Semi-fermented zero-sucrose monk fruit concentrated juice and preparation method thereof

Abstract

The present invention relates to a semi-fermented zero-sucrose monk fruit concentrated juice, comprising the following ingredients: glucose, fructose, erythritol, mogroside V, water, and the mass ratio of glucose, fructose, and erythritol is 1-10:2-5:1, and the sugar content of the semi-fermented zero-sucrose monk fruit concentrated juice is 50-80 brix; the preparation process of the semi-fermented zero-sucrose monk fruit concentrated juice includes enzymolysis and fermentation, and the fermentation end point is to control the mass ratio of glucose and erythritol to be 1-10:1. After the invertase is modified by trehalose, the present invention allows the enzymolysis to be fully carried out under the synergistic action of the auxiliary reagent citric acid, thereby finally obtaining the zero-sucrose monk fruit concentrated juice. In addition, the present invention controls the degree of fermentation, and when the glucose and erythritol in the system reach a certain ratio, the fermentation is stopped by inactivation, and the GI value of the concentrated juice is further reduced, so as to obtain the semi-fermented zero-sucrose monk fruit concentrated juice containing erythritol.

Description

Technical Field

[0001] The invention relates to a fresh fruit concentrated juice and a production method thereof, and in particular to a semi-fermented zero-sucrose monk fruit concentrated juice and a preparation method thereof. Background Art

[0002] Monk fruit contains mogroside, which is a natural sweetener that is 400 times sweeter than sucrose. However, it does not produce calories, is purely natural, and has a good taste. Therefore, it is an ideal natural and healthy sugar substitute sweetener for people with diabetes, obesity, and other conditions who are not suitable for eating sucrose. Mogroside is a natural high-intensity sweetener that is widely used as an additive in various foods, beverages, and health products. Compared with chemically synthesized high-intensity sweeteners such as aspartame, mogroside comes entirely from monk fruit, is more environmentally friendly and safe, conforms to people's current consumption habits, and is welcomed by the market. Various types of mogroside products currently sold on the market, such as V50 (the content of mogroside is about 50%), V25 (the content of mogroside is about 25%), and V10 (the content of mogroside is about 10%), use a macroporous adsorption resin separation process in the preparation process of the above-mentioned mogroside to separate and remove sugars such as sucrose, so the sucrose content is relatively low. However, the separation process of macroporous adsorption resin will also remove fructose and / or glucose. If you want to retain a higher content of fructose and / or glucose, the sucrose content will also be relatively high. However, if you want to retain fructose, glucose and other sugars in the monk fruit concentrated juice products on the market, you cannot use macroporous resins. Therefore, the monk fruit concentrated juice products currently containing fructose and glucose will have a relatively high content of sucrose.

[0003] If you want to achieve zero sucrose or low sucrose content, then the corresponding fructose and glucose content will also be reduced; on the other hand, even if various complex processes are used, it is still difficult to achieve true zero sucrose. At present, there is a strong demand for "zero sucrose" sweeteners in the market. On the one hand, it comes from the improvement of people's living standards and the pursuit of natural health; on the other hand, it is also a rigid demand for upstream products. Reducing sugar or even going sugar-free has become a trend in the global food industry. Countries have begun to increase sugar taxes on beverages, especially monk fruit extract exports are mainly to European and American countries. At present, these countries have increasingly strict standards for monk fruit extract, among which low sugar and sugar-free are important criteria for evaluating product quality.

[0004] CN107969532A discloses a monk fruit instant drink, which uses monk fruit as a raw material, and obtains a monk fruit instant drink with a total plant protein content of 15-35% through the steps of crushing, hot water extraction, ultrafiltration, nanofiltration, concentration, etc. The product obtained by this method has a high content of plant protein, so the astringency brought by the plant protein has a great influence on the taste. In addition, if too high a content of protein exists in the drink, precipitation will inevitably occur over a long period of time, which is not conducive to consumption.

[0005] CN112617147A discloses a concentrated monk fruit juice and a preparation method thereof, comprising the following steps: S1) crushing: crushing the monk fruit to obtain the crushed monk fruit; the monk fruit includes fresh monk fruit and dried monk fruit; S2) extraction: extracting the crushed monk fruit with water to obtain an extract; S3) enzymolysis: adding an enzyme preparation to the extract for enzymolysis to obtain an enzymolysis solution; S4) fermentation: adding a fermentation agent to the enzymolysis solution for fermentation to obtain a fermentation solution; S5) membrane separation: separating the fermentation solution by membrane to obtain a permeate; S6) concentration: concentrating the permeate to obtain a concentrated solution; S7) browning: subjecting the concentrated solution to ascorbic acid browning, Maillard browning and caramelization browning in sequence to obtain a concentrated monk fruit juice. The components such as glucose, fructose, lactose, maltose, sucrose and starch in the patented product account for ≤0.3% of the total solid content by mass, meeting the requirements of "low sugar" and "low calories". However, the fermentation process consumes too much sugar and the product is too dark in color, limiting its application range.

[0006] The inventor's previous patent CN202311298595.9 discloses a zero-sucrose monk fruit juice concentrate and a production method thereof. The present invention removes macromolecular impurities such as pectin and protein from the monk fruit extract, thereby creating a more favorable environmental condition for the enzymatic hydrolysis of sucrase. After the sucrase is modified with trehalose, under the synergistic effect of the auxiliary reagent citric acid, the enzymatic hydrolysis reaction can be fully carried out in the positive direction, achieving a thorough enzymatic hydrolysis of sucrose, thereby finally obtaining a zero-sucrose monk fruit juice concentrate. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a semi-fermented zero-sucrose monk fruit juice concentrate containing erythritol. Furthermore, the technical problem to be solved by the present invention is to provide a method for preparing monk fruit juice concentrate, wherein the monk fruit juice concentrate obtained by the method contains erythritol but does not contain sucrose, and the content ratio of glucose can be adjusted by process control, which not only improves the taste, but also reduces the overall calories and GI value of the concentrated juice product, thereby achieving "sugar reduction" from multiple aspects.

[0008] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0009] A semi-fermented zero-sucrose monk fruit concentrated juice comprises the following ingredients: glucose, fructose, erythritol, mogroside V, and water, wherein the mass ratio of glucose, fructose, and erythritol is 1-10:2-5:1, and the sugar content of the semi-fermented zero-sucrose monk fruit concentrated juice is 50-80 brix; the preparation process of the semi-fermented zero-sucrose monk fruit concentrated juice comprises enzymolysis and fermentation, and the fermentation endpoint is to control the mass ratio of glucose to erythritol to be 1-10:1.

[0010] Preferably, the mass ratio of glucose, fructose and erythritol in the semi-fermented zero-sucrose monk fruit concentrated juice is 1.7-2.25:3.8-4.2:1, and the sugar content of the semi-fermented zero-sucrose monk fruit concentrated juice is 60-75 brix, preferably 65-70 brix.

[0011] Preferably, the semi-fermented zero sucrose monk fruit concentrated juice may also include mogroside, which may be contained in the raw material, or added after the concentrated juice is prepared, or both. The proportion of mogroside can be flexibly adjusted according to demand. For example, in a specific embodiment of the present invention, the mass ratio of glucose, fructose, erythritol, and mogroside in the semi-fermented zero sucrose monk fruit concentrated juice is 1.7-2.25:3.8-4.2:1:0.1-10; preferably 1.7-2.25:3.8-4.2:1:0.5-2. Furthermore, the mogroside is selected from at least one of mogroside V, mogroside III, mogroside IV, 11-oxy-mogroside V, mogroside VI, and simonoside.

[0012] There is no particular limitation on the water content in the semi-fermented zero-sucrose monk fruit concentrated juice, as long as the sugar content of the final concentrated juice is within the above range.

[0013] Those skilled in the art should understand that sucrose may still exist in the semi-fermented zero-sucrose monk fruit concentrated juice of the present invention, but its content is very low and may be lower than the detection limit of the instrument. Therefore, the zero sucrose of the present invention means that it cannot be detected for an instrument with a detection limit of 0.001wt%, that is, in the present invention, the meaning of "zero" sucrose is that the sucrose content is ≤0.001wt%. The test result is 0.

[0014] Those skilled in the art should also understand that the semi-fermented zero-sucrose monk fruit concentrated juice of the present invention may contain trace amounts of components carried by the monk fruit itself (such as maltose, mannitol, etc.) and trace amounts of by-products produced during the fermentation process (such as arabitol, mannitol, ribitol, etc.), in addition to the above-mentioned main ingredients, namely glucose, fructose, erythritol, and mogroside V.

[0015] The present invention also provides a method for preparing the semi-fermented zero-sucrose monk fruit concentrated juice, comprising the following steps:

[0016] (1) Preparation of raw material liquid: Take the liquid material from the production and processing step of monk fruit extract;

[0017] (2) Sterilization and enzyme inactivation: Sterilize the liquid material using a continuous sterilization device and collect the sterilization liquid;

[0018] (3) Centrifugation: The sterilized liquid is continuously passed through a horizontal screw centrifuge and a disc centrifuge to obtain a centrifugal filtrate;

[0019] (4) Ceramic membrane filtration: Filter the centrifugal filtrate through a ceramic membrane to obtain a ceramic membrane filtrate;

[0020] (5) Enzymatic hydrolysis: adding trehalose-modified sucrase and auxiliary enzymatic hydrolysis reagent to the ceramic membrane filtrate for enzymatic hydrolysis to obtain enzymatic hydrolyzate;

[0021] (6) Fermentation: the enzymatic hydrolysate is placed in a fermentation tank, sterilized at high temperature to kill the enzyme, and then fermentation bacteria and fermentation auxiliary materials are added to carry out fermentation; during the fermentation process, the ratio of glucose to erythritol is monitored by detecting the ratio of glucose to erythritol. When the mass ratio of glucose to erythritol is within the range of 1-10:1, the fermentation liquid is inactivated, and the fermentation is terminated to obtain an inactivated fermentation liquid;

[0022] (7) Ceramic membrane filtration again: Filter the inactivated fermentation liquid through a ceramic membrane to obtain a fermentation filtrate;

[0023] (8) Desalting, decolorizing and removing impurities: The fermentation filtrate is passed through a cation exchange resin column and anion exchange resin column and a mixed bed to obtain a desalting, decolorizing and impurity-removing liquid;

[0024] (9) Membrane concentration: The desalted, decolorized and impurity-removed liquid is concentrated using a reverse osmosis membrane to obtain a membrane concentrate;

[0025] (10) Ultrafiltration: Filter the membrane concentrate using an ultrafiltration membrane to obtain an ultrafiltration filtrate;

[0026] (11) Concentration: The ultrafiltration filtrate is concentrated under reduced pressure using a falling film concentrator to a specified sugar content to obtain semi-fermented zero-sucrose monk fruit concentrated juice.

[0027] Optionally, the method for preparing the semi-fermented zero-sucrose monk fruit juice concentrate of the present invention may further include step (12): blending: adding a component containing mogroside to the semi-fermented zero-sucrose monk fruit juice concentrate obtained in step (11) to increase the content of glycoside V in the semi-fermented zero-sucrose monk fruit juice concentrate to obtain the blended semi-fermented zero-sucrose monk fruit juice concentrate. Preferably, the component containing mogroside is selected from mogroside dry powder (such as V50, V25, V10), or it may be a concentrated juice containing mogroside. Preferably, the added component containing mogroside has a sucrose content of ≤0.001wt%.

[0028] Preferably, in step (1), the liquid material is selected from various materials containing sugar components produced during the extraction and processing of monk fruit, for example, the liquid material is selected from at least one of extraction concentrate, horizontal screw centrifugal filtrate, disc centrifugal filtrate, tubular centrifugal filtrate, plate and frame filtration filtrate, ceramic membrane filtrate, ultrafiltration membrane filtrate, nanofiltration membrane filtrate, macroporous resin column effluent, anion and cation resin decolorization liquid; further, the content of mogroside V in the liquid material is 0-10 wt%.

[0029] Preferably, in step (2), the sterilization is continuous sterilization, the highest temperature during the sterilization process is 100-150°C, and the sterilization time is 10-120 seconds. One of the purposes of using continuous sterilization equipment is to kill microorganisms in the fresh fruit extract to prevent the growth of microorganisms from affecting the yield of mogrosides, and to prevent the presence of microorganisms from affecting the catalytic activity of sucrose; the second purpose of using continuous sterilization equipment is to denature various monk fruit enzymes in the extract at high temperature to precipitate them, and to prevent the monk fruit enzymes from affecting the solubility and taste of the monk fruit concentrated juice product. If the sterilization temperature is too low or the sterilization time is too short, the above two purposes cannot be fully achieved; if the sterilization temperature is too high or the sterilization time is too long, it will not only cause a waste of energy, but also lead to adverse consequences such as degradation of monk fruit glycosides, darkening of product color, and the appearance of burnt smell.

[0030] In step (3), the centrifugation can be carried out by a horizontal screw centrifuge and a disc centrifuge, and there is no special requirement for the power and speed of the horizontal screw centrifuge and the disc centrifuge. The purpose of continuously passing the sterilizing liquid through the horizontal screw centrifuge and the disc centrifuge is to remove a large amount of fine peel and pomace debris, monk fruit crude fiber, monk fruit pectin, and protein (monk fruit enzyme) precipitated due to high temperature denaturation contained in the sterilizing liquid. The presence of these components will affect the catalytic activity of sucrase.

[0031] Preferably, in step (4), the pore size of the ceramic membrane is 1-10 μm, and the filtration pressure is 0.1-0.5 MPa. The purpose of using the ceramic membrane is to further remove a small amount of fine denatured protein and pectin that cannot be completely removed in the centrifugation step of step (3), so as to make the material clear and transparent, thereby eliminating the adverse effects of the above impurities on the enzymatic hydrolysis of sucrase.

[0032] Preferably, in step (5), the amount of the trehalose-modified sucrase is 0.05-0.1 wt% of the total sugar weight in the ceramic membrane filtrate (ceramic membrane filtrate weight × sugar content brix%), the enzymatic hydrolysis temperature is 20-60°C, the enzymatic hydrolysis pH is 3.0-8.0, and the enzymatic hydrolysis time is 1-10 hours. The purpose of using sucrase is to completely enzymatically hydrolyze the sucrose in the material into glucose and sucrose. If the amount of sucrase added is too little, the enzymatic hydrolysis temperature is too low, the enzymatic hydrolysis pH is too low, or the enzymatic hydrolysis time is too short, the enzymatic hydrolysis will not be complete; if the amount of sucrase added is too much, the enzymatic hydrolysis temperature is too high, the enzymatic hydrolysis pH is too high, or the enzymatic hydrolysis time is too long, it will not only cause a waste of materials and energy, but also may reduce the activity of the enzyme, which will also lead to incomplete enzymatic hydrolysis. The sucrase is not particularly limited, and conventional sucrase in the art can be used. Its temperature range is 20-80°C, and the pH applicable range is 3-8.

[0033] Preferably, in step (5), the trehalose-modified sucrase is obtained by a preparation method comprising the following steps:

[0034] (S1) Sucrase is dissolved in a buffer solution with a pH of 6-7, sodium periodate is added, the resulting mixture is placed at 10-15° C. in the dark for 2-4 hours, ethylene glycol is added, and buffer dialyzed at a pH of 6-7 to obtain activated sucrase;

[0035] (S2) adding a protective substrate to the activated sucrase, adding trehalose, reacting at 30-40° C. for 10-15 hours, performing buffer dialysis under a pH value of 6-7, and freeze-drying to obtain trehalose-modified sucrase.

[0036] Furthermore, in steps (S1) and (S2), the buffer solution of the buffer dialysis is a citric acid-sodium citrate buffer solution; the protective substrate is sucrose; the buffer dialysis time is 20-30 hours; and the material ratio meets the following conditions: the mass ratio of sucrase, sodium periodate, ethylene glycol, protective substrate, and trehalose is 10:10-20:2-3:50-100:7-10.

[0037] The purpose of using trehalose to modify sucrase is to fully activate and enhance the enzymatic hydrolysis ability of sucrase, so that sucrase can continuously, efficiently and thoroughly hydrolyze sucrose to achieve 0 sucrose. The inventors have also tried to modify sucrase with modification reagents such as chitosan and dextran, but the effect is obviously not as good as trehalose.

[0038] Preferably, in step (5), the auxiliary reagent is citric acid. The amount of citric acid used is 0.4-0.7 times the mass of the trehalose-modified sucrase. One of the purposes of adding citric acid is to adjust the pH value of the material to meet the optimal pH value for the sucrase to exert its enzymatic hydrolysis effect; the second purpose of adding citric acid is that the inventors found that citric acid can increase the activity of sucrase under this specific environment, so that sucrose is completely enzymatically hydrolyzed to achieve the purpose of "zero sucrose". If the amount of citric acid added is too little, the above purpose cannot be fully achieved; if the amount of citric acid added is too much, it will not only cause waste of materials, but also cause the pH value of the material to be too low, which is not conducive to the enzymatic hydrolysis of sucrose.

[0039] Preferably, in step (6), when the mass ratio of glucose:erythritol is in the range of 1.7-2.25:1, the fermentation broth is inactivated.

[0040] Preferably, in step (7), the pore size of the ceramic membrane is 1-10 μm, and the filtration pressure is 0.1-0.5 MPa. The purpose of using the ceramic membrane again is to filter out impurities such as suspended matter and insoluble matter in the inactivated fermentation broth, so as to clarify the material and facilitate subsequent desalination, decolorization and impurity removal.

[0041] Preferably, in step (8), the type of the cation exchange resin is a gel-type styrene-based cation exchange resin or a macroporous styrene-based cation exchange resin, and specific models include but are not limited to: 001×7, 001×8, 001×16, and D001. The volumetric dosage of the cation exchange resin and the weight of the fresh monk fruit are in a ratio of 0.3–1L:1kg. The height-to-diameter ratio of the cation exchange resin column is 0.5:1-10:1. The flow rate of the fermentation filtrate through the cation exchange resin column is 0.5–10 BV / h. The purpose of using the cation exchange resin is to remove impurities such as salt and protein that exist in the material itself or are generated in the sucrose enzymatic hydrolysis and fermentation steps. If the amount of the cation exchange resin is too small, the height-to-diameter ratio is too small, or the flow rate of the material through the cation exchange resin column is too fast, the desalination and impurity removal will be incomplete; if the amount of the cation exchange resin is too large, the height-to-diameter ratio is too large, or the flow rate of the material through the cation exchange resin column is too slow, it will cause a waste of material and energy.

[0042] Preferably, in step (8), the type of the anion exchange resin is a macroporous styrene anion exchange resin or a macroporous acrylic anion exchange resin, and specific models include but are not limited to: D941, D945, LX-T5, LXD-762, LX-94. The volume dosage of the anion exchange resin is 0.3-1L:1kg based on the weight of the fresh monk fruit. The height-to-diameter ratio of the anion exchange resin column is 0.5:1-10:1. The flow rate of the fermentation filtrate through the anion exchange resin column is 0.5-10 BV / h. The purpose of using anion exchange resin is to remove impurities such as pigments that exist in the material itself or are produced in the sucrose enzymatic hydrolysis and fermentation steps. If the amount of anion exchange resin used is too little, the aspect ratio is too small, or the flow rate of the material through the anion exchange resin column is too fast, the decolorization will not be complete; if the amount of anion exchange resin used is too much, the aspect ratio is too large, or the flow rate of the material through the anion exchange resin column is too slow, it will cause waste of materials and energy.

[0043] Preferably, in step (8), the mixed bed is a mixed column bed of cation exchange resin and anion exchange resin, wherein the ratio of cation exchange resin to anion exchange resin is 1:1-10:1 (V / V). The ratio of the total volume of ion exchange resin in the mixed bed to the weight of fresh monk fruit is 0.3-1L:1kg. The height-to-diameter ratio of the mixed bed is 0.5:1-10:1. The flow rate of the material through the mixed bed is 0.5-10 BV / h. One of the purposes of using a mixed bed is to make the desalination, decolorization and impurity removal of the material more thorough; the second purpose is to adjust the pH value of the material to ensure that the final pH value of the material in this step is weakly acidic to meet the product quality requirements. If the total amount of ion exchange resin in the mixed bed is too little, the aspect ratio is too small, or the flow rate of the material through the mixed bed is too fast, the above purpose cannot be achieved; if the total amount of ion exchange resin in the mixed bed is too much, the aspect ratio is too large, or the flow rate of the material through the mixed bed is too slow, it will not only cause waste of materials and energy, but also cause abnormal pH value of the material.

[0044] Preferably, in step (9), the molecular weight cutoff of the reverse osmosis membrane is 50-200DA, the pressure of membrane concentration is 1-15Mpa, and the degree of membrane concentration is that the sugar content of the membrane concentrate is 10-25brix. One purpose of using reverse osmosis membrane concentration is to save steam; the second purpose is to increase the concentration of the material by low temperature, which can prevent the color of the concentrate from darkening and abnormal taste and odor caused by long-term high temperature.

[0045] Preferably, in step (10), the pore size of the ultrafiltration membrane is 10-100 nanometers, and the filtration pressure is 0.1-0.5 MPa. The purpose of ultrafiltration is to improve the clarity of the material.

[0046] Preferably, in step (11), the falling film concentrator includes but is not limited to a triple-effect falling film concentrator, a quadruple-effect falling film concentrator and a quintuple-effect falling film concentrator, and the sugar content of the semi-fermented zero-sucrose monk fruit concentrated juice is 50-80 brix.

[0047] Preferably, in step (12), the content of mogroside V (on a dry basis) in the high-content monk fruit extract dry powder (or concentrated liquid) is 3%-85%; the added amount is 0.5%-200% by weight of the semi-fermented zero-sucrose monk fruit concentrated juice; after blending, the content of mogroside V in the concentrated juice is 0.5-20%.

[0048] The principle of the method of the present invention is as follows:

[0049] The main sugars in monk fruit are fructose and glucose, and it contains a small amount of sucrose. After removing macromolecular impurities such as pectin and protein from the monk fruit extract, a relatively favorable environmental condition is created for the enzymatic hydrolysis of sucrase. Sucrase can hydrolyze sucrose into fructose and glucose. However, the monk fruit extract itself contains a large amount of fructose and glucose, and the products of sucrase hydrolysis are also fructose and glucose. When the concentration of the products (fructose and glucose) of the sucrase hydrolysis reaction is higher, the more difficult or slower the enzymatic reaction proceeds in the positive direction, so it is difficult to completely hydrolyze sucrose in the industry. The inventors found that after the sucrase is modified with trehalose, under the synergistic effect of the auxiliary reagent citric acid, the enzymatic reaction can be fully carried out in the positive direction, achieving complete enzymatic hydrolysis of sucrose, thereby finally obtaining zero-sucrose monk fruit concentrated juice. Citric acid can improve the activity of sucrase under this specific environment. One of the reasons may be that citric acid complexes with certain metal ions (derived from monk fruit itself) in the material that have an inhibitory effect on sucrase, eliminating their negative effects on sucrase.

[0050] In addition, by utilizing the glucose contained in monk fruit itself and the glucose produced by the hydrolysis of sucrose, a portion of the glucose is converted into erythritol under the action of erythritol-producing bacteria, thereby obtaining semi-fermented zero-sucrose monk fruit concentrated juice containing erythritol.

[0051] The beneficial effects of the method of the present invention are as follows:

[0052] (1) In the semi-fermented zero-sucrose monk fruit concentrated juice obtained by the method of the present invention, the mass content of sucrose is 0, and the sucrose is completely enzymatically hydrolyzed, truly achieving "zero sucrose".

[0053] (2) Compared with the traditional monk fruit concentrated juice, in addition to "zero sucrose", the semi-fermented zero sucrose monk fruit concentrated juice obtained by the method of the present invention has another important advantage - part of the glucose is converted into erythritol (which basically does not cause blood sugar to rise), which not only improves the taste, but also reduces the overall calories and glycemic index (GI) value of the concentrated juice product, achieving "sugar reduction" from multiple aspects;

[0054] (3) The semi-fermented zero-sucrose monk fruit concentrated juice obtained by the method of the present invention is a light yellow, transparent, thick liquid with a fresh aroma, a sweet, refreshing, saturated taste, and no peculiar smell. In addition, the method of the present invention also provides a blended semi-fermented zero-sucrose monk fruit concentrated juice, which can achieve different sweetness multiples by adjusting the content of glycoside V to meet the needs of different customers.

[0055] (4) The process of the method of the present invention is highly operable, safe, environmentally friendly, pollution-free, and suitable for industrial production.

[0056] The semi-fermented zero-sucrose monk fruit concentrated juice produced according to the method of the present invention can be applied to food, medicine, dairy products, health products and the like. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 This is a liquid chromatogram of the semi-fermented zero-sucrose monk fruit concentrated juice obtained in Example 1.

[0058] Figure 2 This is a liquid chromatogram of the semi-fermented zero-sucrose monk fruit concentrated juice obtained in Example 2.

[0059] Figure 3 This is the liquid chromatogram of the zero-sucrose monk fruit concentrated juice obtained in Comparative Example 1.

[0060] Figure 4 This is the liquid chromatogram of the monk fruit concentrated juice obtained in Comparative Example 2. DETAILED DESCRIPTION

[0061] The present invention will be further described below in conjunction with the embodiments.

[0062] The fresh Momordica fruit used in the embodiment of the present invention was purchased from Longsheng, Guangxi, wherein the mass content of sucrose was 1.10%, and the mass content of mogroside V was 0.47%; the Momordica fruit macroporous resin upper column effluent used in the embodiment of the present invention is the extract after the fresh Momordica fruit is extracted with water, and the upper column effluent after passing through the macroporous adsorption resin is purchased from Hunan Huacheng Biological Resources Co., Ltd.; the edible sucrase used in the embodiment of the present invention was purchased from Cangzhou Xiasheng Enzyme Biotechnology Co., Ltd., with the brand GDG-2028; the 001×7, 001×16 type cation exchange resins, LXD-762, LX-94 type anion exchange resins used in the embodiment of the present invention were all purchased from Xi'an Lanxiao Technology New Materials Co., Ltd.; the ceramic membrane, reverse osmosis membrane and ultrafiltration membrane used in the embodiment of the present invention were all purchased from Nanjing Fulinde Environmental Protection Technology Co., Ltd.; the raw materials or chemical reagents used in the embodiment of the present invention, unless otherwise specified, were obtained through conventional commercial channels.

[0063] The embodiment of the present invention adopts the high performance liquid chromatography evaporative light scattering detection method to detect the contents of sucrose, fructose, glucose and erythritol, and adopts the high performance liquid chromatography external standard method to detect the content of mogroside V.

[0064] Preparation Example 1

[0065] The preparation method of trehalose-modified sucrase can refer to the previous patent CN202311298595.9.

[0066] (S1) 100 parts by weight of sucrase are dissolved in a citric acid-sodium citrate buffer solution at pH=6, 100 parts by weight of sodium periodate are added, the resulting mixture is placed at 10°C in the dark for 2 hours, 25 parts by weight of ethylene glycol is added, and then dialyzed with a citric acid-sodium citrate buffer solution at pH=6 for 24 hours to obtain activated sucrase;

[0067] (S2) adding 800 parts by mass of sucrose and 100 parts by mass of trehalose to the material obtained in step (S1), reacting at 40° C. for 10 h, then dialyzing with a citric acid-sodium citrate buffer solution of pH=6 for 24 h, and freeze-drying to obtain trehalose-modified sucrase.

[0068] Preparation Example 2

[0069] Strain culture: Take the newly cultured yeast strain Torula sp and inoculate it into 10 ml slant medium (ratio: 20 g glucose, 3 g beef extract, 5 g yeast extract, 30 g peptone, 20 g agar, 1000 ml distilled water), and culture at 30℃ for 2 days.

[0070] Shake flask seed culture: inoculate the cultured bacteria into a 100 ml shake flask containing 30 ml seed culture medium (ratio: 20 g glucose, 3 g beef extract, 5 g yeast extract, 30 g peptone, 1000 ml distilled water), and culture at 30°C and 160 rpm for 2 days.

[0071] The secondary seeds are used for expanded culture to obtain fermentation seed liquid.

[0072] Example 1

[0073] (1) Preparation of raw material liquid: Select 1000 kg of mature, non-rotten fresh monk fruit, clean it, crush it, and use 90°C hot water for countercurrent extraction. The total amount of hot water used is about 4 tons. Collect the extract for later use.

[0074] (2) Sterilization and enzyme inactivation: Sterilize the extract using a continuous sterilization device at a maximum temperature of 110°C for 30 seconds. Collect the sterilized liquid for later use.

[0075] (3) Centrifugation: The sterilized liquid is continuously passed through a horizontal screw centrifuge and a disc centrifuge to obtain a centrifugal filtrate.

[0076] (4) Ceramic membrane filtration: The centrifugal filtrate is filtered through a ceramic membrane (the pore size of the ceramic membrane is 1 micron and the filtration pressure is 0.3 MPa) to obtain about 4460 kg of ceramic membrane filtrate (sugar content 1.9 brix).

[0077] (5) Enzymatic hydrolysis: 0.05 kg of trehalose-modified sucrase prepared in Preparation Example 1 and 0.035 kg of citric acid were added to the ceramic membrane filtrate, and the enzymatic hydrolysis was carried out for 10 hours at a temperature of 25°C and a pH value of 6.0. After the enzymatic hydrolysis was completed, the enzyme was inactivated to obtain an enzymatic hydrolyzate.

[0078] (6) Fermentation: The enzymatic hydrolysate was placed in a fermentation tank, sterilized at high temperature to inactivate the enzyme, and then the fermentation seed solution (inoculation amount of 1%) and fermentation auxiliary materials (0.1% yeast extract, 0.1% KH2PO4) obtained in Preparation Example 2 were added, and fermentation was carried out at a temperature of 32°C and pH = 5. After 48 hours, the ratio of glucose to erythritol was detected to be about 2.25:1, and the fermentation was terminated, and the fermentation liquid was inactivated to obtain an inactivated fermentation liquid.

[0079] (7) Ceramic membrane filtration again: The inactivated fermentation liquid is filtered through a ceramic membrane (the pore size of the ceramic membrane is 1 micron and the filtration pressure is 0.3 MPa) to obtain the fermentation filtrate.

[0080] (8) Desalting, decolorizing and impurity removal: The fermentation filtrate is first passed through a cation exchange resin column (the cation exchange resin model is 001×16; the amount of cation exchange resin is 400 L; the height-to-diameter ratio of the cation exchange resin column is 8:1; the flow rate of the material passing through the cation exchange resin column is 1 BV / h), then through an anion exchange resin column (the anion exchange resin model is LX-94; the amount of anion exchange resin is 400 L; the height-to-diameter ratio of the anion exchange resin column is 8:1; the flow rate of the material passing through the anion exchange resin column is 1 BV / h), and finally through a mixed bed (the volume ratio of cation exchange resin 001×16 and anion exchange resin LX-94 is 1:1; the total amount of ion exchange resin in the mixed bed is 400 L; the height-to-diameter ratio of the mixed bed is 8:1; the flow rate of the material passing through the mixed bed is 1 BV / h) to obtain a desalting, decolorizing and impurity removal liquid.

[0081] (9) Membrane concentration: The desalted, decolorized and impurity-removed liquid is concentrated using a reverse osmosis membrane with a molecular weight cutoff of 100DA. The membrane concentration pressure is 5 MPa and the concentration is performed until the sugar content of the membrane concentrate is 13.6 brix to obtain a membrane concentrate.

[0082] (10) Ultrafiltration: The membrane concentrate is filtered through an ultrafiltration membrane (the pore size of the ultrafiltration membrane is 100 nanometers and the filtration pressure is 0.3 MPa) to obtain a filtrate treated with ultrafiltration.

[0083] (11) Concentration: The filtrate treated with ultrafiltration was concentrated under reduced pressure using a five-effect falling film concentrator to a sugar content of 66.10 brix to obtain 121.63 kg of semi-fermented zero-sucrose monk fruit concentrated juice.

[0084] The semi-fermented zero-sucrose monk fruit concentrated juice obtained in the embodiment of the present invention was detected by high performance liquid chromatography evaporative light scattering detection method (instrument: Waters 2414 Refractive Index Detector), and the sucrose content was 0, the fructose content was 23.53wt%, the glucose content was 14.63wt%, and the erythritol content was 6.50wt%; the mass content of mogroside V was 2.30wt% detected by high performance liquid chromatography external standard method, and the yield of mogroside V was 59.52%.

[0085] The semi-fermented zero-sucrose monk fruit concentrated juice obtained in Example 1 is a light yellow, transparent, thick liquid with a fragrant smell, a sweet, cool, saturated taste, and no peculiar smell.

[0086] Figure 1 This is a liquid chromatogram of the semi-fermented zero-sucrose monk fruit concentrated juice obtained in Example 1. In the figure, the peaks at 5.674 min, 7.109 min, and 8.151 min correspond to erythritol, fructose, and glucose, respectively.

[0087] Example 2

[0088] (1) Preparation of raw material solution: Take about 3400L of the effluent from the Luo Han Guo macroporous resin column (sugar content 2.5 brix, glycoside V content not detected; obtained from the production of 1000kg of fresh Luo Han Guo raw material).

[0089] (2) Sterilization and enzyme inactivation: Sterilize the extract using a continuous sterilization device at a maximum temperature of 120°C for 20 seconds. Collect the sterilized liquid for later use.

[0090] (3) Centrifugation: The sterilized liquid is continuously passed through a horizontal screw centrifuge and a disc centrifuge to obtain a centrifugal filtrate.

[0091] (4) Ceramic membrane filtration: The centrifugal filtrate is filtered through a ceramic membrane (pore size of the ceramic membrane is 10 microns, and the filtration pressure is 0.4 MPa) to obtain about 3350 kg of ceramic membrane filtrate (sugar content 2.5 brix).

[0092] (5) Enzymatic hydrolysis: 0.08 kg of trehalose-modified sucrase prepared in Preparation Example 1 and 0.03 kg of citric acid were added to the ceramic membrane filtrate, and enzymatic hydrolysis was performed for 3 hours at a temperature of 40°C and a pH value of 5.5. After the enzymatic hydrolysis was completed, the enzyme was inactivated to obtain an enzymatic hydrolyzate.

[0093] (6) Fermentation: The enzymatic hydrolyzate was placed in a fermentation tank, sterilized at high temperature to inactivate the enzyme, and then the fermentation seed solution (inoculation amount of 1.5%) and fermentation auxiliary materials (0.1% yeast extract, 0.1% KH2PO4) obtained in Preparation Example 2 were added, and fermentation was carried out at a temperature of 32°C and pH = 5. After 72 hours, the ratio of glucose to erythritol was detected to be about 1.7:1, and the fermentation was terminated, and the fermentation liquid was inactivated to obtain an inactivated fermentation liquid.

[0094] (7) Ceramic membrane filtration again: The inactivated fermentation liquid is filtered through a ceramic membrane (the pore size of the ceramic membrane is 10 microns and the filtration pressure is 0.4 MPa) to obtain the fermentation filtrate.

[0095] (8) Desalting, decolorizing and impurity removal: The fermentation filtrate is first passed through a cation exchange resin column (the cation exchange resin model is 001×7; the amount of cation exchange resin is 500 L; the height-to-diameter ratio of the cation exchange resin column is 5:1; the flow rate of the material passing through the cation exchange resin column is 2 BV / h), then through an anion exchange resin column (the anion exchange resin model is LXD-762; the amount of anion exchange resin is 500 L; the height-to-diameter ratio of the anion exchange resin column is 5:1; the flow rate of the material passing through the anion exchange resin column is 2 BV / h), and finally through a mixed bed (the volume ratio of cation exchange resin 001×7 and anion exchange resin LXD-762 is 3:1; the total amount of ion exchange resin in the mixed bed is 500 L; the height-to-diameter ratio of the mixed bed is 5:1; the flow rate of the material passing through the mixed bed is 2 BV / h) to obtain a desalting, decolorizing and impurity removal liquid.

[0096] (9) Membrane concentration: The desalted, decolorized and impurity-removed liquid is concentrated using a reverse osmosis membrane with a molecular weight cutoff of 150DA. The membrane concentration pressure is 4 MPa and the concentration is performed until the sugar content of the membrane concentrate is 12.4 brix to obtain a membrane concentrate.

[0097] (10) Ultrafiltration: The membrane concentrate is filtered through an ultrafiltration membrane (the pore size of the ultrafiltration membrane is 50 nanometers and the filtration pressure is 0.4 MPa) to obtain a filtrate treated with ultrafiltration.

[0098] (11) Concentration: The filtrate treated with ultrafiltration was concentrated under reduced pressure using a five-effect falling film concentrator to a sugar content of 68.3 brix to obtain 109.8 kg of semi-fermented zero-sucrose monk fruit concentrated juice.

[0099] (12) Blending: Add 50 kg of dry powder of monk fruit extract with a glycoside V content of 50% (previously dissolved in 40 kg of hot pure water) to the semi-fermented zero-sucrose monk fruit concentrated juice obtained in step (11), mix well, and obtain the blended semi-fermented zero-sucrose monk fruit concentrated juice.

[0100] The semi-fermented zero-sucrose monk fruit concentrated juice obtained in step (11) of the embodiment of the present invention was tested by high performance liquid chromatography evaporative light scattering detection method, and the sucrose content was 0, the fructose content was 24.39wt%, the glucose content was 13.36wt%, and the erythritol content was 7.96wt%. The mass content of mogroside V was 0wt% as detected by high performance liquid chromatography external standard method.

[0101] The semi-fermented zero-sucrose monk fruit concentrated juice obtained in step (11) of the embodiment of the present invention is a light yellow, transparent, thick liquid with a fragrant smell and a sweet, cool, saturated taste without any peculiar smell.

[0102] Figure 2 This is a liquid chromatogram of the semi-fermented zero-sucrose monk fruit concentrated juice obtained in Example 2. In the figure, the peaks at 5.681min, 7.118min, and 8.164min correspond to erythritol, fructose, and glucose, respectively.

[0103] The blended semi-fermented zero-sucrose monk fruit concentrated juice obtained in step (12) of the embodiment of the present invention is detected by high performance liquid chromatography external standard method, and the mass content of mogroside V is 12.5wt%, and the sweetness multiple is about 50 times the sweetness of sucrose.

[0104] Comparative Example 1

[0105] The other steps are consistent with those in Example 1, except that steps (6) and (7) are omitted, i.e., the fermentation and fermentation liquid filtration steps are omitted, and the enzymatic hydrolyzate obtained in step (5) is directly subjected to the desalting, decolorizing and impurity removal in step (8), and finally 125.07 kg of zero sucrose monk fruit concentrate is obtained, with a sugar content of 66.1 brix. The zero sucrose monk fruit concentrated juice obtained in Comparative Example 1 is tested to have a sucrose content of 0, a fructose content of 23.07 wt%, and a glucose content of 25.90 wt%; the mass content of mogroside V is 3.62%, and the yield of mogroside V is 96.3%.

[0106] Figure 3 This is the liquid chromatogram of the zero-sucrose monk fruit concentrated juice obtained in Comparative Example 1. In the figure, the peaks at 7.106min and 8.148min correspond to fructose and glucose, respectively.

[0107] Comparative Example 2

[0108] The other steps are consistent with those in Example 1, except that steps (5), (6) and (7) are omitted, i.e., the steps of enzymolysis, fermentation and filtration of fermented liquid are omitted, and the ceramic membrane liquid obtained in step (4) is directly subjected to desalting, decolorization and impurity removal in step (8), and finally 127.10 kg of monk fruit concentrate is obtained, with a sugar content of 65.0 brix. The monk fruit concentrated juice obtained in Comparative Example 2 is tested to have a sucrose content of 6.15 wt%, a fructose content of 20.20 wt%, and a glucose content of 22.91 wt%; the mass content of mogroside V is 3.57%, and the yield of mogroside V is 96.5%.

[0109] Figure 4 The liquid chromatogram of the concentrated monk fruit juice obtained in Comparative Example 2 is shown in FIG. In the figure, the peaks at 7.106 min, 8.147 min, and 11.840 min correspond to fructose, glucose, and sucrose, respectively.

Claims

1. A method for preparing semi-fermented zero-sucrose monk fruit concentrated juice, characterized in that: The following steps are involved: (1) Preparation of raw material liquid: taking liquid material from the production and processing step of monk fruit extract; the liquid material contains sucrose; (2) Sterilization and enzyme inactivation: Sterilize the liquid material using a continuous sterilization device and collect the sterilization liquid; (3) Centrifugation: The sterilized liquid is continuously passed through a horizontal screw centrifuge and a disc centrifuge to obtain a centrifugal filtrate; (4) Ceramic membrane filtration: Filter the centrifugal filtrate through a ceramic membrane to obtain a ceramic membrane filtrate; (5) Enzymatic hydrolysis: adding trehalose-modified sucrase and auxiliary enzymatic hydrolysis reagent to the ceramic membrane filtrate for enzymatic hydrolysis to obtain an enzymatic hydrolysis solution; the amount of the trehalose-modified sucrase is 0.05-0.1 wt% of the total sugar weight in the ceramic membrane filtrate, the enzymatic hydrolysis temperature is 20-60°C, the enzymatic hydrolysis pH is 3.0-8.0, and the enzymatic hydrolysis time is 1-10 hours; the auxiliary enzymatic hydrolysis reagent is citric acid, and the amount of citric acid is 0.4-0.7 times the mass of the trehalose-modified sucrase; the trehalose-modified sucrase is obtained by a preparation method comprising the following steps: (S1) dissolving the sucrase in a buffer solution with a pH of 6-7, adding sodium periodate, and placing the resulting mixture at 10-15°C in the dark for 2-4 hours, adding Ethylene glycol, buffer dialyzed at pH 6-7 to obtain activated sucrase; (S2) adding a protective substrate to the activated sucrase, adding trehalose, reacting at 30-40°C for 10-15h, buffer dialyzed at pH 6-7, and freeze-dried to obtain trehalose-modified sucrase; the protective substrate is sucrose; the material ratio meets the following conditions: the mass ratio of sucrase, sodium periodate, ethylene glycol, protective substrate, and trehalose is 10:10-20:2-3:50-100:7-10; (6) Fermentation: adding the enzymatic hydrolysate into a fermentation tank, sterilizing and killing the enzyme at high temperature, adding fermentation bacteria and fermentation auxiliary materials, and fermenting; monitoring the fermentation process by detecting the content ratio of glucose: erythritol, when the mass ratio of glucose: erythritol is within the range of 1-10:1, the fermentation liquid is inactivated, and the fermentation is terminated to obtain an inactivated fermentation liquid; the fermentation bacteria is yeast; (7) Ceramic membrane filtration again: Filter the inactivated fermentation liquid through a ceramic membrane to obtain a fermentation filtrate; (8) Desalting, decolorizing and removing impurities: The fermentation filtrate is passed through a cation exchange resin column and anion exchange resin column and a mixed bed to obtain a desalting, decolorizing and impurity-removing liquid; (9) Membrane concentration: The desalted, decolorized and impurity-removed liquid is concentrated using a reverse osmosis membrane to obtain a membrane concentrate; (10) Ultrafiltration: Filter the membrane concentrate using an ultrafiltration membrane to obtain an ultrafiltration filtrate; (11) Concentration: The ultrafiltration filtrate is concentrated under reduced pressure using a falling film concentrator to a specified sugar content to obtain semi-fermented zero-sucrose monk fruit concentrated juice.

2. The method for preparing the semi-fermented zero-sucrose monk fruit concentrated juice according to claim 1, characterized in that: The step (11) further includes the following steps: (12) Blending: Adding a component containing mogroside to the semi-fermented zero sucrose monk fruit concentrated juice obtained in step (11) to increase the content of mogroside V in the semi-fermented zero sucrose monk fruit concentrated juice, thereby obtaining a blended semi-fermented zero sucrose monk fruit concentrated juice; the component containing mogroside has a sucrose content of ≤0.001 wt %.

3. The preparation method according to claim 2, characterized in that: The ingredient containing mogroside is selected from mogroside dry powder or concentrated juice containing mogroside.

4. The preparation method according to claim 1, characterized in that: In step (1), the liquid material is selected from at least one of an extract concentrate, a decanter centrifugal filtrate, a disc centrifugal filtrate, a tubular centrifugal filtrate, a plate and frame filtration filtrate, a ceramic membrane filtrate, an ultrafiltration membrane filtrate, a nanofiltration membrane filtrate, a macroporous resin column effluent, and an anion and cation resin decolorization liquid; In step (2), the sterilization is continuous sterilization, the highest temperature during the sterilization process is 100-150°C, and the sterilization time is 10-120 seconds; In step (4), the pore size of the ceramic membrane is 1-10 μm, and the filtration pressure is 0.1-0.5 MPa; In step (7), the pore size of the ceramic membrane is 1-10 μm, and the filtration pressure is 0.1-0.5 MPa; In step (8), the type of the cation exchange resin is a gel-type styrene-based cation exchange resin, or a macroporous styrene-based cation exchange resin, and the volume ratio of the cation exchange resin to the weight of the fresh monk fruit is 0.3-1L:1kg; the height-to-diameter ratio of the cation exchange resin column is 0.5:1-10:1; the type of the anion exchange resin is a macroporous styrene-based anion exchange resin, or a macroporous acrylic anion exchange resin, and the volume ratio of the anion exchange resin to the weight of the fresh monk fruit is 0.3-1L:1kg, and the height-to-diameter ratio of the anion exchange resin column is 0.5:1-10:1; the flow rate of the fermentation filtrate through the cation and anion exchange resin columns is 0.5-10 BV / h; In step (9), the molecular weight cut-off of the reverse osmosis membrane is 50-200DA, the pressure of membrane concentration is 1-15Mpa, and the degree of membrane concentration is that the sugar content of the membrane concentrate is 10-25brix; In step (10), the pore size of the ultrafiltration membrane is 10-100 nanometers, and the filtration pressure is 0.1-0.5 MPa; In step (11), the falling film concentrator includes a triple-effect falling film concentrator, a quadruple-effect falling film concentrator or a quintuple-effect falling film concentrator, and the sugar content of the semi-fermented zero-sucrose monk fruit concentrated juice is 50-80 brix.

5. The preparation method according to claim 4, characterized in that: In step (1), the content of mogroside V in the liquid material is 0-10 wt%.

6. The preparation method according to claim 4, characterized in that: In step (8), the mixed bed is a mixed column bed of cation exchange resin and anion exchange resin, wherein the ratio of cation exchange resin to anion exchange resin is 1:1-10:1, V / V, and the ratio of the total volume of ion exchange resin in the mixed bed to the weight of fresh monk fruit is 0.3-1L:1kg; the height-to-diameter ratio of the mixed bed is 0.5:1-10:1, and the flow rate of the fermentation filtrate through the mixed bed is 0.5-10 BV / h.

7. The preparation method according to claim 1, characterized in that: In steps (S1) and (S2), the buffer solution for the buffer dialysis is a citric acid-sodium citrate buffer solution; and the buffer dialysis time is 20-30 hours.

8. The preparation method according to claim 1, characterized in that: When the mass ratio of glucose:erythritol is in the range of 1.7-2.25:1, the fermentation broth is inactivated.

9. A semi-fermented zero-sucrose monk fruit concentrated juice, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 8, and comprises the following ingredients: glucose, fructose, erythritol, and water, and the mass ratio of glucose, fructose, and erythritol is 1-10:2-5:1, and the sugar content of the semi-fermented zero-sucrose monk fruit concentrated juice is 50-80 brix.

10. The semi-fermented zero-sucrose monk fruit concentrated juice according to claim 9, characterized in that: The semi-fermented zero-sucrose monk fruit concentrated juice has a mass ratio of glucose, fructose and erythritol of 1.7-2.25:3.8-4.2:1, and the sugar content of the semi-fermented zero-sucrose monk fruit concentrated juice is 60-75 brix.

11. The semi-fermented zero-sucrose monk fruit concentrated juice according to claim 10, characterized in that: The sugar content of the semi-fermented zero-sucrose monk fruit concentrated juice is 65-70 brix.

12. The semi-fermented zero-sucrose monk fruit concentrated juice according to claim 9, characterized in that: Also includes mogrosides.

13. The semi-fermented zero-sucrose monk fruit concentrated juice according to claim 12, characterized in that: The mogroside is selected from at least one of mogroside V, mogroside III, mogroside IV, 11-oxo-mogroside V, mogroside VI and simanoside.

14. The semi-fermented zero-sucrose monk fruit concentrated juice according to claim 13, characterized in that: In the semi-fermented zero-sucrose monk fruit concentrated juice, the mass ratio of glucose, fructose, erythritol and mogroside is 1.7-2.25:3.8-4.2:1:0.1-10.

15. The semi-fermented zero-sucrose monk fruit concentrated juice according to claim 13, characterized in that: The mass ratio of glucose, fructose, erythritol and mogroside is 1.7-2.25:3.8-4.2:1:0.5-2.

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