Low-fat compound protein solid beverage and preparation method thereof

Abstract

The invention belongs to the technical field of food, and particularly relates to a low-fat compound protein solid beverage and a preparation method thereof. The soybean protein isolate powder and the skimmed milk powder are used as main components of the compound protein powder, and are combined to provide high protein content and maintain the characteristic of low fat, so that the compound protein powder conforms to the pursuit of consumers for healthy diet. Through glycosylation, galactooligosaccharide and other sugar molecules are introduced to the surface of the whey protein, the hydrophilicity of the whey protein is greatly improved, the glycosylated whey protein and the chitosan are used for crosslinking, the compound protein powder is embedded, and a microcapsule shell with strength and stability is formed. The glycosylated whey protein has a better emulsifying characteristic, which is beneficial for uniformly forming an emulsion in the process of compounding with chitosan, so that a uniform and compact microcapsule shell layer is constructed in a cross-linking reaction. The compactness of the microcapsule shell is beneficial to covering peculiar smell, improving the solubility and controlling the release of active ingredients for embedding the vegetable protein.

Description

Technical Field

[0001] The invention belongs to the technical field of food, and in particular relates to a low-fat composite protein solid beverage and a preparation method thereof. Background Art

[0002] In recent years, with the continuous improvement of people's health awareness, consumers' demand for high-protein, low-fat foods and beverages has been growing. Protein is an essential nutrient for the human body and plays an important role in maintaining body functions, promoting muscle growth and repairing tissues. However, traditional high-protein foods and beverages often contain high fat and sugar, which is not suitable for the low-fat healthy diet concept pursued by modern people. Therefore, the development of a low-fat compound protein solid beverage to meet consumers' needs for balanced nutrition and health has important market potential.

[0003] Compound protein solid beverages are instant drinkable products made from a variety of protein sources through powder processing. This type of beverage can provide a variety of amino acids, has high nutritional value, and has the advantages of being easy to carry and having a long storage period. Common compound proteins include animal proteins (such as whey protein, casein) and plant proteins (such as soy protein, pea protein, rice protein, etc.). Compared with single proteins, compound proteins have better amino acid balance and absorption efficiency. In order to meet the needs of different consumers, low-fat solid beverages based on plant proteins have also appeared on the market to reduce fat content and enhance their health attributes.

[0004] However, the research and development of low-fat compound protein solid beverages faces a series of technical challenges. First of all, plant proteins usually have odor problems, such as soy protein has a beany smell and pea protein has a grassy smell, which will seriously affect the taste of the product and consumer acceptance. Although traditional deodorization methods such as water washing, acid-base treatment and fermentation can reduce odor to a certain extent, they often have an adverse effect on the solubility and functionality of the protein. In addition, plant protein has poor solubility and is prone to precipitation and agglomeration during processing and mixing, affecting the texture and taste of the product. Therefore, how to remove the odor of plant protein and improve the solubility of protein is a key problem in the research and development of low-fat compound protein solid beverages.

[0005] Secondly, in order to improve the nutritional value and taste of low-fat compound protein solid beverages, it is often necessary to add other functional ingredients to the product, such as dietary fiber, vitamins, minerals, etc. However, the physical and chemical properties of different ingredients vary, which can easily lead to unevenness during mixing and processing, affecting the stability and solubility of the product. At the same time, the added dietary fiber may increase the viscosity of the powder, further reducing the solubility and taste of the beverage. Therefore, how to reasonably add various ingredients to compound protein solid beverages, maintain the low-fat characteristics and nutritional balance of the product, and ensure good taste and solubility, is a comprehensive technical challenge.

[0006] In order to solve the above problems, this patent provides a low-fat composite protein solid beverage and its preparation method. By optimizing the raw material formula, adopting a specific deodorization process and modification technology, and combining appropriate processing and drying methods, the problem of peculiar smell and poor solubility of plant protein is solved to a certain extent. The present invention can not only remove the peculiar smell of plant protein, improve the taste and consumer acceptance of low-fat composite protein solid beverages, but also maintain the high solubility and functionality of protein, and provide the market with a composite protein solid beverage with high nutritional value, low fat and good taste. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides a low-fat composite protein solid beverage and a preparation method thereof.

[0008] A method for preparing a low-fat composite protein solid beverage comprises the following steps:

[0009] (1) Preparation of glycosylated whey protein: whey protein and galacto-oligosaccharide are mixed in a mass ratio of 1:4 to obtain a reactant A; the reactant A is dissolved in a phosphate buffer solution, wherein the concentration of the buffer solution is 0.1 M, the pH value is 7.0, and the mass ratio of the reactant A to the phosphate buffer solution is 1:(5-10) to obtain a reaction solution; the reaction solution is freeze-dried to obtain a freeze-dried powder; the freeze-dried powder is then subjected to a glycosylation reaction at 50-60° C. for 48-120 h to obtain a glycosylated whey protein;

[0010] (2) Preparation of chitosan solution: adding chitosan to a 1-2 wt % acetic acid solution and stirring until completely dissolved to form a chitosan solution with a concentration of 1-2 wt %; placing the chitosan solution in an ultrasonic disperser for 3-5 min to remove bubbles in the solution to obtain a uniform chitosan solution;

[0011] (3) Preparation of a glycosylated whey protein solution: adding the glycosylated whey protein to water and stirring until it is completely dissolved to form a glycosylated whey protein solution with a concentration of 5-10 wt %;

[0012] (4) Adding an emulsifier and a composite protein: Adding gum arabic and a composite protein powder to the glycosylated whey protein solution obtained in step (3), wherein the amount of gum arabic added is 0.5-2wt% of the mass of the glycosylated whey protein, and the amount of the composite protein powder added is 15-20wt% of the mass of the glycosylated whey protein solution, and stirring uniformly to obtain a reaction precursor;

[0013] (5) Mixing the reaction precursor and chitosan: under stirring conditions, the reaction precursor obtained in step (4) is added dropwise to the uniform chitosan solution obtained in step (2) at a rate of 5-10 ml / min, and continuous stirring is maintained during the addition process to ensure the uniformity of the mixed solution. At this time, the glycosylated whey protein and chitosan form an initial complex through electrostatic interaction;

[0014] (6) Cross-linking formation of microcapsules: adding a 0.5-1wt% calcium chloride solution to the initial complex obtained in step (5) at a rate of 5-10 ml / min, wherein the amount of calcium chloride solution added is 5-10% of the volume of the initial complex, and stirring is continued for 1-2 hours at room temperature to ensure that the cross-linking reaction is fully carried out to form stable chitosan-glycosylated whey protein microcapsules; filtering, washing, and freeze-drying to obtain the low-fat complex protein solid beverage.

[0015] The composite protein powder is prepared by mixing isolated soy protein powder and skimmed milk powder in a mass ratio of (2-9):1.

[0016] The present invention uses soy protein isolate powder and skim milk powder as the main components of the composite protein powder. The combination of the two can provide a high protein content while maintaining the characteristics of low fat, which meets the consumer's pursuit of a healthy diet. The fat content in skim milk powder is relatively low, and it can be prepared with soy protein isolate to produce a low-fat composite food protein with good nutritional value. Soy protein isolate contains plant ingredients such as isoflavones and saponins, which have potential effects on cardiovascular health. Skim milk powder contains nutrients such as calcium, phosphorus, and vitamin B, which help to enhance multiple nutrients such as the newborn and immune systems. The combination of the two can provide rich nutrients and enhance the functionality of the product.

[0017] In order to improve the solubility and mouthfeel of the composite protein, the present invention introduces sugar molecules such as oligogalactose on the surface of whey protein by glycosylation, greatly improving the hydrophilicity of whey protein, which enhances the solubility of whey protein in aqueous solution. In addition, the introduction of glycosylation not only improves the hydrophilicity of whey protein, but also provides additional reaction sites for molecular protein, promoting the combination with chitosan. Through hydrogen bonds, van der Waals forces and electrostatic response, a tighter network can be constructed between chitosan and glycosylated whey protein. When calcium chloride is added, the cross-linked network between chitosan molecules is further strengthened, and glycosylated whey protein, as a cross-linked structure, is better embedded in the chitosan cross-linked network, thereby forming a microcapsule shell with strength and stability. Whey protein after glycosylation has better emulsifying properties, which is conducive to uniformly forming an emulsion in the process of compounding with chitosan, thereby constructing a uniform and dense microcapsule shell in the cross-linking reaction. The compactness of the microcapsule shell is helpful for embedding plant protein to cover up peculiar smell, improve solubility and control the release of active ingredients. As a result, a low-fat compound protein solid beverage with good solubility and excellent taste was obtained.

[0018] Beneficial effects of the present invention:

[0019] The present invention adopts soy protein isolate powder and skim milk powder as the main components of composite protein powder. The combination of the two can provide high protein content while maintaining the characteristics of low fat, which meets the consumer's pursuit of healthy diet. The present invention introduces sugar molecules such as oligosaccharides on the surface of whey protein through glycosylation, greatly improving the hydrophilicity of whey protein, and cross-linking with glycosylated whey protein and chitosan to embed the composite protein powder to form a microcapsule shell with strength and stability. The glycosylated whey protein has better emulsifying properties, which is conducive to uniformly forming an emulsion during the composite process with chitosan, thereby constructing a uniform and dense microcapsule shell layer in the cross-linking reaction. The density of the microcapsule shell is helpful for embedding plant protein to cover up peculiar smell, improve solubility and control the release of active ingredients. Thus, a low-fat composite protein solid beverage with good solubility and excellent taste is obtained. DETAILED DESCRIPTION

[0020] Whey protein, product number: JK-007, Nanjing Jinke Biotechnology Co., Ltd.

[0021] Galacto-oligosaccharide, product number: QF5628, Hubei Qifei Pharmaceutical Chemical Co., Ltd.

[0022] Chitosan, model: CP2020, Xi'an Tianzheng Pharmaceutical Excipients Co., Ltd.

[0023] Gum Arabic, product number: 12478, Hebei Yaxin Biotechnology Co., Ltd.

[0024] Soy protein isolate powder, item number: 451231, Hebei Tuohai Biotechnology Co., Ltd.

[0025] Skim milk powder, item number: 929607, Anhui Zhonghong Bioengineering Co., Ltd.

[0026] Example 1

[0027] A method for preparing a low-fat composite protein solid beverage comprises the following steps:

[0028] (1) Preparation of glycosylated whey protein: whey protein and galacto-oligosaccharide are mixed in a mass ratio of 1:4 to obtain a reactant A; the reactant A is dissolved in a phosphate buffer solution, the concentration of the buffer solution is 0.1 M, the pH value is 7.0, and the mass ratio of the reactant A to the phosphate buffer solution is 1:6 to obtain a reaction solution; the reaction solution is freeze-dried to obtain a freeze-dried powder; the freeze-dried powder is then subjected to a glycosylation reaction at 60° C. for 96 hours to obtain a glycosylated whey protein;

[0029] (2) Preparation of chitosan solution: chitosan was added to a 1.4 wt% acetic acid solution and stirred until completely dissolved to form a chitosan solution with a concentration of 2 wt%; the chitosan solution was placed in an ultrasonic disperser for 4 min to obtain a uniform chitosan solution;

[0030] (3) Preparation of a glycosylated whey protein solution: adding the glycosylated whey protein to water and stirring until it is completely dissolved to form a glycosylated whey protein solution with a concentration of 8 wt %;

[0031] (4) Adding an emulsifier and a composite protein: Adding gum arabic and a composite protein powder to the glycosylated whey protein solution obtained in step (3), wherein the amount of gum arabic added is 1 wt % of the mass of the glycosylated whey protein, and the amount of the composite protein powder added is 18 wt % of the mass of the glycosylated whey protein solution; stirring uniformly to obtain a reaction precursor;

[0032] (5) Mixing the reaction precursor and chitosan: under stirring conditions, the reaction precursor obtained in step (4) is added dropwise to the uniform chitosan solution obtained in step (2) at a rate of 6 ml / min, and stirring is maintained during the dropping process to obtain an initial composite;

[0033] (6) Cross-linking formation of microcapsules: A 0.6 wt% calcium chloride solution was added dropwise to the initial complex obtained in step (5) at a rate of 6 ml / min, wherein the amount of calcium chloride solution added was 7% of the volume of the initial complex. The mixture was stirred for 2 h at room temperature, filtered, washed, and freeze-dried to obtain the low-fat composite protein solid beverage.

[0034] The composite protein powder is prepared by mixing isolated soy protein powder and skimmed milk powder in a mass ratio of 4:1.

[0035] Example 2

[0036] A method for preparing a low-fat composite protein solid beverage comprises the following steps:

[0037] (1) Preparation of glycosylated whey protein: whey protein and galacto-oligosaccharide are mixed in a mass ratio of 1:4 to obtain a reactant A; the reactant A is dissolved in a phosphate buffer solution, the concentration of the buffer solution is 0.1 M, the pH value is 7.0, and the mass ratio of the reactant A to the phosphate buffer solution is 1:6 to obtain a reaction solution; the reaction solution is freeze-dried to obtain a freeze-dried powder; the freeze-dried powder is then subjected to a glycosylation reaction at 60° C. for 96 hours to obtain a glycosylated whey protein;

[0038] (2) Preparation of chitosan solution: chitosan was added to a 1.4 wt% acetic acid solution and stirred until completely dissolved to form a chitosan solution with a concentration of 2 wt%; the chitosan solution was placed in an ultrasonic disperser for 4 min to obtain a uniform chitosan solution;

[0039] (3) Preparation of a glycosylated whey protein solution: adding the glycosylated whey protein to water and stirring until it is completely dissolved to form a glycosylated whey protein solution with a concentration of 8 wt %;

[0040] (4) Adding an emulsifier and a composite protein: adding composite protein powder to the glycosylated whey protein solution obtained in step (3), wherein the amount of the composite protein powder added is 18 wt % of the mass of the glycosylated whey protein solution, and stirring uniformly to obtain a reaction precursor;

[0041] (5) Mixing the reaction precursor and chitosan: under stirring conditions, the reaction precursor obtained in step (4) is added dropwise to the uniform chitosan solution obtained in step (2) at a rate of 6 ml / min, and stirring is maintained during the dropping process to obtain an initial composite;

[0042] (6) Cross-linking formation of microcapsules: A 0.6 wt% calcium chloride solution was added dropwise to the initial complex obtained in step (5) at a rate of 6 ml / min, wherein the amount of calcium chloride solution added was 7% of the volume of the initial complex. The mixture was stirred for 2 h at room temperature, filtered, washed, and freeze-dried to obtain the low-fat composite protein solid beverage.

[0043] The composite protein powder is prepared by mixing isolated soy protein powder and skimmed milk powder in a mass ratio of 4:1.

[0044] Example 3

[0045] A method for preparing a low-fat composite protein solid beverage comprises the following steps:

[0046] (1) Preparation of glycosylated whey protein: mixing whey protein and galacto-oligosaccharide in a mass ratio of 1:4 to obtain a reactant A; performing a glycosylation reaction of the reactant A at 60° C. for 96 hours to obtain a glycosylated whey protein;

[0047] (2) Preparation of chitosan solution: chitosan was added to a 1.4 wt% acetic acid solution and stirred until completely dissolved to form a chitosan solution with a concentration of 2 wt%; the chitosan solution was placed in an ultrasonic disperser for 4 min to obtain a uniform chitosan solution;

[0048] (3) Preparation of a glycosylated whey protein solution: adding the glycosylated whey protein to water and stirring until it is completely dissolved to form a glycosylated whey protein solution with a concentration of 8 wt %;

[0049] (4) Adding an emulsifier and a composite protein: Adding gum arabic and a composite protein powder to the glycosylated whey protein solution obtained in step (3), wherein the amount of gum arabic added is 1 wt % of the mass of the glycosylated whey protein, and the amount of the composite protein powder added is 18 wt % of the mass of the glycosylated whey protein solution; stirring uniformly to obtain a reaction precursor;

[0050] (5) Mixing the reaction precursor and chitosan: under stirring conditions, the reaction precursor obtained in step (4) is added dropwise to the uniform chitosan solution obtained in step (2) at a rate of 6 ml / min, and stirring is maintained during the dropping process to obtain an initial composite;

[0051] (6) Cross-linking formation of microcapsules: A 0.6 wt% calcium chloride solution was added dropwise to the initial complex obtained in step (5) at a rate of 6 ml / min, wherein the amount of calcium chloride solution added was 7% of the volume of the initial complex. The mixture was stirred for 2 h at room temperature, filtered, washed, and freeze-dried to obtain the low-fat composite protein solid beverage.

[0052] The composite protein powder is prepared by mixing isolated soy protein powder and skimmed milk powder in a mass ratio of 4:1.

[0053] Example 4

[0054] A method for preparing a low-fat composite protein solid beverage comprises the following steps:

[0055] (1) Preparation of glycosylated whey protein: whey protein and galacto-oligosaccharide are mixed in a mass ratio of 1:4 to obtain reactant A; reactant A is dissolved in a phosphate buffer solution, wherein the concentration of the buffer solution is 0.1 M, the pH value is 7.0, and the mass ratio of reactant A to phosphate buffer solution is 1:6 to obtain a reaction solution; the reaction solution is freeze-dried to obtain a freeze-dried powder; the freeze-dried powder is then subjected to a glycosylation reaction at 80° C. for 96 hours to obtain glycosylated whey protein;

[0056] (2) Preparation of chitosan solution: chitosan was added to a 1.4 wt% acetic acid solution and stirred until completely dissolved to form a chitosan solution with a concentration of 2 wt%; the chitosan solution was placed in an ultrasonic disperser for 4 min to obtain a uniform chitosan solution;

[0057] (3) Preparation of a glycosylated whey protein solution: adding the glycosylated whey protein to water and stirring until it is completely dissolved to form a glycosylated whey protein solution with a concentration of 8 wt %;

[0058] (4) Adding an emulsifier and a composite protein: Adding gum arabic and a composite protein powder to the glycosylated whey protein solution obtained in step (3), wherein the amount of gum arabic added is 1 wt % of the mass of the glycosylated whey protein, and the amount of the composite protein powder added is 18 wt % of the mass of the glycosylated whey protein solution; stirring uniformly to obtain a reaction precursor;

[0059] (5) Mixing the reaction precursor and chitosan: under stirring conditions, the reaction precursor obtained in step (4) is added dropwise to the uniform chitosan solution obtained in step (2) at a rate of 6 ml / min, and stirring is maintained during the dropping process to obtain an initial composite;

[0060] (6) Cross-linking formation of microcapsules: A 0.6 wt% calcium chloride solution was added dropwise to the initial complex obtained in step (5) at a rate of 6 ml / min, wherein the amount of calcium chloride solution added was 7% of the volume of the initial complex. The mixture was stirred for 2 h at room temperature, filtered, washed, and freeze-dried to obtain the low-fat composite protein solid beverage.

[0061] The composite protein powder is prepared by mixing isolated soy protein powder and skimmed milk powder in a mass ratio of 4:1.

[0062] Example 5

[0063] A method for preparing a low-fat composite protein solid beverage comprises the following steps:

[0064] (1) Preparation of glycosylated whey protein: whey protein and galacto-oligosaccharide are mixed in a mass ratio of 1:4 to obtain a reactant A; the reactant A is dissolved in a phosphate buffer solution, wherein the concentration of the buffer solution is 0.1 M, the pH value is 7.0, and the mass ratio of the reactant A to the phosphate buffer solution is 1:6 to obtain a reaction solution; the reaction solution is freeze-dried to obtain a freeze-dried powder; the freeze-dried powder is then subjected to a glycosylation reaction at 50° C. for 96 hours to obtain a glycosylated whey protein;

[0065] (2) Preparation of chitosan solution: chitosan was added to a 1.4 wt% acetic acid solution and stirred until completely dissolved to form a chitosan solution with a concentration of 2 wt%; the chitosan solution was placed in an ultrasonic disperser for 4 min to obtain a uniform chitosan solution;

[0066] (3) Preparation of a glycosylated whey protein solution: adding the glycosylated whey protein to water and stirring until it is completely dissolved to form a glycosylated whey protein solution with a concentration of 8 wt %;

[0067] (4) Adding an emulsifier and a composite protein: Adding gum arabic and a composite protein powder to the glycosylated whey protein solution obtained in step (3), wherein the amount of gum arabic added is 1 wt % of the mass of the glycosylated whey protein, and the amount of the composite protein powder added is 18 wt % of the mass of the glycosylated whey protein solution; stirring uniformly to obtain a reaction precursor;

[0068] (5) Mixing the reaction precursor and chitosan: under stirring conditions, the reaction precursor obtained in step (4) is added dropwise to the uniform chitosan solution obtained in step (2) at a rate of 6 ml / min, and stirring is maintained during the dropping process to obtain an initial composite;

[0069] (6) Cross-linking formation of microcapsules: A 0.6 wt% calcium chloride solution was added dropwise to the initial complex obtained in step (5) at a rate of 6 ml / min, wherein the amount of calcium chloride solution added was 7% of the volume of the initial complex. The mixture was stirred for 2 h at room temperature, filtered, washed, and freeze-dried to obtain the low-fat composite protein solid beverage.

[0070] The composite protein powder is prepared by mixing isolated soy protein powder and skimmed milk powder in a mass ratio of 4:1.

[0071] Comparative Example 1

[0072] A method for preparing a low-fat composite protein solid beverage comprises the following steps:

[0073] (1) Preparation of chitosan solution: chitosan was added to a 1.4 wt% acetic acid solution and stirred until completely dissolved to form a chitosan solution with a concentration of 2 wt%; the chitosan solution was placed in an ultrasonic disperser for 4 min to obtain a uniform chitosan solution;

[0074] (2) Preparation of whey protein solution: adding whey protein into water and stirring until completely dissolved to form a whey protein solution with a concentration of 8 wt %;

[0075] (3) Adding an emulsifier and a composite protein: Adding gum arabic and a composite protein powder to the whey protein solution obtained in step (2), wherein the amount of gum arabic added is 1 wt % of the mass of the whey protein, and the amount of the composite protein powder added is 18 wt % of the mass of the whey protein solution; stirring uniformly to obtain a reaction precursor;

[0076] (4) Mixing the reaction precursor and chitosan: under stirring conditions, the reaction precursor obtained in step (3) is added dropwise to the uniform chitosan solution obtained in step (1) at a rate of 6 ml / min, and stirring is maintained during the dropping process to obtain an initial composite;

[0077] (5) Cross-linking formation of microcapsules: A 0.6 wt% calcium chloride solution was added dropwise to the initial complex obtained in step (4) at a rate of 6 ml / min, wherein the amount of calcium chloride solution added was 7% of the volume of the initial complex. The mixture was stirred for 2 h at room temperature, filtered, washed, and freeze-dried to obtain the low-fat composite protein solid beverage.

[0078] The composite protein powder is prepared by mixing isolated soy protein powder and skimmed milk powder in a mass ratio of 4:1.

[0079] Comparative Example 2

[0080] A method for preparing a low-fat composite protein solid beverage comprises the following steps:

[0081] (1) Preparation of glycosylated whey protein: whey protein and galacto-oligosaccharide are mixed in a mass ratio of 1:4 to obtain a reactant A; the reactant A is dissolved in a phosphate buffer solution, the concentration of the buffer solution is 0.1 M, the pH value is 7.0, and the mass ratio of the reactant A to the phosphate buffer solution is 1:6 to obtain a reaction solution; the reaction solution is freeze-dried to obtain a freeze-dried powder; the freeze-dried powder is then subjected to a glycosylation reaction at 60° C. for 96 hours to obtain a glycosylated whey protein;

[0082] (2) Preparation of a glycosylated whey protein solution: adding the glycosylated whey protein to water and stirring until it is completely dissolved to form a glycosylated whey protein solution with a concentration of 8 wt %;

[0083] (3) Adding emulsifier and composite protein: Adding gum arabic and composite protein powder to the glycosylated whey protein solution obtained in step (2), wherein the amount of gum arabic added is 1wt% of the mass of the glycosylated whey protein, and the amount of composite protein powder added is 18wt% of the mass of the glycosylated whey protein solution, and stirring evenly to obtain a reaction precursor;

[0084] (4) Cross-linking formation of microcapsules: A 0.6 wt% calcium chloride solution was added dropwise to the reaction precursor obtained in step (3) at a rate of 6 ml / min, wherein the amount of calcium chloride solution added was 7% of the initial complex volume. The mixture was stirred for 2 h at room temperature, filtered, washed, and freeze-dried to obtain the low-fat complex protein solid beverage.

[0085] The composite protein powder is prepared by mixing isolated soy protein powder and skimmed milk powder in a mass ratio of 4:1.

[0086] Comparative Example 3

[0087] A low-fat composite protein solid beverage is prepared by mixing isolated soy protein powder and skimmed milk powder in a mass ratio of 4:1.

[0088] Test Example 1

[0089] Solubility test: 10 g of the low-fat composite protein solid beverages prepared in Examples 1-5 and Comparative Examples 1-3 were respectively dissolved in 100 ml of water, stirred for 30 min, centrifuged at 800 r / min for 10 min, and the supernatant was taken to measure its protein content. The results are shown in Table 1.

[0090] Table 1: Solubility test results

[0091] Protein content of supernatant g / 100g Example 1 6.8 Example 2 6.2 Example 3 5.7 Example 4 6.7 Example 5 6.3 Comparative Example 1 4.8 Comparative Example 2 5.1 Comparative Example 3 3.5

[0092] Test Example 2

[0093] Sensory evaluation: 20 professional sensory evaluators were assigned to set up single-person evaluation rooms in accordance with the requirements of GB / T13868-2009. The evaluators conducted sensory evaluation on the numbered samples, and the results are shown in Table 2.

[0094] Table 2: Sensory evaluation results

[0095]

[0096]

[0097] As can be seen from Table 1 and Table 2, embodiment 1 has the highest protein solubility and the best mouthfeel. The present invention believes that this is due to the fact that in order to improve the solubility and mouthfeel of the composite protein, the present invention introduces sugar molecules such as oligogalactose on the surface of lactalbumin by glycosylation, greatly improving the hydrophilicity of lactalbumin, which enhances the solubility of lactalbumin in aqueous solution. In addition, the introduction of glycosylation not only improves the hydrophilicity of lactalbumin, but also provides additional reaction sites for molecular protein, promoting the combination with chitosan. Through hydrogen bonds, van der Waals forces and electrostatic response, a tighter network can be constructed between chitosan and glycosylated lactalbumin. When adding calcium chloride, the cross-linked network between the chitosan molecules is further strengthened, and glycosylated lactalbumin, as a cross-linked structure, is better embedded in the chitosan cross-linked network, thereby forming a microcapsule shell with strength and stability. Whey protein after glycosylation has better emulsifying properties, which is conducive to uniformly forming an emulsion in the process of compounding with chitosan, thereby building a uniform and dense microcapsule shell in the cross-linking reaction. The density of the microcapsule shell helps to mask off-flavors, improve solubility and control the release of active ingredients for encapsulating plant proteins.

[0098] In Example 2, no gum arabic is added for emulsification, and the glycosylated whey protein and the composite protein powder are dispersed unevenly. This is not conducive to the subsequent embedding reaction. In Example 3, no phosphate buffer is added, and its protein solubility is significantly reduced. The present invention believes that the phosphate buffer provides an appropriate ionic strength, which helps the whey protein and oligosaccharide to fully dissolve and form a uniform reaction solution. In this way, the glycosylation reaction can be carried out more evenly during the additional freeze-drying and heating process, thereby improving the glycosylation efficiency. The phosphate ions in the buffer help maintain the natural structure of the protein and avoid the denaturation and aggregation of the whey protein due to environmental changes during the dissolution and freeze-drying process. Maintaining the stability of the whey protein is the key to ensuring the smooth progress of the glycosylation reaction, because the structure of the whey protein will affect its binding efficiency with oligosaccharide. The phosphate buffer helps to maintain the coordination between the protein and the sugar during the freeze-drying process, and avoids the damage of the protein structure due to the lack. This lays the foundation for the subsequent heating glycosylation reaction, ensuring that the reactant has a suitable structure and activity. Example 4 and Example 5 show that the saccharification temperature also has a certain effect on the glycosylated whey protein.

[0099] Comparative Example 1 only uses ordinary whey protein and chitosan for cross-linking, and does not perform glycosylation treatment, resulting in low affinity between whey protein and plant protein, affecting solubility. Although Comparative Example 2 uses glycosylated whey protein, it lacks the chitosan embedding step, and the plant protein is not fully encapsulated, resulting in its solubility performance being lower than that of Example 1. Comparative Example 3 simply mixes protein powder without any embedding or glycosylation treatment, has poor solubility, is easy to precipitate, has the lowest protein content in the supernatant, and has the worst taste.

Claims

1. A method for preparing a low-fat composite protein solid beverage, It is characterized in that The following steps are involved: (1) preparing glycosylated whey protein to obtain glycosylated whey protein; (2) preparing a chitosan solution to obtain a uniform chitosan solution; (3) preparing a glycosylated whey protein solution to form a glycosylated whey protein solution with a concentration of 5-10 wt %; (4) adding an emulsifier and a complex protein to obtain a reaction precursor; (5) mixing the reaction precursor with chitosan to obtain an initial composite; (6) Cross-linking of microcapsules to obtain the low-fat composite protein solid beverage.

2. The method for preparing the low-fat composite protein solid beverage according to claim 1, It is characterized in that The preparation of the glycosylated whey protein comprises the following steps: mixing whey protein and galacto-oligosaccharide at a mass ratio of 1:4 to obtain a reactant A; dissolving the reactant A in a phosphate buffer, wherein the concentration of the buffer is 0.1M, the pH value is 7.0, and the mass ratio of the reactant A to the phosphate buffer is 1:(5-10) to obtain a reaction solution; freeze-drying the reaction solution to obtain a freeze-dried powder; and then subjecting the freeze-dried powder to a glycosylation reaction at 50-60°C for 48-120h to obtain the glycosylated whey protein.

3. The method for preparing the low-fat composite protein solid beverage according to claim 1, It is characterized in that The preparation of the chitosan solution comprises the following steps: adding chitosan to an acetic acid solution with a concentration of 1-2 wt%, stirring until the chitosan is completely dissolved to form a chitosan solution with a concentration of 1-2 wt%; placing the chitosan solution in an ultrasonic disperser for 3-5 minutes to perform ultrasonic treatment to remove bubbles in the solution to obtain a uniform chitosan solution.

4. The method for preparing the low-fat composite protein solid beverage according to claim 1, It is characterized in that The preparation of the glycosylated whey protein solution comprises the following steps: adding the glycosylated whey protein into water and stirring until the glycosylated whey protein is completely dissolved to form a glycosylated whey protein solution with a concentration of 5-10 wt%.

5. The method for preparing the low-fat composite protein solid beverage according to claim 1, It is characterized in that The addition of the emulsifier and the composite protein comprises the following steps: adding gum arabic and composite protein powder to the glycosylated whey protein solution obtained in step (3), wherein the amount of gum arabic added is 0.5-2wt% of the mass of the glycosylated whey protein, and the amount of composite protein powder added is 15-20wt% of the mass of the glycosylated whey protein solution; and stirring the mixture evenly to obtain a reaction precursor.

6. The method for preparing the low-fat composite protein solid beverage according to claim 1, It is characterized in that The mixing of the reaction precursor and chitosan comprises the following steps: under stirring conditions, the reaction precursor obtained in step (4) is added dropwise to the uniform chitosan solution obtained in step (2) at a rate of 5-10 ml / min, and continuous stirring is maintained during the dropping process to ensure the uniformity of the mixed solution. At this time, the glycosylated whey protein and chitosan form an initial complex through electrostatic interaction.

7. The method for preparing the low-fat composite protein solid beverage according to claim 1, It is characterized in that The cross-linking formation of the microcapsules comprises the following steps: adding a calcium chloride solution with a concentration of 0.5-1wt% to the initial complex obtained in step (5) at a rate of 5-10 ml / min, wherein the amount of the calcium chloride solution added is 5-10% of the volume of the initial complex; stirring continuously for 1-2 hours at room temperature to ensure that the cross-linking reaction is fully carried out to form stable chitosan-glycosylated whey protein microcapsules; filtering, washing, and freeze-drying to obtain the low-fat complex protein solid beverage.

8. The method for preparing the low-fat composite protein solid beverage according to claim 5, It is characterized in that The composite protein powder is prepared by mixing isolated soy protein powder and skimmed milk powder in a mass ratio of (2-9):

1.

9. A low-fat compound protein solid beverage, It is characterized in that The low-fat composite protein solid beverage is prepared by the preparation method of any one of claims 1 to 8.

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