CN114403426B

CN114403426B - Application of sericin hydrolysate as protein stick anti-hardening agent, product and method

Info

Publication number: CN114403426B
Application number: CN202210102920.9A
Authority: CN
Inventors: 魏兆军; 诸鸿韬; 章建国; 胡飞
Original assignee: Hefei University of Technology
Current assignee: Hefei University of Technology
Priority date: 2022-01-27
Filing date: 2022-01-27
Publication date: 2024-02-20
Anticipated expiration: 2042-01-27
Also published as: CN114403426A

Abstract

The invention discloses an application of sericin hydrolysate in serving as a protein rod anti-hardening agent, a product and a method thereof, belonging to the technical field of food additives, wherein the invention utilizes the hydrophilicity and the inoxidizability of the sericin hydrolysate, and finally relieves the hardening problem of protein rods by slowing down the phase separation of the protein rod product, reducing disulfide bond generation and maintaining the stability of a matrix, and the protein rods comprise the following components in percentage by weight: 42-49% of protein powder, 1-8% of sericin hydrolysate, 10-15% of water-soluble humectant, 5-23% of sweetener, 0.5-1% of shortening and the balance of water; the prepared protein stick product has good taste, high nutritive value and stable property, and can better play a role in relieving hardening no matter refrigerating, freezing at 0 ℃ or preserving at normal temperature.

Description

Application of sericin hydrolysate as protein stick anti-hardening agent, product and method

Technical Field

The invention relates to the technical field of food additives, in particular to application of sericin hydrolysate as a protein stick anti-hardening agent, a protein stick product containing the sericin hydrolysate and a preparation method of the product.

Background

The high protein nutrition bar (protein bar) is a food with a protein content up to 15-70%. The manufacturing process of protein sticks generally includes: the steps of raw material mixing, rolling, shaping, dicing, packaging and the like are carried out, and some products may be subjected to coating treatment. The protein stick has extremely high nutritive value, has the advantages of being capable of being stored at room temperature, long in shelf life, convenient to eat and the like, and is widely applied to the fields of special foods such as military, aerospace and the like. In recent years, with the improvement of the quality of life level of people and the rapid expansion of the sports and body-building market, the protein sticks have the product efficacy and nutritional and healthy product attributes of helping to reduce fat and weight, and auxiliary materials and functional components can be added in a customized way according to the dietary preference of consumers, so that the protein sticks are rapidly developed in the sports and body-building market, the annual growth rate is about ten percent, and the protein sticks have the trend of replacing traditional snacks. In the protein bar product, the main raw materials of the protein generally include sodium caseinate (casein), whey protein, soy protein, or the like. The major carbohydrate sources of the protein bars are glucose syrup, fructose syrup and maltose syrup, and cocoa butter and shortening are the major sources of their fats. In addition, small molecular polyhydroxy compounds such as glycerin and sorbitol are also commonly added as humectants and sweeteners for protein sticks. At the same time, because the protein bar product does not need to be heated during processing, the moisture content of the system must be tightly controlled to inhibit microbial growth, and small amounts of water also act as sweeteners and stabilizers in the protein bar. And auxiliary materials such as nuts, vitamins, dietary fibers and the like are selectively added according to the taste of consumers, so that the nutritional value of the protein stick can be improved, and the taste of the product can be further improved.

The texture and mouthfeel of food are important factors in determining the sensory experience of consumers, and have important effects on consumer acceptance and purchase will. Protein bar products are currently on the market, and the water activity of the system is generally between 0.5 and 0.6, and the storage period of the product can reach 6 to 12 months. However, during storage, the flavor, texture, color, etc. of the protein bars are significantly changed, wherein the hardness is most significantly increased, and the hardening phenomenon of the protein bars also greatly limits the shelf life of the product and the eating experience of consumers. However, the mechanism of hardening the protein bars is very complex, and different components, processing techniques, storage modes and the like can influence the hardening process.

In recent years, in order to solve the problem of hardening of protein sticks during the storage period, scholars at home and abroad have conducted a great deal of research and found that the cause of hardening of protein sticks is mainly several aspects such as sugar crystallization, phase separation, moisture migration, protein self-aggregation, maillard reaction and the like. The hardening process of a nutritional bar is generally divided into two stages, an early stage and a middle and late stage, the early stage usually being several weeks or one month after the nutritional bar is manufactured, the physical change between the different components plays a major role in the increase of hardness. The middle and late stages are mainly those after several months of storage, and the hardness is greatly increased due to the influence of storage conditions and protein aggregation caused by Maillard reaction.

Currently, in order to improve the hardening of protein sticks, researchers have made various attempts, the effective means mainly consisting of: optimizing raw material formula, using protein hydrolysate to replace protein raw material, adding cysteine, adding polyphenol, inhibiting Maillard reaction, etc. For example, mcMahon et al, have made the protein sticks more flexible by using hydrolysates of whey proteins to varying degrees instead of whey proteins. Banach, etc., through carrying out jet milling, freeze drying and grinding on the concentrated milk protein, the hydrophobic residues inside the protein particles are exposed, so that the surface hydrophobicity of the protein particles is increased, the rehydration capability of the particles is improved, the cohesiveness among the components of the system is finally improved, and the hardening phenomenon of protein rods is relieved. And Khalifa and the like, by adding microencapsulated mulberry polyphenol into the protein stick, maillard reaction in the protein stick is inhibited, the hardness of the protein stick in the storage period is reduced, and the stability of the product is enhanced. However, these methods are still in laboratory stage, and the economical and convenient application of these methods still needs to be further improved.

Silkworm is an ancient class of insects with important agricultural economic value and has long been used for the production of silk, a textile material. Silk is a natural protein fiber material, and consists of two parts, namely sericin and silk fibroin, wherein during the production and processing process of silk, silk fibroin with good performance and capable of continuously reeling silk is required in factories. And the sericin which is wrapped on the periphery of the silk and accounts for about 30% of the total mass of the silk is removed as waste in the silk reeling industry. With the continuous progress and development of science and technology, sericin is also studied deeply. As an important natural protein resource, sericin has obvious advantages in various aspects of biocompatibility, oxidation resistance, hygroscopicity and the like. At present, research on sericin is mostly developed in the fields of medical materials and cosmetics, and application of sericin in the food industry is still in a starting stage, and related research is in progress. According to some existing researches, sericin is used as food, so that the blood pressure of mice can be reduced, and hypertension can be relieved and prevented; the edible sericin has obvious influence on blood sugar, and can effectively reduce the blood sugar content of a subject or a mouse; meanwhile, the method also has obvious help to prognosis of the enteritis. However, no report has been found on the production of a protein stick product from a sericin hydrolysate as a raw material.

Disclosure of Invention

Accordingly, it is an object of the present invention to provide an application of sericin hydrolysate as a protein stick anti-hardening agent; another object of the present invention is to provide a protein stick product containing the sericin hydrolysate; the third object of the present invention is to provide a method for producing a protein rod containing the sericin hydrolysate. The invention aims to improve the hardening problem of the protein stick on one hand and further improve and raise the functions of resisting obesity and reducing blood sugar of the protein stick on the other hand by adding the sericin hydrolysate into the raw material and preparing the protein stick product, and the sericin hydrolysate is waste in the silk reeling industry, thereby having important significance in reducing resource waste, sustainable development, recycling of natural resources and the like;

in order to achieve the above purpose, the present invention provides the following technical solutions:

1. application of sericin hydrolysate as protein rod anti-hardening agent

Preferably, the protein stick comprises the following components in percentage by weight: 30-50% of protein powder, 1-15% of sericin hydrolysate, 10-15% of water-soluble humectant, 5-23% of sweetener and the balance of water; the sericin hydrolysate is derived from silkworm cocoons, and has a molecular weight of 10-150kDa, wherein more than 70% of the sericin hydrolysate is between 10-70 kDa.

2. A protein stick comprising sericin hydrolysate, comprising the following components in weight percent:

30-50% of protein powder, 1-15% of sericin hydrolysate, 10-15% of water-soluble humectant, 5-23% of sweetener and the balance of water; the sericin hydrolysate is derived from silkworm cocoons, and has a molecular weight of 10-150kDa, wherein more than 70% of the sericin hydrolysate is between 10-70 kDa.

Preferably, the protein powder is one or more of casein, sodium caseinate, whey protein, soy protein and peanut protein.

Preferably, the water-soluble humectant is one or more of glycerin, pectin and gelatin.

Preferably, the sweetener is one or more of sorbitol, maltitol and erythritol.

The invention preferably also comprises the following components in percentage by weight: 0.5-1% shortening.

Further preferred according to the present invention, the shortening is one or more of soybean lecithin, palm oil, coconut oil, butter.

Preferably, the protein stick comprises the following components in percentage by weight: 42-49% of protein powder, 1-8% of sericin hydrolysate, 12% of glycerol, 23% of sorbitol, 0.5% of soybean lecithin and 14.5% of water.

3. The preparation method of the protein stick comprises the following steps:

a. weighing the components according to a proportion, firstly, dissolving humectant, sericin hydrolysate and sweetener with water, then adding shortening and protein powder, and fully mixing to obtain a mixture;

b. and d, putting the mixture obtained in the step a into a die for extrusion plasticity, and cutting into the required size after the shape is stable, thus obtaining the corresponding protein stick product.

The invention has the beneficial effects that: the invention utilizes the hydrophilicity and oxidation resistance of sericin hydrolysate, and finally relieves the hardening problem of protein bars by slowing down the phase separation of protein bar products, reducing disulfide bond formation, maintaining the stability of matrix. And the prepared product has good taste, high nutritive value and stable property by reasonably setting the proportion of various raw materials, and can better play a role in relieving hardening no matter refrigerating, freezing at 0 ℃ or preserving at normal temperature. Meanwhile, the advantages of the protein stick product are maintained, the functionality of the product is further improved, the product is instant after being opened, and the product can serve as leisure food and functional food for consumers to eat throughout the year, and has the functions of assisting in reducing fat, reducing blood sugar, preventing and relieving intestinal diseases and the like. In summary, the invention not only solves the key problem of hardening the protein stick product and enriches the variety of the protein stick product, but also improves the functionality of the product and increases the economic benefit.

On the other hand, the sericin hydrolysate used in the invention can be prepared by degumming silkworm cocoons or extracting degummed wastewater in silk reeling industry, so the invention has important significance in environmental protection, sustainable development, secondary utilization of resources and the like.

Drawings

In order to make the objects, technical solutions and advantageous effects of the present invention more clear, the present invention provides the following drawings for description:

FIG. 1 is a graph depicting the oxidation resistance of sericin hydrolysates using DPPH radical scavenging rate;

FIG. 2 shows the morphological changes before and after compaction of the bars of whey protein with different sericin hydrolysate content (SRP: sericin hydrolysate) after storage for 0h, 72 h;

FIG. 3 shows the results of the whole texture analysis of whey protein bars with different sericin hydrolysate contents after storage for 0h and 72 h;

wherein A is a full-texture TPA curve of whey protein bars with different sericin hydrolysate contents after 0h of storage; b is a full-texture TPA curve of whey protein sticks with different sericin hydrolysate contents after 72 hours of storage; c is hardness; d is elasticity; e is cohesiveness; f is chewiness;

FIG. 4 is a graph of laser confocal scanning imaging of whey protein bars of varying sericin hydrolysate content after storage for 0h, 72h (green fraction for Fluorescein Isothiocyanate (FITC) -dyed protein; orange fraction for Nile red dye (Nile red) -dyed lipid; black fraction for undyed air bubbles);

FIG. 5 shows the morphological changes before and after compaction of the bars of sodium caseinate protein with different sericin hydrolysate content (SRP: sericin hydrolysate) after storage for 0h, 72 h;

FIG. 6 shows the results of the whole texture analysis of sodium caseinate protein bars of different sericin hydrolysate content after storage for 0h and 72 h;

wherein A is a full-texture TPA curve of sodium caseinate protein sticks with different sericin hydrolysate contents after being stored for 0 h; b is a full-texture TPA curve of sodium caseinate protein sticks with different sericin hydrolysate contents after being stored for 72 hours; c is hardness; d is elasticity; e is cohesiveness; f is chewiness;

FIG. 7 is a graph of laser confocal scanning imaging of sodium caseinate protein bars of varying sericin hydrolysate content after storage for 0h and 72h (green fraction for Fluorescein Isothiocyanate (FITC) -dyed protein; orange fraction for Nile red dye (Nile red) -dyed lipid; black fraction for undyed air bubbles);

FIG. 8 shows the morphology change of the soy protein isolate bars with different sericin hydrolysate content after storage for 0h and 72h before and after compaction by a physical property instrument;

FIG. 9 shows the whole texture analysis test of soy protein isolate bars of varying sericin hydrolysate content after 0h and 72h storage;

FIG. 10 shows laser confocal scanning imaging (green part is Fluorescein Isothiocyanate (FITC) dyed protein; orange part is Nile red (Nile red) dyed lipid; black part is undyed air bubble) of soy protein isolate bars with different sericin hydrolysate content after storage for 0h and 72 h;

FIG. 11 shows the results of atomic force microscopy of protein rod samples of different systems after addition of different amounts of sericin hydrolysate (whey protein isolate: whey protein isolate system; casein sodium: sodium caseinate system; soy protein isolate: soy protein isolate system);

FIG. 12 shows the results of scanning electron microscopy of protein rod samples of different systems after addition of different amounts of sericin hydrolysate (whey protein isolate: whey protein isolate system; casein sodium: sodium caseinate system; soy protein isolate: soy protein isolate system);

FIG. 13 shows the change in disulfide bond content of different systems of protein rod samples (whey protein isolate, sodium caseinate, soy protein isolate system in sequence from left to right) after addition of different amounts of sericin hydrolysate;

fig. 14 shows the water activity change (whey protein isolate, sodium caseinate, soy protein isolate system in sequence from left to right) of protein stick samples of different systems after addition of different amounts of sericin hydrolysate.

Detailed Description

The present invention will be further described with reference to the accompanying drawings and specific examples, which are not intended to limit the invention, so that those skilled in the art may better understand the invention and practice it.

The sericin hydrolysate (sericin powder) used in the examples was purchased from the Huzhou new tencel biotechnology Co., ltd, and had a molecular weight of between 10 and 150kDa, of which 70% or more was between 10 and 70 kDa.

EXAMPLE 1 protein rod System Using whey protein as the Main raw Material

The protein stick containing sericin hydrolysate of the embodiment has whey protein as a protein powder raw material, and comprises the following raw materials in percentage by weight: 42-49% of whey protein isolate, 1-8% of sericin hydrolysate, 12% of glycerol, 23% of sorbitol, 0.5% of soybean lecithin and 14.5% of water.

Wherein other humectant such as pectin and gelatin can be selected to replace glycerol, sweetener such as maltitol and erythritol can be selected to replace sorbitol, and lipid such as palm oil, coconut oil and butter can be selected to replace soybean lecithin.

The preparation method of the protein stick containing sericin hydrolysate in the embodiment specifically comprises the following steps:

according to the proportion of the raw materials, firstly, the glycerol, the sericin hydrolysate and the sorbitol are dissolved by water, then, the soybean lecithin and the whey separated protein powder are added and fully mixed to obtain a mixture. And (3) filling the mixture into a die, extruding, shaping, standing for 5-10 minutes until the mixture is stable, and cutting into the required size according to the requirement.

The protein rod containing sericin hydrolysate prepared by the method of the embodiment has the advantages of complete shape, good elasticity, moderate softness and uniform color.

DPPH radical scavenging was used to characterize the antioxidant properties of the added sericin hydrolysate and 1% (w/v) vitamin C was used as positive control. As a result, as shown in FIG. 1, it was found that the sericin hydrolysate had good oxidation resistance, the radical scavenging rate was 20.5% at the addition amount of 0.01%, and the scavenging rate was also increased with the increase of the concentration, and the radical scavenging rate was 64.7% at the increase of the concentration to 8%.

The total texture analysis of the obtained products was carried out by a physical property instrument (TA-XTPLUS, stable Micro System, UK) after 0h and 72h of completion of the preparation, the morphological change results of the whey protein bars with different sericin hydrolysate before and after the storage for 0h and 72h in the physical property instrument are shown in FIG. 2, the total texture analysis test results of the whey protein bars with different sericin hydrolysate after the storage for 0h and 72h are shown in FIG. 3, and the total texture analysis results statistics of the whey protein bars with different sericin hydrolysate after the storage for 0h and 72h are shown in Table 1.

TABLE 1 statistics of the results of the full texture analysis of whey protein bars with different sericin hydrolysate content after 0h and 72h storage

Note that: the different letter superscripts (a, b, c, d, e) in the same column indicate that there is a significant difference (p < 0.05).

The result shows that the addition of sericin hydrolysate can effectively relieve the hardening phenomenon of whey protein as the raw material in the initial storage period of the protein rod. When 8% sericin hydrolysate was added, the hardness was decreased from 1794.226.+ -. 58.539g (0 h) and 3817.269.+ -. 132.44g (72 h) to 936.842.+ -. 62.031g (0 h) and 1385.193.+ -. 82.586g (72 h) when not added. And, the anti-hardening effect increases with the content of sericin hydrolysate.

Characterization of the phase separation of the samples at storage for 0h and 72h by confocal laser scanning microscopy revealed that the addition of sericin hydrolysate slowed down the phase separation of the matrix and improved the stability of the matrix, and the specific results are shown in fig. 4.

EXAMPLE 2 protein rod System Using sodium caseinate as the Main raw Material

The protein rod containing sericin hydrolysate in the embodiment has the protein powder raw material of sodium caseinate, and comprises the following raw materials in percentage by weight: 42-49% of sodium caseinate, 1-8% of sericin hydrolysate, 12% of glycerol, 23% of sorbitol, 0.5% of soybean lecithin and 14.5% of water.

The preparation method of the protein stick containing sericin hydrolysate in the embodiment comprises the following steps: as in example 1.

The sericin-containing hydrolysate anti-sclerostin rod prepared by the method has the advantages of complete shape, good elasticity, moderate softness and uniform color. The total texture analysis is carried out on the obtained products after the completion of the preparation for 0h and 72h respectively by a physical property instrument, the morphological changes of the sodium caseinate protein rods with different sericin hydrolysate before and after the compression of the physical property instrument are shown in figure 5, the total texture analysis test results of the sodium caseinate protein rods with different sericin hydrolysate after the storage for 0h and 72h are shown in figure 6, and the total texture analysis results statistics of the sodium caseinate protein rods with different sericin hydrolysate after the storage for 0h and 72h are shown in table 2.

TABLE 2 statistics of the results of the full texture analysis of sodium caseinate protein bars of different sericin hydrolysate content after 0h and 72h storage

The results show that, although sodium caseinate has the characteristic of easily forming a network structure after swelling by absorbing water, the addition of sericin hydrolysate can effectively relieve the hardening phenomenon of the sodium caseinate as a raw material in the initial storage period of a protein rod, and the anti-hardening effect is improved along with the increase of the content of the sericin hydrolysate, and when 8% of sericin hydrolysate is added, the hardness of the sericin hydrolysate is reduced from 5823.033 +/-559.508 g (0 h) and 28623.295 +/-1665.024 g (72 h) to 3168.153 +/-165.498 g (0 h) and 13018.5 +/-1117.51 g (72 h). However, for the sodium caseinate system, it can be seen from the morphological changes after compression of fig. 4 and the specific indices of fig. 5 and table 2 that when the sericin hydrolysate addition amount is higher than 5%, the structure of the protein rod matrix is greatly affected, which is disadvantageous for the maintenance of cohesiveness and chewiness. This problem can be solved by reducing the amount of sericin hydrolysate to be added or by adding an appropriate amount of plasticizer (glycerin or sorbitol) to be added.

Meanwhile, the addition of sericin hydrolysate slows down the phase separation of the sodium caseinate protein rod matrix, improves the stability of the matrix, and the specific result is shown in figure 7.

Example 3 protein rod system using isolated soy protein as the main material.

The protein stick containing sericin hydrolysate in the embodiment has the protein powder raw material of soy protein isolate, and comprises the following raw materials in percentage by weight: 42-49% of soybean protein isolate, 1-8% of sericin hydrolysate, 12% of glycerol, 23% of sorbitol, 0.5% of soybean phospholipid and 14.5% of water.

The sericin hydrolysate-containing protein rod prepared by the method has the advantages of complete shape, good elasticity, moderate softness and uniform color. The results of the analysis of the whole texture of the obtained products after the completion of the production for 0h and 72h respectively are shown in FIG. 8, the morphology changes of the soybean protein isolate bars with different sericin hydrolysate before and after the storage for 0h and 72h are shown in FIG. 8, the results of the analysis of the whole texture of the soybean protein isolate bars with different sericin hydrolysate after the storage for 0h and 72h are shown in FIG. 9, and the statistics of the analysis of the whole texture of the soybean protein isolate bars with different sericin hydrolysate after the storage for 0h and 72h are shown in Table 3.

TABLE 3 analysis of the results of the full texture analysis of soy protein isolate bars with different sericin hydrolysate content after 0h and 72h storage

The results show that the soy protein isolate has poor solubility, and the prepared protein bars have high hardness and poor cohesiveness and chewiness. The addition of sericin hydrolysate resulted in a alleviation of the hardening phenomenon at the initial stage of storage and an increase in the anti-hardening effect with an increase in the content of sericin hydrolysate, and when 8% of sericin hydrolysate was added, the hardness was reduced from 3512.226.+ -. 387.796g (0 h) and 9711.662.+ -. 1552.377g (72 h) to 1593.595.+ -. 167.911g (0 h) and 5203.78.+ -. 275.577g (72 h) when not added. In addition, for the soy protein isolate system, when the sericin hydrolysate is added in an amount equal to or higher than 5%, the texture of the matrix is more uniform, the brittleness of the protein bars is eliminated, and the mouthfeel is enhanced.

Meanwhile, the addition of sericin hydrolysate slows down the phase separation of the sodium caseinate protein rod matrix, improves the stability of the matrix, and the specific result is shown in figure 10.

Example 4 investigation of the mechanism of inhibition of protein rod hardening by sericin hydrolysate

The atomic force microscope detection results of the protein rod samples of different systems after adding different amounts of sericin hydrolysate are shown in fig. 11, and the scanning electron microscope detection results of the protein rod samples of different systems after adding different amounts of sericin hydrolysate are shown in fig. 12, and the two results show that: the addition of sericin hydrolysate can slow down the self-aggregation of protein in the matrix, reduce the aggregation degree of protein phase and reduce the particle size, thereby slowing down the hardening process of protein rods. Consistent with the previous detection results (fig. 4, 7 and 10) of the laser confocal microscope, fig. 4, 7 and 10 illustrate that the stability of the matrix can be maintained by adding sericin on a macroscopic level, and the movement and change of each phase and each phase are reduced, so that the hardening process of the protein rod is slowed down.

Further explaining the reason for this phenomenon, self-aggregation of proteins is mainly caused by intermolecular disulfide bond formation or non-covalent interactions. The change of disulfide bond content of the protein rod added with the sericin hydrolysate with different contents after 72 hours of storage is detected, and the result is shown in figure 13, the disulfide bond is found to be integrally increased, but the formation of the disulfide bond can be well inhibited by adding the sericin hydrolysate, so that the self aggregation of the protein is reduced. The principle of this phenomenon is that sericin hydrolysate has good oxidation resistance and can prevent disulfide bond production by oxidation.

Sericin hydrolysates, on the other hand, are a class of very hydrophilic proteins with more than 70% of the polar amino acids in their amino acid composition. The sericin hydrolysate is added into the protein rod, so that the hydrophilicity of the whole system is improved, the sericin hydrolysate can be understood as a plasticizer, and the glass transition temperature of the hygroscopic matrix is reduced to a certain extent, so that the protein rod matrix can absorb more water in a liquid phase, the stability of the matrix is maintained, and the separation of different phases is slowed down. The water activity changes of the protein bar samples of different systems after adding different amounts of sericin hydrolysate are shown in fig. 14.

The above-described embodiments are merely preferred embodiments for fully explaining the present invention, and the scope of the present invention is not limited thereto. Equivalent substitutions and modifications will occur to those skilled in the art based on the present invention, and are intended to be within the scope of the present invention. The protection scope of the invention is subject to the claims.

Claims

1. The use of sericin hydrolysate as a protein rod anti-sclerosant characterized in that: the protein stick comprises the following components in percentage by weight: 30-50% of protein powder, 1-8% of sericin hydrolysate, 10-15% of water-soluble humectant, 5-23% of sweetener and the balance of water; the sericin hydrolysate is derived from silkworm cocoons, and has a molecular weight of 10-150kDa, wherein more than 70% of the sericin hydrolysate is between 10-70 kDa.

2. A protein stick comprising sericin hydrolysate, characterized by comprising the following components in weight percentage: 30-50% of protein powder, 1-8% of sericin hydrolysate, 10-15% of water-soluble humectant, 5-23% of sweetener and the balance of water; the sericin hydrolysate is derived from silkworm cocoons, and has a molecular weight of 10-150kDa, wherein more than 70% of the sericin hydrolysate is between 10-70 kDa.

3. The protein bar of claim 2, wherein the protein powder is one or more of casein, sodium caseinate, whey protein, soy protein, peanut protein.

4. The protein stick of claim 2, wherein the water soluble humectant is one or more of glycerin, pectin, gelatin.

5. The protein stick of claim 2, wherein the sweetener is one or more of sorbitol, maltitol, erythritol.

6. The protein stick of claim 2, further comprising the following components in weight percent: 0.5-1% shortening.

7. The method for producing a protein stick according to claim 2, comprising the steps of:

a. weighing the components according to a proportion, firstly dissolving a water-soluble humectant, a sericin hydrolysate and a sweetener with water, then adding shortening and protein powder, and fully mixing to obtain a mixture;