Pea starch-quinoa protein soft gel and preparation method thereof

Abstract

The invention discloses pea starch-quinoa protein soft gel and a preparation method thereof. The pea starch-quinoa protein soft gel is prepared from pea starch and quinoa protein. The mass ratio of the pea starch to the quinoa protein is 10: (2-3); the IDDSI rating of the pea starch-quinoa protein soft gel is grade 4, the water binding capacity is 76.71 + / -0.12%, the hardness is 1.514 + / -0.017 N, the breaking strength is 0.976 + / -0.004 N, and the apparent viscosity is 473.6 + / -9.1 Pa.s. By optimizing the proportion and processing conditions of the pea starch and the quinoa protein, the soft gel which is easy to swallow and has high nutritional value and good taste is prepared, so that the special diet requirements of old people with dysphagia are met.

Description

Technical Field

[0001] The invention relates to pea starch-quinoa protein soft gel and a preparation method thereof, and belongs to the field of food science. Background Art

[0002] Dysphagia, also known as swallowing disorder, is a disease that is prevalent among the elderly, which can lead to problems related to food swallowing, such as choking, aspiration, aspiration pneumonia, and even death. Designing special diets, such as thickened liquids (such as water, milk, soup, and juice) is an important way to solve the swallowing problem of patients with dysphagia. Currently, the food products on the market for elderly people with dysphagia mainly include soft food, pureed food, and liquid food. These products are designed to provide food forms that are easy to swallow and digest, but they often lack nutritional value and have a bland taste, which cannot meet the sensory and nutritional needs of the elderly. To solve this problem, researchers are developing new food products, such as gel products based on plant proteins and starches, which are not only easy to swallow, but also have high nutritional value and good taste by improving the texture of food, which can meet the special dietary needs of the elderly. However, most studies focus on the development of pure starch gel products, and rarely mix them with protein, so it is necessary to develop high-protein fluid foods, which can greatly reduce the pressure of eating caused by the need for adequate protein supplementation in the elderly.

[0003] Pea is the third soybean crop after soybean and peanut. It has the characteristics of high nutritional value, low price, low allergenicity and great potential for developing low GI food. Quinoa, as a nutritious grain crop, has a high protein content and a balanced amino acid composition, and can be used as a high-quality protein source. Gelation is an important functional property of protein. Studies have shown that modification of quinoa protein can improve gelation, which is helpful for the research and application of quinoa protein gel. Therefore, the present invention contemplates combining pea starch with quinoa protein to improve the nutritional value of food and optimize the rheological properties of the composite gel to meet the needs of patients with dysphagia. Summary of the invention

[0004] The purpose of the present invention is to provide a pea starch-quinoa protein soft gel, by optimizing the ratio of the two and processing conditions, to prepare a soft gel that is easy to swallow and has high nutritional value and good taste, so as to meet the special dietary needs of elderly people with dysphagia.

[0005] The pea starch-quinoa protein soft gel provided by the present invention is made of pea starch and quinoa protein; The mass ratio of the pea starch to the quinoa protein is 10:2-3.

[0006] Specifically, the pea starch-quinoa protein soft gel has an IDDSI rating of 4, a water holding capacity of 76.71±0.12%, a hardness of 1.514±0.017N, a rupture strength of 0.976±0.004N, and an apparent viscosity of 473.6±9.1Pa·s.

[0007] The present invention also provides a method for preparing the pea starch-quinoa protein soft gel, comprising the following steps: S1, mixing the pea starch suspension and the quinoa protein suspension, and magnetically stirring to obtain a mixed suspension; S2. Heating the mixed suspension in a water bath, and then cooling it overnight to obtain the pea starch-quinoa protein soft gel.

[0008] In the above preparation method, in step S1, in the mixed suspension, the mass ratio of pea starch to quinoa protein is 10:2-3, preferably 10:2.4; The liquid-to-solid ratio of the mixed suspension is 100:6-6.5 (g / ml), and the preferred solid-to-liquid ratio is 100:6.25.

[0009] In the above preparation method, in step S1, the magnetic stirring is performed at room temperature for 30-40 minutes.

[0010] In the above preparation method, in step S2, the water bath heating temperature is 95-100° C., and the time is 30-40 minutes; preferably, the water bath heating temperature is 98° C., and the time is 35 minutes.

[0011] In the above preparation method, the quinoa protein is prepared by the following steps: (a) dispersing defatted quinoa powder in distilled water, adjusting the pH to 8.9-9.1, and centrifuging to obtain the supernatant; (b) adjusting the pH of the supernatant to 4.4-4.6, centrifuging to obtain a precipitate, neutralizing and freeze-drying the precipitate, and grinding and sieving to obtain the quinoa protein.

[0012] The present invention investigates the effects of PS / QP, water bath heating temperature, and water bath heating time on the International Dysphagia Diet Standardization Initiative (IDDSI) rating, water holding capacity, and texture characteristics of PS-QP composite gels. After detailed experimental analysis and statistical processing, it was found that except for the PS / QP of 10 / 0, which was rated as level 6-soft and one-bite, the IDDSI ratings of other PS-QP composite gels were all level 4-paste / highly thick. In addition, these three factors had a significant effect on the water holding capacity and texture characteristics of PS-QP composite gels. Therefore, the present invention selected these three factors to conduct response surface experiments.

[0013] On the basis of the single factor experiment, the present invention further optimizes the process formula for preparing PS-QP composite gel by response surface experiment, and determines the optimal process conditions for preparing PS-QP composite gel: water bath heating temperature is 98 ° C, water bath heating time is 35 min, PS / QP is 10 / 2.4. Under this formula, the prepared PS-QP composite gel can meet the needs of some people with dysphagia, and has certain stability and appropriate texture. The optimized PS-QP composite gel IDDSI rating is level 4-paste / highly thick, with high water holding capacity (76.71%), high hardness (1.514N), large rupture strength (0.976N), low apparent viscosity (473.6Pa.s), and low viscoelasticity. The experimental results verify the accuracy of the Box-Behnken design response surface experiment prediction, and the fitting model is significantly higher than the experimental model, indicating that the prediction results are more accurate. The experiment shows that the water holding capacity of the PS-QP composite gel has good reproducibility under the predicted conditions, and the deviation from the predicted results is small. Therefore, it can be considered that the Box-Behnken design response surface experiment prediction conditions are suitable for optimizing the preparation conditions of PS-QP composite gel. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the process of the present invention.

[0015] Figure 2 are the IDDSI ratings for different PS-QP mixture concentrations.

[0016] Figure 3 It is the effect of heating temperature on the water holding capacity, rupture strength and hardness of the composite gel.

[0017] Figure 4 It is the effect of heating time on the water holding capacity, bursting strength and hardness of the composite gel.

[0018] Figure 5 It is the effect of PS / QP on the water holding capacity, bursting strength and hardness of the composite gel.

[0019] Figure 6 It is the response surface diagram and contour diagram of the interaction between heating temperature and heating time on the water holding capacity of composite gel.

[0020] Figure 7 It is the response surface diagram and contour diagram of the effect of heating temperature and PS / QP interaction on the water holding capacity of composite gel.

[0021] Figure 8 It is the response surface diagram and contour diagram of the effect of heating time and PS / QP interaction on the water holding capacity of composite gel.

[0022] Fig. 9It is the optimal prescription prediction chart of the model established by response surface methodology.

[0023] Fig.10 is the IDDSI rating of the PS gel and the sample under the best formulation (PS-QP(10 / 2.4)). DETAILED DESCRIPTION

[0024] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0025] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0026] The method for extracting quinoa protein (QP) in the following examples is as follows: The quinoa rice was ground and passed through an 80-mesh sieve. The quinoa powder was mixed with petroleum ether (1:3, w / v) at room temperature for 24 hours, and the petroleum ether was evaporated to obtain defatted quinoa powder. It was dispersed in distilled water (15%, w / v), 2M NaOH was added to adjust the pH to 9, stirred at room temperature for 30 minutes, centrifuged at 10,000×g (20°C) for 20 minutes, and the supernatant was collected. The pH was adjusted to 4.6 with 2M HCl, centrifuged at 10,000×g (5°C) for 20 minutes, and the precipitate was collected. It was resuspended in distilled water and neutralized by adding 2N NaOH to adjust the pH to 7. The suspension was frozen in a -80°C refrigerator and then frozen for 72 hours. The dried isolated protein was ground for 1 minute to make it into powder and passed through a 100-mesh sieve to obtain quinoa protein (QP). The method for preparing the pea starch (PS) and QP suspension in the following example is as follows: Weigh 10.0 g of PS powder and add deionized water to prepare a starch suspension. The suspension was magnetically stirred at room temperature (22 ± 1 °C) for 1 min and then fixed to 100 mL to obtain a 10% PS suspension.

[0027] The QP powder was resuspended in deionized water and magnetically stirred for 2 h to obtain a 5% QP suspension.

[0028] The method of IDDSI rating in the following examples is as follows: The composite gel was subjected to flow test, fork pressure test, fork drip test, spoon tilt test and spoon pressure test, and the grade of the sample was determined according to the IDDIS framework requirements. Flow test: remove the rubber stopper of the syringe, block the syringe nozzle with a finger, inject 10mL of liquid, remove the finger and count for 10s, block the nozzle with a finger, and observe the amount of residual liquid; Fork pressure test: use a fork to gently press the food and observe whether the fork teeth can form obvious marks on the food surface; Fork drip test: observe whether the food can be piled on the fork and whether the food flows or drips from the fork gap; Spoon tilt test: use a standard smooth spoon to scoop up the sample, observe the state of the food ball on the spoon, then tilt the spoon steadily to the side, observe the state of the sample sliding, and the state of the spoon surface after the sample slides; Spoon pressure test: use the side of the spoon to apply pressure to the food. The pressure applied should be enough to turn the thumb nail white. Observe whether the food sample is flattened, cracked, deformed, and whether it returns to its original shape after the spoon is removed.

[0029] The method for detecting water holding capacity (WHC) in the following examples is as follows: 5.0 g of gel was centrifuged at 2000×g for 30 min at 4°C. The ratio of the mass of the gel after centrifugation to the mass of the original gel was the water holding capacity of the gel.

[0030] The method for determining the TPA characteristics in the texture characteristics in the following examples is as follows: A cylindrical gel sample (20 mm in diameter and 15 mm in height) was placed in a texture analyzer for TPA testing. A double-cycle compression test was performed using a 5 mm diameter cylindrical probe (P / 5), a pre-test speed of 0.5 mm / s, a compression speed of 0.5 mm / s, a target distance of 5.0 mm, and a time of 5 s. The software recorded the force-time curve and required parameters during the double-cycle compression-decompression test, and analyzed and processed them to obtain the hardness, elasticity, cohesion, adhesiveness, chewiness, and resilience of the sample.

[0031] The method for measuring gel rupture in the texture properties in the following examples is as follows: Take a cylindrical gel sample (60mm in diameter, 30mm in height) and conduct a gel penetration test in a texture analyzer. Use a 12.7mm black cylindrical probe and set the parameters as follows: 30 mm / min in-test rate, 600 mm / min after-test rate, and 15.0 mm downward pressure distance. The gel rupture strength and distance can be obtained, where the gel rupture strength is the initial pressure (N) required to penetrate the gel; the rupture distance is the distance corresponding to the maximum force (mm).

[0032] The method for measuring the static rheological properties in the following examples is as follows: The PP50 plate was used for measurement. The prepared composite gel was placed between the rheometer plates. The plate clamp diameter was 40 mm, the plate spacing was set to 2.5 mm, the frequency was 1 Hz, the strain was 1%, the test temperature was 25 °C, and the shear rate was 0.1 s -1 -100s -1 The apparent viscosity-shear rate curve was drawn within a certain range.

[0033] The method for measuring the dynamic rheological properties in the following examples is as follows: The measurement was performed using a plate of model PP50. The composite gel was placed between the rheometer plates, and the plate spacing was set to 2.5 mm. Strain-related measurements were first performed to obtain the linear viscoelastic region of the hydrogel. Then the dynamic rheological properties were measured at a small constant strain (1.0%), which was in the linear region of all samples. The dynamic temperature was scanned from 93-25°C at a frequency of 1 Hz, and the dynamic frequency was scanned from 0.6283 to 62.83 rad / s at 25°C; the dynamic time scan was performed at a frequency of 1 Hz and 93°C for 20 min, and the storage modulus (G') and loss modulus (G") were recorded as a function of temperature, frequency and time.

[0034] Example 1, single factor experiment (1) Effect of PS-QP mixture concentration on the texture properties, fracture characteristics and IDDSI rating of PS-QP composite gel The water bath heating temperature was set to 95°C and the water bath heating time was set to 30 min. An appropriate amount of 10% PS suspension was mixed with 5% QP suspension to prepare a PS / QP suspension of 10 / 2. The effect of PS-QP mixture concentrations of 1.2%, 3%, 6%, 9%, 12%, and 15% on the composite gel was investigated.

[0035] The samples with 1.2% and 3% concentrations were both flowing liquids, and the texture and fracture properties were not measured. The effect of PS-QP mixture concentration on the texture properties of PS-QP composite gel is shown in Table 1, the effect on the fracture properties is shown in Table 2, and the effect on the IDDSI rating is shown in Table 3. Figure 2 .

[0036] Table 1 Texture properties of different PS-QP mixture concentrations

[0037] Table 2 Rupture characteristics of different PS-QP mixture concentrations

[0038] As shown in Tables 1 and 2, with the increase in the concentration of the PS-QP mixture (6% to 15%), the hardness, rupture strength and adhesion of the composite gel were significantly improved (such as the hardness increased from 0.140 to 1.815), indicating that the increase in solid content strengthened the gel network structure. However, the cohesion decreased slightly at a liquid-to-solid ratio of 100:15, which may be due to the partial breakage of the gel due to the high solid content. Among them, the sample with a liquid-to-solid ratio of 100:6 showed low hardness (0.140), low adhesion (0.036) and moderate cohesion (25.981), making it easy to disperse in the mouth and not easy to adhere, which meets the needs of people with dysphagia for "no need for strong chewing" and "low adhesion risk".

[0039] like Figure 2 As shown, 1.2% of the samples flowed out completely within 10 seconds in the flow test, and 0 ml (less than 1 ml) of liquid remained in the syringe, which was rated as 0-thin. 3% of the samples flowed out of a 10 ml syringe within 10 seconds in the flow test, and 7 ml (4-8 ml) of liquid remained in the syringe, which was rated as 2-slightly thick.

[0040] 6% of the samples were easily crushed by the pressure of the fork in the fork pressure test (the pressure used did not turn the nail white), the fork tines could leave obvious marks on the surface of the food, and the food had the impression of the fork being pressed and no lumps; in the fork drip test, the food could be piled on the fork without dripping; in the spoon tilt test, the texture had enough cohesion to keep its shape on the spoon, and a whole spoonful would fall off when the spoon was tilted, and was rated as 4-paste / highly thick. 9% and 12% of the samples were flattened and changed in shape when the thumb pressed the food with the bottom of the fork until the thumb nail turned white in the fork pressure test, and the food would not return to its original shape after the fork was removed; the food could be cut with the side of the fork. In the spoon pressure test, the food was flattened and changed in shape when the thumb pressed the food with the bottom of the spoon until the thumb nail turned white, and the food would not return to its original shape after the spoon was removed, and was rated as 6-soft and bite-sized. 15% of the samples were rated as level 7 - easy to chew when the food was changed in shape when the thumb pressed the food with the bottom of the fork until the thumb nail turned white in the fork pressure test. After the fork was removed, the food did not return to its original shape. The food could be cut with the side of the fork.

[0041] Among them, 6% of the samples were rated as Level 4 (paste / highly thick) by the IDDSI test. Their flow test showed controllable slow fluidity, no juice separation in the fork pressure test, and uniform consistency in the spoon tilt test. These characteristics strictly meet the international dysphagia dietary standards, can reduce the risk of aspiration in the elderly, and avoid the problem of oral residue caused by excessive cohesion of high liquid-to-solid ratio samples (such as Level 7 of 100:15), taking into account safety, palatability and functionality. Therefore, the PS-QP mixture concentration was selected as 6%, because it showed the best performance between texture characteristics (low hardness, moderate elasticity) and IDDSI rating (Level 4 paste).

[0042] (2) Effect of water bath heating temperature on water holding capacity, breaking strength and hardness of PS-QP composite gel The water bath heating time was set to 30 min. An appropriate amount of 10% PS suspension was mixed with 5% QP suspension to prepare a PS / QP suspension of 10 / 2.5 (liquid-solid ratio of 100:6.25). The effect of water bath heating temperature at 90, 93, 95, 98, and 100 °C on the composite gel was investigated.

[0043] Effects of water bath heating temperature on water holding capacity, breaking strength and hardness of PS-QP composite gel Figure 3 As shown. With the increase of heating temperature, water holding capacity first increases, reaches a maximum value at 98℃, and then decreases, and the breaking strength and hardness are roughly consistent with its trend. The thermal denaturation temperature of quinoa protein is 98.1℃±0.1℃, which is crucial to the structural and functional properties of quinoa protein. When heated to the thermal denaturation temperature, the structure of quinoa protein is destroyed, further affecting its functional properties in the composite gel. At this time, quinoa protein undergoes moderate denaturation, and the interaction between protein molecules and between protein molecules and pea starch is enhanced, thereby promoting the formation of a gel network. The enhancement of this network structure helps to improve the hardness and water holding capacity of the gel, because a more complete network can capture and retain water more effectively. When the protein is denatured, the hydrophobic interaction and disulfide bond formation between molecules may increase, which helps to form a stronger gel network. When the heating temperature is too high (>98℃), the protein is over-denatured, which in turn destroys the gel network and reduces the water holding capacity and texture properties. Therefore, in the process of preparing PS-QP composite gel, in order to ensure its stability and appropriate texture characteristics, 96 °C, 98 °C, and 100 °C were selected as the factor level values ​​for response surface optimization.

[0044] (3) Effect of water bath heating time on water holding capacity, breaking strength and hardness of PS-QP composite gel The water bath heating temperature was set at 95°C, and an appropriate amount of 10% PS suspension was mixed with 5% QP suspension to prepare a PS / QP suspension of 10 / 2.5 (liquid-to-solid ratio of 100:6.25). The effect of heating time at 20, 25, 30, 35, and 40 min on the water retention, breaking strength, and hardness of the composite gel was investigated.

[0045] Effect of water bath heating time on water holding capacity, breaking strength and hardness of PS-QP composite gel Figure 4 As shown in the figure, as the heating time progresses, the water holding capacity first remains stable, then begins to increase from 25 min and reaches a maximum value at 35 min. The breaking strength is roughly consistent with its trend, and there is no significant difference in hardness. Therefore, in the process of preparing PS-QP composite gel, in order to ensure its stability and moderate texture characteristics, 30 min, 35 min, and 40 min were selected as the factor level values ​​for response surface optimization.

[0046] (4) Effect of PS / QP on water holding capacity, breaking strength and hardness of PS-QP composite gel The water bath heating temperature was set to 95℃, the water bath heating time was set to 30min, and an appropriate amount of 10% PS suspension was mixed with 5% QP suspension to prepare suspensions containing 5 different concentration combinations of PS+QP (10%+0%, 10%+0.5%, 10%+1.5%, 10%+2.5%, 10%+3.5%), and the effects of PS / QP on the water holding capacity, bursting strength and hardness of the composite gel were investigated at 10 / 0, 10 / 0.5, 10 / 1.5, 10 / 2.5 and 10 / 3.5. The liquid-to-solid ratios of the suspensions were 100:5, 100:5.25, 100:5.75, 100:6.25 and 100:6.75, respectively.

[0047] Effects of PS / QP on water holding capacity, bursting strength and hardness of PS-QP composite gels Figure 5 As shown. With the increase of protein content, the water holding capacity showed an overall downward trend. Compared with 1.5% protein, there was no significant difference in the water holding capacity of 2.5% protein. Considering the amount of protein added, the protein content at 2.5% was determined to be the optimal value, and the trends of the changes in rupture strength and hardness were similar. At low protein content, the gel network has not been fully formed, resulting in low water holding capacity. When the protein content increases to a certain level, the gel network structure is more perfect and the water holding capacity is improved. However, with the further increase of protein content, the protein aggregation degree is high and the amorphous state is enhanced, resulting in the decrease of its texture, water holding capacity and other characteristics. Therefore, in the process of preparing PS-QP composite gel, in order to ensure its stability and moderate texture characteristics, 2%, 2.5%, and 3% were selected as the factor level values ​​for response surface optimization.

[0048] Example 2, response surface experiment The preparation process of PS-QP composite gel was further optimized based on the single factor experiment. According to the Box-Behnken experimental design principle, Design Expert 13 software was used to design the experiment with water holding capacity as the response value, including three factors and three levels of water bath heating temperature, heating time and PS / QP, to determine the optimal process parameters and prepare PS-QP composite gel with better stability and texture performance.

[0049] 1. Response surface optimization experiment Based on the single factor experiment, heating temperature (X1), heating time (X2) and PS / QP (X3) were selected as the three factors of the response surface experiment, and PS-QP composite gel WHC (Y) was used as the evaluation index. The experimental factors and level design are shown in Table 3. The experimental design scheme and results are shown in Table 4.

[0050] Table 3 Factors and levels of response surface experiment

[0051] Table 4 Box-Behnken test design and its response values

[0052] 2. Regression model fitting and variance analysis Design-Expert 13.0 was used to perform response surface analysis on the results in Table 5, and the quadratic polynomial regression equation of PS-QP composite gel WHC (Y) on heating temperature (X1), heating time (X2) and PS / QP (X3) was obtained: Y=76.13+0.2553X1-0.1647X2-0.7512X3-0.912X1X2-0.3075X1X3-0.315X2X3-2.74X 12 -3.94 X 22 -1.66 X 32 From the significance and F value in Table 5, it can be seen that the order of influencing factors of water holding capacity of PS-QP composite gel is heating temperature > PS / QP > heating time. The first-order term of the equation X3 has a significant effect on the water holding capacity of the composite gel; the interaction term X1 2 , X2 2 and X3 2 The effect on the water holding capacity of the composite gel is extremely significant, and the interaction term X1X2 has a significant effect on the water holding capacity of the composite gel. It can be seen that the influence of each specific experimental factor on the response value is not a simple linear relationship. The regression model term is extremely significant, and the determination coefficient R 2It reached 0.9784, indicating that the model has a good fit and that the model can well predict the water holding capacity of the composite gel. 2 Adj It reached 0.9507, indicating that the composite gel water retention model can explain the test results to a degree of 95.07%, and only 4.93% cannot be expressed by the model. The model lack of fit term is not significant (P>0.05), further indicating that the model has a good fit.

[0053] Sufficient precision, measuring the signal-to-noise ratio, is a metric used in response surface methodology to evaluate the quality of a fitted model, and a ratio greater than 4 indicates that the model is a good representation of the actual process. The signal-to-noise ratio of the experimental model of the present invention is 15.7190, indicating that the model has a high predictive ability and can better reflect the true value. In summary, the regression model has a good degree of fit, a small experimental error, and can accurately analyze and predict the water retention of the composite gel.

[0054] Table 5 Analysis of variance of the multivariate regression model with the water holding capacity of the composite gel as the response value

[0055] Note: *.P<0.05, significant difference; **.P<0.01, extremely significant difference.

[0056] 3. Analysis of the interaction of various factors on response surface Based on the regression model designed by Design-Expert 13 software, the interaction of the three factors of heating temperature (X1), heating time (X2) and PS / QP (X3) was used to generate contour maps and response surface plots in order to analyze the effects of the interactions between different single factors on the water holding capacity of PS-QP composite gel. Figures 6 to 8 The contour plots and response surface plots of X1X2, X1X3, and X2X3 are shown respectively. These plots allow for an in-depth analysis of the significant interactions between factors on sensory scores.

[0057] (1) If Figure 6 When X3 (PS / QP) is 10:2.5, there is an interactive effect between X1 (heating temperature) and X2 (heating time) on water holding capacity. The contour lines of X1 (heating temperature) and X2 (heating time) are close to ellipse, and the slope of the response surface curve is very steep, indicating that there is an interactive effect between the two factors of heating temperature and heating time, and it is very significant.

[0058] (2) If Figure 7When the heating time is 35 min, there is an interactive effect between X1 (heating temperature) and X3 (PS / QP) on water holding capacity. The contour lines of X1 (heating temperature) and X3 (PS / QP) are close to ellipses, and the slope of the response surface curve is steep, indicating that there is an interactive effect between the two factors of heating temperature and PS / QP.

[0059] (3) If Figure 8 It is the interactive effect of X2 (heating time) and X3 (PS / QP) on water holding capacity when the heating temperature is 98°C. The contour lines of X2 (heating time) and X3 (PS / QP) are close to ellipses, and the slope of the response surface curve is steep, indicating that there is an interaction between the two factors of heating time and PS / QP.

[0060] 4. Verification test and results like Fig. 9 As shown in the figure, according to the analysis of Design-Expert 13 software, the best preparation process formula of PS-QP composite gel is obtained: heating temperature 98.1249 ℃, heating time 34.9063min, PS / QP 10: 2.3849. Combined with the actual production situation, the drying temperature is set to an integer, and combined with the convenience of experimental operation, the optimal process formula is fine-tuned. Therefore, the formula after a series of corrections is: heating temperature 98℃, heating time 35min, PS / QP 10: 2.4. The optimized WHC of PS-QP composite gel reaches 76.22%.

[0061] Three batches of PS-QP composite gels were prepared according to the above formulas. WHC was determined and hardness, burst strength, apparent viscosity and IDDSI rating were measured. Fig.10. In the fork pressure test, the PS gel sample was pressed with the thumb with the bottom of the fork until the thumb nail turned white. The food was flattened and changed in shape. After the fork was removed, the food did not return to its original shape. The food could be cut with the side of the fork. In the spoon pressure test, the food was pressed with the thumb with the bottom of the spoon until the thumb nail turned white. The food was flattened and changed in shape. After the spoon was removed, the food did not return to its original shape. It was rated as 6-soft and bite-sized. In the fork pressure test, the PS-QP (10 / 2.4) sample was easily crushed by the fork pressure (the pressure used did not make the nail turn white), the fork tines could form obvious marks on the surface of the food, and the food had the impression of the pressed fork without lumps. In the fork drip test, the food could be piled on the fork without dripping. In the spoon tilt test, the texture had enough cohesion to maintain its shape on the spoon. When the spoon was tilted, a whole spoonful would fall off. It was rated as 4-paste / highly thick. It can be seen that the optimized formula can reduce the IDDSI rating of the sample from level 6 to level 4, which is suitable for people with weak tongue control, pain when chewing and swallowing, missing teeth or wearing inappropriate dentures, and meets the requirements of some people with swallowing difficulties and the elderly.

[0062] According to the model prediction, the predicted value and actual value of the optimized best process formula are shown in Table 6. The final results show that the actual WHC value of the PS-QP composite gel is 76.71±0.12, which is very close to the predicted value of the model, proving that the regression model has good predictive power and the optimization of the PS-QP composite gel formula by response surface methodology is stable and feasible, which has certain guiding significance.

[0063] Table 6 Predicted value of the best process formula and actual value of the optimized formula

[0064] On the basis of the single factor experiment, the present invention further optimizes the response surface experiment and determines the optimal process conditions for preparing PS-QP composite gel: heating temperature 98°C, heating time 35min, PS / QP 10:2.4. Under this formula, the prepared PS-QP composite gel can meet the needs of some people with dysphagia, and has certain stability and appropriate texture. The optimized PS-QP composite gel IDDSI rating is level 4-paste / highly thick, with high water holding capacity (76.71%), high hardness (1.514N), large rupture strength (0.976N), low apparent viscosity (473.6Pa.s), and low viscoelasticity. The experimental results verify the accuracy of the Box-Behnken design response surface experiment prediction, and the fitting model is significantly higher than the experimental model, indicating that the prediction results are more accurate. The experiment shows that the water holding capacity of the PS-QP composite gel has good reproducibility under the predicted conditions, and the deviation from the predicted results is small. Therefore, it can be considered that the Box-Behnken design response surface experiment prediction conditions are suitable for optimizing the preparation conditions of the PS-QP composite gel.

Claims

1. A pea starch-quinoa protein soft gel, made from pea starch and quinoa protein; The mass ratio of the pea starch to the quinoa protein is 10:2-3.

2. The pea starch-quinoa protein soft gel according to claim 1, characterized in that: The pea starch-quinoa protein soft gel has an IDDSI rating of 4, a water holding capacity of 76.71±0.12%, a hardness of 1.514±0.017N, a rupture strength of 0.976±0.004N, and an apparent viscosity of 473.6±9.1Pa·s.

3. The method for preparing the pea starch-quinoa protein soft gel according to claim 1 or 2, comprising the following steps: S1, mixing the pea starch suspension and the quinoa protein suspension, and magnetically stirring to obtain a mixed suspension; S2. Heating the mixed suspension in a water bath, and then cooling it overnight to obtain the pea starch-quinoa protein soft gel.

4. The preparation method according to claim 3, characterized in that: In step S1, in the mixed suspension, the mass ratio of pea starch to quinoa protein is 10:2-3; The liquid-to-solid ratio of the mixed suspension is 100:6-6.5 (g / ml).

5. The preparation method according to claim 3 or 4, characterized in that: In step S1, the magnetic stirring is performed at room temperature for 30-40 min.

6. The preparation method according to any one of claims 3 to 5, characterized in that: In step S2, the water bath is heated at a temperature of 95-100° C. for 30-40 minutes.

7. The preparation method according to claim 6, characterized in that: The water bath was heated at 98° C. for 35 minutes.

8. The preparation method according to any one of claims 3 to 7, characterized in that: The quinoa protein is prepared by the following steps: (a) dispersing defatted quinoa powder in distilled water, adjusting the pH to 8.9-9.1, and centrifuging to obtain the supernatant; (b) adjusting the pH of the supernatant to 4.4-4.6, centrifuging to obtain a precipitate, neutralizing and freeze-drying the precipitate, and grinding and sieving to obtain the quinoa protein.

9. Use of the pea starch-quinoa protein soft gel according to claim 1 or 2 in preparing food for patients with dysphagia.

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