Rice bran protein, low-fat ice cream and preparation method thereof

Abstract

The invention provides a preparation method of rice bran protein. The preparation method comprises the following steps: A) degreasing rice bran by adopting a supercritical fluid extraction method; b) mixing the degreased rice bran with water, and performing ultrasonic treatment; c) performing enzymolysis on the rice bran subjected to ultrasonic treatment under the action of phytase, and then performing enzymolysis again under the action of compound protease; and D) purifying the rice bran protein crude product. The invention further provides the rice bran protein prepared according to the scheme and the low-fat ice cream containing the rice bran protein. The rice bran protein prepared by the method is added into the ice cream, so that on one hand, the fat content of the ice cream is reduced, the protein content is increased, and the development trend of the health concept of consumers at present is met; on the other hand, high expansion rate and low melting rate can be obtained on the basis of keeping good sensory quality, the effect is more remarkable compared with that of rice bran protein prepared by other methods, and the quality of ice cream products is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of dairy products, and particularly relates to a rice bran protein, low-fat ice cream and a preparation method thereof. Background Art

[0002] Ice cream is a frozen drink made from raw and auxiliary materials such as drinking water, dairy products, fruit products, edible sugar, etc. through processes such as mixing, sterilization, homogenization, cooling, aging, freezing, etc., and mainly contains protein, fat, carbohydrates, etc. Ice cream is deeply loved by consumers for its delicate, smooth, sweet and delicious taste, and its ability to relieve heat and quench thirst.

[0003] With the development of society and the improvement of consumption levels, people's demand for food has gradually changed from basic food and clothing to nutrition and health. Green foods, functional foods, organic foods, etc. on the market are increasingly favored by consumers, and the growing concern for health has also promoted the development of the low-sugar, low-fat, and low-calorie product market. Traditional ice cream has a high content of sugar and fat, which discourages many diabetic patients, people losing weight, and consumers who attach importance to the concept of health. Therefore, the future ice cream industry needs to develop in the direction of low-sugar, low-fat, and functional, and is committed to developing healthy and delicious products.

[0004] Fat substitutes can not only reduce the total calories of ice cream, prevent excess calories from being converted into fat, but also improve the functional and nutritional characteristics of ice cream. Fat substitutes are divided into three types: protein matrix, carbohydrate matrix, and composite matrix. Among them, the fat substitute with a protein matrix has good emulsifying and water-retaining effects, can make the water distribution in ice cream more uniform, showing a dense sensory characteristic, and can also improve the anti-melting property of the product. At present, there is an urgent need to seek good plant proteins to provide consumers with new ice cream products with low fat, low calories, and high protein. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a rice bran protein, low-fat ice cream and a preparation method thereof. The rice bran protein provided by the present invention has high solubility, good emulsifying property, foaming property and foam stability, and has good sensory quality, high expansion rate and anti-melting property when used in ice cream.

[0006] Rice bran is the main by-product of rice processing. It is rich in nutrients, and the protein content is as high as 18%. At present, most of the rice bran in China is used as animal feed or directly discarded, resulting in serious waste of protein resources. Rice bran protein contains 8 essential amino acids for the human body, and the amino acid composition is balanced, closer to the FAO / WHO recommended pattern. The biological value (PER) is 2.0-2.5, similar to casein in milk (PER is 2.5). In addition, rice bran protein does not contain anti-nutritional factors, has low allergenicity, does not contain cholesterol, and has a low cost. Therefore, rice bran, as a high-quality natural protein source, has great development potential and utilization value. The prior art has disclosed various methods for extracting rice bran protein. For example, the alkaline method is used to extract rice bran protein. However, under the condition of high alkali concentration, serine or cysteine residues in the protein will combine with the ε-amino group of lysine to generate toxic lysine amide, resulting in loss of nutritional value. The enzymatic method can also be used to extract rice bran protein. The reaction conditions are mild, no harmful substances are produced, and more nutritional value can be retained. However, the extraction rate of the single enzymatic method is low, and the properties such as solubility, emulsifying property, foaming property, and foam stability of the obtained rice bran protein need to be improved.

[0007] Based on this, the present application provides a method for preparing rice bran protein, comprising the following steps:

[0008] A) Degreasing rice bran by supercritical fluid extraction method;

[0009] B) Mixing the degreased rice bran with water and then performing ultrasonic treatment;

[0010] C) First enzymatically hydrolyzing the ultrasonically treated rice bran with phytase, and then performing a second enzymatic hydrolysis with compound protease;

[0011] D) Purifying the crude rice bran protein after enzymatic hydrolysis.

[0012] The present application uses rice bran as the raw material. First, the rice bran is degreased by supercritical fluid extraction method, and then the degreased rice bran is mixed with water and subjected to ultrasonic treatment to accelerate the dissolution of protein. The ultrasonically treated rice bran is first enzymatically hydrolyzed with phytase to remove the phytic acid cross-linked with the protein, and then a second enzymatic hydrolysis is performed with compound protease, and then rice bran protein is obtained after purification. The method provided by the present application not only improves the extraction rate of rice bran protein, but also improves the solubility, emulsifying property, foaming property, and foam stability of rice bran protein. The experimental results show that the method provided by the present application increases the extraction rate of rice bran protein by 11.96%.

[0013] Before degreasing, it is preferred to remove impurities and pulverize rice bran in this application. Specifically, impurities such as sand, stones, and grass debris in the rice bran can be removed by screening, and then it is pulverized. In some specific implementation manners, it is preferred to pulverize the rice bran to 20 - 60 meshes, more preferably 30 - 50 meshes.

[0014] The pulverized rice bran is degreased by using supercritical fluid. In some specific implementation manners, the supercritical fluid is supercritical CO 2 , the pressure of the supercritical extraction is preferably 25 - 45 MPa, the temperature is preferably 35 - 55 °C, the time is preferably 80 - 100 min, and the CO 2 flow rate is preferably 20 - 22 L / h. In some specific implementation manners, the pressure of the supercritical extraction is preferably 30 - 40 MPa, the temperature is preferably 40 - 50 °C, the time is preferably 85 - 95 min, and the CO 2 flow rate is preferably 20.5 - 21.5 L / h. Using supercritical fluid to degrease rice bran can improve the degreasing efficiency, reduce the influence on subsequent protein extraction, and improve the protein extraction rate.

[0015] In this application, the degreased rice bran (extraction residue) is mixed with water and then ultrasonic treatment is carried out to accelerate the dissolution of proteins in the rice bran and effectively improve the protein extraction rate. In some specific implementation manners, the material - liquid ratio of the rice bran to water is preferably 1:5 - 15, more preferably 1:10. In some specific implementation manners, the power of the ultrasonic treatment is 200 - 220 W and the time is 20 - 30 min.

[0016] After the ultrasonic treatment, the obtained rice bran is enzymatically hydrolyzed. In this application, phytase is first used for the first enzymatic hydrolysis, and then a compound protease is used for the second enzymatic hydrolysis, which can make the obtained rice bran protein have higher solubility, emulsifying property, foaming property and foam stability. In some specific implementation manners, the enzyme activity of the phytase is preferably 3-10 U / mg. In some specific implementation manners, the compound enzyme includes trypsin, papain and subtilisin, and the mass ratio of trypsin, papain and subtilisin is preferably 1:1:1-5. In some specific implementation manners, the enzyme activity of the compound protease is 50-200 U / mg. In some specific implementation manners, the temperature of the first enzymatic hydrolysis is 40-50 °C, the pH value is 4.0-6.0, the time is 1-2 h, and the enzyme addition amount is 1 wt%-2 wt%. In some specific implementation manners, the temperature of the second enzymatic hydrolysis is 50-60 °C, the pH value is 7.0-8.0, the time is 1-2 h, and the enzyme addition amount is 0.2 wt%-0.6 wt%. In some specific implementation manners, after the first enzymatic hydrolysis is completed, there is also a step of inactivating the phytase, such as inactivating the enzyme in a boiling water bath for 10 min. In some specific implementation manners, after the second enzymatic hydrolysis is completed, there is also a step of inactivating the compound protease, such as inactivating the enzyme in a boiling water bath for 10 min.

[0017] After the enzymatic hydrolysis is completed, the enzymatically hydrolyzed solution is centrifuged, and the obtained supernatant is freeze-dried under vacuum to obtain crude rice bran protein. In some specific implementation manners, the rotation speed of the centrifugation is 3000-5000 r / min, preferably 3500-4500 r / min, the time is 5-20 min, preferably 10-15 min.

[0018] After obtaining the crude rice bran protein, it is purified, and preferably purified by a gel chromatography column. Specifically, the gel chromatography column can use Sephadex G-75 or Sephadex G-50 gel particles, which are swollen, packed into the column and equilibrated for later use. The crude rice bran protein is dissolved to form a solution of 5-15 mg / mL, preferably 10 mg / mL. After filtration through a 0.45 μm microporous membrane, it is loaded onto a pre-equilibrated Sephadex G-75 or Sephadex G-50 gel column (1.6×60 cm) for separation. The sample loading amount is preferably 1-5 mL, more preferably 2 mL; the flow rate is preferably 0.1-1.5 mL / min, more preferably 0.5 mL / min. The detection wavelength of the ultraviolet sampler is 220 nm, the eluent is 0.1 mol / L NaCl solution, and the main components are collected and freeze-dried under vacuum to obtain the purified rice bran protein.

[0019] After obtaining rice bran protein, it is characterized, and its extraction rate can reach more than 60%; the molecular weight of the rice bran protein is preferably 2-10 kDa, more preferably 3-8 kDa; the emulsifying power of the rice bran protein can reach more than 60%, the foaming property can reach more than 150%, and the foam stability can reach more than 75%.

[0020] The rice bran protein provided by the present invention can be used as a fat substitute in the food field, having good solubility, emulsifying property, foaming property and foam stability while obtaining low-fat food. Especially when used in ice cream, it can improve the overrun and anti-melting property of ice cream without affecting the overall sensory quality of ice cream, and reduce the production cost of ice cream.

[0021] The present invention also provides a low-fat ice cream, and its raw materials include:

[0022] 10 wt% - 20 wt% of milk-containing raw materials;

[0023] 5 wt% - 20 wt% of sweeteners;

[0024] 1 wt% - 10 wt% of thickeners;

[0025] 0.1 wt% - 5 wt% of emulsifying stabilizers;

[0026] 0.5 wt% - 10 wt% of the rice bran protein prepared by the above scheme;

[0027] The balance of water.

[0028] In some specific implementation manners, the milk-containing raw materials include skim milk and light cream, and the mass ratio of the skim milk to the cream is 6-10:4-6. In some specific implementation manners, the dosage of the milk-containing raw materials is 10 wt% - 16 wt%.

[0029] In some specific implementation manners, the sweeteners include, but are not limited to, one or more of granulated sugar, maltose, glucose, fructose, lactose, galactose, isomaltulose, xylo-oligosaccharide, fructo-oligosaccharide, L-arabinose, xylitol, lactitol, mannitol, sorbitol, erythritol, isomaltitol, sucralose, stevioside, aspartame, sodium saccharin, neotame, sodium cyclamate, acesulfame potassium; preferably granulated sugar. The dosage of the sweeteners is preferably 7-15 wt%, more preferably 8-12 wt%.

[0030] In some specific implementations, the thickener includes but is not limited to one or more of microcrystalline cellulose, carrageenan, xanthan gum, guar gum, locust bean gum, carboxymethyl cellulose, sodium carboxymethyl cellulose, sodium alginate, gum arabic, propylene glycol alginate and maltodextrin; preferably one or more of maltodextrin, guar gum and sodium carboxymethyl cellulose, more preferably a combination of maltodextrin, guar gum and sodium carboxymethyl cellulose. In some specific implementations, the thickener is a combination of maltodextrin, guar gum and sodium carboxymethyl cellulose, and the mass ratio of maltodextrin, guar gum and sodium carboxymethyl cellulose is preferably 3-5:0.3-0.5:0.1-0.3. The amount of the thickener is preferably 2-8wt%, more preferably 3-7wt%.

[0031] In some specific implementations, the emulsion stabilizer includes, but is not limited to, one or more of glyceryl monostearate, sucrose fatty acid ester, molecular distilled monoglyceride, polyglycerol fatty acid ester, lecithin, modified soybean lecithin, citric acid fatty acid glyceride and sorbitan monooleate, preferably glyceryl monostearate (monoglyceride). In some specific implementations, the amount of the emulsion stabilizer is preferably 0.2-1wt%, more preferably 0.3-0.5wt%.

[0032] In some specific implementations, the amount of rice bran protein is 0.5wt% to 10wt%, preferably 1 to 5wt%. The rice bran protein provided in the present application has good solubility, emulsification, foaming and foam stability, and can improve the expansion rate and melting resistance of ice cream without affecting the overall sensory quality of ice cream, thereby reducing the production cost of ice cream.

[0033] The present application also provides a method for preparing the low-fat ice cream, comprising the following steps:

[0034] Mixing the raw materials to obtain a feed liquid;

[0035] The material liquid is sterilized, homogenized, aged, frozen and hardened in sequence to obtain low-fat ice cream.

[0036] Specifically, the present application first mixes the sweetener, emulsifier stabilizer, and part of the thickener (such as sodium carboxymethyl cellulose) evenly and then dissolves them in warm water, then sequentially adds the milk-containing raw materials, other thickeners (such as maltodextrin, guar gum), etc., then adds rice bran protein, and makes up with enough water, and fully stirs until all the raw and auxiliary materials are dissolved to obtain a liquid.

[0037] After pasteurizing the liquid material, homogenization is carried out, and the pressure of the homogenization is 18-25 MPa; then it is preferably aged at 0-4 °C for 8-12 h, the aged liquid material is frozen in a freezer for 25-35 min, the discharging temperature is controlled at -4 °C to -8 °C, and it is hardened at -18 to -25 °C, then low-fat ice cream can be obtained.

[0038] In this application, the rice bran protein prepared by the above method is added to ice cream. On the one hand, it reduces the fat content of ice cream and increases its protein content, meeting the current development trend of consumers' health concepts; on the other hand, it can obtain a high expansion rate and a low melting rate on the basis of maintaining good sensory quality, and the effect is more significant than that of rice bran protein prepared by other methods, improving the quality of ice cream products.

[0039] This application uses rice bran as the raw material. First, the rice bran is defatted by the supercritical fluid extraction method, and then the defatted rice bran is mixed with water and subjected to ultrasonic treatment to accelerate the dissolution of proteins; the ultrasonic-treated rice bran is first enzymatically hydrolyzed for the first time under the action of phytase to remove the phytic acid cross-linked with proteins, and then enzymatically hydrolyzed for the second time under the action of compound protease, and then purified to obtain rice bran protein. The method provided by this application not only improves the extraction rate of rice bran protein, but also improves the solubility, emulsifying property, foaming property and foam stability of rice bran protein. Adding the rice bran protein prepared by the above method to ice cream can obtain a high expansion rate and a low melting rate on the basis of maintaining good sensory quality, and the effect is more significant than that of rice bran protein prepared by other methods. The test results show that by the method provided by this application, the extraction rate of rice bran protein can reach more than 60%; the molecular weight of rice bran protein is preferably 2-10 kDa, more preferably 3-8 kDa; the emulsifying power of rice bran protein can reach more than 60%, the foaming property can reach more than 150%, and the foam stability can reach more than 75%. Description of the Drawings

[0040] Figure 1 It is the solubility of the rice bran protein provided by the examples and comparative examples of this application. Detailed Embodiments

[0041] The present invention provides a preparation method of rice bran protein, low-fat ice cream and its preparation method. Those skilled in the art can draw on the content of this article and appropriately modify the process parameters to achieve. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art, and they are all regarded as included in the present invention. The methods and applications of the present invention have been described through preferred embodiments, and those related can obviously make changes or appropriate changes and combinations to the methods and applications in this article without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0042] Example 1

[0043] The preparation method of rice bran protein is as follows:

[0044] (1) Degreasing: First, screen and remove impurities such as sand, stones, and grass debris mixed in the rice bran, then crush and pass through a 40-mesh sieve to obtain rice bran powder. Using supercritical fluid extraction technology, under the conditions of a pressure of 30 MPa, a temperature of 40 °C, a time of 80 min, and a CO 2 flow rate of 20 L / h, degrease the rice bran powder.

[0045] (2) Ultrasonic treatment: Take the degreased rice bran obtained in step (1), add deionized water at a solid-liquid ratio of 1:10, stir evenly, then use an ultrasonic power of 200 W and ultrasonic treatment for 20 min to accelerate the dissolution of proteins.

[0046] (3) Enzymatic hydrolysis: Adjust the temperature of the solution obtained by ultrasonic treatment to 40 °C and the pH value to 4.0. First, add 1 wt% phytase (enzyme activity 5 U / mg) and react for 1 h to remove the phytic acid cross-linked with proteins. After completion, inactivate the enzyme in a boiling water bath for 10 min. Then adjust the solution temperature to 50 °C and the pH value to 7.0, add 0.2 wt% of a compound protease composed of trypsin, papain, and subtilisin with a mass ratio of 1:1:5 (enzyme activity 100 U / mg) and react for 1 h. After completion, inactivate the enzyme in a boiling water bath for 10 min, cool to room temperature, centrifuge at 4000 r / min for 10 min, and take the supernatant as the extracted rice bran protein, which is then freeze-dried under vacuum for standby.

[0047] (4) Purification: Purify the rice bran protein by gel filtration chromatography. Weigh Sephadex G-75 gel particles, swell, pack the column, and equilibrate. Configure the rice bran protein obtained in step (3) into a 10 mg / mL solution, filter it through a 0.45 μm microporous filter membrane, and then load it onto an equilibrated Sephadex G-75 gel column (1.6×60 cm) for separation. The sample loading volume is 2 mL, the flow rate is 0.5 mL / min, the detection wavelength of the ultraviolet sampler is 220 nm, the eluent is 0.1 mol / L NaCl solution, collect the main components and freeze-dry them under vacuum to obtain the purified rice bran protein.

[0048] The low-fat ice cream added with rice bran protein has the following formula (component content is in mass percentage): granulated sugar 8%, non-fat milk powder 10%, light cream 4%, maltodextrin 3%, rice bran protein 1%, sodium carboxymethylcellulose 0.3%, monoglyceride 0.3%, guar gum 0.1%, and the rest is deionized water; its preparation method includes the following steps:

[0049] (1) Weigh accurately white granulated sugar, sodium carboxymethyl cellulose, and monoglyceride, mix them evenly, add warm water to dissolve, then add skim milk powder, light cream, maltodextrin, and guar gum in sequence, and finally add rice bran protein powder. Make up the remaining amount with deionized water and stir thoroughly until all the raw and auxiliary materials are dissolved.

[0050] (2) Perform pasteurization on the feed liquid obtained in step (1), and then homogenize it under a pressure of 18 MPa.

[0051] (3) Age the homogenized feed liquid at 0 °C for 8 h.

[0052] (4) Inject the aged feed liquid into a freezer and freeze it for 25 min, controlling the discharge temperature to be -4 °C.

[0053] (5) Harden the ice cream obtained in step (4) at -18 °C to obtain the low-fat ice cream added with rice bran protein.

[0054] Example 2

[0055] The preparation method of rice bran protein is as follows:

[0056] (1) Defatting: First, screen and remove impurities such as sand, stones, and grass debris mixed in rice bran, then crush it through a 40-mesh sieve to obtain rice bran powder. Use the supercritical fluid extraction technology to defat the rice bran powder under the conditions of a pressure of 35 MPa, a temperature of 45 °C, a time of 90 min, and a CO 2 flow rate of 21 L / h.

[0057] (2) Ultrasonic treatment: Take the defatted rice bran obtained in step (1), add deionized water at a material-liquid ratio of 1:10, stir evenly, and then perform ultrasonic treatment at an ultrasonic power of 210 W for 25 min.

[0058] (3) Enzymatic hydrolysis: Adjust the temperature of the solution obtained by ultrasonic treatment to 45 °C and the pH value to 5.0. First, add 1.5 wt% phytase (enzyme activity 5 U / mg) and react for 1.5 h to remove the phytic acid cross-linked with proteins. After the reaction, inactivate the enzyme in a boiling water bath for 10 min. Then adjust the solution temperature to 55 °C and the pH value to 7.5, add 0.4 wt% of a compound protease composed of trypsin, papain, and subtilisin protease with a mass ratio of 1:1:5 (enzyme activity 100 U / mg) and react for 1.5 h. After the reaction, inactivate the enzyme in a boiling water bath for 10 min, cool to room temperature, centrifuge at 4000 r / min for 12 min, and take the supernatant as the extracted rice bran protein, which is reserved after vacuum freeze-drying.

[0059] (4) Purification: The rice bran protein was purified by gel filtration chromatography. Weigh Sephadex G-75 gel particles, and perform swelling, column packing, and equilibration. The rice bran protein obtained in step (3) was prepared into a 10 mg / mL solution, filtered through a 0.45 μm microporous filter membrane, and then loaded onto an equilibrated Sephadex G-75 gel column (1.6×60 cm) for separation. The sample loading volume was 2 mL, the flow rate was 0.5 mL / min, the detection wavelength of the ultraviolet sampler was 220 nm, the eluent was 0.1 mol / L NaCl solution, and the main components were collected and freeze-dried under vacuum to obtain the purified rice bran protein.

[0060] The low-fat ice cream added with rice bran protein has the following formula (component contents are in mass percentage): granulated sugar 10%, skim milk powder 8%, light cream 5%, maltodextrin 4%, rice bran protein 3%, sodium carboxymethylcellulose 0.4%, monoglyceride 0.4%, guar gum 0.2%, and the rest is deionized water; its preparation method includes the following steps:

[0061] (1) Accurately weigh granulated sugar, sodium carboxymethylcellulose, and monoglyceride, mix them evenly, add warm water to dissolve, then add skim milk powder, light cream, maltodextrin, and guar gum in sequence, and finally add rice bran protein powder. Make up the balance with deionized water and stir well until all the raw and auxiliary materials are melted.

[0062] (2) The material liquid obtained in step (1) was pasteurized and then homogenized under a pressure of 22 MPa.

[0063] (3) The homogenized material liquid was aged at 2°C for 10 h.

[0064] (4) The aged material liquid was injected into a freezing machine and frozen for 30 min, and the discharging temperature was controlled at -6°C.

[0065] (5) The ice cream obtained in step (4) was hardened at -22°C to obtain the low-fat ice cream added with rice bran protein.

[0066] Example 3:

[0067] The preparation method of the rice bran protein is as follows:

[0068] (1) Defatting: First, screen and remove impurities such as sand, stones, and grass debris mixed in the rice bran, then crush and pass through a 40-mesh sieve to obtain rice bran powder. Using supercritical fluid extraction technology, under the conditions of a pressure of 40 MPa, a temperature of 50°C, a time of 100 min, and a CO 2 flow rate of 22 L / h, the rice bran powder was defatted.

[0069] (2) Ultrasonic treatment: Take the defatted rice bran obtained in step (1), add deionized water at a solid-liquid ratio of 1:10, stir evenly, then carry out ultrasonic treatment at a power of 220 W for 30 min to accelerate the dissolution of proteins.

[0070] (3) Enzymatic hydrolysis: Adjust the temperature of the solution obtained by ultrasonic treatment to 50 °C and the pH value to 6.0. First, add 2 wt% phytase (enzyme activity 5 U / mg) and react for 2 h to remove the phytic acid cross-linked with proteins. After completion, inactivate the enzyme in a boiling water bath for 10 min. Then adjust the solution temperature to 60 °C and the pH value to 8.0, add 0.6 wt% of a compound protease composed of trypsin, papain, and subtilisin in a mass ratio of 1:1:5 (enzyme activity 100 U / mg) and react for 2 h. After completion, inactivate the enzyme in a boiling water bath for 10 min, cool to room temperature, centrifuge at 4000 r / min for 15 min, and take the supernatant as the extracted rice bran protein, which is then freeze-dried under vacuum for standby.

[0071] (4) Purification: Purify the rice bran protein by gel filtration chromatography. Weigh Sephadex G-75 gel particles, swell, pack the column, and equilibrate. Configure the rice bran protein obtained in step (3) into a 10 mg / mL solution, filter it through a 0.45 μm microporous filter membrane, and then load it onto an equilibrated Sephadex G-75 gel column (1.6×60 cm) for separation. The sample loading volume is 2 mL, the flow rate is 0.5 mL / min, the detection wavelength of the ultraviolet sampler is 220 nm, the eluent is 0.1 mol / L NaCl solution, collect the main components and freeze-dry them under vacuum to obtain the purified rice bran protein.

[0072] The low-fat ice cream added with rice bran protein has the following formula (component content is in mass percentage): white granulated sugar 12%, skim milk powder 6%, light cream 6%, maltodextrin 5%, rice bran protein 5%, sodium carboxymethylcellulose 0.5%, monoglyceride 0.5%, guar gum 0.3%, and the rest is deionized water; its preparation method includes the following steps:

[0073] (1) Accurately weigh white granulated sugar, sodium carboxymethylcellulose, and monoglyceride, mix them evenly, add warm water to dissolve, then successively add skim milk powder, light cream, maltodextrin, and guar gum, and finally add rice bran protein powder, make up the balance with deionized water, and stir thoroughly until all the raw materials are dissolved.

[0074] (2) Pasteurize the feed liquid obtained in step (1), and then homogenize it under a pressure of 25 MPa.

[0075] (3) Age the homogenized feed liquid at 4 °C for 12 h.

[0076] (4) Inject the aged feed liquid into a freezer and freeze for 35 min, controlling the discharge temperature to -8 °C.

[0077] (5) Harden the ice cream obtained in step (4) at -25°C to obtain the low-fat ice cream added with rice bran protein.

[0078] Comparative Example 1

[0079] Compared with Example 3, the difference in Comparative Example 1 is that the extraction of rice bran protein does not go through ultrasonic treatment, phytase and compound protease are not added, and 3 wt% of Alcalase 2.4L alkaline protease (enzyme activity 200 U / mg) is used for enzymatic hydrolysis at 60°C and pH 8.0 for 2 h.

[0080] Comparative Example 2

[0081] Compared with Example 3, the difference in Comparative Example 2 is that rice bran protein is not added in the preparation formula of the ice cream, and 11% of skim milk powder is added.

[0082] Comparative Example 3

[0083] Compared with Example 3, the difference in Comparative Example 3 is that modified rice bran protein is used instead of rice bran protein, and the modified rice bran protein is prepared according to the following method:

[0084] Disperse the rice bran protein prepared in Example 3 in water under magnetic stirring, and obtain a rice bran protein dispersion after overnight hydration; after adjusting the pH value of the rice bran protein dispersion to 2.0 with 1 mol / L hydrochloric acid solution, heat it in a 92°C water bath for 10 h, and immediately place it in an ice bath to cool to room temperature after heating to obtain modified rice bran fiber.

[0085] Test Example 1

[0086] Determine the protein content in the sample according to the first method of GB 5009.5-2010, calculate the extraction rate and solubility of the rice bran protein obtained in Example 3 and Comparative Example 1, and analyze the molecular weight of the protein by SDS-PAGE electrophoresis; measure the emulsifying power, foaming property and foam stability of Examples 1-3, Comparative Example 1 and Comparative Example 3, and the results are as follows:

[0087] (1) Protein extraction rate: The protein extraction rate is calculated according to the following formula:

[0088] Protein extraction rate = protein content in the extract / total protein content in the sample × 100%;

[0089] The results are shown in Table 1.

[0090] Table 1 Extraction rate of rice bran protein

[0091] Sample Extraction rate (%) Example 3 61.64±2.58 Comparative Example 1 49.68±2.12

[0092] (2) Solubility: Prepare a 0.05 g / mL rice bran protein solution, adjust the pH of the solution to 2, 3, 4, 5, 6, 7, 8, 9, 10, stir for 1 h at 25 °C, and centrifuge at 3000 r / min for 20 min. The solubility of the protein is calculated according to the following formula:

[0093] Solubility = Protein content in supernatant / Total protein content in sample × 100%

[0094] The results are shown in Figure 1 , Figure 1 which is the solubility of the rice bran protein provided in the examples and comparative examples of this application.

[0095] (3) Prepare a 0.05 g / mL rice bran protein solution, add an equal amount of peanut oil, stir with a high-speed dispersing homogenizer at 8000 r / min for 2 min, and then measure the volume of the emulsion at this time. Centrifuge the emulsion at 2000 r / min for 5 min, measure the volume of the emulsion layer at this time, and the emulsifying power is calculated according to the following formula:

[0096] Emulsifying power = Volume of emulsion layer / Volume of emulsion × 100%

[0097] The results are shown in Table 2, and Table 2 shows the emulsifying property, foaming property, and foam stability of the rice bran protein.

[0098] (4) Foaming property and foam stability:

[0099] Prepare a 0.05 g / mL rice bran protein solution, homogenize it with a high-speed dispersing homogenizer at a rotation speed of 8000 r / min for 2 min, and then record the foam volume. After standing for 30 min, measure the foam volume again, and the foaming property is calculated according to the following formula:

[0100] Foaming property = Foam volume / Initial volume of solution × 100%;

[0101] Foam stability = Foam volume after 30 min / Initial foam volume × 100%;

[0102] The results are shown in Table 2, and Table 2 shows the emulsifying property, foaming property, and foam stability of the rice bran protein.

[0103] Table 2 Emulsifying property, foaming property, and foam stability of rice bran protein

[0104] Sample Emulsifying power (%) Foaming capacity (%) Foam stability (%) Example 1 59.13±2.62 133.12±2.92 75.27±1.91 Example 2 62.55±3.11 151.92±3.44 78.02±4.73 Example 3 61.02±3.58 153.41±3.97 78.64±4.51 Comparative Example 1 54.77±2.69 117.12±3.03 64.27±2.09 Comparative Example 3 57.09±1.98 162.21±3.25 72.24±3.31

[0105] (5) SDS-PAGE electrophoresis analysis

[0106] The molecular weight of the protein was determined and analyzed by SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis) technology. The results showed that the molecular weight of the rice bran protein obtained in Example 3 was about 3.5 kDa, and the molecular weight of the rice bran protein obtained in Comparative Example 1 was about 12.7 kDa. Therefore, the molecular weight of the rice bran protein extracted by the method described in the present invention is smaller than that of the rice bran protein obtained by the traditional extraction method, and small molecule proteins are more conducive to human digestion and absorption.

[0107] Table 1, Table 2 and Figure 1 The results showed that, compared with Comparative Example 1, the extraction rate and solubility of the rice bran protein obtained in Example 3 were increased, and the emulsifying property, foaming property and foam stability were all enhanced. Compared with Comparative Example 3, the emulsifying property and foam stability of Examples 1 to 3 were better. In summary, by using the method for extracting and purifying rice bran protein described in the present invention, the extraction rate of rice bran protein can be increased, the functional properties of rice bran protein can be improved, and it is more suitable for application in the food field.

[0108] Test Example 2

[0109] The sensory scores of the ice creams prepared in Examples 1 to 3 and Comparative Examples 2 to 3 were evaluated, and the overrun rate and melting rate were measured. The results are as follows.

[0110] (1) Sensory evaluation: Considering factors such as the color, taste, smell, texture, and mouthfeel of the ice cream, 10 professional ice cream tasters were invited to give scores after tasting, and the average value was taken. The full score was 10 points. The scoring criteria are shown in Table 3, and Table 3 is the sensory scoring criteria for the ice creams obtained in the examples and comparative examples.

[0111] Table 3 Sensory Scoring Criteria for Ice Cream

[0112]

[0113] (2) Overrun rate measurement: Weigh the ice cream mixture before and after freezing with the same volume, and the ratio of the mass change to the mass of the taken ice cream is the overrun rate.

[0114] (3) Melting rate measurement: Place the ice cream in an incubator at 26 °C for 30 min, weigh the melted ice cream, and the ratio of the melted amount of the ice cream to the original mass of the ice cream is the melting rate.

[0115] The results are shown in Table 4, and Table 4 is the results of the sensory evaluation and index measurement of the ice cream.

[0116] Table 4 Results of Sensory Evaluation and Index Measurement of Ice Cream

[0117] Group Sensory score Swelling ratio Melting rate Example 1 8.3 62.75％ 24.52％ Example 2 8.4 63.28％ 21.33％ Example 3 8.2 61.79％ 23.74％ Comparative Example 2 8.4 54.66％ 30.41％ Comparative Example 3 8.2 56.27％ 28.44％

[0118] As can be seen from Table 4, the ice creams prepared in Examples 1 to 3 showed good acceptability in the sensory evaluation, and the sensory quality was not significantly affected. The overrun and anti-melting properties were superior to those of Comparative Example 2 and Comparative Example 3, indicating that the addition of rice bran protein improved the overrun and anti-melting properties of the ice cream without affecting the overall sensory quality, and Example 2 had better effects. Compared with the modified rice bran protein (Comparative Example 3), rice bran protein showed better overrun and anti-melting properties when applied to ice cream.

[0119] Determination of main nutritional components: The nutritional components of Examples 1 to 3 and Comparative Example 2 were analyzed, and the results are shown in Table 5, which is the determination result of the nutritional components of the ice cream. Among them, the total solids were determined with reference to GB / T 31321-2014 "Inspection Methods for Frozen Drinks"; the protein was determined by the first method of GB 5009.6-2016; the fat was determined by the second method of GB 5009.6-2016; the total sugar was determined by the first method of GB 5009.8-2016.

[0120] Table 5 Determination results of the nutritional components of the ice cream

[0121]

[0122] As shown in Table 5, compared with Comparative Example 2, the fat content of the ice creams in Examples 1 to 3 decreased, while the protein content increased.

[0123] In summary, the sensory quality of the ice cream added with rice bran protein is comparable to that of the ice cream added with whole milk powder, the overrun and anti-melting properties are improved, the fat content is low, the protein content is high, the cost is reduced, and there is great room for research and development and application.

[0124] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of rice bran protein, characterized in that, it comprises the following steps: A) Using supercritical fluid extraction method to degrease rice bran; B) Mixing the degreased rice bran with water and then performing ultrasonic treatment; C) First subjecting the ultrasonically treated rice bran to a first enzymatic hydrolysis under the action of phytase, and then subjecting it to a second enzymatic hydrolysis under the action of compound protease; D) Purifying the crude rice bran protein after enzymatic hydrolysis.

2. The preparation method according to claim 1, characterized in that, In step A), the supercritical fluid is supercritical CO 2 , the pressure of the supercritical extraction is 25 to 45 MPa, the temperature is 35 to 55 °C, the time is 80 to 100 min, and the CO 2 flow rate is 20 to 22 L / h.

3. The preparation method according to claim 2, characterized in that, Before supercritical fluid extraction, it also includes: removing impurities and pulverizing the rice bran.

4. The preparation method according to claim 1, characterized in that, In the step B), the material-liquid ratio of the rice bran to water is 1:5 - 15; the ultrasonic power is 200 - 220 W, and the ultrasonic time is 20 - 30 min.

5. The preparation method according to claim 1, characterized in that, In the step C), the temperature of the first enzymatic hydrolysis is 40 - 50 °C, the pH value is 4.0 - 6.0, the time is 1 - 2 h, and the enzyme addition amount is 1 wt% - 2 wt%; The temperature of the second enzymatic hydrolysis is 50 - 60 °C, the pH value is 7.0 - 8.0, the time is 1 - 2 h, and the enzyme addition amount is 0.2 wt% - 0.6 wt%; the compound protease includes trypsin, papain, and subtilisin.

6. The preparation method according to claim 5, characterized in that, it also includes: Centrifuging the solution after the second enzymatic hydrolysis, and vacuum freeze-drying the obtained supernatant to obtain the crude rice bran protein.

7. The preparation method according to claim 1, characterized in that, The step D) is specifically: Purifying the crude rice bran protein using a gel chromatography column.

8. The rice bran protein prepared by the method according to any one of claims 1 - 7.

9. A low-fat ice cream, characterized in that, its raw materials include: 10 wt% - 20 wt% of milk-containing raw materials; 5 wt% - 20 wt% of sweeteners; 1 wt% - 10 wt% of thickeners; 0.1 wt% - 5 wt% of emulsifying stabilizers; 0.5 wt% - 10 wt% of the rice bran protein prepared by the method according to any one of claims 1 - 7 or the rice bran protein according to claim 8; The balance is water.

10. The low-fat ice cream according to claim 9, characterized in that, The milk-containing raw materials include skim milk and light cream, and the mass ratio of the skim milk to the cream is 6 - 10:4 - 6; The sweeteners are selected from one or more of white granulated sugar, maltose, glucose, fructose, lactose, galactose, isomaltulose, xylo-oligosaccharide, fructo-oligosaccharide, L-arabinose, xylitol, lactitol, mannitol, sorbitol, erythritol, isomaltitol, sucralose, stevioside, aspartame, sodium saccharin, neotame, sodium cyclamate, and acesulfame potassium; The thickeners are selected from one or more of microcrystalline cellulose, carrageenan, xanthan gum, guar gum, locust bean gum, carboxymethyl cellulose, sodium carboxymethyl cellulose, sodium alginate, gum arabic, propylene glycol alginate, and maltodextrin; The emulsifying stabilizer is selected from one or more of glycerol monostearate, sucrose fatty acid ester, molecular distilled monoglyceride, polyglycerol fatty acid ester, lecithin, modified soybean phospholipid, citric acid fatty acid glyceride and sorbitan monooleate.

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