentrating the raw material liquid by membrane distillation will be described in detail below. The porous membrane has pores (through-holes) that communicate from one surface of the membrane to the other surface. These through-holes may be included in the network of the membrane material such as a polymer, and may be branched pores or straight through-holes. These pores have the characteristic of allowing steam to pass through but not allowing the water to be treated (liquid) to pass through.

[0029] The porous membrane is preferably hydrophobic to prevent wetting. The water contact angle is an index representing hydrophobicity. In the present embodiment, it is preferable that the water contact angle of any part of the porous membrane is 90° or more, more preferably 110° or more, and still more preferably 120° or more. There is no particular upper limit to the water contact angle, but in reality, it is preferably about 150° or less. The water contact angle is a value measured at 25°C by the droplet method. The droplet method is a method of, for example, dropping 2 μL of pure water onto the surface of the measurement object and quantifying the angle formed by the measurement object and the droplet by analysis from a projection image.

[0030] The pore size and pore size distribution of the porous membrane also have a strong causal relationship with wetting suppression. The average pore size of the porous membrane of the present embodiment is preferably in the range of 0.01 μm or more and 1.0 μm or less, and more preferably in the range of 0.03 μm or more and 0.6 μm or less. When the average pore size is 0.01 μm or more, the permeation resistance of the vapor does not become too large, and the production rate of the raw material liquid concentrate does not decrease. When it is 1.0 μm or less, the wetting suppression effect by improving the hydrophobicity of the membrane is highly preferable. From the viewpoint of achieving both the production rate of the raw material liquid concentrate and wetting suppression, a narrower pore size distribution of the porous membrane is preferable. Specifically, it is preferable to have a pore size distribution in which the ratio of the maximum pore size to the average pore size is in the range of 1.2 to 2.5. The pore size of the porous membrane is a value measured by the average pore size measurement method (also known as the half-dry method) described in ASTM:F316-86.

[0031] From the perspective of the production rate of the raw material liquid concentrate, the porosity of the porous membrane is preferably 50% by volume or more and 85% by volume or less. When this value is 50% by volume or more, the production rate of the raw material liquid concentrate is good. When it is 85% by volume or less, the strength of the membrane itself is good, and problems such as breakage are less likely to occur during long-term use.

[0032] In the porous membrane according to the present embodiment, by flowing a heated raw material liquid on one side of the membrane and keeping the other side in a reduced-pressure state, only the volatile components mainly composed of water can be taken out from the raw material liquid while retaining the non-volatile valuable substances. At this time, the vapor moves using the vapor pressure difference, which is the difference between the vapor pressure of the raw material liquid and the absolute pressure on the reduced-pressure side, as the driving force. For membrane distillation at low temperatures, it is preferable to use a membrane that can efficiently pass vapor even with a slight vapor pressure difference. In addition, food raw material liquids often become highly viscous as they are concentrated. Therefore, in the low-temperature concentration of highly viscous raw material liquids, the inter-membrane differential pressure tends to increase, and membrane wetting is likely to occur. Therefore, it is preferable to use a membrane with a high liquid intrusion pressure.

[0033] In the process of concentrating a raw material solution derived from a natural product containing a solute containing sugar and a liquid medium, as the degree of concentration (concentration ratio) increases, the viscosity of the solution gradually increases. In the case of the conventional membrane distillation method, when the viscosity of the solution reaches 3 cP or more, the pressure loss associated with passing the raw material solution through the flow path of the raw material solution increases, so efficient concentration cannot be achieved. Further, when operating for a long time in such a state, wetting of the membrane, that is, wetting occurs and the concentration performance deteriorates over time. Furthermore, when the viscosity of the solution exceeds 600 cP, it becomes difficult to feed the solution by a feed pump.

[0034] In this embodiment, a porous membrane particularly suitable for concentrating the raw material solution may be used. Specifically, the air permeability of the porous membrane is, in one aspect, 500 L / h·m 2 ·kPa or more, preferably 1000 L / h·m 2 ·kPa or more, or 2000 L / h·m 2 ·kPa or more, or 2500 L / h·m 2 ·kPa or more. The air permeability is preferably 5000 L / h·m 2 ·kPa or less. When the air permeability is 500 L / h·m 2 ·kPa or more, the membrane resistance to vapor transfer does not become too large, and the concentration operation under a slight vapor pressure difference under low temperature conditions is easy. Further, when the air permeability is 5000 L / h·m 2 ·kPa or less, the air permeability does not become too large and the pressure resistance of the membrane is good.

[0035] In this embodiment, from the viewpoints of water permeation performance in membrane distillation and mechanical strength of the membrane, the membrane thickness of the porous membrane is preferably 10 μm to 1,000 μm, and more preferably 15 μm to 1,000 μm. If the membrane thickness is 1,000 μm or less, a decrease in the production efficiency of distilled water can be suppressed. On the other hand, if the membrane thickness is 10 μm or more, deformation of the membrane during use under reduced pressure can be prevented.

[0036] The shape of the porous membrane may be hollow fiber-shaped or sheet-shaped. The sheet-shaped porous membrane may be, for example, pleated or spiral. FIG. 1 is a schematic diagram showing an example of a hollow fiber-shaped porous membrane. Referring to FIG. 1, the porous membrane 11 has a hollow filamentous (tubular) shape, and the outer wall portion is constituted by the porous membrane. The water to be treated A is introduced, for example, into the hollow portion of the porous membrane 11. Then, the vapor B separated from the water to be treated passes through the outer wall of the hollow fiber and diffuses to the outside of the hollow fiber, and the treated water A' after distillation passes through the hollow portion of the porous membrane 11 and is discharged to the outside. It may also be configured such that the water to be treated A is introduced from the outer wall of the porous membrane 11, and the vapor B separated from the water to be treated passes through the outer wall of the hollow fiber and diffuses into the hollow portion of the hollow fiber. When the porous membrane is hollow fiber-shaped, the axial direction of the membrane cartridge for membrane distillation preferably coincides with the axial direction of the hollow fiber-shaped porous membrane.

[0037] FIG. 2 is a schematic diagram showing an example of a pleated porous membrane. Referring to FIG. 2, the porous membrane 11 is formed by alternately folding a rectangular sheet-shaped porous membrane into mountain folds and valley folds by fold lines parallel to one side of the rectangle, and then rolling it up with the direction parallel to the fold lines as the axis to form a cylindrical shape having a number of pleats. The water to be treated A is introduced, for example, into the central cavity portion of the porous membrane 11. Then, the vapor B separated from the water to be treated passes through the porous membrane 11 and diffuses to the outside, and the treated water A' after distillation passes through the central cavity portion of the porous membrane 11 and is discharged to the outside. It may also be configured such that the water to be treated A is introduced from the outside of the porous membrane 11, and the vapor B separated from the water to be treated passes through the porous membrane 11 and diffuses into the central cavity portion. When the porous membrane is pleated, the axial direction of the membrane cartridge for membrane distillation preferably coincides with the axial direction of the cylinder in the cylindrical porous membrane having pleats.

[0038] FIG. 3 is a schematic diagram showing an example of a spiral porous membrane. Referring to FIG. 3, for example, two porous membranes 11, together with a liquid-phase part spacer 18 and a gas-phase part spacer 19, are stacked in the order of porous membrane 11, liquid-phase part spacer 18, porous membrane 11, and gas-phase part spacer 19 to form a four-layer laminate, and a structure is shown in which the rod-shaped body 17 is wound around the winding axis. The water to be treated A is introduced, for example, into the liquid phase part formed by the liquid-phase part spacer 18. The vapor B separated from the water to be treated A passes through the porous membrane 11, diffuses into the gas phase part formed by the gas-phase part spacer 19, and is discharged to the outside through the rod-shaped body 17. Reference numeral B in FIG. 3 * shows the state where the vapor separated from the water to be treated A passes through the porous membrane 11 and diffuses into the gas phase part.

[0039] When the membrane distillation membrane cartridge is housed in the membrane distillation housing, the rod-shaped body 17 functions as a vapor extraction pipe that communicates with the gas phase part of the membrane distillation module and extracts the vapor in the gas phase part to the outside of the membrane distillation module. Therefore, this rod-shaped body 17 may be configured such that gas can pass from the side surface of the rod into the rod. For example, it may have a hollow structure with holes in the side wall surface, or it may be a porous body. Further, this rod-shaped body 17 may protrude from the membrane module to the outside.

[0040] When the porous membrane is spiral, it is preferable that the axial direction of the membrane distillation membrane cartridge coincides with the direction of the winding axis of the wound body composed of two porous membranes, a liquid-phase part spacer, and a gas-phase part spacer.

[0041] As described above, the porous membrane may be hollow fiber-shaped, pleated, or sheet-shaped, but the hollow fiber shape is preferable in terms of increasing the membrane area per unit volume and making the membrane module compact.

[0042] When the porous membrane is a hollow fiber membrane, in one aspect, the inner diameter is 0.3 mm or more and 2.0 mm or less, preferably 0.5 mm or more and 1.5 mm or less. When the inner diameter is 0.3 mm or more, even if the pressure loss increases with the increase in the concentration of the raw material liquid, the liquid feeding does not become difficult. When the inner diameter is 2.0 mm or less, the internal volume of the hollow fiber per unit membrane area does not become too large, and the dead volume of the concentration system does not become too large.

[0043] When the porous membrane is a hollow fiber membrane, at 25 °C, an ethanol (EtOH) aqueous solution with a concentration of 20% by mass is filled inside the hollow fiber (i.e., the hollow part), and when pressurized to 200 kPa, the water permeation rate of the EtOH aqueous solution permeating to the outside of the hollow fiber is, in one aspect, 100 mL / h·m 2 Preferably, 50 mL / h·m or less 2 The following. When the water permeation rate is within the above range, since the membrane is difficult to wet, the disadvantage that the membrane is wetted due to the increase in the differential pressure between the membranes with the increase in the concentration of the raw material liquid and the concentration performance deteriorates is preferably avoided. From the perspective of suppressing membrane wetting, a lower water permeation rate is preferred. However, from the perspective of obtaining good membrane distillation performance, in one aspect, it may be 0.1 mL / h·m 2 Or more, or 1.0 mL / h·m 2 Or more.

[0044] The porous membrane according to this embodiment preferably contains a hydrophobic polymer as a main constituent. A hydrophobic polymer is a polymer with low affinity for water. From this perspective, the porous membrane is preferably composed of at least one resin selected from the group consisting of polysulfone, polyethersulfone, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, and polychlorotrifluoroethylene. From the perspectives of hydrophobicity, film-forming property, mechanical durability, and thermal durability, polyvinylidene fluoride, ethylene-tetrafluoroethylene copolymer, and polychlorotrifluoroethylene are more preferred. It is more preferred that impurities such as plasticizers are removed by refining after the polymerization of these polymers or after forming a membrane from these polymers.

[0045] As a method for producing a porous membrane, a thermally induced phase separation method in which a resin membrane in a molten state is cooled to cause phase separation to form a porous layer, or a dry-wet method (non-solvent phase separation method) in which a resin membrane in a solution state is brought into contact with a non-solvent to cause phase separation to form a porous layer can be preferably used.

[0046] From the viewpoints of pressure resistance for flowing a high-viscosity raw material liquid and efficient vapor transfer, it is preferable to apply a coating of a hydrophobic polymer to the porous membrane obtained by the thermally induced phase separation method or the non-solvent phase separation method. By forming a hydrophobic coating on all or part of the surface on the raw material liquid side (liquid phase part side), the vapor permeation side (gas phase part side), and the inside of the membrane (wall surface in the pores) of the porous membrane, water repellency can be imparted to the membrane or the water repellency of the membrane can be improved.

[0047] Examples of the hydrophobic polymer to be coated on the porous membrane include the following: (A) A silicone-based polymer and a polymer gel that form a crosslinked structure by reacting with a silane coupling agent; (I) Resins having a siloxane bond, such as dimethyl silicone gel, methylphenyl silicone gel, a reactive modified silicone gel into which an organic functional group such as an amino group is introduced, and a silicone gel subjected to fluoroalkyl modification; (U) A polymer having a (per)fluoroalkyl group, a (per)fluoropolyether group, an alkylsilyl group, a fluorosilyl group, etc. in the side chain dissolved in a solvent; (E) A hydrophobic polymer thin film having a fluoroalkyl group, an alkylsilyl group, a fluorosilyl group, etc. in the side chain; (O) A water repellent having a fluoroalkyl group, an alkylsilyl group, a fluorosilyl group, etc. in the side chain, etc. As the hydrophobic polymer, in particular, one or more polymers selected from (meth)acrylate-based monomers and vinyl-based monomers having a (per)fluoroalkyl group or a (per)fluoropolyether group having 1 to 12 carbon atoms are preferable.

[0048] 《Membrane Module》 In this embodiment, a membrane module particularly suitable for concentrating a raw material liquid containing sugar may be used. FIGS. 4 and 5 are schematic views showing an example of the membrane module. Referring to FIGS. 4 and 5, in one aspect, the membrane module 10 has a porous hollow fiber membrane 1 and a module case 2 having a substantially cylindrical or substantially polygonal column shape that houses the hollow fiber membrane 1. The hollow fiber membrane 1 may be the hollow fiber membrane according to the above-described embodiment in one aspect. Here, the "substantially cylindrical shape" includes, for example, a cylindrical shape, an elliptical columnar shape, etc., and shapes similar thereto. The "substantially polygonal column shape" includes, for example, a polygonal columnar shape having a polygon with 3 to 100 vertices as a bottom surface, and shapes similar thereto. The "shapes similar thereto" is a concept including shapes in which the corners of a cylinder, a polygonal column, etc. are cut, shapes in which the corners are rounded, shapes in which the axis is bent or curved, and combinations thereof. As the shape of the membrane module, a cylindrical shape, an elliptical columnar shape, a polygonal columnar shape having a polygon with 4 to 12 vertices as a bottom surface, and shapes similar thereto are preferable, and a cylindrical shape, an elliptical columnar shape, a quadrangular columnar shape, and shapes similar thereto are more preferable.

[0049] The module case 2 may have, at both axial ends, a membrane fixing portion 21 in which the hollow fiber membrane 1 is fixed with an opening end by a fixing resin, and a raw material liquid flow opening 22 for allowing the raw material liquid to flow from the opening end into the hollow fiber membrane 1. The module case 2 may have, on its side surface, a vapor outlet 23 that communicates with the gas phase portion of the membrane module 10 and takes out the vapor in the gas phase portion to the outside of the membrane module 10.

[0050] The membrane module may be composed of a cartridge and a housing. In that case, by setting a cartridge in which the hollow fiber membrane is fixed with a fixing resin in a housing having a vapor outlet, it can be used as a membrane module. The hollow fiber membrane bundle fixed in the membrane module may optionally have one or more members selected from a net, a non-woven fabric, a cartridge case, etc.

[0051] 〈Membrane fixing portion〉 In the membrane fixing part 21, the fixing resin for adhering and fixing the hollow fiber membrane desirably has good mechanical strength and heat resistance up to about 100°C, for example. Examples of the resin that can be used as the fixing resin include thermosetting epoxy resins and thermosetting urethane resins. From the viewpoint of heat resistance, epoxy resins are preferred, but from the viewpoint of handleability, urethane resins are preferred.

[0052] The filling rate of the hollow fiber membrane based on the cross-sectional area obtained by cutting the membrane fixing part in a plane perpendicular to the axial direction of the membrane module is preferably 15% or more, more preferably 20% or more, from the viewpoint of miniaturization of the membrane module. Also, in order to uniformly fix the hollow fibers with the fixing resin, this filling rate is preferably 74% or less, more preferably 70% or less. The filling rate (%) of the hollow fiber membrane is calculated by (total cross-sectional area of the hollow fiber membrane) ÷ (cross-sectional area of the membrane fixing part) × 100. Note that the cross-sectional area of the hollow fiber membrane refers to the area of the portion surrounded by the outer circumference of the hollow fiber and is a concept including the area of the hollow part.

[0053] 〈Effective length of the membrane〉 The effective length of the hollow fiber membrane 1 in the membrane module 10 is defined as the shortest distance between two membrane fixing parts respectively arranged at both axial ends of the membrane module.

[0054] When flowing a high-viscosity raw material liquid inside the hollow fiber membrane, the pressure loss in the laminar flow region is proportional to the effective length and inversely proportional to the inner diameter. From the viewpoint of increasing the effective length ratio per total length of the hollow fiber membrane (that is, using the membrane more effectively), the effective length of the hollow fiber membrane is preferably 100 times or more, or 250 times or more, or 500 times or more of the inner diameter of the hollow fiber membrane. To reduce the pressure loss, it is preferably 1000 times or less, or 800 times or less of the inner diameter of the hollow fiber membrane.

[0055] 〈Vapor outlet〉 The vapor outlet 23 in the membrane module 10 communicates with the gas phase part of the membrane module and can take out the vapor in the gas phase part to the outside of the membrane module. The vapor taken out to the outside of the membrane module can be condensed, for example, by a vapor condensation part described later and recovered.

[0056] In order to prevent pressure loss associated with an increase in vapor flow velocity under reduced pressure, the vapor outlet preferably has an area sufficient to keep the vapor flow velocity below a desired value. From this perspective, the opening area of the vapor outlet 23 of the module is preferably 1 / 1500 or more, more preferably 1 / 1000 or more, of the membrane area of the hollow fiber membrane 1. When the module case 2 body has a plurality of vapor outlets 23, the opening area of the vapor outlet is evaluated as the total area of all the openings. There is no limitation on the size of the vapor outlet, but as described above, since the membrane module has a substantially cylindrical or substantially polygonal columnar shape, it is more preferable that the vapor outlet is within a range that does not impair the mechanical strength of the membrane module. From this perspective, the opening area of the vapor outlet 23 of the membrane module 10 is more preferably 1 / 250 or less of the membrane area of the hollow fiber membrane 1.

[0057] 〈Raw material liquid flow-through opening〉 The raw material liquid flow-through opening 22 in the membrane module 10 is installed outside the membrane fixing portions 21 arranged at both axial ends of the membrane module 10. The membrane module 10 is connected to the raw material liquid flow path of the raw material liquid concentration system through the raw material liquid flow-through opening 22, and the raw material liquid can flow inside the hollow fiber membrane.

[0058] In order to prevent an increase in pressure loss when flowing a highly viscous raw material liquid to be concentrated, the opening area of the raw material liquid flow-through opening 22 is preferably 0.2 times or more of the total opening cross-sectional area of the hollow fibers. Also, in order to reduce the dead space in the raw material liquid flow path piping, it is preferably 8.0 times or less, more preferably 5.0 times or less, of the total opening cross-sectional area of the hollow fibers.

[0059] 〈Module case〉 As described above, in the membrane distillation according to the present embodiment, since the gas phase portion of the hollow fiber membrane is operated under a reduced pressure state, a compressive stress is applied to the module case 2 in its axial direction. In order to suppress the dimensional change of the membrane module due to this compressive stress, the portion of the membrane module other than both axial end portions may be covered with the module case. The module case may be composed of a single or a plurality of members, and may have an arbitrary member configuration as desired, for example, a configuration having a main body portion and a cap portion having an opening for flowing a raw material liquid attached to the main body portion. The module case has a vapor outlet 23 having a sufficient area so as not to obstruct the flow of vapor generated from the raw material liquid. The module case may be made of, for example, resin and / or metal. From the viewpoints of workability when attaching the vapor outlet 23 and durability against compressive stress, the module case is, for example, at least one resin selected from the group consisting of polypropylene, polysulfone, polyethersulfone, polyvinylidene fluoride, polyphenylene ether, ABS resin, fiber-reinforced plastic, and vinyl chloride resin, and / or It is preferably composed of at least one metal selected from the group consisting of stainless steel, brass, brass, and titanium.

[0060] 《Raw material liquid concentration system and raw material liquid concentration method》 One aspect of the present invention provides a raw material liquid concentration system for producing a food product which is the above-described concentrated liquid, the system comprising a vacuum distillation section. The vacuum distillation section has a function of extracting water vapor from the raw material liquid in an atmosphere of less than 100° C. and concentrating the raw material liquid by reducing the pressure of the gas phase portion in contact with the heated raw material liquid. Since the raw material liquid can be concentrated while maintaining an appropriate temperature, a concentrated liquid in which flavor components in the raw material liquid are well maintained can be produced. In addition, raw material liquids derived from natural products often contain insoluble components, and aggregation or charring of the insoluble components occurs with excessive heating. Therefore, it is advantageous in that charring can be suppressed and long-term operation becomes possible if concentration can be performed at a lower temperature. Specifically, by heating the raw material liquid to 30° C. or higher and 80° C. or lower and heating and concentrating the raw material liquid under the condition that the gas phase in contact with the raw material liquid is reduced to -80 kPa or lower, the above-described high-quality concentrated liquid can be efficiently obtained.

[0061] One aspect of the present invention is a raw material liquid concentration system for manufacturing the food product of the present embodiment, the raw material liquid concentration system comprising a heating unit that heats the raw material liquid to 30°C or higher and 80°C or lower, and a vacuum distillation unit that distills and concentrates the raw material liquid by reducing the pressure of the gas phase in contact with the raw material liquid to -80 kPa or lower. One aspect of the present invention also provides a method for manufacturing the food product of the present embodiment using the above raw material liquid concentration system, that is, a raw material liquid concentration method. In one aspect, the vacuum distillation unit may be a membrane distillation unit having a porous membrane.

[0062] FIG. 6 and FIG. 7 are conceptual diagrams for explaining the raw material liquid concentration system and the raw material liquid concentration method of the present embodiment. Referring to FIGS. 6 and 7, the raw material liquid concentration system 100 according to the present embodiment includes a raw material liquid tank 101 for storing the raw material liquid, a heating unit 103 for heating the raw material liquid, a membrane distillation unit 104 composed of a membrane module having a porous membrane for concentrating the raw material liquid heated by the heating unit 103, and a circulation pump 102 (for example, a gear pump) for circulating the raw material liquid from the raw material liquid tank 101 through the heating unit 103 and the membrane distillation unit 104 in this order and returning it to the raw material liquid pump 101. The porous membrane is arranged to receive the raw material liquid on one side of the membrane and discharge the vapor to the opposite side. The membrane distillation unit 104 is divided by the porous membrane into a liquid phase part through which the raw material liquid flows and a gas phase part through which the vapor generated from the raw material liquid passes through the porous membrane and diffuses, and has a structure capable of reducing the pressure of the gas phase part to a reduced pressure state. In one aspect, the membrane module constituting the membrane distillation unit 104 may be the above-mentioned hollow fiber membrane module or flat membrane module.

[0063] The raw material liquid concentration system 100 is configured such that, in one aspect, the temperature of the raw material liquid is 30°C or higher and 80°C or lower at the raw material liquid inflow site of the membrane distillation unit, and in one aspect, the gas phase part in the membrane distillation unit is configured to be depressurized to -80 kPa or lower.

[0064] Referring to FIGS. 6 and 7, the method for manufacturing a raw material liquid concentrate, which is a form of food product according to this embodiment, includes, for example, a step of heating the raw material liquid in a heating unit 103, and a concentration step of circulating the heated raw material liquid through a vapor phase portion in a vacuum distillation unit and concentrating it by membrane distillation. In one aspect, the vacuum distillation unit may be a membrane distillation unit having a porous membrane. In this method, the raw material liquid concentrated in the concentration step is circulated and merged into the raw material liquid before concentration, for example, the raw material liquid in the raw material liquid tank 101.

[0065] In the method for manufacturing the raw material liquid concentrate of this embodiment, at the raw material liquid inflow site of the membrane distillation unit, in one aspect, the raw material liquid temperature is 30°C or higher and 80°C or lower, and in one aspect, the pressure on the vapor phase side of the porous membrane is reduced to -80 kPa or lower.

[0066] The raw material liquid concentration system 100 may have a vapor condensation unit 105 that condenses the vapor generated in the membrane distillation unit 104. In one aspect, the vapor condensation unit 105 is connected to the vapor outlet 23 of the membrane module 10 via a vapor pipe. A demister may be installed in the vapor pipe to prevent the raw material liquid from mixing into the condensed water.

[0067] In addition to the above, the raw material liquid concentration system 100 may further include, for example, a condensate tank 106, a withdrawal pump 107, a vacuum device 108, a flow regulator (not shown), a pressure regulator (not shown), etc. Also, the raw material liquid concentration system 100 may further have a structure that can keep warm the raw material liquid flow path including the raw material liquid tank 101 and the vapor condensation unit in addition to the heating unit 103.

[0068] The vapor condensation part 105 may have a gas phase part communicating with the membrane distillation part 104 (for example, the vapor outlet 23 of the membrane module 10), and a cooling body for aggregating the vapor diffused from the membrane distillation part 104 (for example, the vapor outlet 23 of the membrane module 10). The cooling body maintains a low temperature by allowing a cooling medium (for example, cooling water) to flow through it. The structure of the cooling body may be, for example, a structure in which tubes are gathered or a structure in which plates are overlapped. When the cooling body part comes into contact with the vapor diffused into the gas phase part of the vapor condensation part 105, the vapor is cooled and condensed to become distilled water (permeated water). By storing this in the condensate tank 106 and recovering it, distilled water can be obtained.

[0069] In the membrane distillation part 104, by reducing the pressure on one side (gas phase part) separated by the porous membrane in the membrane distillation part, using the vapor pressure difference, which is the difference between the vapor pressure of the raw material liquid and the absolute pressure of the reduced pressure part, as the driving force, vapor can be taken out from the raw material liquid. When the raw material liquid is at a high temperature, the vapor pressure difference becomes large and the concentration efficiency becomes good. On the other hand, from the viewpoint of suppressing the deterioration of the concentrated liquid, the decomposition or discoloration of valuable substances, it is advantageous to keep the raw material liquid below a predetermined temperature. That is, in order to improve the concentration efficiency while maintaining the quality of the concentrated liquid, at the raw material liquid inflow site of the membrane module in the membrane distillation part 104, the raw material liquid temperature is preferably 30°C or higher and 80°C or lower, and more preferably 40°C or higher and 70°C or lower. If it is below the above upper limit temperature, it is easy to maintain the quality, and if it is above the above lower limit temperature, the vapor pressure of the raw material liquid does not become too small and the concentration proceeds well.

[0070] When the pressure of the gas phase part of the membrane distillation part 104 is reduced, the vapor pressure difference between the raw material liquid and the gas phase part becomes large, so the concentration efficiency is improved. When performing membrane distillation at a low temperature, it is advantageous to set the pressure of the gas phase part to a predetermined value or less. Specifically, when the atmospheric pressure is set to 0 kPa, the pressure of the gas phase part is preferably -80 kPa or less, and more preferably -90 kPa or less. Although the above pressure is preferably lower, from the viewpoint of facilitating process control, in one aspect, it may be -99 kPa or higher, or -97 kPa or higher.

[0071] When circulating the raw material liquid through the membrane distillation unit 104, in order to uniformly circulate the raw material liquid throughout the porous membrane, a raw material liquid pressure equal to or higher than a predetermined value is advantageous. Specifically, the raw material liquid pressure is preferably 10 kPa or higher, and more preferably 30 kPa or higher. Considering the pressure resistance of the porous membrane and the module case, it is advantageous to keep the raw material liquid pressure below a predetermined value. Specifically, it is preferably 300 kPa or lower, or 210 kPa or lower.

[0072] In membrane distillation, when the transmembrane differential pressure, which is the pressure difference between the liquid phase part and the gas phase part, becomes equal to or higher than the liquid entry pressure (LEP), the raw material liquid moves from the liquid phase part to the gas phase part, leading to a loss of the raw material liquid. Therefore, in the membrane distillation unit 104, it is advantageous to keep the transmembrane differential pressure below the liquid entry pressure. Specifically, the difference in pressure between the liquid phase part and the gas phase part (i.e., the differential pressure between the raw material liquid pressure and the gas phase part pressure) is preferably 395 kPa or lower, or 380 kPa or lower, or 300 kPa or lower. From the perspective of obtaining good concentration efficiency, the above differential pressure is preferably 50 kPa or higher, or 80 kPa or higher, or 90 kPa or higher.

[0073] In membrane distillation, it is difficult to directly heat the membrane surface where the water in the raw material liquid evaporates. Therefore, in order to supply the latent heat required for evaporation, it is advantageous to keep the linear velocity of the raw material liquid above a predetermined value. Specifically, the linear velocity of the raw material liquid at the membrane surface in the liquid phase part within the membrane distillation unit is preferably 0.05 m / s or higher. On the other hand, since the pressure in the liquid phase part also increases as the linear velocity of the raw material liquid increases, it is advantageous to keep the linear velocity below a predetermined value. Specifically, the linear velocity of the raw material liquid at the surface of the porous membrane within the membrane distillation unit is preferably 1.0 m / s or lower, and more preferably 0.5 m / s or lower.

[0074] 〈Heating of the raw material liquid〉 In the heating step, from the viewpoint of suppressing decomposition or denaturation of the raw material liquid due to heating, it is preferable to heat the raw material liquid by bringing it into contact with a heating section at 90°C or lower. The heating section 103 for heating the raw material liquid, which is useful in the heating step, may have a structure in which the raw material liquid is heated by heating a part of the raw material liquid flow path. As a method for heating the raw material liquid, a method of supplying heat from a heat medium to the raw material liquid by a heat exchanger to heat the raw material liquid, or a method of heating a pipe portion by an electric heating wire, a flame, or the like can be used. Since the highest temperature in the raw material liquid flow path is the pipe surface of the heating section, from the viewpoint of suppressing decomposition or denaturation of the raw material liquid due to heating, the surface temperature of the heating section 103 (that is, the temperature of the portion in contact with the raw material liquid) is preferably 90°C or lower.

[0075] In order to make the surface temperature of the heating section 103 as low as possible, a method of heating the raw material liquid by supplying heat from a heat medium to the raw material liquid by a heat exchanger is more preferable, and it is more preferable to use warm water or steam (for example, steam depressurized to below atmospheric pressure) as the heat medium. From the viewpoint of heat utilization efficiency, the temperature of the warm water or steam is preferably 50°C or higher. The temperature of the warm water or steam is preferably 100°C or lower from the viewpoint of avoiding deterioration, decomposition, discoloration, etc. of the target component in the raw material liquid. Also, from the viewpoint of reducing the concentration energy cost, the raw material liquid may be heated using waste heat generated in steps other than the concentration step.

[0076] 〈Pretreatment〉 In the raw material liquid concentration method of the present embodiment, in order to improve the energy efficiency of the entire concentration method, before the concentration step, pretreatment may be performed for the purpose of pre-concentration, removal of impurities (for example, fiber components in sap), etc. Referring to FIG. 7, in one aspect, the raw material liquid is first supplied to a preliminary tank 109 upstream of the raw material liquid tank 101, and after the raw material liquid is introduced into a pretreatment section 111 via a liquid feed pump 110 for pretreatment, it may be supplied to the raw material liquid pump 101. The pretreatment section 111 may be a filtration membrane for removing impurities, a reverse osmosis membrane for pre-concentration, a combination thereof, etc. In one aspect, the concentration step and the filtration step and / or pre-concentration step as the pretreatment step are performed in independent raw material liquid flow paths.

[0077] More specifically, in one aspect, as shown in FIG. 7, the raw material liquid concentrated in the membrane distillation unit 104 may be circulated to the raw material liquid tank 101 without passing through the pretreatment unit 111. That is, in one aspect, the raw material liquid concentrated in the concentration step may be circulated and merged with the raw material liquid before concentration after the pretreatment step (that is, the pretreatment unit may be arranged in series with the membrane distillation unit).

[0078] On the other hand, in another aspect, separately from the raw material liquid circulation path that returns from the raw material liquid tank 101 through the membrane distillation unit 104 to the raw material tank 101, a pretreatment path for circulating the raw material liquid from the raw material liquid tank 101 through the pretreatment unit 111 to the raw material liquid tank 101 may be provided (that is, the pretreatment unit may be arranged in parallel with the membrane distillation unit). Such a pretreatment mode is advantageous in that it can remove impurities newly generated due to the increase in concentration accompanying the concentration of the raw material liquid over time while maintaining the raw material liquid circulation flow rate in the raw material liquid circulation flow path.

[0079] 〈Filter membrane〉 In one aspect, the pretreatment unit may have a filter membrane. In the raw material liquid, there is a high possibility of the presence of insoluble components such as dietary fiber. If membrane distillation is performed as it is, it may cause problems such as excessive pressure increase in the liquid phase part, damage to the membrane due to rubbing, and membrane clogging due to the deposition of insoluble components on the membrane surface. Therefore, in order to perform membrane distillation more efficiently, it is preferable to remove insoluble components. The membrane filtration method is suitable for removing insoluble components. In one aspect, from the viewpoint of efficiently removing insoluble components in the raw material liquid, a filter membrane with a pore size of 20 μm or less is preferable. The pore size of the filter membrane is more preferably 1.0 μm or less. The pore size of the filter membrane may be, for example, 0.1 μm or more, or 0.3 μm or more from the viewpoint of filtration efficiency.

[0080] 〈Cross-flow filtration〉 Performing the removal of insoluble components by the above-described membrane filtration in a crossflow filtration mode is preferable from the viewpoint of preventing clogging of the filtration membrane. In crossflow filtration, a crossflow filtration membrane module having a flat membrane or a hollow fiber membrane can be used. In one aspect, the filtration membrane module has two or more inlets and outlets combined on the flow path side of the liquid to be filtered, and one or more outlets on the flow path side of the permeate. By applying pressure while circulating the liquid to be filtered through such a filtration membrane module, it is possible to obtain a permeate while preventing the deposition of insoluble components on the membrane surface. There are no particular restrictions on the circulation flow rate of the liquid to be filtered and the flow rate of the permeate, but from the viewpoint of performing efficient filtration, the circulation flow rate of the liquid to be filtered is preferably at least 3 times, more preferably at least 10 times, the flow rate of the permeate.

[0081] 〈Backwashing of the Filtration Membrane〉 In the removal of insoluble components by the filtration membrane, backwashing may be periodically performed for the purpose of removing the insoluble components deposited on the surface of the filtration membrane and maintaining the membrane performance. Examples of the fluid used for backwashing include water, the permeate in the membrane filtration step, the condensed water obtained by membrane distillation, etc. Also, an air backwash method, the air backwash method, may be used. The timing for performing backwashing can be determined from an increase in the transmembrane differential pressure of the filtration membrane, a decrease in the permeate flow rate, etc. Also, backwashing may be performed at a preset cycle (for example, once per hour).

[0082] 〈Reverse Osmosis Membrane〉 The reverse osmosis membrane is not particularly limited, but preferred examples are hollow fiber membranes made of cellulose acetate and composite membranes having a separation layer containing polyamide. The reverse osmosis membrane is used for the preliminary concentration of the raw material liquid. By arranging the raw material liquid on the separation layer side of the reverse osmosis membrane and applying pressure, only the water in the raw material liquid can permeate and be removed. In this case, as the raw material liquid is concentrated, the solute concentration in the raw material liquid may exceed the saturation concentration and precipitate as insoluble components. Also, as a pretreatment section, the reverse osmosis membrane and the above-described filtration membrane may be used in combination. In this case, it is more preferable from the viewpoint of improving the removal efficiency of insoluble components to flow the raw material liquid, for example, in the order of the reverse osmosis membrane and the filtration membrane (that is, to arrange the reverse osmosis membrane upstream of the filtration membrane).

[0083] <Cleaning of the porous membrane> In the raw material liquid concentration method according to the present embodiment, for the purpose of removing insoluble components precipitated with the concentration of the raw material liquid, preventing the mixing of the raw material liquid during the raw material liquid switching, etc., particularly for removing the raw material liquid adhering to the porous membrane, the liquid phase part of the membrane module can be periodically cleaned. Specifically, it is preferable to pass water through the liquid phase part of the membrane module once or more a day for cleaning. Further, for the purpose of removing components that are hardly soluble in water, sterilizing the inside of the system, etc., particularly for removing membrane contaminants adhering to the porous membrane, it is also preferable to perform cleaning using a chemical solution once or more a week. As the water used for cleaning, drinking water, permeated water of a reverse osmosis membrane, condensed water obtained in the raw material liquid concentration system of the present embodiment, etc. may be used. As the chemical solution used for cleaning, a chemical solution with a pH of 5 or less (for example, an acidic aqueous solution such as hydrochloric acid, aqueous citric acid solution, etc.), or a chemical solution with a pH of 9 or more (for example, an alkaline aqueous solution such as an aqueous sodium hydroxide solution, an aqueous sodium hypochlorite solution, etc.) can be used. Further, by using the acidic aqueous solution and the alkaline aqueous solution in order, both inorganic components and organic components can be efficiently removed.

[0084] <Additional concentration by evaporation> In the raw material liquid concentration method of the present embodiment, for the purpose of sterilizing the concentrated raw material liquid, flavoring by heating, etc., in order to improve the energy efficiency of the entire concentration method, an additional concentration step by an evaporator (not shown) can be included after the concentration step. In order to obtain the desired sterilization or flavoring effect, in the additional concentration step, it is preferable to heat the concentrated raw material liquid to a temperature equal to or higher than the raw material liquid temperature in the concentration step by membrane distillation. In one aspect, the evaporator may be disposed downstream of the aforementioned filtration membrane.

Examples

[0085] Hereinafter, exemplary embodiments of the present invention will be described more specifically with reference to examples, but the present invention is not limited by the following examples in any way.

[0086] (Brix of the concentrated liquid) The sugar content of the raw material solution and the concentrated solution was measured using a sugar refractometer (Atago PAL-1). The sugar refractometer was calibrated to 0% with distilled water before measurement.

[0087] (Visible light transmittance of the raw material solution) The transmittance of the concentrated solution was determined by measuring the UV / vis spectrum. The concentrated solution was filtered using an ultrafiltration filter (Amicon Ultra-0.5, PLGC UltraCel-10 membrane, 10 kDa, UFC501008). Then, a sufficient amount of the filtrate was placed in a double-sided transparent quartz cell with a screw cap for a spectrophotometer (GL Science Inc. S15-UV-10, optical path length 10 mm, optical path width 10 mm), and the measurement was carried out. Glycerin was used as the blank. The UV / vis analysis conditions are as follows. -UV / vis conditions- UV / vis instrument: JASCO V-770 manufactured by JASCO Corporation Measurement mode: Abs Measurement wavelength: 800 - 200 nm Data acquisition interval: 0.5 nm Light source: D2, WI Light source switching: 340 nm Correction: Baseline

[0088] (Aroma component analysis) The aroma components were collected from the concentrated solution at 50°C. Specifically, 1 g of the concentrated solution was added to a 20 mL screw-cap vial with a septum, heated at 50°C for 20 minutes, then SPME was inserted and the gas components were adsorbed for an additional 10 minutes. The adsorbed components were thermally desorbed at the GC / MS injection port and GC / MS measurement was performed. Vanillin and acetophenone in the aroma components were analyzed using SPME-GC / MS. The analysis conditions of SPME-GC / MS are as follows. -SPME-GC / MS conditions- SPME-GC / MS instrument: GC-7890 MSD-5977B manufactured by Agilent Ionization method: EI (70 eV) Mass range: 29 - 800 Column: DB-WAX (30 m × 0.25 mm × 0.25 μm) Carrier gas: Helium Flow rate: 1.2 mL / min Transfer temperature: 250 °C Temperature condition: 40 °C (hold for 7 minutes) ⇒ increase by 10 °C / min ⇒ 250 °C (hold for 7 minutes) Inlet temperature: 250 °C SPME Fiber: 65μm PDMS / DVB Injection method: Splitless Heating temperature: 50 °C × 30 min (extract volatile components for 20 min ⇒ adsorb for 10 min) Area range: Vanillin 23:31 - 23:38 Acetophenone 14:32 - 14:41

[0089] (Measurement of magnesium ion concentration) The measurement of magnesium ion concentration was performed using an ICP-MS, model "iCAP Q" manufactured by Thermo Fisher Scientific. In this measurement, for each measurement date of the sample, calibration curves were updated by measuring standards obtained by diluting "ICP Mixed Standard Solution D" manufactured by Kanto Chemical Co., Inc. 10-fold, 100-fold, 1000-fold, and 10000-fold.

[0090] (Sensory evaluation of flavor) The obtained raw material liquid concentrate was provided to 5 panelists for tasting, and the flavor was evaluated according to the following two criteria. 1. Original flavor of the raw material A: All 5 panelists judged that the original flavor of the raw material was strong. B: One or more but less than 4 panelists judged that the original flavor of the raw material was strong. C: None of the panelists judged that the original flavor of the raw material was strong. 2. Balance of flavor A: All 5 panelists judged that the balance of flavor (sweetness, fragrance, bitterness) was good. B: One or more but less than 4 panelists judged that the balance of flavor (sweetness, fragrance, bitterness) was good. C: None of the panelists judged that the balance of flavor (sweetness, fragrance, bitterness) was good.

[0091] [Coloring] It was evaluated according to the following criteria. A: Visible light transmittance at 560 nm is 85% or more B: Visible light transmittance at 560 nm is 80% or more and less than 85% C: Visible light transmittance at 560 nm is 75% or more and less than 80% D: Visible light transmittance at 560 nm is less than 75%

[0092] (Measurement of various physical properties of the hollow fiber membrane) [Outer diameter, inner diameter, and film thickness] Regarding the outer diameter and inner diameter of the hollow fiber membrane, the hollow fiber membrane was thinly cut with scissors in a direction perpendicular to its longitudinal direction, and the outer diameter and inner diameter of the cross section were measured using a microscope, respectively. The film thickness was calculated by the following formula (2). Film thickness (mm) = [Outer diameter (mm) - Inner diameter (mm)] / 2 (2)

[0093] [Average pore diameter] The average pore diameter of the hollow fiber membrane was measured by the method for measuring the average pore diameter described in ASTM: F316 - 86 (also known as the half - dry method). The measurement was carried out on a hollow fiber membrane about 10 cm long using ethanol as the liquid under the standard measurement conditions of 25°C and a pressure increase rate of 0.01 atm / second. The average pore diameter was obtained by the following formula (3). Average pore diameter [μm] = 2,860 × (Surface tension of the liquid used [dyne / cm]) / (Half - dry air pressure [Pa]) (3) Here, as the surface tension of ethanol at 25°C, a value of 21.97 dyne / cm was used.

[0094] [Maximum pore diameter] The maximum pore size of the hollow fiber membrane was measured using the bubble point method. One end of a hollow fiber membrane with a length of 8 cm was blocked, and a nitrogen gas supply line was connected to the other end via a pressure gauge. In this state, after supplying nitrogen gas to replace the inside of the line with nitrogen, the hollow fiber membrane was immersed in ethanol. At this time, the hollow fiber membrane was immersed in ethanol while applying a very slight pressure with nitrogen to the line so that ethanol did not flow back into the line. With the hollow fiber membrane immersed, the pressure of the nitrogen gas was slowly increased, and the pressure P at which nitrogen gas bubbles began to stably emerge from the outer wall of the hollow fiber membrane was recorded. From this value, the maximum pore size d [μm] of the hollow fiber membrane was calculated using the following formula (4): d = C1γ / P (4) {In the formula, C1 is a constant, γ is the surface tension [dyne / cm], and P is the pressure [Pa].} It was calculated by. When ethanol was used as the immersion liquid, the value of the product of the constant C1 and the surface tension γ was set to C1γ = 0.0879 [N / m].

[0095] [Porosity] The porosity of the hollow fiber membrane was determined by the method described below. The hollow fiber membrane was cut to a certain length, its weight was measured, and the porosity was calculated using the following formula (5): Porosity (%) = 100 - [mass of hollow fiber membrane (g) × 100] / [polymer density (g / cm 3 ) × {(outer diameter (cm) / 2) 2 - (inner diameter (cm) / 2) 2} × 3.14 × length (cm)] (5) It was determined by.

[0096] [Air permeability] It was measured in accordance with ISO 9237. Dry air was allowed to flow into the membrane module, and the pressure (kPa) at the inlet and outlet of the membrane module and the dry air flow rate (L / h) at the outlet of the membrane module were measured. The dry air flow rate (L / h) was divided by the differential pressure (kPa) between the above inlet and the above outlet and the membrane area to calculate the air permeability (L / m 2 ·h·kPa).

[0097] [Viscosity of the raw material liquid] The viscosity of the raw material liquid was measured as the solution viscosity using a viscometer manufactured by Thermo Scientific (model name "HAAKE ViscoTester iQ").

[0098] 《Implementation of Membrane Distillation》 In Examples 1 to 10 and Comparative Examples 3 and 4, membrane distillation was carried out using a raw material liquid concentration system having a configuration according to FIG. 6 or FIG. 7, in which a membrane module having a configuration according to FIGS. 4 and 5 was provided as the membrane distillation section.

[0099] The membrane module as the membrane distillation section had the configuration as described in each Example and Comparative Example, and the outlet of the vapor condensation section was connected to the condensate tank by piping. Then, the pressure in the system was adjusted by connecting the gas phase part of the condensate tank to a pressure reducing device via a pressure regulator.

[0100] In the raw material liquid flow path, a heating section using a heat exchanger was provided, and warm water was used as the heat medium. A gear pump was used as the circulation pump to circulate the raw material liquid in the raw material liquid flow path, and the pressure of the raw material liquid was adjusted using a back pressure valve provided at the outlet of the membrane module. Cooling water (CW) at 10°C was circulated through the vapor condensation section at a flow rate of 10 L / min.

[0101] [Measurement of Flux] Membrane distillation was performed, and the weight of the distilled water flowing into the condensate tank was measured using a weighing scale or an integrated flow meter, according to the following formula (6): Flux = weight of distilled water obtained by membrane distillation for 1 hour of operation ÷ membrane area ÷ operation time (1 hour) (6) The Flux was calculated according to this formula.

[0102] 《Example 1》 [Hydrophobization of Hollow Fiber Membrane] For 1000 hollow fiber membranes made of PVDF (polyvinylidene fluoride) with an inner diameter of 0.68 mm, an outer diameter of 1.25 mm, an average pore diameter of 0.21 μm determined from ASTM-F316-86, a maximum pore diameter of 0.29 μm, and a porosity of 72%, after completely immersing them once in a fluororesin-based water repellent FS-392B (0.5 wt%) manufactured by Fluoro Technology Co., Ltd., lifting them up and drying them, a hydrophobic polymer was applied to the inner and outer surfaces of the hollow fiber membranes.

[0103] [Fabrication of Hollow Fiber Membrane Module] In the fabrication of the membrane module, a thermosetting epoxy resin was used as the fixing resin, and the hollow fiber membranes were adhesively fixed inside the module case by centrifugal adhesion to form membrane fixing parts at both axial ends. The membrane fixing parts were configured such that the shortest distance between the two membrane fixing parts (i.e., the effective length of the hollow fiber membranes) was approximately 300 mm.

[0104] As the module case, a cylindrical polysulfone case with an inner diameter of 55 mm and an outer diameter of 60 mm was used. This case was provided with three steam outlets with an area of 0.0010 m by 2.5S piping on the outer peripheral side surface. Also, caps for connecting the module to the raw material liquid flow path of the membrane distillation system were attached to both ends of this case. The caps were provided with openings of 2.0S and 0.0018 m as raw material liquid flow-through openings. The air permeability of the obtained membrane module was 4800 L / h·m·kPa, and the water permeation rate of a 20 wt% EtOH aqueous solution at 200 kPa pressure was 40 mL / h·m. 2 2 2 2

[0105] Using the membrane module obtained in the above [Fabrication of Membrane Module], a raw material liquid concentration system with a configuration according to Fig. 6 was assembled, and 140 kg of maple water was concentrated by membrane distillation according to the conditions in Table 1. The time taken to concentrate unfiltered maple water (Brix 2.0, viscosity 3.2 cP) to Brix 70 (viscosity 370 cP) was 9.9 hours, and the cumulative Flux in all concentration tests was 13.3 kg / m. 2·h. The visible light transmittance of the obtained raw material liquid concentrate was 83%, the peak area of vanillin was 8.0 times that of acetophenone, and the weight ratio of sugar to Mg ions was 99% of the initial value. As a result of the sensory evaluation of the flavor, the original flavor of the raw material was B, and the flavor balance was A.

[0106] From the above results, it was verified that the concentrate obtained by the method of Example 1 was a high-quality syrup with good flavor balance while maintaining the flavor of the raw material liquid to some extent without excessive coloring.

[0107] 《Example 2》 A concentration test was carried out under the same conditions as in Example 1 except that warm water at 50°C was used as the heat medium in the heating section, the maximum temperature on the surface of the heating section was 45°C, the temperature of the raw material liquid at the raw material liquid inlet of the membrane distillation membrane module was 35°C, and the reduced pressure section was -95 kPa. The time taken to concentrate the maple water to Brix 70 was 30.5 hours, and the total Flux of the entire concentration test was 4.3 kg / m 2 ·h. The visible light transmittance of the obtained raw material liquid concentrate was 90%, the peak area of vanillin was 1.4 times that of acetophenone, and the weight ratio of sugar to Mg ions was 98% of the initial value. As a result of the sensory evaluation of the flavor, the original flavor of the raw material was A, and the flavor balance was B.

[0108] From the above results, it was verified that the concentrate obtained by the method of Example 2 was a high-quality syrup with little coloring while maintaining the flavor of the raw material liquid and having a somewhat good flavor balance.

[0109] 《Example 3》 Before the raw material liquid concentration operation by membrane distillation, the raw material liquid was vacuum filtered using filter paper with a pore size of 20 μm. A concentration test was carried out under the same conditions as in Example 2 except that warm water at 70°C was used as the heat medium in the heating section and the maximum temperature on the surface of the heating section was 65°C, and the temperature of the raw material liquid at the raw material liquid inlet of the membrane distillation membrane module was 55°C. The time taken to concentrate the maple water to Brix 70 was 12.9 hours, and the total Flux of the entire concentration test was 10.2 kg / m 2·h. The visible light transmittance of the obtained raw material liquid concentrate was 86%, the peak area of vanillin was 1.9 times that of acetophenone, and the weight ratio of sugar to Mg ions was 101% of the initial value. As a result of the sensory evaluation of the flavor, the original flavor of the raw material was A, and the flavor balance was A.

[0110] From the above results, it was verified that the concentrate obtained by the method of Example 3 is a very high-quality syrup with almost no coloring, maintaining the flavor of the raw material liquid and having a good flavor balance.

[0111] 《Example 4》 Before the raw material liquid concentration operation by membrane distillation, a cross-flow filtration was carried out while periodically backwashing using a PVDF hollow fiber membrane with a pore size of 0.8 μm. A concentration test was conducted under the same conditions as in Example 3 except for this. The time taken to concentrate maple water to Brix 70 was 10.9 hours, and the total flux of the entire concentration test was 12.0 kg / m 2 ·h. The visible light transmittance of the obtained raw material liquid concentrate was 87%, the peak area of vanillin was 3.0 times that of acetophenone, and the weight ratio of sugar to Mg ions was 102% of the initial value. As a result of the sensory evaluation of the flavor, the original flavor of the raw material was A, and the flavor balance was A.

[0112] From the above results, it was verified that the concentrate obtained by the method of Example 4 is a very high-quality syrup with almost no coloring, maintaining the flavor of the raw material liquid and having a good flavor balance.

[0113] 《Example 5》 Simultaneously with the start of the raw material liquid concentration operation by membrane distillation, a cross-flow filtration was carried out while periodically backwashing using a PVDF hollow fiber membrane with a pore size of 0.8 μm in a raw material liquid circulation channel different from the membrane distillation module. A concentration test was conducted under the same conditions as in Example 3 except for this. The time taken to concentrate maple water to Brix 70 was 10.7 hours, and the total flux of the entire concentration test was 12.2 kg / m 2·h. The visible light transmittance of the obtained raw material liquid concentrate was 87%, the peak area of vanillin was 3.3 times that of acetophenone, and the weight ratio of sugar to Mg ions was 104% of the initial value. As a result of the sensory evaluation of the flavor, the original flavor of the raw material was A, and the flavor balance was A.

[0114] From the above results, it was verified that the concentrate obtained by the method of Example 5 is a very high-quality syrup with almost no coloring, maintaining the flavor of the raw material liquid and having a good flavor balance.

[0115] 《Example 6》 A concentration test was conducted under the same conditions as in Example 4, except that the industrial wastewater at 70 °C was used as the heat medium in the heating section. The time taken to concentrate the maple water to Brix 70 was 10.5 hours, and the cumulative Flux for the entire concentration test was 12.5 kg / m 2 ·h. The visible light transmittance of the obtained raw material liquid concentrate was 88%, the peak area of vanillin was 3.6 times that of acetophenone, and the weight ratio of sugar to Mg ions was 100% of the initial value. As a result of the sensory evaluation of the flavor, the original flavor of the raw material was A, and the flavor balance was A.

[0116] From the above results, it was verified that the concentrate obtained by the method of Example 6 is a very high-quality syrup with almost no coloring, maintaining the flavor of the raw material liquid and having a good flavor balance.

[0117] 《Example 7》 A concentration test was conducted under the same conditions as in Example 4, except that the raw material liquid was concentrated to Brix 20 by a reverse osmosis membrane before the raw material liquid concentration operation by membrane distillation. The time taken to concentrate the maple water to Brix 70 was 2.2 hours, and the cumulative Flux for the entire concentration test was 6.0 kg / m 2 ·h. The visible light transmittance of the obtained raw material liquid concentrate was 92%, the peak area of vanillin was 1.4 times that of acetophenone, and the weight ratio of sugar to Mg ions was 95% of the initial value. As a result of the sensory evaluation of the flavor, the original flavor of the raw material was A, and the flavor balance was B.

[0118] From the above results, it was verified that the concentrated liquid obtained by the method of Example 7 is a high-quality syrup with almost no coloring, maintaining the flavor of the raw material liquid while having a somewhat good balance of flavors.

[0119] 《Example 8》 A concentration test was conducted under the same conditions as in Example 4, except that after concentrating the raw material liquid to Brix 50 by membrane distillation, it was further concentrated by heating at a temperature of 100 °C or higher to Brix 70 using an atmospheric distillation apparatus. The time taken to concentrate maple water to Brix 50 was 6.2 hours, and the cumulative Flux for the entire concentration test was 15.0 kg / m 2 ·h. The visible light transmittance of the obtained raw material liquid concentrate with Brix 70 was 81%, the peak area of vanillin was 10.3 times that of acetophenone, and the weight ratio of sugar to Mg ions was 99% of the initial value. As a result of the sensory evaluation of the flavor, the original flavor of the raw material was B, and the balance of flavors was B.

[0120] From the above results, it was verified that the concentrated liquid obtained by the method of Example 8 is a high-quality syrup with no excessive coloring, maintaining the flavor of the raw material liquid to some extent while having a somewhat good balance of flavors.

[0121] 《Example 9》 Using 140 kg of maple water with an initial Brix of 2.0 as the raw material liquid, after concentrating it to Brix 20 by reverse osmosis membrane, it was further concentrated to Brix 50 by membrane distillation under the same conditions as in Example 1, and then concentrated by heating at a temperature of 100 °C or higher to Brix 70 using an atmospheric distillation apparatus. The time taken to concentrate maple water to Brix 50 by membrane distillation was 5.9 hours, and the cumulative Flux for the entire concentration test was 16.0 kg / m 2 ·h. The visible light transmittance of the obtained raw material liquid concentrate with Brix 70 was 83%, the peak area of vanillin was 10.6 times that of acetophenone, and the weight ratio of sugar to Mg ions was 94% of the initial value. As a result of the sensory evaluation of the flavor, the original flavor of the raw material was B, and the balance of flavors was B.

[0122] From the above results, it was verified that the concentrated liquid obtained by the method of Example 9 is a high-quality syrup with no excessive coloring, maintaining the flavor of the raw material liquid to a certain extent and having a somewhat good balance of flavors.

[0123] 《Example 10》 A concentration test was conducted under the same conditions as in Example 4, except that 93 kg of coconut water with an initial Brix of 3.0 was used as the raw material liquid. The time taken to concentrate to Brix 70 was 8.8 hours, and the total flux for the entire concentration test was 9.5 kg / m 2 ·h. The visible light transmittance of the obtained raw material liquid concentrate was 80%. Although vanillin was detected in the aroma components, acetophenone was not detected. The weight ratio of sugar to Mg ions was 102% of the initial value. As a result of the sensory evaluation of the flavor, the original flavor of the raw material was rated B, and the balance of the flavors was rated B.

[0124] From the above results, it was verified that the concentrated liquid obtained by the method of Example 10 is a high-quality syrup with no excessive coloring, maintaining the flavor of the raw material liquid to a certain extent and having a somewhat good balance of flavors.

[0125] 《Example 11》 A concentration test was conducted under the same conditions as in Example 4, except that 112 kg of birch sap with an initial Brix of 2.5 was used as the raw material liquid. The time taken to concentrate to Brix 70 was 11.2 hours, and the total flux for the entire concentration test was 9.0 kg / m 2 ·h. The visible light transmittance of the obtained raw material liquid concentrate was 82%. Although vanillin was detected in the aroma components, acetophenone was not detected. The weight ratio of sugar to Mg ions was 99% of the initial value. As a result of the sensory evaluation of the flavor, the original flavor of the raw material was rated B, and the balance of the flavors was rated B.

[0126] From the above results, it was verified that the concentrated liquid obtained by the method of Example 11 is a high-quality syrup with no excessive coloring, maintaining the flavor of the raw material liquid to a certain extent and having a somewhat good balance of flavors.

[0127] 《Example 12》 [Preparation of Forward Osmosis Hollow Fiber Membrane Module] A hollow fiber membrane made of polyethersulfone with an outer diameter of 1.0 mm, an inner diameter of 0.7 mm, and a micropore diameter on the inner surface of 0.05 μm was used as the support layer. 1600 of the hollow fiber support layers were filled into a cylindrical plastic housing with an inner diameter of 55 mm and a length of 460 mm, and both ends were fixed with an adhesive to produce a hollow fiber support layer module with an effective membrane inner surface area of 1.6 m 2 . For the hollow fiber support layer module, interfacial polymerization was carried out using an aqueous solution of m-phenylenediamine and an n-hexane solution of trimesic acid chloride to produce a forward osmosis hollow fiber membrane module having a polyamide separation layer on the inside.

[0128] Using the above forward osmosis hollow fiber membrane module, concentration was carried out using a forward osmosis concentration system. The forward osmosis concentration system has a function of flowing a raw material liquid inside the hollow fiber membrane and flowing an inducing solution having an osmotic pressure outside the hollow fiber membrane. By bringing the raw material liquid into contact with the inducing solution through the forward osmosis membrane, water in the raw material liquid can be moved to the inducing solution, and the raw material liquid can be concentrated.

[0129] Using 140 kg of maple water with an initial Brix of 2.0 as the raw material liquid and 280 kg of an aqueous magnesium chloride solution with a concentration of 20% by mass as the inducing solution, the raw material liquid and the inducing solution were flowed in parallel to conduct a concentration test. The temperature of the raw material liquid at the raw material liquid inlet of the forward osmosis hollow fiber membrane module was 25°C. The time taken to concentrate the maple water to Brix 70 was 8.5 hours, and the total flux of the entire concentration test was 10.0 kg / m 2 ·h. The visible light transmittance of the obtained raw material liquid concentrate was 95%, the peak area of vanillin was 0.3 times that of acetophenone, and the weight ratio of sugar to Mg ions was 106% of the initial value. As a result of the sensory evaluation of the flavor, the original flavor of the raw material was B, and the flavor balance was B.

[0130] From the above results, it was verified that the concentrated liquid obtained by the method of Example 11 is a high-quality syrup with almost no coloring, maintaining the flavor of the raw material liquid, and having a somewhat good flavor balance.

[0131] Example 13 140 kg of maple water with an initial Brix of 2.0 was used as the raw material solution, and it was heated and concentrated to Brix 70 at a temperature of 100 °C or higher using a vacuum distillation apparatus. The maximum temperature on the surface of the heating section was 65 °C, the average temperature of the raw material solution in the vacuum distillation apparatus was 55 °C, and the vacuum section was -95 kPa. The time taken to concentrate to Brix 70 was 42.0 hours. The visible light transmittance of the obtained raw material solution concentrate with Brix 70 was 83%, the peak area of vanillin was 2.9 times that of acetophenone, and the weight ratio of sugar to Mg ions was 100% of the initial value. As a result of the sensory evaluation of the flavor, the original flavor of the raw material was B, and the flavor balance was A.

[0132] From the above results, it was verified that the concentrated liquid obtained by the method of Example 12 is a high-quality syrup with no excessive coloring, maintaining the flavor of the raw material solution to a certain extent and having a relatively good flavor balance.

[0133] Example 14 A flat film module was produced in the same manner as in Example 1, except that a porous flat film with an air permeability of 4800 L / h·m 2 ·kPa and a film thickness of 20 μm was folded into a pleated shape and stored in a cylindrical case. Using the flat film module, a concentration test was conducted under the same conditions as in Example 2, except that the temperature of the raw material solution at the raw material solution inlet of the membrane module was 55 °C. The time taken to concentrate to Brix 70 was 10.2 hours, and the total Flux for all concentration tests was 8.0 kg / m 2 ·h. The visible light transmittance of the obtained raw material solution concentrate with Brix 70 was 82%, the peak area of vanillin was 3.0 times that of acetophenone, and the weight ratio of sugar to Mg ions was 99% of the initial value. As a result of the sensory evaluation of the flavor, the original flavor of the raw material was B, and the flavor balance was A.

[0134] From the above results, it was verified that the concentrated liquid obtained by the method of Example 13 is a high-quality syrup with no excessive coloring, maintaining the flavor of the raw material solution to a certain extent and having a good flavor balance.

[0135] Comparative Example 1 Visible light transmittance measurement, aroma component analysis, and sensory evaluation were carried out on commercially available maple syrup (Grade A, golden / delicate taste). The visible light transmittance was 75%, and the peak area of vanillin was 5.0 times that of acetophenone. As a result of the sensory evaluation of the flavor, the original flavor of the raw material maple water was C, and the flavor balance was B.

[0136] From the above results, it was verified that the syrup of Comparative Example 1, although having a certain degree of good flavor balance, was overly colored, lacked the flavor of the raw material liquid, and was not a high-quality syrup.

[0137] 《Comparative Example 2》 Using maple water with an initial Brix of 2.0 as the raw material liquid, 50 g of the raw material liquid was placed in an eggplant flask and frozen with liquid nitrogen, and then connected to a freeze dryer (manufactured by Tokyo Rika Kikai Co., Ltd., FD-1000), and freeze-dried for 72 hours under a reduced pressure condition of -95 kPa. The Brix of the raw material liquid concentrate obtained by concentration was 70, and the visible light transmittance was 97%. Vanillin and acetophenone were not detected in the aroma components, and the weight ratio of sugar to Mg ions was 100% of the initial value. As a result of the sensory evaluation of the flavor, the original flavor of the raw material was C, and the flavor balance was C.

[0138] From the above results, it was verified that the concentrated liquid obtained by the method of Comparative Example 2, although not colored, lacked the flavor of the raw material liquid, had a low flavor balance, and was not a high-quality syrup.

[0139] 《Comparative Example 3》 Using a pipe wrapped with a ribbon heater as the heating section, the raw material liquid was heated at a surface temperature of 110 °C, and a concentration test was carried out under the same conditions as in Example 2 except that the temperature of the raw material liquid at the raw material liquid inlet of the membrane module was 90 °C. The time taken to concentrate the maple water to Brix 70 was 7.3 hours, and the total Flux of all concentration tests was 18.0 kg / m 2·h. The visible light transmittance of the raw material liquid concentrate was 73%, the peak area of vanillin was 8.3 times that of acetophenone, and the weight ratio of sugar to Mg ions was 106% of the initial value. As a result of the sensory evaluation of the flavor, the original flavor of the raw material was C, and the flavor balance was B.

[0140] From the above results, it was verified that the concentrated liquid obtained by the method of Comparative Example 3, although having a certain degree of good flavor balance, was excessively colored, had a poor flavor of the raw material liquid, and was not a high-quality syrup.

[0141] 《Comparative Example 4》 A concentration test was carried out under the same conditions as in Example 2 except that the temperature of the raw material liquid at the raw material liquid inlet of the membrane module was 80 °C and the pressure in the decompression section was -20 kPa. The time taken to concentrate the maple water to Brix 70 was 262 hours, and the total Flux for the entire concentration test was 0.5 kg / m 2 ·h. The visible light transmittance of the raw material liquid concentrate was 65%, the peak area of vanillin was 13.1 times that of acetophenone, and the weight ratio of sugar to Mg ions was 94% of the initial value. As a result of the sensory evaluation of the flavor, the original flavor of the raw material was C, and the flavor balance was C.

[0142] From the above results, it was verified that the concentrated liquid obtained by the method of Comparative Example 4 was excessively colored, had a poor flavor of the raw material liquid, had a low flavor balance, and was not a high-quality syrup. The operating conditions, operating results in the concentration test, and the evaluation results of the obtained concentrated liquid are shown in Table 1.

[0143]

Table 1

Explanation of Symbols

[0144] 1 Hollow fiber membrane 2 Module case 10 Membrane module 11 Porous membrane 17 Rod-shaped body 18 Liquid-phase spacer 19 Gas-phase spacer 21 Membrane fixing part 22 Raw material liquid flow-through opening 23 Steam outlet 100, 200 Raw material liquid concentration system 101 Raw material liquid tank 102 Circulation pump 103 Heating part 104 Membrane distillation part 105 Steam condensation part 106 Condensate tank 107 Extraction pump 108 Vacuum device 109 Reserve tank 110 Liquid delivery pump 111 Pretreatment part A Water to be treated A’ Treated water after distillation B Steam separated from the water to be treated B * Steam separated from the water to be treated and diffusing into the gas phase part through the porous membrane

Claims

1. A raw material liquid concentration system for manufacturing food products, wherein the food product is a concentrated liquid of a raw material liquid derived from natural products containing a solute containing sugar and a liquid medium, the concentrated liquid has a Brix value of 50 or more, the visible light transmittance of the concentrated liquid at a wavelength of 560 nm by ultraviolet-visible spectrophotometer measurement is 80% or more and 99% or less, the aroma components collected from the concentrated liquid in a 50°C atmosphere contain vanillin, the raw material liquid concentration system has a heating unit for heating the raw material liquid to 30°C or more and 80°C or less, and a vacuum distillation unit for distilling and concentrating the raw material liquid by reducing the pressure of the gas phase in contact with the raw material liquid to -80 kPa or less, and the vacuum distillation unit is a membrane distillation unit having a porous membrane, the raw material liquid concentration system.

2. The raw material liquid concentration system according to claim 1, wherein the visible light transmittance of the concentrated liquid at a wavelength of 560 nm by ultraviolet-visible spectrophotometer measurement is 85% or more and 99% or less.

3. The aroma components collected from the concentrated liquid in a 50°C atmosphere contain vanillin and acetophenone, and the peak area of vanillin when the aroma components are analyzed by gas chromatography is 1.5 times or more and 10 times or less that of acetophenone, the raw material liquid concentration system according to claim 1 or 2.

4. The raw material liquid concentration system according to any one of claims 1 to 3, wherein the change rate of the value of the sugar concentration / magnesium ion concentration of the concentrated liquid compared to the value of the sugar concentration / magnesium ion concentration of the raw material liquid is 5% or less.

5. The raw material liquid concentration system according to any one of claims 1 to 4, wherein the raw material liquid is at least one selected from the group consisting of sapium sebiferum sap, birch sap, and coconut liquid endosperm.

6. The raw material liquid concentration system has a raw material liquid tank for storing the raw material liquid, the heating unit, the membrane distillation unit having a porous membrane, and a circulation pump for circulating the raw material liquid from the raw material liquid tank through the heating unit and the membrane distillation unit in this order and returning it to the raw material liquid tank, the membrane distillation unit is divided by the porous membrane into a liquid phase part through which the raw material liquid flows and a gas phase part through which the vapor generated from the raw material liquid passes through the porous membrane and diffuses, at the raw material liquid inflow site of the membrane distillation unit, the raw material liquid temperature is 30°C or more and 80°C or less, and the pressure of the gas phase part in the membrane distillation unit is reduced to -80 kPa or less and is configured as such. The raw material liquid concentration system according to any one of claims 1 to 5.

7. The raw material liquid concentration system according to any one of claims 1 to 6, wherein the porous membrane is a hollow fiber membrane.

8. The raw material liquid concentration system according to any one of claims 1 to 7, wherein the porous membrane is composed of at least one resin selected from the group consisting of polysulfone, polyethersulfone, polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, and polychlorotrifluoroethylene.

9. A method for manufacturing a food product using the raw material liquid concentration system according to any one of claims 1 to 8, wherein the food product is a concentrated liquid of a raw material liquid derived from a natural product containing a solute containing sugar and a liquid medium, the concentrated liquid has a Brix value of 50 or more, the visible light transmittance of the concentrated liquid at a wavelength of 560 nm as measured by ultraviolet-visible spectrophotometry is 80% or more and 99% or less, the aroma components collected from the concentrated liquid in an atmosphere of 50 ° C contain vanillin, the method is a heating step of heating the raw material liquid to 30 ° C or more and 80 ° C or less in the heating section, a concentration step of circulating the heated raw material liquid through the vacuum distillation section and concentrating it by vacuum distillation at -80 kPa or less, including.

10. The method according to claim 9, wherein the contact portion of the heating section with the raw material liquid is 90 ° C or less.

11. The method according to claim 9 or 10, wherein the heating section is a heat exchanger that circulates a heat medium that is steam at 50 ° C or more or warm water at 50 ° C or more.

12. The method according to any one of claims 9 to 11, wherein the heating section utilizes waste heat.

13. The method according to any one of claims 9 to 12, further comprising an additional concentration step of circulating the concentrated raw material liquid through an evaporator after the concentration step, and the temperature of the raw material liquid in the additional concentration step is equal to or higher than the temperature of the raw material liquid in the concentration step.

14. The method according to any one of claims 9 to 13, further comprising a preliminary concentration step of preliminarily concentrating the raw material liquid with a reverse osmosis membrane.

15. The method according to any one of claims 9 to 14, further comprising a filtration step of filtering the raw material liquid with a filtration membrane to remove impurities, and supplying the filtered raw material liquid to the concentration step.

16. The method according to claim 15, wherein the pore size of the filtration membrane is 20 μm or less.

17. The method according to claim 16, wherein the pore size of the filtration membrane is 1.0 μm or less.

18. The method according to any one of claims 15 to 17, wherein the filtration membrane is arranged in a cross-flow configuration.

19. The method according to any one of claims 15 to 18, further comprising a backwashing step of backwashing the filtration membrane.

20. The method according to any one of claims 15 to 19, wherein the concentration step and the filtration step are performed in raw material liquid flow paths independent of each other.

21. The vacuum distillation section is a membrane distillation section having a porous membrane, and a step of removing the raw material liquid adhering to the porous membrane by passing water through the porous membrane is performed once or more per day. The method according to any one of claims 9 to 20.

22. The method according to claim 21, wherein a step of removing membrane contaminants adhering to the porous membrane by passing a chemical solution having a pH of 5 or less or a pH of 9 or more through the porous membrane is performed once or more per week.

23. The method according to any one of claims 9 to 22, wherein the visible light transmittance of the concentrated liquid at a wavelength of 560 nm by ultraviolet-visible spectrophotometer measurement is 85% or more and 99% or less.

24. The aroma components collected from the concentrated liquid in an atmosphere of 50 ° C. include vanillin and acetophenone, The method according to any one of claims 9 to 23, wherein the peak area of vanillin when the aroma components are analyzed by gas chromatography is 1.5 times or more and 10 times or less that of acetophenone.

25. The method according to any one of claims 9 to 24, wherein the change rate of the value of the sugar concentration / magnesium ion concentration of the concentrated liquid compared to the value of the sugar concentration / magnesium ion concentration of the raw material liquid is 5% or less.

26. The method according to any one of claims 9 to 25, wherein the raw material liquid is at least one selected from the group consisting of maple sap, birch sap, and coconut liquid endosperm.

Images