Preparation method of anti-saccharification high-protein composite rice

Abstract

The invention discloses a preparation method of anti-saccharification high-protein composite rice, and belongs to the technical field of food processing. The composite rice is prepared by taking whey protein, broken rice flour and polyphenol as main raw materials, so that the problems that natural rice is insufficient in protein and the content of AGEs in high-protein rice is too high are effectively solved; the product is high in protein content, multiple in amino acid variety, reasonable in proportion and easy to digest and absorb by a human body, the nutritional ingredients of the raw materials are reserved, and the sensory value of the product is improved. The preparation method is simple in process, low in production cost, high in nutritional value and good in color and fragrance, generation of AGEs in the cooking process is greatly reduced, the application ways of the broken rice, the whey protein and other raw materials are expanded, and the comprehensive value of the product is improved.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, and in particular to a method for preparing anti-glycation high-protein composite rice. Background Art

[0002] Advanced glycation end products (AGEs) are a group of compounds formed by the non-enzymatic glycation reaction (also known as Maillard reaction) between the ketone or aldehyde groups of sugars and the amino groups of proteins. Food-borne AGEs originate from the Maillard reaction between reducing sugars and amino groups in food components. The production process is a non-enzymatic reaction with relatively intense conditions and a short production time. Food-borne AGEs can accumulate in the human body, accelerate human aging or lead to the occurrence of chronic degenerative diseases, so they should be taken seriously.

[0003] Broken rice refers to rice food that retains the outer shell (husk, bran and part of the germ) during rice processing, and has a low cost. Broken rice retains most of the natural nutrients of grains, including fiber, vitamins and minerals. Compared with white rice, it has a higher nutritional density and contains more dietary fiber, vitamin B and minerals. High fiber is beneficial to promote digestive health and stabilize blood sugar levels, and has a positive effect on preventing constipation and diabetes. Using broken rice with a simplified processing flow as raw material or auxiliary material for food processing can save costs and improve the nutritional value of food.

[0004] The sources of protein are rich and diverse. For example, crops such as soybeans and wheat can be used as raw materials for extracting plant protein. However, most of them are incomplete proteins and lack certain essential amino acids. For example, the lysine content in cereal protein is low, and the methionine content in bean protein is relatively insufficient. This may lead to the inability of the human body to obtain comprehensive and balanced amino acid nutrition when relying solely on plant protein, affecting the synthesis and utilization efficiency of protein. Whey protein is a high-quality protein with high nutritional value. Its essential amino acids are complete in variety, sufficient in quantity and appropriate in proportion. A high-protein composite rice made from whey protein and broken rice flour by extrusion, moderate maturation, cooling and granulation has high nutritional value and is easily absorbed and digested by the human body. However, it faces the same problem as ordinary plant-based high-protein composite rice. A large amount of AGEs will be produced during the cooking process of high-protein composite rice, which reduces the nutritional value of high-protein composite rice and causes harm to human health. Therefore, it is necessary to develop a processing technology to effectively reduce the problem of AGEs produced during the cooking process of high-protein composite rice.

[0005] Natural polyphenols have a wide range of biological activities and pharmacological effects, and have strong anti-glycation activity. +Free radicals and DPPH free radicals have strong scavenging ability, and have many beneficial effects such as enhancing metabolism and anti-aging. It is a good oxygen free radical scavenger and lipid peroxidation inhibitor. Taking proanthocyanidins as an example, its anti-glycation effect in the body is much higher than that of vitamin E and vitamin C. Its anti-glycation ability in the body is about 50 times that of vitamin E and 20 times that of vitamin C. It is one of the best natural anti-glycation agents discovered so far.

[0006] Therefore, researchers hope to prepare a highly nutritious whey protein composite rice with added polyphenols in order to reduce the content of AGEs in protein rice. However, experiments have shown that when whey protein is directly mixed with broken rice, the quality of the protein rice is poor. Therefore, how to add polyphenols and optimize the production process to prepare a composite rice with high protein content and quality and the ability to inhibit the production of AGEs is a technical problem that technicians in this field need to solve urgently. Summary of the invention

[0007] In view of the above-mentioned defects of the prior art, in a first aspect of the present invention, a method for preparing anti-glycation high-protein composite rice with rich nutritional ingredients, high sensory value, low AGEs content, simple process and low production cost is provided, comprising the following steps: (1) collecting and screening broken rice during rice processing, grinding it into powder, and then drying it to obtain broken rice flour; (2) treating whey with low-temperature spray drying technology to obtain whey protein, adjusting its pH and sterilizing it to obtain whey protein raw material; (3) mixing the broken rice flour, polyphenols, and whey protein raw materials according to a certain mass ratio to form a mixture; (4) Pour the mixed material into a screw extruder, add water to adjust the moisture content of the mixed material to 30 wt.%-40 wt.%; the screw extruder is set to six temperature zones in the order of inputting the mixed material to outputting the product, and the temperatures of the six temperature zones are: T1: 40-50 ℃, T2: 50-60 ℃, T3: 60-70 ℃, T4: 65-70 ℃, T5: 55-65 ℃, T6: 50-55 ℃; Among them, T1 and T2 represent the first and second temperature zones, which are preheating zones; T3 and T4 represent the third and fourth temperature zones, which are gelatinization zones; T5 and T6 represent the fifth and sixth temperature zones, which are cooling zones; After preheating, the mixed material is gelatinized in the gelatinization zone, extruded and granulated in the cooling zone, and the product is collected; (5) The product is dried to obtain anti-glycation high-protein composite rice.

[0008] Preferably, in step (1), drying is performed by drying at a temperature of 40-50°C.

[0009] When the pH of whey protein is 5.1-5.3, it has good thermal stability during the sterilization process and can effectively maintain its quality and functional properties.

[0010] Preferably, in step (2), the pH of the whey protein is adjusted to 5.1-5.3, and the sterilization temperature is 68-70° C. Preferably, in step (3), the broken rice flour and polyphenols are sieved through a 60-mesh sieve before mixing to remove impurities.

[0011] Preferably, in step (3), the polyphenols include proanthocyanidins, curcumin and apigenin.

[0012] When the mass ratio of broken rice flour is too low and the mass ratio of polyphenols to whey protein is too high, the composite rice cannot be formed; when the mass ratio of broken rice flour is too high and the mass ratio of polyphenols to whey protein is too low, the protein content and polyphenol content of the composite rice are insufficient. Therefore, those skilled in the art can adjust the mass ratio of each component in the mixture according to actual needs, and the mass ratio of broken rice flour, polyphenols and whey protein raw materials is 10:0.3:2 as the best choice.

[0013] Preferably, in step (3), the broken rice flour, polyphenols and whey protein raw materials are mixed in a mass ratio of 10:0.3:2 to form a mixture.

[0014] When the cutting blade rotates slowly, the composite rice is short and thick round; when the cutting blade rotates quickly, the composite rice is slender. Therefore, technicians in this field can adjust the rotation speed of the cutting blade according to actual needs, and the best choice is to control the rotation speed in the range of 700-900 rpm. Before the cutting and granulation step, when the composite powder is extruded from the oblate holes of the die head in the twin-screw extruder, it is generally in the form of slender strips. At this time, the amount of liquid added needs to be reduced (not less than 30%) so that the slender strips do not stick to each other before cutting and granulation.

[0015] Preferably, in step (4), the mixed material is fed into the screw extruder at a feed rate of 10-15 kg / h.

[0016] Preferably, in step (4), the screw speed is 110-130 rpm, and the cutter speed is 700-900 rpm.

[0017] Preferably, in step (5), a microwave and hot air combination is used for drying, the microwave energy is 280-320 W, and the hot air temperature is 60-70 °C.

[0018] Most composite rice uses plant protein as raw material, but the protein content and quality of plant protein are still relatively low compared to traditional animal protein. Even if the amino acid composition is optimized by adding multiple plant protein sources, it is difficult to achieve the high biological value and high-quality amino acid ratio of animal protein to meet the daily needs of the human body.

[0019] Among the raw materials used in this process, whey protein contains β-lactoglobulin, α-lactalbumin and other ingredients, which are easy to digest and absorb and have antioxidant properties; broken rice retains most of the natural nutrients of grains, including fiber, vitamins and minerals, and its nutritional density is higher than that of white rice. High fiber is conducive to promoting stable blood sugar levels. In addition, broken rice can save resources and costs and achieve high-value utilization of crops.

[0020] Based on the above technical scheme, the design concept of the present invention is to use antioxidant and anti-glycation polyphenols as raw materials to achieve the purpose of neutralizing free radicals in the body, reducing the damage of oxidative stress to cells, and inhibiting the formation of advanced glycation end products; at the same time, the covalent bonds and hydrogen bonds of polyphenols, hydrophobic interactions and other non-covalent interactions are used to bridge starch and protein, cross-link with them to form a gel grid structure, promote the combination of starch and protein, and further improve the product quality of composite rice. In addition, compared with plant protein, whey protein is used as a raw material. The essential amino acids contained in whey protein are complete in variety and reasonable in proportion, including 8 essential amino acids that the human body cannot synthesize on its own, and the proportion of these essential amino acids is close to the required pattern of the human body, which can be efficiently absorbed and utilized by the human body. At the same time, whey protein can also change the gel properties of starch, making the structure of the gel more compact and stable, thereby improving the texture and taste of the food. And by changing the extrusion parameters and the raw material ratio, a composite rice with high protein content and good quality is prepared.

[0021] The present invention controls the moisture content of the mixture and the screw extrusion temperature zone, so that the composite rice has advantages in important parameters such as elasticity, cohesion, chewiness, adhesion, and resilience. If the moisture content is lower than 30%, the prepared composite rice is too hard; if the moisture content is higher than 40%, the prepared composite rice is not formed. If the temperature is lower than 60°C, the prepared composite rice is in a paste state; if the temperature is higher than 70°C, the whey protein and polyphenols in the prepared composite rice are easily decomposed and the composite rice itself is easily coked.

[0022] Compared with the traditional extrusion process (such as directly adding materials and extruding and granulating at a certain temperature), the present invention sets its unique temperature zone and adopts a pre-gelatinization process to treat the raw materials. While retaining more of the raw material's own structure, it prevents it from being destroyed and decomposed, reduces the loss rate of the composite rice, and maintains it within a normal range. The gelatinization degree of composite rice is higher than that of ordinary rice. The higher the gelatinization degree of rice product starch, the easier it is to be hydrolyzed by enzymes, which is conducive to digestion and absorption. After the composite rice is subjected to the above-mentioned extrusion process, the original microcrystalline structure in the starch granules is destroyed, the structure is looser, the porosity is better, the gelatinization degree is correspondingly higher, and the quality is better.

[0023] On a deeper level, the starch extruded by extrusion pre-gelatinization heat treatment is easier to gelatinize. The processing and extrusion steps of composite rice cause the starch molecular chain to break and affect the redistribution of water in the composite rice. The whey protein competes with the starch for water during the heating stage, inhibiting the gelatinization of the starch paste and the increase in viscosity, because the viscosity value of composite rice is lower than that of ordinary rice. However, due to the interaction and physical effect between whey protein and starch molecules, the binding between starch molecules is weakened, delaying the regeneration of starch molecules during the cooling stage or forming strong hydrogen bonds with starch. These factors will correspondingly increase the shear thinning degree and apparent viscosity of the system. Therefore, although the viscosity of composite rice is lower than that of ordinary rice, it still has a suitable viscosity.

[0024] During the screw extrusion process, the protein and starch in the mixture undergo cross-linking reaction to form a dense network structure. This structure can prevent water from entering the rice particles, thereby reducing the rehydration properties of the composite rice. In addition, during the extrusion process in the above temperature range, the protein and starch can react to form new chemical bonds to affect the absorption path and speed of water. This can significantly reduce the water absorption rate, swelling rate and rehydration of the composite rice, achieve stable fusion of whey protein and broken rice powder, and maintain a high protein content in the composite rice.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects: The invention provides a method for preparing anti-glycation high-protein composite rice. The composite rice is prepared with whey protein raw materials, broken rice flour and polyphenols as main raw materials, which effectively solves the problems of insufficient protein in natural rice and excessively high AGEs content in high-protein rice. The composite rice has high protein content and multiple types of amino acids and is easy for human body to digest and absorb, which not only retains the nutritional components of the raw materials but also improves the sensory value of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a physical picture of the anti-glycation high-protein composite rice; Figure 2 The test results of the nutritional value (protein, fat, total phenolic content) of composite rice; Figure 3The test results of the cooking quality of composite rice (cooking loss rate, water absorption rate, volume expansion rate, gelatinization degree, and rehydration capacity); Figure 4 The test results of the texture (hardness, elasticity, cohesion, chewiness, adhesion, and resilience) of the composite rice; Figure 5 The test results of in vitro digestion and hydrolysis degree of composite rice starch; Figure 6 The test results of AGEs inhibition rate of composite rice; Figure 7 The antioxidant capacity of rice (ABTS + Free radical scavenging rate, DPPH free radical scavenging rate) test results; Figure 8 The test results of rheological properties (viscosity, modulus) of composite rice; Fig. 9 This is a physical picture of the composite rice made with proanthocyanidins, curcumin and apigenin. DETAILED DESCRIPTION

[0027] The present invention is further described below by way of examples, but the present invention is not limited to the scope of the examples. The experimental methods in the following examples without specifying specific conditions are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0028] Example 1 A method for preparing anti-glycation high-protein composite rice, comprising the following steps: (1) Collect and screen the broken rice during rice processing, grind it into powder using a grinder, and dry it in an oven at 40 °C for 24 h to obtain broken rice powder; (2) treating whey with low-temperature spray drying technology to obtain whey protein, then adjusting the pH to between 5.1 and 5.3, sterilizing at 68°C to obtain whey protein raw material; (3) Sieve the broken rice flour and polyphenols through a 60-mesh sieve, and mix the broken rice flour, polyphenols, and whey protein raw materials in a mass ratio of 10:0.3:2 to form a mixture; (4) Pour the mixed material into a screw extruder, add water to adjust the moisture content of the mixed material to 36 wt.%; the screw extruder is set to six temperature zones in the order of inputting the mixed material to outputting the product, and the temperatures of the six temperature zones are: T1: 45 ℃, T2: 55 ℃, T3: 65 ℃, T4: 70 ℃, T5: 60 ℃, T6: 50 ℃; Among them, T1 and T2 represent the first and second temperature zones, which are preheating zones; T3 and T4 represent the third and fourth temperature zones, which are gelatinization zones; T5 and T6 represent the fifth and sixth temperature zones, which are cooling zones; The screw speed was 120 rpm, the feed rate was 14 kg / h, and the cutter speed was 800 rpm; After preheating, the mixed material is gelatinized in the gelatinization zone, extruded and granulated in the cooling zone, and the product is collected; (5) The product was dried using a combination of microwave and hot air, with the microwave at 300 W and the hot air temperature at 70 °C. Figure 1 The anti-glycation high-protein complex rice (hereinafter referred to as complex rice) shown.

[0029] Example 2 This example uses ordinary rice as a comparison (broken rice source) to analyze the nutritional value (protein, fat, and total phenol content) of the composite rice of Example 1. The results are as follows: Figure 2 shown.

[0030] Protein content determination: The protein content was determined by the Kjeldahl method in GB 5009.5-2016. Figure 2 It can be seen that the average protein content of the composite rice under the extrusion parameters of the present invention is 17.258%, while the average protein content of the common rice is 6.184%. The extrusion temperature is controlled within the range of the present invention to avoid the decomposition of whey protein due to high temperature, so that the protein content of the composite rice with added whey protein is significantly higher than that of the common rice (about 6%), which meets the requirement of "high protein food" with a protein content of >12%.

[0031] Fat content determination: The fat content was determined by Soxhlet extraction method in GB 5009.6-2016.

[0032] The fat content of compound rice is higher than that of ordinary rice. The reason may be that the protein added to compound rice contains a certain amount of milk fat, which makes the fat content of compound rice higher than that of ordinary rice, thus improving its nutritional value.

[0033] Determination of total phenol content: crush the composite rice sample, add ethanol-water solution to extract, filter to remove solid matter and dilute to 5 times. Take 0.5 mL of sample, add 1.5 mL of Folin-Ciocalteu reagent, mix thoroughly and let stand for 3 min. Then add 1 mL of 15 g / 100 mL Na 2 CO 3 Solution was reacted in the dark for 30 min. The absorbance was measured at 765 nm using an ELISA reader, and three parallel experiments were performed in each group. Gallic acid was used as a standard with a concentration range of 0.1 mg / mL, 0.2 mg / mL, 0.4 mg / mL, 0.6 mg / mL, 0.8 mg / mL and 1 mg / mL, and a standard curve was drawn to quantify the total phenol content in the sample.

[0034] The decomposition temperature of polyphenols is 70-80℃. Controlling the extrusion temperature in the above range can prevent polyphenols from being decomposed during processing. The total phenol content of composite rice is significantly higher than that of ordinary rice. Total phenol content is one of the important indicators for measuring the quality of natural products such as food. It is a phenolic compound with multiple functions such as antioxidant, anti-inflammatory, and anti-cancer. The experimental results show that the nutritional value and health benefits of composite rice are higher than those of ordinary rice.

[0035] Example 3 This example uses ordinary rice as a comparison to analyze the cooking quality (cooking loss rate, water absorption rate, volume expansion rate, gelatinization degree, and rehydration property) of the composite rice of Example 1. The results are as follows: Figure 3 shown.

[0036] Determination of cooking loss rate: weigh 3 g (m 0 ) in a beaker and steam in 30 mL boiling water for the optimal steaming time. After steaming, pour the rice soup into a constant weight (m 1 ) in a weighing dish and dried at 105 °C to constant weight (m 2 ). The calculation formula of cooking loss rate is as follows: Cooking loss rate (%) = (m 2 -m 1 ) / m 0 ×100% Depend on Figure 3 It can be seen that the loss rate of ordinary rice is 8.6%, and the loss rate of composite rice is 15.3%. The loss rate of composite rice is higher than that of ordinary rice. It may be due to the extrusion molding process of composite rice, and the degree of bonding cannot be compared with the single starch component of ordinary rice, but the loss rate of composite rice is still within the normal range. This process uses pre-gelatinization to treat raw materials. Compared with the traditional extrusion process, it can retain more of the raw material's own structure, prevent it from being destroyed and decomposed, and reduce the loss rate of composite rice, keeping it within the normal range.

[0037] Water absorption rate determination: weigh 3 g of composite rice sample (m 0 ) in a beaker and boil in 30 mL boiling water. After boiling, cool to room temperature. Transfer the sample cooled to room temperature to a centrifuge tube (m 1 ) and weigh the total mass of the centrifuge tube and the sediment after centrifugation (m 2 ). The calculation formula of water absorption is as follows: Water absorption rate (%) = (m 2 -m 1 ) / m 0 ×100% The water absorption rate of ordinary rice is 228.77%, and that of composite rice is 131.03%. The water absorption rate of composite rice is lower than that of ordinary rice. High cooking temperature will strengthen the microcrystalline bundle structure of stored rice starch and reduce the water-soluble substances, resulting in increased water absorption during cooking. However, since composite rice contains protein, under high cooking temperature conditions, the attachment of high protein may inhibit water from entering starch, resulting in decreased water absorption and proton mobility.

[0038] Determination of volume expansion rate: weigh 3 g of composite rice sample into a measuring cylinder and record the volume V of the composite rice grains. 0 Transfer the rice grains to 30 mL of boiling water and cook. After cooking, drain the sample until no more rice soup drips. After the sample cools to room temperature, use a measuring cylinder to measure the volume V of the sample rice grains. 1 The volume expansion rate is calculated as follows: Volume expansion rate (%) = (V 1 -V 0 ) / V 0 ×100% The expansion rate of ordinary rice is 133.33%, and the expansion rate of composite rice is 30.65%. The volume expansion rate of composite rice is lower than that of ordinary rice. In the starch protein system, when the protein content is high, the protein and starch are distributed in thin layers, the cross-sectional expansion index decreases, and the starch properties are affected, thus resulting in a lower volume expansion rate.

[0039] Determination of gelatinization degree: crush the sample and sieve it (80 mesh), weigh 0.1 g of composite rice sample, add 49 mL of distilled water and 1 mL of KOH solution (10 mol / L), and stir magnetically for 5 min. Centrifuge at 4500 rpm for 10 min, take 0.2 mL of the upper clear liquid, add 0.2 mL of HCL solution (0.2 mol / L), then add 15 mL of distilled water, and finally add iodine solution (4 g potassium iodide, 1 g iodine dissolved in 100 mL of distilled water), and measure the absorbance A at 600 nm. 1 Weigh 0.1 g of composite rice sample, add 47.5 mL of distilled water and 2.5 mL of KOH solution (10 mol / L), and stir magnetically for 5 min. Centrifuge at 4500 rpm for 10 min, take 0.2 mL of the supernatant, add 0.2 mL of HCL solution (0.5 mol / L), 15 mL of distilled water, and finally add 0.2 mL of iodine solution, and measure the absorbance A at 600 nm. 2 The calculation formula of gelatinization degree is as follows: Gelatinization degree (%) = (A 1 / A 2 )×100% The gelatinization degree of composite rice is higher than that of ordinary rice. The higher the gelatinization degree of rice starch, the easier it is to be hydrolyzed by enzymes, which is beneficial for digestion and absorption. After the composite rice is extruded, the original microcrystalline structure in the starch granules is destroyed, the structure becomes looser and more porous, so its gelatinization degree is correspondingly higher and the quality is better.

[0040] Rehydration test: Take 10 g of composite rice sample, immerse it in 50 mL boiling water for 5 min, drain it immediately and absorb the surface water with absorbent paper, and weigh it. The calculation formula of rehydration is as follows: Rehydration (%) = (mass of sample after rehydration / mass of sample before rehydration) × 100% The rehydration of ordinary rice is 0.951%, and the rehydration of composite rice is 0.458%, which means that composite rice is lower than ordinary rice in terms of rehydration. The reason may be that during the high-temperature extrusion process, protein and starch undergo a cross-linking reaction to form a dense network structure. This structure will hinder the entry of water into the rice particles, thereby reducing the rehydration properties of composite rice. In addition, during the high-temperature extrusion process, protein and starch may react to form new chemical bonds, affecting the absorption path and speed of water. The obvious reduction in the water absorption rate, swelling rate and rehydration of composite rice proves that whey protein and broken rice powder can be stably fused under this process, and the protein content of composite rice is high.

[0041] Example 4 This example uses ordinary rice as a comparison to analyze the texture (hardness, elasticity, cohesiveness, chewiness, adhesion, and resilience) of the composite rice of Example 1. The results are as follows: Figure 4 shown.

[0042] Texture analysis: After the composite rice sample is drained of water, the rice grains with complete morphology are selected and laid flat on the test platform of the texture analyzer. The sample is tested in the TPA mode of the texture analyzer, using a P / 36R probe, a deformation variable of 50%, a trigger force of 5 g, and a uniform rate of 2 mm / s before, during and after the test. Repeat the test multiple times to take the average value.

[0043] Depend on Figure 4 It can be seen that the average hardness (508.438) and adhesion (183.381) of ordinary rice are greater than the average hardness (201.017) and adhesion (142.059) of composite rice, while the average elasticity (0.376), cohesion (0.349), chewiness (75.021) and recovery (0.328) of ordinary rice are significantly lower than those of composite rice (average elasticity is 0.807, cohesion is 0.713, chewiness is 115.618 and recovery is 0.595).

[0044] Compared with ordinary rice, composite rice has better elasticity, cohesion, chewiness and resilience, and lower stickiness and hardness. Therefore, composite rice is easier to maintain its intact shape, has a good taste, is not easy to age and regenerate, and while ensuring the viscoelasticity of the rice grains, it is not easy to stick to teeth and has a suitable soft and hard taste.

[0045] Example 5 This example uses ordinary rice as a comparison to analyze the in vitro digestion and hydrolysis degree of starch of the composite rice of Example 1. The results are as follows: Figure 5 shown.

[0046] Determination of starch in vitro digestion hydrolysis degree: Add 3 mL of working enzyme solution to the prepared completely gelatinized starch milk and oscillate at 37°C. Take samples of 0.20 mL at 0 min, 5 min, 10 min, 20 min, 30 min, 45 min, 60 min, 90 min, 120 min, and 180 min after adding the enzyme solution. Add 4 mL of anhydrous ethanol to each sample and oscillate at 3000 rp. m Centrifuge for 20 minutes and take the supernatant. Wash the precipitate with 3 mL of distilled water, centrifuge at 3000 rpm for 20 minutes, combine the supernatant, and oscillate to mix. Take 2 mL of the supernatant, add 1.5 mL of 3,5-dinitrosalicylic acid reagent, react in a boiling water bath for 7 minutes, cool for 3 minutes, make up to 25 mL, measure the absorbance at 520 nm, and calculate the reducing sugar concentration contained in the reaction solution. The results use the reducing sugar concentration and the sample hydrolysis degree to represent the starch digestion characteristics. The calculation formula for the sample hydrolysis degree is as follows: Sample hydrolysis degree = (reducing sugar release in the reaction solution at the sampling time point / total dry matter mass) × 100% Depend on Figure 5 It can be seen that the starch hydrolysis rates of the two samples were 17.25% and 20.73% at 20 minutes, respectively; and 39.98% and 41.57% at 60 minutes, respectively. From the overall starch hydrolysis rate of the curve, the starch hydrolysis rate of the control group was slightly higher than that of the composite rice. It is possible that the protein and functional component polyphenols added to the composite rice will combine with starch molecules and inhibit the enzymatic activity of amylase to a certain extent, thereby reducing the digestibility of starch and achieving the purpose of low glycemic index.

[0047] Example 6 This example uses ordinary rice as a comparison to analyze the AGEs inhibition rate of the composite rice of Example 1. The results are as follows: Figure 6 shown.

[0048] Determination of AGEs inhibition rate: accurately weigh 1.8016 g of α-lactose and 0.731 g of L-lysine (molar ratio of 1:1), dilute to 50 mL with distilled water, weigh 2 g of broken rice (composite rice / ordinary rice), dilute to 10 mL with distilled water, centrifuge at 4500 rpm for 10 min, and take the supernatant. Take 4.5 mL of 0.1 mol / L α-lactose solution, 4.5 mL of 0.1 mol / L L-lysine solution, and 1 mL of broken rice solution to make 10 mL of reaction solution. Set the reaction time at 90 °C to 0.5 h, 1 h, 1.5 h, and 2 h. According to the experimental results, select the time with the best inhibition effect. Set the control group without broken rice and heating, and the blank group without broken rice and neither heating, and set three parallels for each group. Take 1 mL of reaction solution in a glass stoppered test tube, place it in a water bath at the corresponding temperature for reaction, and then quickly place it in an ice water bath to prevent the reaction from continuing. Then add 9 mL of distilled water to dilute the reaction solution, and use a fluorescence spectrophotometer to detect the fluorescence value of the diluted reaction solution (EX=370nm, EM=440nm, the incident and exit slit widths are both 5 nm). The calculation formula for the inhibition rate is as follows: Inhibition rate = [(F 样品 -F 空白 ) / (F 对照 -F 空白 )]×100% Depend on Figure 6 It can be seen that the two groups of rice have an inhibitory effect on the formation of AGEs in the α-lactose / L-lysine simulation system. The experimental results show that the proanthocyanidins added to the composite rice have certain activity and have a good effect in inhibiting the formation of AGEs.

[0049] Example 7 This example uses ordinary rice as a comparison to compare the antioxidant capacity (ABTS + The free radical scavenging rate, DPPH free radical scavenging rate) were analyzed, and the results were as follows Figure 7 shown.

[0050] Antioxidant capacity determination: (1) ABTS + The antioxidant activity was determined by the method. 2 mL of sample extract was placed in a test tube and 2 mL of ABTS was added. + The working solution was mixed and reacted at room temperature for 120 min, and the absorbance value A was measured at a wavelength of 734 nm. 1 . Add 2 mL of ABTS to 2 mL of 95% ethanol solution. + The working solution was used as a blank control and the absorbance was measured as A 0 The calculation formula of ABTS+ free radical scavenging rate is as follows: ABTS + free radical scavenging rate = (A0-A1 / A0) × 100% (2) Determination of antioxidant activity by DPPH method: Take 2 mL of sample extract into a test tube, add 2 mL of 0.16 mmol / LDPPH solution, mix well, incubate in a constant temperature water bath at 25 °C for 30 min, and then measure the absorbance value A at 517 nm. 1 . 2 mL of 95% ethanol solution plus 2 mL of 0.16 mmol / L DPPH solution was used as a blank control, and the absorbance was measured as A 0 The calculation formula of DPPH free radical scavenging rate is as follows: DPPH free radical scavenging rate = (A0-A1 / A0) × 100% Depend on Figure 7 It can be seen that ABTS + : The free radical scavenging rate of ordinary rice (control group) was 10.67%, and the free radical scavenging rate of compound rice (experimental group) was 85.03%; DPPH: The free radical scavenging rate of ordinary rice (control group) was 22.69%. The free radical scavenging rate of compound rice (experimental group) was 57.8%. The data show that compound rice has a significant effect on ABTS + The scavenging rate of DPPH free radicals in the composite rice was significantly higher than that in ordinary rice, which proved that the process could retain the activity of polyphenols and give the composite rice certain advantages in antioxidant function.

[0051] Example 8 This example uses ordinary rice as a comparison to analyze the rheological properties (viscosity, modulus) of the composite rice of Example 1. The results are as follows: Figure 8 shown.

[0052] Rheological properties: The rheological properties of composite rice were investigated using a rheometer. The plate diameter was 35 mm, the spacing was 1 mm, the temperature was set at 25 °C, and the shear rate range was 1 s -1 -300 s -1 , measure the change of the apparent viscosity of the sample. Set the temperature to 25 ℃, strain to 0.5%, frequency range to 0.1-20 Hz, and measure the change of the storage modulus (G') and loss modulus (G") of the sample.

[0053] Depend on Figure 8It can be seen that compared with the traditional extrusion process, the starch extruded by extrusion pre-gelatinization heat treatment is easier to gelatinize. The processing and extrusion steps of composite rice cause the starch molecular chain to break and affect the redistribution of water in the composite rice. The whey protein competes with the starch for water in the heating stage, which inhibits the gelatinization of the starch paste and the increase in viscosity, because the viscosity value of the composite rice is lower than that of ordinary rice. However, due to the interaction and physical effect between whey protein and starch molecules, the binding between starch molecules is weakened, delaying the regeneration of starch molecules in the cooling stage or forming strong hydrogen bonds with starch. These factors will correspondingly increase the shear thinning degree and apparent viscosity of the system. Therefore, although the viscosity of the composite rice is lower than that of ordinary rice, it still has a certain viscosity.

[0054] In the frequency range of 0 Hz-100 Hz, the loss modulus (G") of all samples is significantly smaller than their storage modulus (G'). The G' and G" values ​​of the composite rice are increased compared with those of ordinary rice, indicating that the protein and starch are cross-linked to form a network during the extrusion process, which enhances the gel network strength of the system.

[0055] Example 9 In this example, ordinary rice is used as a comparison to analyze the temperament of the composite rice of Example 1. The results are shown in Table 1.

[0056] Gas chromatography-mass spectrometry: Weigh an appropriate amount of composite rice sample, grind it thoroughly, place it in a headspace bottle, and seal the headspace bottle with a crimp cap of a silicone headspace septum. Place it in an 80 °C water bath for 20 min, then insert the SPME needle into the headspace, continue to place it in an 80 °C water bath for 30 min, and desorb it at the 250 °C injection port for 5 min. Gas chromatography conditions: GC-MS conditions: Agilent HP-5 capillary column (30 m × 250 μm × 0.25 μm); carrier gas: high-purity helium (99.999%); carrier gas flow rate: 1 mL / min; heating conditions: initial temperature is 40 °C, stay for 5 min, then increase to 70 °C at a rate of 5 °C / min, hold for 2 min, then increase to 150 °C at a rate of 5 °C / min, then increase to 230 °C at a rate of 25 °C / min, and hold for 15 min. The temperature of the auxiliary heater and the electron impact ion source was set to 250 °C.

[0057] Table 1: Temperament analysis results

[0058] In the table, “ND” stands for not detected.

[0059] According to the analysis of the temperament results in Table 1, hexanal, heptanal, nonanal, decanal, 1-hexanol, 1-heptanol and 1-octanol are all flavor substances that may be originally contained in rice, and the content of composite rice is greater than that of ordinary rice. Other fruity and fragrant flavor substances may be introduced by adding grape seed proanthocyanidins to composite rice, and 2-nonenal, ethyl hexadecanoate, 2-heptanone, methoxyphenyl oxime and other fatty and milky flavor substances may be introduced by the added whey protein. In summary, the flavor of composite rice is richer than that of ordinary rice, and it adds fruity fragrance, fat fragrance, milky fragrance and other substances that are not originally part of the rice fragrance. The additional addition of polyphenols and proteins enhances the sensory value of composite rice.

[0060] Example 10 This example is basically the same as Example 1, except that curcumin and apigenin are used as polyphenols to prepare the anti-glycation high-protein composite rice. Fig. 9 The process of the present invention successfully prepares composite rice of different colors with the above polyphenols, meeting the processing requirements of different food uses.

[0061] Embodiment 11 In this example, the high-protein composite rice prepared by the same preparation method as Example 1 without adding polyphenols was used as a control group. The quality (cooking loss rate, gelatinization degree), texture characteristics (hardness, elasticity, chewiness), and nutrition (protein, fat, total phenols, proanthocyanidins) of the composite rice of Example 1 were analyzed. The test method was the same as the above example. The results are shown in Table 2.

[0062] Table 2: Quality analysis results of composite rice with and without polyphenols

[0063] In the table, ① represents the composite rice prepared in Example 1, and ② represents the comparative group prepared in this example.

[0064] According to the results in Table 2, the hardness, elasticity and chewiness of composite rice ① are better than those of composite rice ②. The reason is that in the composite rice with polyphenols added, polyphenols can bridge starch and protein through covalent bonds and non-covalent bonds such as hydrogen bonds and hydrophobic interactions. The three are cross-linked to form a gel network, which effectively solves the problem of poor taste and hard texture of high-protein composite rice.

[0065] Comprehensive evaluation shows that the nutritional content of composite rice is far higher than that of ordinary rice in terms of protein content, fat content, total phenolic content and proanthocyanidin content. +The DPPH free radical scavenging rate is significantly higher than that of ordinary rice; in terms of anti-glycation ability, it can significantly inhibit the formation of AGEs; in terms of cooking quality, the cooking time is short and the gelatinization degree is high; in terms of texture characteristics, the hardness and adhesion are low, the elasticity and cohesion are better, and the taste is suitable; in terms of appearance, it is brightly colored, which stimulates people's appetite.

[0066] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for preparing anti-glycation high-protein composite rice, characterized in that: The steps include: (1) collecting and screening broken rice during rice processing, grinding it into powder, and then drying it to obtain broken rice flour; (2) treating whey with low-temperature spray drying technology to obtain whey protein, adjusting its pH and sterilizing it to obtain whey protein raw material; (3) mixing the broken rice flour, polyphenols, and whey protein raw materials according to a certain mass ratio to form a mixture; (4) Pour the mixed material into a screw extruder, add water to adjust the moisture content of the mixed material to 30 wt.%-40 wt.%; the screw extruder is set to six temperature zones in the order of inputting the mixed material to outputting the product, and the temperatures of the six temperature zones are: T1: 40-50 ℃, T2: 50-60 ℃, T3: 60-70 ℃, T4: 65-70 ℃, T5: 55-65 ℃, T6: 50-55 ℃; T1 and T2 represent the first and second temperature zones, which are preheating zones; T3 and T4 represent the third and fourth temperature zones, which are gelatinization zones; T5 and T6 represent the fifth and sixth temperature zones, which are cooling zones; After preheating, the mixed material is gelatinized in the gelatinization zone, extruded and granulated in the cooling zone, and the product is collected; (5) The product is dried to obtain anti-glycation high-protein composite rice.

2. The method for preparing the anti-glycation high-protein composite rice according to claim 1, characterized in that: In the step (1), drying is performed by drying at a temperature of 40-50°C.

3. The method for preparing the anti-glycation high-protein composite rice according to claim 1, characterized in that: In the step (2), the pH of the whey protein is adjusted to 5.1-5.3; and the temperature of the sterilization treatment is 68-70°C.

4. The method for preparing the anti-glycation high-protein composite rice according to claim 1, characterized in that: In the step (3), the broken rice flour and polyphenols must be sieved through a 60-mesh sieve to remove impurities before mixing.

5. The method for preparing the anti-glycation high-protein composite rice according to claim 1, characterized in that: In the step (3), the polyphenols include proanthocyanidins, curcumin, and apigenin.

6. The method for preparing the anti-glycation high-protein composite rice according to claim 1, characterized in that: In the step (3), the broken rice flour, polyphenols and whey protein raw materials are mixed according to a mass ratio of 10:0.3:2 to form a mixture.

7. The method for preparing the anti-glycation high-protein composite rice according to claim 1, characterized in that: In the step (4), the mixed material is fed into the screw extruder at a feed rate of 10-15 kg / h.

8. The method for preparing the anti-glycation high-protein composite rice according to claim 1, characterized in that: In the step (4), the screw speed is 110-130 rpm, and the cutter speed is 700-900 rpm.

9. The method for preparing the anti-glycation high-protein composite rice according to claim 1, characterized in that: In the step (5), a microwave and hot air combination is used for drying, the microwave energy is 280-320 W, and the hot air temperature is 60-70 °C.

Images