CN114514952A - High-protein nutrition bar and preparation method thereof - Google Patents

Abstract

The invention discloses a high-protein nutrition bar and a preparation method thereof, belonging to the field of food storage. The preparation method includes the following steps: adding a hydrophilic composition to a high-protein nutrition bar model system, the hydrophilic composition is composed of hydroxypropyl methylcellulose and transglutaminase; the high-protein nutrition The rod model system includes a sodium caseinate system and a soybean protein isolate system; according to the weight of sodium caseinate or soybean protein isolate, the addition amount of hydroxypropyl methylcellulose in the hydrophilic composition is 0.5%-2 %, and the addition amount of transglutaminase is 0.5%-3%. The experimental verification found that the addition of hydrophilic colloids can effectively improve the storage stability of the nutrition bar, among which the addition of 1.0% HPMC has the best effect. The system works best when %TG.

Description

A kind of high protein nutrition bar and preparation method thereof

technical field

The invention relates to the field of food storage, in particular to a high-protein nutrition bar and a preparation method thereof.

Background technique

High-protein nutrition bar is a kind of nutritionally balanced convenience food made through the steps of mixing raw materials, cold extrusion and dicing packaging. It can effectively supplement the energy needed by the body in a short time, and is widely used in sports food. and military food. At present, the industrial development of high-protein nutrition bars has gradually taken shape, and some accessories can be customized according to consumers' dietary preferences. The market is gradually expanding, and there is a trend to replace traditional snacks. The water activity of high-protein nutrition bars is generally between 0.5 and 0.6, and the shelf life of high-protein nutrition bars is at least 6 to 12 months when stored at room temperature. The texture of food can affect the sensory experience of consumers and have a significant impact on consumer acceptance. For example, during storage, the flavor, texture, color, etc. of the nutrition bar will change, among which the hardness change is particularly prominent, which greatly limits its shelf life.

The hardening mechanism of nutritional bars is very complex, and different components and external factors will affect its hardening. After the nutritional bar is made, its storage stability will be affected by physical and chemical changes such as sugar crystallization, phase separation, molecular migration and protein aggregation, especially the hardness of the product will increase significantly during the storage period, which seriously restricts the high protein Consumption potential of nutritional bars. Therefore, it is of great significance to study how to slow down the hardness change of high-protein nutritional bars during storage and maintain their storage stability.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a kind of high protein nutrition bar and preparation method thereof, in order to solve the problem existing in the above-mentioned prior art, add in the high protein nutrition bar by hydroxypropyl methylcellulose (HPMC) compound transglutamine The hydrophilic composition composed of enzymes (TG) can significantly improve the storage stability of the nutritional bar.

For achieving the above object, the present invention provides the following scheme:

The invention provides a preparation method of a high-protein nutritional bar, comprising the following steps: adding a hydrophilic composition to a high-protein nutritional bar model system, the hydrophilic composition is composed of hydroxypropyl methylcellulose and transglutamin Amidase composition.

Preferably, the high-protein nutrition bar model system includes a sodium caseinate system and a soy protein isolate system.

Preferably, according to the weight of sodium caseinate or soybean protein isolate, the added amount of hydroxypropyl methylcellulose in the hydrophilic composition is 0.5%-2%, and the added amount of transglutaminase is 0.5%-3%.

Preferably, the sodium caseinate system includes sodium caseinate, sorbitol, glycerin and water, wherein the mass ratio of sodium caseinate:sorbitol:glycerol:water is 40:30:15:15 .

Preferably, the soybean protein isolate system comprises soybean protein isolate, sorbitol, glycerol and water, wherein the mass ratio of soybean protein isolate:sorbitol:glycerol:water is 40:30:15:15.

The present invention provides a high-protein nutritional bar prepared by the preparation method.

The present invention also provides an application of a hydrophilic composition in prolonging the storage stability of a high-protein nutritional bar, wherein the hydrophilic composition is composed of hydroxypropyl methylcellulose and transglutaminase.

Preferably, the mass ratio of the hydroxypropyl methylcellulose and the transglutaminase is (0.5-2):(0.5-3).

The present invention discloses the following technical effects:

In the present invention, sodium caseinate and soybean protein isolate are used as raw materials to explore the effect of different hydrophilic colloids on molecular migration in the early stage of storage; maltitol and fructose are used as raw materials to explore the effect of HPMC addition on nutrition bars stored at 37 ° C for 35 days At the same time, the effect of HPMC combined with different concentrations of TG enzyme on the stability of the fructose system nutrition bar stored at 45 °C for 20 days was also explored. When adding 1.0% HPMC, the effect was the best. The inhibitory effect of HPMC complex TG enzyme on fructose system was better than adding HPMC alone. When the addition amount was 3.0% TG, the system had the best effect. Therefore, adding a hydrophilic composition composed of HPMC and TG to the high-protein nutritional bar can significantly improve the storage stability of the high-protein nutritional bar, providing a novel and convenient method for the storage of the high-protein nutritional bar.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the present invention. In the embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without any creative effort.

Figure 1 shows the TPA pressure chart of the sodium caseinate system added with different hydrophilic colloids; A and a are the control groups, B and b are the CMC-Na groups, C and c are the HPMC groups, and D and d are the GG groups; A-D Represents before pressing, a-d represents after pressing;

Figure 2 shows the TPA pressure chart of soybean protein isolate system added with different hydrophilic colloids; A and a are the control groups, B and b are the CMC-Na groups, C and c are the HPMC groups, and D and d are the GG groups; A-D represent Before pressing down, a-d represent after pressing down;

Fig. 3 is the change of effective amino group in the initial stage of storage of sodium caseinate system;

Fig. 4 is the change of effective amino group in the early stage of storage of soybean protein isolate;

Fig. 5 is the scanning electron microscope image (magnification is 500 times) of sodium caseinate system added with different hydrophilic colloids; A and a are blank control groups, B and b are CMC-Na groups, C and c are HPMC groups, D and d are GG groups; A-D represents the shape after 0d storage, a-d represents the shape after 4d storage;

Figure 6 is the scanning electron microscope images of the soybean protein isolate system added with different hydrophilic colloids (magnification is 200 times); A and a are blank control groups, B and b are CMC-Na groups, C and c are HPMC groups, D , d is the GG group; A-D represents the shape after 0d storage, a-d represents the shape after 4d storage;

Fig. 7 is the overall appearance of adding different concentrations of HPMC nutrition bar;

Fig. 8 is the color change of the maltitol system of adding different concentrations of HPMC;

Fig. 9 is the color change of the fructose system of adding different concentrations of HPMC;

Fig. 10 is the change of effective amino group content of the maltitol system of adding different concentrations of HPMC;

Fig. 11 is the change of effective amino group content of fructose system adding different concentrations of HPMC;

Fig. 12 is the change of insoluble protein in maltitol system adding different concentrations of HPMC;

Figure 13 is the change of insoluble protein in fructose system added with different concentrations of HPMC;

Figure 14 is the change of the microstructure of the maltitol system added with different concentrations of HPMC (magnification is 500 times); A, F, K are the blank control group, B, G, L are the 0.2% HPMC group, C, H, M are the 0.2% HPMC group 0.5% HPMC group, D, L, N are 1.0% HPMC group, E, J, O are 2.0% HPMC group; among them, the left (A, B, C, D, E) is the form at 0d storage, the middle (F , G, H, I, J) is the state when stored for 14d, and the right (K, L, M, N, O) is the state when stored for 35d;

Figure 15 is the change of the microstructure of the fructitol system added with different concentrations of HPMC (magnification is 500 times);

Figure 16 is the sensory score change of adding HPMC nutrition bar system; A: maltitol system; B: fructose system;

Figure 17 is the overall change in the color of different sample nutrition bars during storage;

Figure 18 is the effect of HPMC combined with different concentrations of TG enzyme on the color of nutrition bar storage period;

The effect of Figure 19 HPMC combined with different concentrations of TG enzyme on the effective amino groups during the storage period of nutritional bars;

Figure 20 The effect of HPMC combined with different concentrations of TG enzyme on the content of insoluble protein in the storage period of nutritional bars;

Figure 21 shows the effect of HPMC combined with different concentrations of TG enzyme on the microstructure of the nutrition bar (magnification is 500 times); A, F, K are blank control groups, B, G, L are HPMC groups, C, H, M are 0.5 %TG+HPMC group, D, L, N are 1.5%TG+HPMC group, E, J, O are 3.0%TG+HPMC group; among them, the left (A, B, C, D, E) is at 0 d of storage Form, the middle (F, G, H, I, J) is the state when stored for 12 days, and the right (K, L, M, N, O) is the state when stored for 20 days;

Figure 22 is the sensory score of HPMC combined with different concentrations of TG enzyme system.

Detailed ways

Various exemplary embodiments of the present invention will now be described in detail, which detailed description should not be construed as a limitation of the invention, but rather as a more detailed description of certain aspects, features, and embodiments of the invention.

The main raw materials used in the following examples are shown in Table 1:

Table 1 Test raw materials

The main drugs are shown in Table 2:

Table 2 The main drugs tested

Example 1

1. Test method

1.1 Preparation of high protein nutrition bar

The production of the high-protein nutrition bar model system refers to the formula of commercial nutrition bars with some adjustments. The model system used sodium caseinate and soybean protein isolate as protein components, and designed three types of hydrophilic colloid system and control system. The addition amount and other components are shown in Table 3.

Table 3 Nutrition bar formulas of different models

First, in order to explore the effect of different hydrophilic colloids on the initial storage stability of high-protein nutrition bars, two protein systems of sodium caseinate and soybean protein isolate were designed respectively, and the mass ratio of sorbitol, water and glycerol was 30: Mix in a ratio of 15:15, take a water bath at 55°C and stir evenly to make a mixed solution of the control group. The mixed solution of the control group was mixed with CMC-Na, HPMC and GG according to a mass ratio of 60:1, respectively, to prepare a hydrophilic colloid mixed system. Different protein powders with a content of 40% were added to the mixed solution of the control group and the mixed system of hydrophilic colloids to obtain the control group, the CMC-Na group, the HPMC group and the GG group, respectively. The obtained protein dough was evenly divided into 2.50g equal doughs, put into a sealed box and sealed with plastic wrap, and stored in a constant temperature incubator at 37 ° C for 0-4 d. Each sample was randomly selected on 0 d and 4 d. The samples were subjected to index detection, and the samples were equilibrated at room temperature for 0.5h-1h before detection. The sampling after equilibration at room temperature for 2 h was taken as the 0d sample.

Secondly, in order to explore the effect of the concentration of hydrophilic colloids on the long-term storage stability of nutrition bars, sodium caseinate-fructose and sodium caseinate-sorbitol systems were designed, and the best additions were selected according to the results of the first part of the experiment. , and made sodium caseinate protein nutrition bar samples according to different concentrations (Table 4). The obtained protein dough was stored in a constant temperature incubator at 37°C for 0-35d, and 3 samples were randomly selected at 0d, 7d, 14d, 28d, and 35d for index detection, and equilibrated at room temperature for 0.5h-1h before detection. The sampling after equilibration at room temperature for 2 h was taken as the 0d sample.

Table 4 Hydrocolloid nutrition bar model with different concentrations

Finally, in order to explore the effect of hydrocolloids combined with TG enzyme on the storage stability of nutrition bars, a sodium caseinate-TG enzyme-hydrocolloid composite system was designed (Table 5). The addition amount of TG enzyme was 4U/g, 12U/g and 24U/g sodium caseinate, respectively, according to the proportion of addition amount, they were 0.5%TG+HPMC group, 1.5%TG+HPMC group and 3.0%TG+HPMC group respectively group, the rest of the steps are the same as above. The obtained protein dough was stored in a constant temperature incubator at 45°C for 0-20d, and 3 samples were randomly selected at 0d, 4d, 8d, 12d, 16d, and 20d for index detection, and equilibrated at room temperature for 0.5h-1h before detection. . The sampling after equilibration at room temperature for 2 h was taken as the 0d sample.

Table 5 Hydrocolloid nutrition bar models with different concentrations

1.2 Texture determination

The hardness and brittleness of the high-protein nutrition bar model system were measured by a physical property analyzer. In the experiment, a cylindrical probe (P36) with a diameter of 36 mm was used for full texture analysis (TPA). 1.00mm/s, trigger force 5g, deformation 50%. The hardness of the sample is represented by the maximum stress during the pressing process, and the viscosity is represented by the absolute value of the maximum stress during the pressing process. At least 3 parallel samples are selected for each sample.

1.3 Color determination

In order to observe the overall appearance changes of the samples during the storage period, the samples at each observation time were placed under a white background in sequence, and a camera was used to take pictures and record. The ZE6000 colorimeter was used to measure the L ^* , a ^* and b ^* values of each sample. D65 was used as the light source during the measurement, and calibration was performed before each measurement, and the measurement was repeated at least 3 times at different positions for each sample, and the average value was taken.

1.4 Determination of effective amino group content

The effective amino group content in the high-protein nutrition bar model system was determined by the ortho-phthalaldehyde method. Take 1 g of high-protein nutrition bar sample, equilibrate for 0.5 h at room temperature, extract with 50 mL of 20 g/L SDS solution for 2 h, and then centrifuge at 6000 rpm/min for 15 min. Take 200 μL of supernatant and add it to 4 mL of prepared o-phthalaldehyde solution (80 mg o-phthalaldehyde, 2 mL 95% ethanol, 0.20 mL β-mercaptoethanol, 10 mL 10 g/L SDS solution, 50 mL 0.05 mol/L tetraboric acid) sodium solution and adjusted to pH 9.0) and kept at room temperature for 2 min. The absorbance value was read at 340nm using a UV-Vis spectrophotometer, and the prepared o-phthalaldehyde solution was used as a blank control. The formula for calculating the relative effective amino acid content is:

1.5 Determination of relative content of insoluble protein

The content of insoluble protein aggregates was calculated from the total amount of soluble protein. Dissolve 500 mg of sample in 10 mL of ultrapure water, stir (500 r/min) for 80 min, centrifuge for 30 min, take 2 mL of supernatant and add 2 mL of NaN ₃ solution (0.5 g/L), mix well and store in a refrigerator (4°C) . Dilute the prepared sample solution (200 μL) by 60 times, take 1 mL of the diluent, add 5 mL of Coomassie brilliant blue solution (take 100 mg of Coomassie brilliant G-250, dissolve it in 50 mL of 95% ethanol, add 100 mL of 85% (w/v) of phosphoric acid, dilute to 1000 mL), place for 20 min, and measure the absorbance value at 595 nm. The formula for calculating the relative content of insoluble protein is:

1.6 Observation of microstructure

S-3400N tungsten filament scanning electron microscope was used to observe the microstructure of the high-protein nutrition bar model system. The samples were cut into 2 × 5 mm strips, and glutaraldehyde solution with a concentration of 2.5% and pH=6.8 was added to fix them and place them together. 2-3h in the refrigerator at 4°C. Rinse twice with 0.10mol pH 6.8 phosphate buffer for 10min each time, then elute with 50%, 70%, 90%, 100%, 100% ethanol for 10min-15min each time, then use 100% ethanol: tert-butanol = 1:1, pure tert-butanol for elution, 15min each time, put the eluted sample in a -20°C refrigerator for 30min, and put it in an ES-2030 freeze dryer to test the sample. After drying, the samples were sprayed with gold and fixed on a stage with conductive adhesive.

1.7 Sensory Analysis

The test samples prepared in the above section 1.1 were stored in an incubator at 37°C for 35d and in an incubator at 45°C for 20d, respectively, and were sampled at 0d, 35d and 0d, 20d and placed in a plate. , A jury composed of Northeast Agricultural University students who like nutritional bar-type foods conduct sensory evaluations. The testers cannot eat or drink functional ingredients within 1 hour before the start of each experiment. The sensory evaluation contents are shown in Table 6.

Table 6 Sensory evaluation criteria for nutritional bars (1-10)

2. Statistical methods

All the above processes were carried out 3 parallel experiments, and the obtained data were subjected to one-way ANOVA and multiple comparisons by SPSS Statistics 20.0 software, (P<0.05) means significant difference, (P>0.05) means no significant difference; Pearson correlation analysis. Origin 9 software was used for mapping.

3. Results and Analysis

3.1 The effect of different hydrophilic colloids on the initial stability of nutrition bars in storage

3.1.1 Changes in the texture of nutrition bars with different hydrocolloids added in the initial storage period

As shown in Table 7, it is the texture change of the sodium caseinate system added with different hydrophilic colloids within 4 days of storage. From the data in Table 7, it can be seen that the hardness of the control group samples was 1636.53 ± 116.38g on the 0th day, and increased after 4 days of storage. Compared with it, the hardness changes of the hydrophilic colloid group were significantly reduced (P<0.05). On the 0th day of storage, the hardness values of the CMC-Na group, HPMC group and GG group decreased to 1137.32±0.44g, 1174.82±11.65g and 944.86±149.38g, respectively; after 4d storage, the hardness values of the three hydrocolloid groups decreased respectively to 7752.17±680.23g, 6288.03±821.61g and 7462.40±170.95g, which indicated that the addition of hydrocolloids could significantly inhibit the hardening problem of the nutrition bar in the early stage of storage (P<0.05). In addition, there were also differences among the three hydrocolloids. On the 0th day of storage, there was no significant difference between the CMC-Na group and the HPMC group, but there was a significant difference between the two and the GG group (P<0.05). After 4 days of storage, there was a significant difference between the HPMC group and the other two groups (P<0.05), which indicated that HPMC had the most significant anti-hardening effect on the nutritional bar system. In addition, it can be seen from the table that only the control group had brittleness on the 0th day, which was 1980.10±50.60, which indicated that the control group was broken during the test. Cohesion indicates the resistance of the sample to the second compression after the first compression deformation. Combined with the data in the table, it can be seen that when stored for 0 d, the cohesion of the GG group is the best, which is 0.22±0.01, and the control group is only 0.11±0.00. After 4 days of storage, the control group showed greater cohesion, 0.78±0.00, and there was no significant difference between the hydrocolloid groups (P>0.05). It can be seen from the photos of the sodium caseinate system tested by TPA (Figure 1) that on the 0th day of storage, the control group was broken after the TPA test, while the hydrophilic colloid group remained intact; on the 4th day of storage, the control group was After pressing, it still maintains a complete structure, and the shape does not change significantly, which shows that the control system has higher recovery, while the three hydrophilic colloid groups have cracks, which shows that the recovery and internal properties of the three systems The aggregation is poor, which may be due to the fact that the addition of hydrocolloid inhibits the aggregation of protein particles in the system, destroys the protein network and causes the system to be easily broken. These results are consistent with the data in Table 7. In conclusion, it can be considered that HPMC can play the best effect in the sodium caseinate nutritional bar system.

Table 7 Changes in the texture of the sodium caseinate system added with different hydrocolloids at the initial storage stage

Note: The data in the table are expressed as mean ± standard deviation, and letters are marked after the data. Among them, A, B, and C indicate significant differences in statistical analysis between different components (P<0.05), and a, b, and c indicate different There were significant differences in statistical analysis between storage periods (P<0.05), the same as in the table below.

As shown in Figure 8, for the texture value of soybean protein isolate system added with different hydrophilic colloids within 4 days of storage, on the 0th day of storage, the hardness of the control group was 1829.77±62.05g, CMC-Na group, HPMC group and GG group The hardness values of the control group decreased to 1517.43±90.10g, 1641.46±135.40g, 1064.76±133.29g, respectively; after 4 days of storage, the hardness of the control group increased to 14876.73±1578.10g, and the hardness values of the hydrophilic colloid group decreased to 6552.12±454.51g, 4015.70±10g, respectively. 392.92g, 5126.45±878.80g, among which, the hardness values of HPMC group and GG group were the lowest, which indicated that HPMC and GG could significantly reduce the hardness change of soybean protein isolate nutrition bar in the early stage of storage (P<0.05). It can be seen from the table that only the control group showed brittleness on the 0th day, which was 1204.13±157.71, and the other three experimental groups were not broken, which indicated that the viscosity of the hydrophilic colloid was good to maintain the integrity of the system. After 4 days of storage, the hydrocolloid group showed brittleness, which may be caused by the thermodynamic incompatibility in the mixture. Combined with the photo of the soybean protein isolate system tested by TPA (Fig. 2), it can be seen that on the 0th day of storage, the control group was broken after the TPA test, and the hydrophilic colloid group remained intact although cracks appeared. After being pressed down, the intact structure is still maintained, and the three groups of hydrophilic colloids are all broken, which is consistent with the data in Table 8. In addition, it can be seen from the table that the control group showed the highest cohesion after 2d and 4d of storage, and was significantly different from the other three groups (P<0.05). In conclusion, it can be considered that HPMC exerts the best effect in the soybean protein isolate system.

Table 8 Changes in early storage texture of soybean protein isolate system with different hydrocolloids added

Note: The letter D indicates that there is a significant difference in statistical analysis between different components (P<0.05), the table below is the same.

3.1.2 Changes of available amino groups in the initial storage period of nutrition bars with different hydrophilic colloids

Figure 3 shows the change of the effective amino group content of the sodium caseinate system in the early stage of storage. It can be seen from the figure that the amino group content of the four groups of samples is lower than that of the 0th day. After 4 days of storage, the percentages of amino groups in the control group, CMC-Na group, HPMC group and GG group were (95.90±0.12)%, (93.30%±0.27)%, (93.50%±0.62)%, and (93.20%±0.52), respectively. %, the percentage of effective amino groups in the system decreased after adding hydrophilic colloid, and the percentage of the control group was the highest and there was a significant difference between it and other components (P<0.05).

Figure 4 shows the change of the effective amino group content of soybean protein isolate system in the early stage of storage. 0.20)%, the effective amino group content of the control group decreased less after 4 days of storage, and there was a significant difference between the control group and the three hydrocolloid groups (P<0.05). Compared with the different hydrocolloid groups, the HPMC group had a higher percentage of amino groups, which was significantly different from the CMC-Na group and the GG group (P<0.05).

3.1.3 Changes in the microstructure of nutrition bars with different hydrocolloids added in the initial storage period

Figure 5 is a scanning electron microscope image of the sodium caseinate system added with different hydrophilic colloids. It can be seen from the figure that the microscopic morphology of each sample has changed significantly after the 0th day of production and the 4th day of storage. In the 0d sample, most of the protein particles can maintain their own shape well, and it can be clearly observed that some protein particles coexist and stick together with the liquid composed of water, glycerol, and sugar alcohol. After 4 days of storage, protein particles piled up with each other, and irregular aggregation occurred, and the volume of protein particles increased at a speed visible to the naked eye, which was more obvious in the hydrophilic colloid group. On the 0th day, more small protein particles can be seen in the hydrocolloid group (B, C, D), and they maintain their intact morphology, while there are fewer intact protein particles in the control group, most of which are initially hydrated and partially aggregated structure. After 4 days of storage, the hydrocolloid group (b, c, d) could still see more small intact protein particles, which were stacked with the swollen protein, while the protein particles in the control group had been basically completely hydrated. Large particle aggregates are formed after water absorption and swelling. This indicates that adding hydrocolloids can slow down the degree of protein water absorption and swelling, maintain the integrity of the protein itself, and reduce the formation of aggregates. Comparing the three hydrophilic colloid systems, on the 0th day of storage, more small protein particles could be observed in the HPMC group; in the GG group, round bubbles and a liquid composed of water, sugar alcohol, glycerol, and GG could be observed. phase, which is also consistent with the greater viscosity of GG; although small protein particles can also be observed in the CMC-Na group, there are still some hydrated and swollen protein particles. After 4 days of storage, the swollen protein particles and the formed protein network can be seen in the CMC-Na system and the GG system. The degree of protein aggregation and the swelling degree of protein particles are both smaller than those of the control group. In the HPMC group, some intact, unhydrated, unswollen protein particles could still be observed, which indicated that HPMC could better inhibit the hydration of sodium caseinate and slow down the aggregation of proteins, which was consistent with the texture data. changes are consistent.

Figure 6 is a scanning electron microscope image of the soybean protein isolate system added with different hydrophilic colloids. The soybean protein isolate has higher hydrophobicity, and clear particle morphology can be observed in the figure. Compared with storage 0d and 4d, the four samples also changed greatly, but the degree of change was weaker than that of the sodium caseinate system. On the 0th day, both the control group and the hydrocolloid group could maintain the complete protein morphology, and the volume of the protein particles was smaller. After 4 days of storage, with the migration of water and other small molecules into the protein particles, the volume of the protein particles gradually increased. In the control group and GG group, the surface hydrated protein particles and stacking morphology can be clearly seen, while in CMC-Na and HPMC system, the protein particles can still be kept intact. This shows that adding a hydrocolloid can inhibit the protein hydration of the soybean protein isolate system in the early stage of storage and slow down the hardening of the nutrition bar.

3.2 The effect of adding HPMC on the long-term storage stability of nutrition bars

3.2.1 The effect of adding HPMC on the long-term storage texture of nutrition bars

Table 9 shows the changes in texture of the maltitol system with different concentrations of HPMC added within 35 days of storage. It can be seen from Table 9 that with the increase of storage time, significant hardening occurred in each sample (P<0.05). The hardness of the control group was 1701.78±109.91g on the 0th day and 24680.61±767.02g after 35d; compared with the control group, the hardness values of the model system after adding different concentrations of HPMC were significantly reduced (P<0.05). On the 0th day of storage, the hardness values of 0.2%HPMC group, 0.5%HPMC group, 1.0%HPMC group and 2.0%HPMC group decreased to 1683.37±135.34g, 1592.64±139.51g, 1383.22±176.32g, 1238.32±112.83g, respectively. After 35 days of storage, the hardness values of the four groups increased to 21919.58±180.99g, 20159.32±910.88g, 18542.26±34.64g, 17796.62±224.60g respectively; the hardness values of the 1.0%HPMC and 2.0%HPMC groups were significantly different from the other three groups ( P<0.05), and there was no significant difference between the two (P>0.05). According to the data, it can be considered that with the increase of the addition amount of HPMC, the hardening phenomenon of the maltitol system is slower, but after the addition amount reaches a certain amount, the difference is not significant. It can be seen from Table 9 that only the control group showed brittleness on the 0th day, which was 1895.29±207.56, which indicates that the 0d control group was broken during the test, while the other components and storage 14d and 35d did not appear brittle. value, indicating that the system remains intact. In addition, there was no significant difference in the cohesion between the control group and the other four groups at 0 d of storage (P>0.05). After 35 d of storage, the cohesion of the 2.0% HPMC group was 0.49±0.01, and it was not significantly different from the other groups. There was a significant difference (P<0.05).

Table 9 Changes in the storage period texture of maltitol system with different concentrations of HPMC added

Table 10 is the change value of the texture of the fructose system added with different concentrations of HPMC within 35d of storage. Since fructose is a reducing sugar, Maillard reaction will occur with free amino groups during the storage period, and the Maillard reaction proceeds to the later stage. Poorly soluble aggregates can cause large changes in the hardness of the samples, which is consistent with the changing trend of the data in the table. The hardness value of the control group was 464.89±26.39g on the 0th day, and increased to 45253.70±378.28g after 35d. After adding HPMC, the hardness value of the system decreased obviously (P<0.05). At 0d, the hardness of 0.2%HPMC group, 0.5%HPMC group, 1.0%HPMC group and 2.0%HPMC group was 414.40±7.29g, 322.96±16.58g, 302.81±15.21g, 267.61±10.06g, and increased to 37853.28 after 35d ±707.11g, 29552.12±1060.66g, 26299.87±280.53g, 24965.36±1330.74g. In addition, there are differences between different addition amounts. The hardness of the 2.0% HPMC group on the 0th day is the smallest, and there is a significant difference between it and other addition amounts (P<0.05). There was no significant difference between the two components (P>0.05), and the difference between the two and other components was significant (P<0.05). Compared with maltitol, the viscosity value of fructose after dissolving is higher. During the whole storage period, the tested samples did not break, which is consistent with the brittleness not measured in the table. In addition, after 35 days of storage, the cohesion of the 2.0% HPMC group was the smallest, and there was also a significant difference between it and other components (P<0.05). In summary, combined with the principle of less addition and the principle of saving, the addition of 1.0% HPMC can be selected for practical application.

Table 10 Changes in the storage period of the fructose system with different concentrations of HPMC added

3.2.2 The effect of adding HPMC on the long-term storage color of nutrition bars

Often the hardening problem of high protein bars is the main cause of quality problems, and changes in color appearance also have an impact on quality. It can be seen from Figure 7 that the maltitol system and the fructose system have a great difference in the 35d storage period. In the maltitol system, maltitol is a non-reducing sugar, no Maillard reaction occurs, and the color of the sample remains white or light yellow. After 35 days of storage, the sample turned slightly yellow. Compared with maltitol, fructose is a reducing sugar, and the Maillard reaction with protein to form melanin in the later stage will deepen the color of food, which can be seen intuitively in the figure. The color of the fructose system changed after 7 days of storage, it was brown after 14 days, and dark brown after 35 days; the color change of the four systems added with HPMC was not as fast as that of the control group, and with the increase of HPMC addition, the color changed. more slowly, which indicates that HPMC can slow down the process of Maillard reaction and slow down the deepening of color, which is consistent with the previous results on the effect of hardness.

In addition, the L* value, a* value and b* value of each sample were also measured. The L* value represents the whiteness, and the larger the L*, the lighter the color, the closer to white. The change of L* value of maltitol system and fructose system is shown in Fig. 12 and Fig. 13. When stored for 0 d, the initial L* of the maltitol system and the fructose system were relatively close, between 86-89, but with the increase of storage time, there was a big difference between the systems. In the maltitol system, the L* of the control group showed a linear downward trend, and the downward trend of the curve slowed down after adding HPMC, and the slowing trend was proportional to the addition amount. After 35 days of storage, the L* of each sample was above 70. In the fructose system, the change trends of the control group and the HPMC group were consistent, showing a rapid decreasing trend, and the decreasing trend slowed down after 28 days of storage. Adding HPMC can slow down the change trend of the curve. After 35 days of storage, the L* of each system is above 60, which is significantly lower than the L* value of the maltitol system, which is consistent with the difference in Figure 3-11.

The a* value and the b* value represent the red-green value and the yellow-blue value of the sample, respectively. The larger the a* value is, the more red the sample is, and the larger the b* value is, the more yellow the sample is. As shown in Fig. 8 and Fig. 9, each system exhibited a yellowish color when stored at 0 d, which was mainly from the color of the sodium caseinate particles themselves. With the increase of storage time, the a* value in the maltitol system increased slowly at first, and then increased rapidly in the later period; while in the fructose system, the a* value showed a trend of first increasing and then tending to be flat or decreasing. The change trend of b* value is similar to that of a* value. In the maltitol system, it gradually increases, and in the fructose system, it first increases and then tends to be flat. After adding HPMC, this change trend is alleviated, and the more the amount added, the more HPMC The effect of alleviating changes in color is more pronounced.

3.2.3 The effect of adding HPMC on the effective amino groups in long-term storage of nutrition bars

As the limiting amino acid in protein foods, the loss of lysine is the most important nutrient loss caused by Maillard reaction. Figure 10 is the change of the percentage of effective amino group content in the maltitol system added with different concentrations of HPMC stored at 37°C for 35d. It can be seen that in the long-term storage, the effective amino group content of each sample has decreased to a certain extent. In the maltitol system, since the sugar alcohol will not combine with the amino group of the protein in the system, the effective amino group still retains more than 85% of the 0d after 35d. After 35 days of storage, the percentages of available amino groups in the control group, 0.2% HPMC group, 0.5% HPMC group, 1.0% HPMC group and 2.0% HPMC group were (86.63±0.19)%, (88.85±0.38)%, (87.24±0.22), respectively. )%, (89.01±0.98)%, (88.23±0.32)%, which indicated that adding HPMC group could slow down the decrease of effective amino group during storage.

Figure 11 shows the change of the percentage of available amino groups in the fructose system added with different concentrations of HPMC. It can be seen that the available amino groups of each sample decreased significantly during storage (P<0.05), and the control group lost 70% of lysine after 35 days. After adding HPMC, the percentage of amino groups in each sample was lower than that in the control group in the first 20 days, and the content was higher than that in the control group after 35 days. When stored for 14 days, the percentages of available amino groups in the control group, 0.2% HPMC group, 0.5% HPMC group, 1.0% HPMC group and 2.0% HPMC group were (60.27±0.53)%, (54.66±0.37)%, (55.69±0.14), respectively. )%, (55.26±0.24)%, (59.28±0.37)%, there were significant differences between the control group and 2.0%HPMC group and other components (P<0.05). After 35 days of storage, the percentages of available amino groups of each component were (21.19±0.28)%, (21.14±0.11)%, (23.42±0.07)%, (24.92±0.17)%, and (26.77±0.05)%, respectively. There were significant differences between samples (P<0.05).

3.2.4 The effect of adding HPMC on the long-term storage of insoluble protein in nutritional bars

Figures 12 and 13 show the changes of insoluble protein in the maltitol system and fructose interest added with different concentrations of HPMC during the storage period. As shown in Figure 12, no obvious protein aggregate formation was observed within 35d. After 35 days of storage, the percentages of insoluble protein in the control group, 0.2% HPMC group, 0.5% HPMC group, 1.0% HPMC group and 2.0% HPMC group were (1.40±0.09)%, (1.40±0.01)%, (1.50±0.01) %, (1.24±0.01)%, (1.44±0.00)%, 1.0% HPMC group and other samples were significantly different (P<0.05). This indicates that there is no obvious Maillard reaction in the maltitol system, which is consistent with the changes in the available amino and texture data in the previous section. In the fructose system, the percentages of insoluble protein in several groups of samples were (8.22±0.13)%, (7.01±0.07)%, (6.15±0.03)%, (5.40±0.16)%, (5.22±0.03)%, and On the 35th day, there was a significant difference between the 2.0% HPMC group and the other groups (P<0.05), which indicated that the addition of 2.0% HPMC had the best inhibitory effect on insoluble protein. The content of insoluble protein measured by the experiment did not increase slowly, but started after the 14th day, especially after the 21st day, which indicated that the insoluble protein aggregates were formed after the Maillard reaction had been in progress for a period of time or reached a certain stage. of.

3.2.5 The effect of adding HPMC on the microstructure of nutrition bars for long-term storage

Figure 14 shows the changes in the microstructure of the maltitol system added with different concentrations of HPMC. Comparing the scanning electron microscope images at different times, it can be found that when stored for 0 d, the protein particles maintain their own complete shape, and only part of the protein particles dissolve, forming aggregates. The body is less, most of the protein particles are still small in size, and the partially hydrated protein forms a loose protein structure. After 14 days of storage, with the migration of small molecules such as water, most of the proteins have absorbed water and swelled, the protein volume has increased, and larger protein aggregates have been formed. close. During this time, it can be observed that there are still protein particles in the system coexisting with the liquid phase consisting of water, glycerol and sugar alcohol. At the later stage of storage, as the protein particles further absorb water, the formed protein network gradually dissipates, and the proteins are gradually dispersed evenly. In addition, bubbles can be seen dispersed in the protein network in the figure. Comparing different samples, it can be seen that on day 0, the volume of protein particles in the control group is larger, indicating that some proteins are hydrated, a cross-linked spatial network is formed between proteins, and fewer small particles are observed. After adding HPMC, the proportion of protein hydration decreased, and with the increase of the addition amount, the proportion of protein hydration and dissolution was smaller. When stored for 14d and 35d, the experimental group added with HPMC also experienced swelling and protein accumulation to varying degrees, but with the increase of the addition amount, some samples could still maintain the protein network (Figure N, O). This shows that the addition of HPMC has a certain effect on maintaining the spatial structure of the system, and the effect is better as the addition amount increases, but when the addition amount exceeds 1%, the addition of HPMC has no more significant effect on the sample, which shows that the addition amount When it is 1%, the colloidal network has been basically constructed.

Figure 15 shows the changes in the microstructure of the fructose system added with different concentrations of HPMC. It can be seen that the changes in the microstructure of the fructose system during storage are similar to those of the maltitol system. When stored for 0 d, some proteins have been dissolved on the surface (as shown in Figure a), aggregates have begun to form between adjacent proteins, and protein spatial networks have begun to form; after 14 d of storage, with the progress of the Maillard reaction, the system formed Irregular large protein aggregates, no small protein particles can be observed; after 35 days of storage, with the increase of the water activity of the system and the water produced by the Maillard reaction, part of the surface protein continues to dissolve, the spatial network begins to collapse, and a large number of bubbles are intertwined in the water. In the protein network (as seen in Figure m and Figure n, a large number of bubbles are scattered in the center and around). After adding HPMC, the process of protein formation of large aggregates was delayed, as shown in Figures f and i, the protein in the 1.0% HPMC group still maintained a state of swelling and expansion, while the control group had formed larger aggregates with irregular surfaces . The changes of proteins in the 2.0% HPMC group were slower than other components, which indicated that both the 1.0% and 2.0% HPMC groups could better alleviate the protein aggregation caused by the Maillard reaction.

3.2.6 The effect of adding HPMC on the sensory score of nutrition bar long-term storage

The effect of adding HPMC on the sensory of the nutritional bar is shown in Figure 16. It can be seen that the total sensory scores of the maltitol system and the fructose system are significantly different before and after storage. On the overall score, the score at 0 d of storage was significantly higher than that after 35 d of storage. This part of the difference was mainly due to the changes in taste and color, which were more obvious in the fructose system. The control group in the maltitol system had a lower score for histological morphology at day 0, mainly due to its higher friability. The scores of each sample after adding HPMC were generally higher than those of the control group, and with the increase of the addition amount, the sensory score was higher, and the 1.0% HPMC and 2.0% HPMC samples had the highest total scores at 0d and 35d of storage. It shows that adding 1.0% or 2.0% HPMC improves people's overall acceptance of nutritional bodies.

3.3 Effect of HPMC combined with TG enzyme on the stability of nutrition bar storage period

3.3.1 Effect of HPMC combined with TG enzyme on the texture of nutritional bars during storage

Table 11 shows the changes in the texture of the HPMC combined with TG enzyme system during storage. Among them, the control group did not add HPMC and TG enzyme, the HPMC group did not add TG enzyme, and the HPMC+0.5%/1.5%/3.0% TG group represented the addition of TG enzyme, respectively. Samples of different concentrations of TGase. It can be seen from the data in the table that after storage at 45 ℃ for 20 days, the hardness value and cohesion of each sample showed an increasing trend, and all of them changed significantly (P<0.05). Comparing 0d and 20d, the hardness value of the control group at 0d was 471.92±23.14g, and the hardness reached the maximum value after 20d, which was 31419.95±2873.81g. The hardness value of HPMC group was 403.51±3.32g on the 0th day, and reached 26490.26±2313.71g after 20d; the hardness value of the 0.5%TG+HPMC group was 429.86±16.22g on the 0th day, and increased to 24078.71±1928.37g after 20d; 1.5%TG+ The hardness value of HPMC group was 421.06±33.92g on the 0th day, which increased to 19839.70±1909.54g after 20 days; the hardness value of the 3.0%TG+HPMC group was 422.32±21.77g on the 0th day, and increased to 16253.17±1047.41g after 20 days. Comparing the hardness values of different systems, it can be found that there are significant differences between the control group and other components on the 0th day (P<0.05). <0.05), which indicated that HPMC combined with TG enzyme effectively improved the hardening problem of the sample. The cohesion of the control group was 0.03±0.00 on the 0th day, 0.78±0.01 on the 8th day, and 0.83±0.01 after the 20th day, and there were significant differences in the three time periods (P<0.05); 1.5%TG+HPMC group There were significant differences (P<0.05) with other samples in the three time periods. In addition, none of the samples showed brittleness during the storage period, indicating that all samples were broken during the test. In conclusion, we believe that HPMC combined with TG enzyme can effectively reduce the hardening problem of nutritional bars, and the 3.0% TG+HPMC group has the best effect.

Table 11 Effects of HPMC combined with TG enzyme on the texture of nutritional bars during storage

3.3.2 The effect of HPMC combined with TG enzyme on the color of nutrition bar storage period

Figure 17 shows the changes in the overall appearance of the HPMC-binding TG enzyme samples during the storage period. It can be seen from the figure that the appearance of each sample has changed significantly during the storage period. On the 0th day, each sample was white-yellow, and the control group began to turn dark brown on the 8th day, and turned black after 20 days of storage. After adding HPMC and TG enzymes, the color change of the samples was delayed, and the appearance of the HPMC+3.0%TG group changed from dark brown to dark brown after 12 days. Figure 18 shows the color data changes of samples with HPMC combined with different concentrations of TG enzyme during storage. The L*, a* and b* values of each group of samples were relatively close at 0 d of storage, and the L* value was stable at 87 -88, the a* value is between 2-3, and the b* value is stable between 20-22. With the increase of storage time, L* showed a downward trend. After 20 days of storage, the L* values of the control group, HPMC group, 0.5%TG+HPMC group, 1.5%TG+HPMC group and 3.0%TG+HPMC group were 65.29, respectively. ±0.31, 68.50±0.28, 70.05±0.39, 70.63±0.18, 72.73±0.95, there were significant differences between the control group and other groups, and there were also significant differences between the 3.0%TG+HPMC group and other components (P<0.05 ). The a* value and b* value showed an upward trend during the storage period. After 20 days, the a* value of each component increased to 16.22±0.06, 15.18±0.20, 14.14±0.15, 15.15±0.23, 13.81±0.12, respectively. There were significant differences between the group and other groups (P<0.05). After 20 days, the b* value of each component increased to 39.52±0.10, 39.76±0.25, 39.28±0.31, 39.17±0.12, 38.94±0.36, and there was no significant difference between the components (P>0.05). According to the data, we can think that adding HPMC combined with TG enzyme can alleviate the color change during the storage period of the nutrition bar, among which, the 3.0% TG+HPMC group has the best effect.

3.3.3 The effect of HPMC combined with TG enzyme on the available amino groups during the storage period of nutritional bars

Figure 19 shows the effect of HPMC combined with TG enzyme on the percentage of available amino groups during the storage period of the nutrition bar. It can be seen from the figure that the curve declined rapidly for 8 days before storage; after 16 days of storage, the downward trend became gentle. The amino content of 1.5%TG+HPMC group and 3.0%TG+HPMC group was lower than that of control group 4d before storage, and the change trend after 4d was smaller than that of control group, and the content was higher than that of control group. The content of available amino groups in HPMC group and 0.5%TG+HPMC group was significantly lower than that in control group, and the content in 0.5%TG+HPMC group was the lowest. After 20 days of storage, the percentages of available amino groups in the control group, HPMC group, 0.5%TG+HPMC group, 1.5%TG+HPMC group and 3.0%TG+HPMC group were (38.98±0.13)%, (37.41±0.13)%, (35.35±0.04)%, (44.05±0.09)%, (46.71±0.31)%, there were significant differences among the components (P<0.05).

3.3.4 The effect of HPMC combined with TG enzyme on the insoluble protein of nutrition bar storage period

Figure 20 represents the effect of HPMC combined with TG enzyme on the percentage of insoluble protein in the nutrition bar. It can be seen that the change trend of the control group, the HPMC group and the 0.5%TG+HPMC group is similar, and the insoluble protein content gradually increases during the storage period. In the 1.5%TG+HPMC group and the 3.0%TG+HPMC group, the insoluble protein content increased rapidly within 4 days before storage, and the change trend in the later storage period was not significant. After 20 days of storage, the percentage of insoluble protein content in the control group, HPMC group, 0.5%TG+HPMC group, 1.5%TG+HPMC group and 3.0%TG+HPMC group reached (10.60±0.37)%, (6.97±0.35)%, (6.15±0.21)%, (7.76±0.21)% and (9.57±0.36)%, there were significant differences among the systems (P<0.05).

3.3.5 Effect of HPMC combined with TG enzyme on the microstructure of nutritional bars during storage

Figure 21 shows the change of the microstructure of the HPMC combined with TG enzyme nutrition bar system. It can be seen from the figure that when stored for 0 d, the proteins in the control group have begun to undergo different degrees of hydration, the protein particles absorb water and swell, and the adjacent proteins are glued together , forming a protein network. After the addition of HPMC and TG enzymes, hydration was relieved, and a liquid phase formed by a large amount of water, HPMC, glycerol and fructose was seen on the surface of the protein in the HPMC sample (Figure 21B). After the addition of TG enzyme, the adjacent proteins were bound together by the action of enzymes to form larger protein particles (Fig. 21E), and the more TG enzyme was added, the more large protein particles were formed. After 12d and 20d of storage, the original protein network disintegrated, and with the passage of time, the surface of the sample formed a uniform morphology with a large number of air bubbles intertwined. However, in the system with TG enzyme added, the original protein form was still retained, the protein particles became larger than the 0d, and the content of air bubbles was also more than that in the control group.

3.3.6 Effect of HPMC combined with TG enzyme on sensory scores of nutritional bars during storage

The effect of HPMC combined with TG enzyme on the sensory evaluation of nutritional bars is shown in Figure 22. Overall, the color, flavor and taste scores of each system after storage for 20 days are lower than those of the 0th day. After the addition of TG enzyme, the scores of each index of the nutrition bar increased, and the 3.0% TG+HPMC system had the highest sensory score at 0d and 20d of storage, which indicated that the addition of 3.0% TG enzyme had the best improvement effect on the system.

The above-mentioned embodiments are only to describe the preferred modes of the present invention, but not to limit the scope of the present invention. Without departing from the design spirit of the present invention, those of ordinary skill in the art can make various modifications to the technical solutions of the present invention. Variations and improvements should fall within the protection scope determined by the claims of the present invention.

Claims (8)

1. A method for preparing a high protein nutritional bar, comprising the steps of: adding to a high protein nutritional bar model system a hydrophilic composition consisting of hydroxypropyl methylcellulose and transglutaminase.

2. The method of making the high protein nutritional bar of claim 1 wherein the high protein nutritional bar model system comprises a sodium caseinate system and a soy protein isolate system.

3. The method of making the high protein nutritional bar of claim 2 wherein the hydrophilic composition comprises hydroxypropyl methylcellulose in an amount of 0.5% to 2% and transglutaminase in an amount of 0.5% to 3% by weight of the sodium caseinate or soy protein isolate.

4. The method of making the high protein nutritional bar of claim 2, wherein the sodium caseinate system comprises sodium caseinate, sorbitol, glycerol, and water, wherein the ratio of sodium caseinate: sorbitol: glycerin: the mass ratio of water is 40:30:15: 15.

5. The method of making the high protein nutritional bar of claim 2 wherein the soy protein isolate system comprises soy protein isolate, sorbitol, glycerin, and water, wherein the soy protein isolate: sorbitol: glycerin: the mass ratio of water is 40:30:15: 15.

6. A high protein nutritional bar produced by the method of any one of claims 1 to 5.

7. Use of a hydrophilic composition for extending the storage stability of a high protein nutritional bar, wherein the hydrophilic composition is comprised of hydroxypropyl methylcellulose and transglutaminase.

8. The use of claim 7, wherein the mass ratio of hydroxypropyl methylcellulose to transglutaminase is (0.5-2) to (0.5-3).

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