Zero-sucrose monk fruit concentrated juice and production method thereof

Abstract

The present invention relates to a zero-sucrose monk fruit concentrated juice and a preparation method thereof. The zero-sucrose monk fruit concentrated juice comprises the following components: glucose, fructose, mogroside V, maltose, and water, and the mass ratio of glucose, fructose, mogroside V, and maltose is 100-130: 100-130: 0.2-0.5: 10-20, and the sugar content of the monk fruit concentrated juice is 50-80 brix. After removing macromolecular impurities such as pectin and protein from the monk fruit extract, the present invention creates a relatively favorable environmental condition for the enzymolysis of sucrase. After the sucrase is modified by trehalose, under the synergistic effect of the auxiliary reagent citric acid, the enzymolysis reaction can be fully carried out in the positive direction, and the complete enzymolysis of sucrose can be achieved, thereby finally obtaining the zero-sucrose monk fruit concentrated juice.

Description

Technical Field

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

[0002] Monk fruit is a traditional Chinese medicinal health food. It is one of the first batch of medicine and food materials approved by the country and is known as the "magic fruit". Monk fruit has high nutritional value and is rich in vitamin C, mogroside, fructose, glucose, sucrose, protein, lipids, etc. Monk fruit is sweet and cool in nature. It belongs to the lung and large intestine meridians. It has the effects of moistening the lungs and relieving coughs, promoting fluid production and quenching thirst. It is suitable for coughs caused by lung heat or dryness, whooping cough, and thirst caused by heat damage to body fluids. In addition, it has the effect of moistening the intestines and relieving constipation. Modern medical research has confirmed that the mogroside contained in monk fruit is a natural sweetener that is 400 times sweeter than sucrose, but it does not produce calories, is pure and natural, and tastes good. Therefore, it is an ideal natural and healthy sugar substitute sweetener for people with diabetes, obesity, etc. who are not suitable for eating sucrose.

[0003] The commercially available mogroside solid powder products, such as mogroside V50%, mogroside V25%, mogroside V10%, etc., do not contain sucrose because they use a macroporous adsorption resin separation process to separate and remove sugars such as sucrose. However, fructose and / or glucose will also be removed at the same time. 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 commercially available monk fruit concentrated juice products, you cannot use macroporous resins. Therefore, the monk fruit concentrated juice products that currently contain fructose and glucose will have a relatively high content of sucrose.

[0004] As people's living standards continue to improve, long-term excessive consumption of sucrose will damage health and lead to adverse consequences such as obesity, tooth decay and increased blood sugar. Studies have shown that drinking sugary drinks will cause weight gain, making people more susceptible to type 2 diabetes, tooth decay and obesity. There is also evidence that drinking a lot of sugary drinks can lead to non-alcoholic fatty liver disease and heart disease. The UK has imposed a "sugar tax" on beverage manufacturers since 2018, and this policy has been followed by countries such as Mexico, France, Ireland and Hungary. The purpose of this policy is to guide beverage manufacturers to adjust the formulation of beverages and reduce the sugar content of beverages. "Zero sucrose" generally means that sucrose is not added as a sweetener during the processing of food, and does not mean that the food does not contain other sugar substances such as fructose and glucose. Although "zero sucrose" does not mean "0 sugar", "0 sucrose" still has the following positive meanings: assisting weight loss, assisting in preventing tooth decay, assisting in controlling blood sugar, etc. Today, "zero sucrose" has become a hot development track in the food field, especially in the dairy field. More and more dairy companies have launched and launched various new products in the "zero sucrose" sub-category. However, due to the process requirements, even if efforts are made to reduce the sucrose content, there is still a small amount of sucrose in the products of monk fruit concentrated juice, which does not meet the current requirements of "zero sucrose" sweetening additives. Therefore, the presence of sucrose has greatly affected the application scope of monk fruit concentrated juice. At present, there is an urgent need for a method for producing zero sucrose monk fruit concentrated juice to bring monk fruit to the market and bring high-quality, high-nutrition, sweet and burden-free consumption needs and experiences to more consumers.

[0005] 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.

[0006] CN108902588A discloses a method for preparing a monk fruit plant beverage, which uses fresh monk fruit as raw material, and obtains the monk fruit plant beverage through vacuum freeze drying, soaking, beating, mixed enzyme (proteolytic enzyme, cellulase, pectinase and glucoamylase) enzymolysis, decoction, centrifugation, ultrafiltration and other steps. The method is costly and has limited processing capacity, especially large-scale freeze drying of fresh raw materials is difficult to implement industrially. In addition, the monk fruit plant beverage obtained by this method cannot achieve zero sucrose.

[0007] CN116098249A discloses a method for preparing a multi-sweetened pure fruit juice of monk fruit with a sugar substitute, including the steps of hydrolysis, glucose isomerization, microfiltration clarification, decolorization and impurity removal, blending, concentration, and sterilization. The hydrolysis is to add sucrase to the monk fruit for hydrolysis, and then add glucose isomerase for isomerization and sweetening, and finally convert sucrose into monosaccharides, and convert low-sweetness glucose into high-sweetness fructose, while removing part of the sucrose, achieving low calories and good taste. However, since the slurry treated with sucrase in this method contains a large amount of impurities (such as protein, pectin, etc.) or microorganisms, and the environment of sucrase enzymolysis is not optimized, the enzymolysis ability of sucrase is greatly affected, so this method cannot completely remove sucrose from monk fruit concentrated juice. It can only be a low-sugar treatment method, which still contains a high content of sucrose and cannot meet the detection requirements for "0 sucrose" in the current high-end beverage market. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a zero-sucrose monk fruit concentrated juice with relatively high glucose and fructose contents. Furthermore, the technical problem to be solved by the present invention is to provide a method for preparing monk fruit concentrated juice, which has a high yield of mogroside V, and the content of glucose and fructose in the obtained monk fruit concentrated juice is also relatively high, and does not contain sucrose.

[0009] The technical solution adopted by the present invention to solve the technical problem is as follows:

[0010] A zero-sucrose monk fruit concentrated juice comprises the following ingredients: glucose, fructose, mogroside V, maltose and water, wherein the mass ratio of glucose, fructose, maltose and mogroside V is 100-130:100-130:0.2-0.5:10-20, and the sugar content of the monk fruit concentrated juice is 50-80 brix.

[0011] Preferably, in the zero-sucrose monk fruit concentrated juice, the mass ratio of glucose, fructose, maltose and mogroside V is 100-110:100-110:0.2-0.3:12-16, and the sugar content of the monk fruit concentrated juice is 60-75 brix.

[0012] Preferably, the glucose content in the monk fruit concentrated juice is 15-30wt%, preferably 22-27wt%, more preferably 24-26wt%.

[0013] Those skilled in the art should understand that sucrose may still be present in the zero sucrose monk fruit concentrated juice of the present invention, but its content is very low, and may be below the detection limit of the instrument. For example, the content is less than 0.1wt%, preferably less than 0.05wt%, more preferably less than 0.01wt%, and most preferably less than 0.001wt%. In a specific embodiment of the present invention, no sucrose is detected in the zero sucrose monk fruit concentrated juice.

[0014] Those skilled in the art should also understand that the zero-sucrose monk fruit concentrated juice of the present invention may contain trace amounts of components carried by monk fruit itself, such as mannitol, in addition to the above-mentioned main ingredients, namely glucose, fructose, mogroside V and maltose.

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

[0016] (1) Fresh fruit extraction: Select mature, non-rotten monk fruit, clean it, crush it, use water as the extractant to extract it, and collect the extract for later use;

[0017] (2) Sterilization and enzyme inactivation: sterilize the extract and collect the sterilized liquid;

[0018] (3) Centrifugation: The sterilized liquid is treated with a 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: Add trehalose-modified sucrase and auxiliary reagents to the ceramic membrane filtrate for enzymatic hydrolysis. After the enzymatic hydrolysis is completed, inactivate the enzyme to obtain an enzymatic hydrolyzate.

[0021] (6) Desalting, decolorizing and removing impurities: The enzymatic hydrolyzate is passed through a cation exchange resin column, an anion exchange resin column and a mixed bed to obtain a desalting, decolorizing and impurity-removing liquid;

[0022] (7) Membrane concentration: The desalted, decolorized and impurity-removed liquid is concentrated using a reverse osmosis membrane to obtain a membrane concentrate;

[0023] (8) Ultrafiltration: Filter the membrane concentrate using an ultrafiltration membrane to obtain an ultrafiltration-treated filtrate;

[0024] (9) Concentration: The filtrate after ultrafiltration is concentrated under reduced pressure using a falling film concentrator to obtain zero-sucrose monk fruit concentrated juice.

[0025] 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.

[0026] 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.

[0027] Preferably, in step (4), the pore size of the ceramic membrane is 1-10 microns, 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.

[0028] Preferably, in step (5), the amount of the sucrase is 0.05%-0.1% 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, it will lead to incomplete enzymatic hydrolysis; 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 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.

[0029] Preferably, in step (5), the trehalose-modified sucrase is obtained by a preparation method comprising the following steps:

[0030] (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;

[0031] (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.

[0032] Furthermore, in steps (S1) and (S2), the buffer solution for the buffer dialysis is a citric acid-sodium citrate buffer solution; the protective substrate is sucrose; and the buffer dialysis time is 20-30 hours.

[0033] Furthermore, in steps (S1) and (S2), the material ratio meets the following conditions: the mass ratio of sucrase, sodium periodate, ethylene glycol, protected substrate, and trehalose is 10:10-20:2-3:50-100:7-10.

[0034] 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.

[0035] 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.

[0036] Preferably, in step (6), the type of the cation exchange resin is a gel-type styrene cation exchange resin or a macroporous styrene cation exchange resin, and specific models include but are not limited to: 001×7, 001×8, 001×16, D001. The volume 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 material through the cation exchange resin column is 0.5-10BV / h. The purpose of using the cation exchange resin is to remove impurities such as salt and sucrase from the material. 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 will not be complete; 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 waste of materials and energy.

[0037] Preferably, in step (6), 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 material passing 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 in the material. If the amount of anion exchange resin is too small, the height-to-diameter ratio is too small, or the flow rate of the material passing through the anion exchange resin column is too fast, the decolorization will not be complete; if the amount of anion exchange resin is too large, the height-to-diameter ratio is too large, or the flow rate of the material passing through the anion exchange resin column is too slow, it will cause waste of materials and energy.

[0038] Preferably, in step (6), 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.

[0039] Preferably, in step (7), 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 the taste and odor from being abnormal due to long-term high temperature.

[0040] Preferably, in step (8), 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.

[0041] Preferably, in step (9), 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, the sugar content of the zero-sucrose monk fruit concentrated juice is 50-80 brix, and the sucrose content in the zero-sucrose monk fruit concentrated juice is 0.

[0042] The principle of the method of the present invention is as follows:

[0043] 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.

[0044] The beneficial effects of the method of the present invention are as follows:

[0045] (1) In the zero-sucrose monk fruit concentrated juice obtained by the method of the present invention, no sucrose can be detected (high performance liquid chromatography evaporative light scattering detection method), which meets the quality control requirements of the beverage market for "0 sucrose", and the mass content of mogroside V is high and the yield is high;

[0046] (2) The zero-sucrose monk fruit concentrated juice obtained by the method of the present invention is a light yellow, transparent, thick liquid with a fresh fragrance, a sweet and saturated taste, and no peculiar smell. The sweetness is close to that of sucrose or honey;

[0047] (3) The process of the method of the present invention is highly operable, safe, environmentally friendly, pollution-free, and suitable for industrial production.

[0048] The 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

[0049] Figure 1 The liquid chromatogram of the concentrated monk fruit juice obtained in Example 1;

[0050] Figure 2 This is the liquid chromatogram of the monk fruit concentrated juice obtained in Comparative Example 1. DETAILED DESCRIPTION

[0051] The present invention will be further described below in conjunction with the embodiments.

[0052] The fresh Momordica grosvenori used in the embodiment of the present invention was purchased from Guilin, Guangxi, wherein the mass content of sucrose was 1.10%, and the mass content of mogroside V was 0.47%; the edible sucrase was purchased from Cangzhou Xiasheng Enzyme Biotechnology Co., Ltd., with the brand name GDG-2028; the 001×7, 001×16, and D001 cation exchange resins, and the LX-T5, LXD-762, and LX-94 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.

[0053] 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 maltose, and adopts the high performance liquid chromatography external standard method to detect the content of mogroside V.

[0054] Preparation Example 1

[0055] (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;

[0056] (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.

[0057] Comparative Preparation Example 1

[0058] Other conditions and operations were the same as those in Preparation Example 1, except that trehalose was replaced by an equal amount of chitosan having a molecular weight of about 8000 to obtain chitosan-modified sucrase.

[0059] Comparative Preparation Example 2

[0060] Other conditions and operations were the same as those in Preparation Example 1, except that trehalose was replaced by an equal amount of dextran to obtain dextran-modified sucrase.

[0061] Example 1

[0062] (1) Fresh fruit extraction: Select 2000 kg of mature, non-rotten monk fruit, clean it, crush it, and use 90℃ hot water for countercurrent extraction. The total amount of hot water used is about 8 tons. Collect the extract for later use.

[0063] (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.

[0064] (3) Centrifugation: The sterilized liquid is continuously passed through a horizontal screw centrifuge and a disc centrifuge to obtain a centrifugal filtrate.

[0065] (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 8,900 kg of ceramic membrane filtrate (sugar content 1.9 brix).

[0066] (5) Enzymatic hydrolysis: 0.1 kg of trehalose-modified sucrase prepared in Preparation Example 1 and 0.07 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.

[0067] (6) Desalting, decolorizing and impurity removal: The enzymatic hydrolyzate is first passed through a cation exchange resin column (the cation exchange resin model is 001×16; the amount of cation exchange resin is 800 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 0.5 BV / h), then through an anion exchange resin column (the anion exchange resin model is LX-94; the amount of anion exchange resin is 800 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 0.5 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 800 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 0.5 BV / h) to obtain a desalting, decolorizing and impurity removal liquid.

[0068] (7) 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 membrane concentrate is concentrated to a sugar content of 15.2 brix to obtain a membrane concentrate.

[0069] (8) 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.

[0070] (9) Concentration: The filtrate treated with ultrafiltration was concentrated under reduced pressure using a five-effect falling film concentrator to a sugar content of 65.3 brix to obtain 253.14 kg of zero-sucrose monk fruit concentrated juice.

[0071] The zero sucrose monk fruit concentrated juice obtained in the embodiment of the present invention is detected by high performance liquid chromatography evaporative light scattering detection method, and the sucrose content is 0, the fructose content is 22.85wt% , the glucose content is 24.09wt% , and the maltose content is 0.06wt%; the mass content of mogroside V is 3.55wt% , and the yield of mogroside V is 95.6% by high performance liquid chromatography external standard method.

[0072] The zero-sucrose monk fruit concentrated juice obtained in Example 1 is a light yellow, transparent, thick liquid with a fresh fragrance, a sweet and saturated taste, and no peculiar smell. The sweetness is close to that of sucrose or honey.

[0073] Example 2

[0074] (1) Fresh fruit extraction: Select 2000 kg of mature, non-rotten monk fruit, clean it, crush it, and use superheated water to pulp and extract it. The total amount of superheated water used is about 6 tons. Collect the extract for later use.

[0075] (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.

[0076] (3) Centrifugation: The sterilized liquid is continuously passed through a horizontal screw centrifuge and a disc centrifuge to obtain a centrifugal filtrate.

[0077] (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 6850 kg of ceramic membrane filtrate (sugar content 2.4 brix).

[0078] (5) Enzymatic hydrolysis: 0.15 kg of trehalose-modified sucrase prepared in Preparation Example 1 and 0.06 kg of citric acid were added to the ceramic membrane filtrate, and the enzymatic hydrolysis was carried out 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.

[0079] (6) Desalting, decolorizing and impurity removal: The enzymatic hydrolyzate is first passed through a cation exchange resin column (the cation exchange resin model is 001×7; the amount of cation exchange resin is 1000L; 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 1000L; 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 1000L; 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.

[0080] (7) 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 14.6 brix to obtain a membrane concentrate.

[0081] (8) 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.

[0082] (9) Concentration: The filtrate treated with ultrafiltration was concentrated under reduced pressure using a five-effect falling film concentrator to a sugar content of 71.2 brix to obtain 226.13 kg of zero-sucrose monk fruit concentrated juice.

[0083] The zero sucrose monk fruit concentrated juice obtained in the embodiment of the present invention is detected by high performance liquid chromatography evaporative light scattering detection method, and the sucrose content is 0, the fructose content is 25.15wt% , the glucose content is 25.33wt% , and the maltose content is 0.07wt%; the mass content of mogroside V is 3.87wt% detected by high performance liquid chromatography external standard method, and the yield of mogroside V is 93.1%.

[0084] Example 3

[0085] (1) Fresh fruit extraction: Select 2000 kg of mature, non-rotten monk fruit, wash it, and squeeze it with a juicer at room temperature. Then use about 7 tons of water to extract the fruit residue once at room temperature (extraction time 1 hour). Combine the juice and ice water extract to obtain the extract for standby use.

[0086] (2) Sterilization and inactivation of enzymes: Sterilize the extract using a continuous sterilization device at a maximum temperature of 150°C for 40 seconds. Collect the sterilized liquid for later use.

[0087] (3) Centrifugation: The sterilized liquid is continuously passed through a horizontal screw centrifuge and a disc centrifuge to obtain a centrifugal filtrate.

[0088] (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 0.5 MPa) to obtain about 7750 kg of ceramic membrane filtrate (sugar content 2.2 brix).

[0089] (5) Enzymatic hydrolysis: 0.12 kg of trehalose-modified sucrase prepared in the preparation example and 0.08 kg of citric acid were added to the ceramic membrane filtrate, and the enzymatic hydrolysis was carried out for 7 hours at a temperature of 30°C and a pH value of 5.5. After the enzymatic hydrolysis was completed, the enzyme was inactivated to obtain an enzymatic hydrolyzate.

[0090] (6) Desalting, decolorizing and impurity removal: The enzymatic hydrolyzate is first passed through a cation exchange resin column (the cation exchange resin model is D001; the amount of cation exchange resin is 1000 L; the height-to-diameter ratio of the cation exchange resin column is 2:1; the flow rate of the material passing through the cation exchange resin column is 5 BV / h), then through an anion exchange resin column (the anion exchange resin model is LX-T5; the amount of anion exchange resin is 1000 L; the height-to-diameter ratio of the anion exchange resin column is 2:1; the flow rate of the material passing through the anion exchange resin column is 5 BV / h), and finally through a mixed bed (the volume ratio of cation exchange resin D001 and anion exchange resin LX-T5 is 2:1; the total amount of ion exchange resin in the mixed bed is 1000 L; the height-to-diameter ratio of the mixed bed is 2:1; the flow rate of the material passing through the mixed bed is 5 BV / h) to obtain a desalting, decolorizing and impurity removal liquid.

[0091] (7) 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 3Mpa and the membrane concentrate is concentrated to a sugar content of 12.4brix to obtain a membrane concentrate.

[0092] (8) 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 0.2 MPa) to obtain a filtrate treated with ultrafiltration.

[0093] (9) Concentration: The filtrate treated with ultrafiltration was concentrated under reduced pressure using a triple-effect falling film concentrator to a sugar content of 69.1 brix to obtain 238.70 kg of zero-sucrose monk fruit concentrated juice.

[0094] The zero sucrose monk fruit concentrated juice obtained in the embodiment of the present invention is detected by high performance liquid chromatography evaporative light scattering detection method, and the sucrose content is 0, the fructose content is 24.93wt% , the glucose content is 25.40wt% , and the maltose content is 0.07wt%; the mass content of mogroside V is 3.63wt% , and the yield of mogroside V is 92.18% by high performance liquid chromatography external standard method.

[0095] Comparative Example 1

[0096] The other steps are consistent with those in Example 1, except that step (5) is omitted, and the ceramic membrane filtrate obtained in step (4) is directly subjected to desalting, decolorizing and impurity removal in step (6), and finally 255.55 kg of monk fruit concentrate is obtained, with a sugar content of 64.7 brix. The monk fruit concentrated juice obtained in Comparative Example 1 is tested to have a sucrose content of 6.03 wt%, a fructose content of 19.01 wt%, a glucose content of 21.52 wt%, and a maltose content of 0.05 wt%; the mass content of mogroside V is 3.65%, and the yield of mogroside V is 96.7%.

[0097] Figure 1 The liquid chromatogram of the monk fruit concentrated juice obtained in Example 1 is shown. Figure 2 The liquid chromatogram of the monk fruit concentrated juice obtained in Comparative Example 1. In the figure, the peaks at 6.40min, 7.17min, 9.67min, and 10.99min correspond to fructose, glucose, sucrose, and maltose, respectively.

[0098] Comparative Example 2

[0099] The other conditions and operations were the same as those in Example 1, except that the trehalose-modified sucrase prepared in Preparation Example 1 was replaced with an equal mass of sucrase. That is, the sucrase was not modified. After testing, the content of sucrose in the concentrated juice (sugar content 66.5 brix) was 0.68 wt%, the content of fructose was 23.85 wt%, the content of glucose was 23.91 wt%, and the content of maltose was 0.06 wt%; the mass content of mogroside V was 3.62 wt%, and the yield of mogroside V was 93.5%.

[0100] Comparative Example 3

[0101] Other conditions and operations were the same as those in Example 1, except that the trehalose-modified sucrase prepared in Preparation Example 1 was replaced by an equal amount of chitosan-modified sucrase prepared in Comparative Preparation Example 1. After testing, the content of sucrose in the concentrated juice (sugar content 67.1 brix) was 0.32 wt%, the content of fructose was 23.61 wt%, the content of glucose was 24.32 wt%, and the content of maltose was 0.05%; the mass content of mogroside V was 3.65 wt%, and the yield of mogroside V was 94.6%.

[0102] Comparative Example 4

[0103] Other conditions and operations were the same as those in Example 1, except that the trehalose-modified sucrase prepared in Preparation Example 1 was replaced by an equal amount of dextran-modified sucrase prepared in Comparative Preparation Example 2. After testing, the sucrose content in the concentrated juice (sugar content 65.9 brix) was 0.24%, the fructose content was 23.24 wt%, the glucose content was 24.57 wt%, the maltose content was 0.05 wt%, the mass content of mogroside V was 3.62 wt%, and the yield of mogroside V was 94.0%.

Claims

1. A method for preparing zero-sucrose monk fruit concentrated juice, characterized in that: The following steps are involved: (1) Fresh fruit extraction: Select mature, non-rotten monk fruit, clean it, crush it, use water as the extractant to extract it, and collect the extract for later use; (2) Sterilization and enzyme inactivation: sterilize the extract and collect the sterilized liquid; (3) Centrifugation: The sterilized liquid is treated with a 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 reagents to the ceramic membrane filtrate, performing enzymatic hydrolysis, and after the enzymatic hydrolysis is completed, inactivating the enzyme to obtain an enzymatic hydrolyzate; the amount of the trehalose-modified sucrase is 0.05%-0.1% of the weight of the total sugar in the ceramic membrane filtrate, and the mass of the total sugar in the ceramic membrane filtrate is the weight of the ceramic membrane filtrate × the 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 auxiliary 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 prepared by the following steps: The preparation method is as follows: (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 the mixture is dialyzed with a buffer solution with a pH of 6-7 to obtain activated sucrase; (S2) a protective substrate and trehalose are added to the activated sucrase in sequence, the mixture is reacted at 30-40°C for 10-15 hours, the mixture is dialyzed with a buffer solution with a pH of 6-7, and the mixture is freeze-dried to obtain trehalose-modified sucrase; the protective substrate is sucrose; the mass ratio of sucrase, sodium periodate, ethylene glycol, protective substrate, and trehalose is 10:10-20:2-3:50-100:7-10; (6) Desalting, decolorizing and removing impurities: The enzymatic hydrolyzate is passed through a cation exchange resin column, an anion exchange resin column and a mixed bed to obtain a desalting, decolorizing and impurity-removing liquid; (7) Membrane concentration: The desalted, decolorized and impurity-removed liquid is concentrated using a reverse osmosis membrane to obtain a membrane concentrate; (8) Ultrafiltration: Filter the membrane concentrate using an ultrafiltration membrane to obtain an ultrafiltration-treated filtrate; (9) Concentration: The filtrate after ultrafiltration is concentrated under reduced pressure using a falling film concentrator to obtain zero-sucrose monk fruit concentrated juice.

2. The preparation method according to claim 1, characterized in that: In step (2), the sterilization is continuous sterilization, the maximum temperature of the continuous sterilization 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 microns, and the filtration pressure is 0.1-0.5Mpa.

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

4. The preparation method according to claim 1, characterized in that: In step (6), the type of the cation exchange resin is a gel-type styrene-based cation exchange resin, or a macroporous styrene-based cation exchange resin; 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, and the flow rate of the material passing through the cation exchange resin column is 0.5-10 BV / h; the type of the anion exchange resin is a macroporous styrene-based anion exchange resin, or a macroporous acrylic anion exchange resin; the volume ratio of the anion exchange resin to the weight of the fresh monk fruit is 0.3-1L:1kg, the height-to-diameter ratio of the anion exchange resin column is 0.5:1-10:1, and the flow rate of the material passing through the anion exchange resin column is 0.5-10 BV / h; the mixed bed is a mixed column bed of cation exchange resin and anion exchange resin, wherein the volume ratio of the cation exchange resin to the anion exchange resin is 1:1-10:1; the ratio of the total volume usage of the ion exchange resin in the mixed bed to the weight of the 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 material through the mixed bed is 0.5-10 BV / h.

5. The preparation method according to claim 1, characterized in that: In step (7), the molecular weight cut-off of the reverse osmosis membrane is 50-200DA, and the pressure of membrane concentration is 1-15Mpa; In step (8), the pore size of the ultrafiltration membrane is 10-100 nanometers, and the filtration pressure is 0.1-0.5 MPa.

6. A zero-sucrose monk fruit concentrated juice, characterized in that: The zero-sucrose monk fruit concentrated juice is prepared by the preparation method according to any one of claims 1 to 5. The zero-sucrose monk fruit concentrated juice comprises the following ingredients: glucose, fructose, mogroside V, maltose, and water. The mass ratio of glucose, fructose, maltose, and mogroside V is 100-130: 100-130: 0.2-0.5: 10-20. The sugar content of the monk fruit concentrated juice is 50-80 brix.

7. The zero-sucrose monk fruit concentrated juice according to claim 6, characterized in that: The mass ratio of glucose, fructose, maltose and mogroside V is 100-110:100-110:0.2-0.3:12-16, and the sugar content of the monk fruit concentrated juice is 60-75 brix.

8. The zero-sucrose monk fruit concentrated juice according to claim 7, characterized in that: The glucose content in monk fruit concentrated juice is 15-30wt%.

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