Preparation method of low-GI recombinant rice

Abstract

The invention discloses a preparation method of low-GI recombinant rice, and belongs to the field of food processing. The recombinant rice prepared by the method disclosed by the invention is relatively low in solid loss rate, nutritional ingredients can be well retained, and the hardness value is much smaller than that of the recombinant rice prepared by adding RS3 resistant starch and is relatively close to that of common rice sold in the market. And the predicted glycemic index of the recombinant rice disclosed by the invention can reach 45.48. The fatty acid is added in the preparation process of the recombinant rice, the resistant starch is synchronously generated, on one hand, the complex step of independently preparing the resistant starch is reduced, and on the other hand, the recombinant rice which is better in taste, moderate in hardness and low in GI value can be prepared through reasonable extrusion temperature setting and reasonable fatty acid matching.

Description

Technical Field

[0001] The invention relates to a preparation method of low GI recombinant rice, belonging to the technical field of food processing. Background Art

[0002] With the change of global dietary structure and the increasing number of chronic diseases, the nutritional value and health function of staple food have gradually attracted more attention. Among them, rice, as one of the main energy sources for Chinese residents, provides rich carbohydrates, but its high GI index limits the intake of patients with metabolic diseases such as obesity and diabetes. In recent years, with the advancement of food processing technology, recombinant rice, as a new staple food product, has gradually entered people's field of vision. The preparation technology of recombinant rice mainly relies on the extrusion process. This technology reorganizes the starch, protein and other ingredients in the raw materials through high temperature, high pressure and shear force, which can not only improve the nutritional structure of traditional rice, but also give it specific functional characteristics, such as low GI and high dietary fiber, so as to meet the health needs of different groups of people and form products with appearance and taste similar to natural rice. The advantage of the extrusion process is that it can flexibly adjust the raw material ratio and add functional ingredients, such as resistant starch, dietary fiber, protein, etc., so as to improve the nutritional value and functional characteristics of the product.

[0003] At present, low GI recombinant rice is mainly made by mixing resistant starch and various grains. 1 Resistant starch actually refers to physically embedded starch, which is the part of starch granules that is physically shielded by mechanical processing and locked in the plant cell wall so that it cannot be acted upon by amylase. 2 Type resistant starch refers to natural resistant starch particles with a certain particle size. These two types of resistant starch can still be digested and absorbed by amylase after proper processing, especially after the extrusion process, their digestion resistance is significantly reduced. In addition, Gao Man and other studies have shown that as the amount of resistant starch added increases, excessive addition will cause the recombinant rice to be too hard and the chewiness to decrease, thereby causing the taste of the rice to decrease. It can be seen that the extruded recombinant rice still has a certain gap in taste compared to ordinary rice. While reducing the GI value of recombinant rice, we should also consider improving its edible quality. Zhang Yang et al. (Optimization of low GI extruded recombinant rice formula and evaluation of edible quality) used rice flour as the main raw material and RS 4 Recombinant rice prepared by mixing resistant dextrin, konjac flour and polyglycerol esters significantly reduced the predicted glycemic index, but RS 4 Resistant starch is a kind of starch obtained by chemical modification, and its safety needs further discussion. Svenja et al. (Low moisture extrusion of pea protein and pea fibre fortified rice starch blends) found that adding RS3 After that, the adhesion of rice grains was significantly reduced. Adhesion usually reflects the strength of the internal structure of rice grains. 3 Relative to RS 1 and RS 2 The thermal stability of RS resistant starch is better, and the digestibility of the prepared recombinant rice can be better guaranteed. 3 The addition of glutinous rice still affects the taste of reconstituted rice, such as making the rice grains too hard or not sticky enough. Therefore, developing a reconstituted rice that can effectively reduce the GI value of rice and take into account the taste of rice can be suitable for most people to eat, especially for the elderly with reduced metabolic capacity and poor gastrointestinal function. Summary of the invention

[0004] In order to solve at least one of the above problems, the present invention adds fatty acids during the preparation process of recombinant rice to simultaneously generate resistant starch, which, on the one hand, reduces the complicated steps of preparing resistant starch alone; on the other hand, through the reasonable extrusion temperature setting and reasonable ratio of fatty acids of the present invention, recombinant rice with better taste, moderate hardness and low GI value can be prepared.

[0005] The first object of the present invention is to provide a method for preparing low GI recombinant rice, comprising the following steps:

[0006] S1. Mix lauric acid and linoleic acid in a mass ratio of 2-4:6-8 to obtain a fatty acid raw material;

[0007] S2, mixing rice flour, fatty acid raw material, chickpea flour, highland barley flour, soy protein, and mono- and di-glycerol fatty acid esters in a weight ratio of 50-60:10-20:5-15:5-15:5-15:1 to obtain a mixed material;

[0008] S3, water content 30-35%, add water to the mixed material;

[0009] S4, setting the zone temperatures of the twin-screw extruder to 75-85° C. for the feeding zone, 115-125° C. for the mixing zone, 140-150° C. for the reaction zone, and 90-100° C. for the homogenizing zone, respectively, adding the material to which water was added in step S3, and cooling and drying after extrusion to obtain the low GI recombinant rice.

[0010] In one embodiment of the present invention, the rice flour is obtained by grinding rice and passing it through a sieve of 80-200 meshes.

[0011] In one embodiment of the present invention, in step S4, the screw speed during extrusion is 40-50 r / min.

[0012] In one embodiment of the present invention, the cooling is performed by gradient cooling at 85-95°C → 65-75°C → 45-55°C.

[0013] In one embodiment of the present invention, the drying is carried out at 40-50° C. to a constant weight.

[0014] The second object of the present invention is to provide a low GI recombinant rice prepared by the method.

[0015] The third object of the present invention is to provide the use of the low GI recombinant rice in preparing low GI products.

[0016] Beneficial Effects

[0017] The solid loss rate of the recombinant rice prepared by the method of the present invention is low, the nutrients can be better retained, and the hardness value is higher than that of the rice with RS added. 3 The hardness of the recombinant rice prepared with resistant starch is much smaller, which is closer to the ordinary rice on the market. And the predicted glycemic index of the recombinant rice of the present invention can reach 45.48. The present invention adds fatty acids during the preparation process of recombinant rice to simultaneously generate resistant starch, which on the one hand reduces the complicated steps of preparing resistant starch alone, and on the other hand, through the reasonable extrusion temperature setting and reasonable ratio of fatty acids of the present invention, recombinant rice with better taste, moderate hardness and low GI value can be prepared. DETAILED DESCRIPTION

[0018] Material:

[0019] Rice variety: Shanghai soft 1212. After crushing, pass through a 100-mesh sieve to obtain rice flour.

[0020] Chickpea flour, Haomeijie Grocery Store, Xishandong Street, Shayibake District; highland barley flour, Ganzi Prefecture Gonggashanzhen E-commerce Co., Ltd.; soy protein, Shandong Zhongsen Biotechnology Co., Ltd.; mono- and di-glycerol fatty acid esters, Henan Maiyoutian Trading Co., Ltd.; RS 3 Type resistant starch, Shanghai Yuanye Biotechnology Co., Ltd.; DNS reagent, Beijing Solebow Technology Co., Ltd.; pepsin (porcine gastric mucosa): 30000U / g, Shanghai Yuanye Biotechnology Co., Ltd.; saccharifying enzyme: 100000U / mL, Shanghai Yuanye Biotechnology Co., Ltd.; pancreatic α-amylase: ≥5U / mg, Shanghai Yuanye Biotechnology Co., Ltd.; anhydrous ethanol, analytical grade, Sinopharm Chemical Reagent Co., Ltd.; glucose analysis reference standard, Shanghai McLean Biochemical Technology Co., Ltd.; sodium hydroxide, analytical grade, Shanghai Titan Technology Co., Ltd.

[0021] Detection method:

[0022] (1) Determination of cooking characteristics

[0023] The recombinant rice was boiled in boiling water 10 times its weight to determine its cooking characteristics. Part of the rice grains were taken out at regular intervals and squeezed with two glass plates until there was no obvious white core in the center of the rice grains, thus obtaining the cooked recombinant rice. The cooked recombinant rice was taken out and the surface moisture was absorbed with filter paper, and the weight of the rice grains before and after cooking was recorded. The water absorption rate was recorded as the weight of water absorbed by each gram (dry basis) of the rice grains after cooking; all the rice soup was transferred to 105°C and dried to constant weight, and the amount of solids contained in each gram (dry weight) of the rice grains was recorded as the cooking loss, expressed as a percentage.

[0024] (2) Sensory evaluation

[0025] Refer to the method described in the national standard GB / T 15682. Evaluate the rice based on five aspects: smell, appearance structure, palatability, taste, and texture of cold rice. The evaluators are selected as junior evaluators with certain sensory analysis capabilities and experience. Repeat the evaluation twice according to the sensory evaluation requirements. Sensory quality evaluation test: evaluators are required not to eat or drink for 1 hour before the test, and rinse their mouths with warm water before evaluating each sample. The steamed rice is distributed to the evaluators. The tasting test interval of each sample is 3 minutes to ensure that the evaluators taste it while it is hot. Each sample is evaluated at least 3 times. The specific evaluation criteria are shown in Table 1. The average score of the evaluators is used as the evaluation result of the quantitative analysis of the sensory quality of the sample.

[0026] Table 1

[0027]

[0028]

[0029] (3) Determination of texture characteristics

[0030] The texture characteristics of reconstituted rice were determined by referring to the method of Wu et al. (WU J, CHEN J, LIU W, et al. Effects of aleurone layer on rice cooking: Ahistological investigation [J]. Food Chemistry, 2016, 191: 28-35.) and appropriately modified. After the rice was cooked, 3 grains were placed flat on the stage. The probe was P / 36R, and the pre-measurement speed, the measurement speed, and the post-measurement speed were set to 2 mm / s, 1 mm / s, and 1 mm / s, the compression deformation rate was 35%, and the trigger force was 5 g.

[0031] (4) Predicted glycemic index (eGI) determination

[0032] Accurately weigh 50 mg of sample, add 10 mL of HCl-KCL buffer at pH 1.5, then add 0.2 mL of pepsin solution, and incubate at 40 ° C for 1 h. Then use Tris-maleic acid buffer at pH 6.9 to make up to 25 mL. Then add 5 mL of pancreatic α-amylase solution and incubate at 37 ° C. From 0 to 180 min, inactivate in a water bath for 2 min at 0, 30, 60, 90, 120 and 180 min. Add 1 mL of 0.4 M, pH 4.75 sodium acetate buffer to each aliquot, incubate at 60 ° C for 45 min, and then add 30 μL of saccharifying enzyme. The starch hydrolysis rate was determined by DNS colorimetry. The obtained curve was fitted to obtain the first-order reaction equation, and the surface area (AUC) under the fitting curve from 0 to 180 min was calculated to obtain the starch hydrolysis index (HI) of the sample, and the eGI value was calculated according to the following formula:

[0033] eGI=8.198+0.862HI

[0034] The technical solution of the present invention is described in detail below in conjunction with specific embodiments. In the following embodiments, unless otherwise specified, the reagents, materials and equipment used can be purchased from commercial sources, or prepared by conventional methods, or are commonly used in the industry.

[0035] Embodiment 1:

[0036] The fatty acid raw material is obtained by mixing lauric acid: linolenic acid = 3:7 in a mass ratio.

[0037] Rice flour was mixed with fatty acid raw materials, chickpea flour, highland barley flour, soy protein, and mono- and diglycerol fatty acid esters in a weight ratio of 55:15:10:10:10:1, and a certain amount of water was added to the final mixture according to the water content of 32%. The recombinant rice was prepared under the conditions of setting the partition temperatures of the twin-screw extruder to 80°C for the feeding zone, 120°C for the mixing zone, 145°C for the reaction zone, 95°C for the homogenization zone, and a screw speed of 45r / min. The recombinant rice was then cooled in a gradient from 90 to 70 to 50°C, and dried at 45°C to constant weight after cooling.

[0038] Embodiment 2:

[0039] The fatty acid raw material is obtained by mixing lauric acid:linolenic acid=4:6 in a mass ratio.

[0040] Rice flour was mixed with fatty acid raw materials, chickpea flour, highland barley flour, soy protein, and mono- and diglycerol fatty acid esters in a weight ratio of 55:15:10:10:10:1, and a certain amount of water was added to the final mixture according to the water content of 32%. The recombinant rice was prepared under the conditions of setting the partition temperatures of the twin-screw extruder to 80°C for the feeding zone, 120°C for the mixing zone, 145°C for the reaction zone, 95°C for the homogenization zone, and a screw speed of 45r / min. The recombinant rice was then cooled in a gradient from 90 to 70 to 50°C, and dried at 45°C to constant weight after cooling.

[0041] Embodiment 3:

[0042] The fatty acid raw material is obtained by mixing lauric acid: linoleic acid = 2:8 in a mass ratio.

[0043] Rice flour was mixed with fatty acid raw materials, chickpea flour, highland barley flour, soy protein, and mono- and diglycerol fatty acid esters in a weight ratio of 55:15:10:10:10:1, and a certain amount of water was added to the final mixture according to the water content of 32%. The recombinant rice was prepared under the conditions of setting the partition temperatures of the twin-screw extruder to 80°C for the feeding zone, 120°C for the mixing zone, 145°C for the reaction zone, 95°C for the homogenization zone, and a screw speed of 45r / min. The recombinant rice was then cooled in a gradient from 90 to 70 to 50°C, and dried at 45°C to constant weight after cooling.

[0044] Comparative Example 1:

[0045] The fatty acid raw material in Example 1 was replaced by lauric acid alone, and the other steps and parameters were consistent with those in Example 1.

[0046] Comparative Example 2:

[0047] The fatty acid raw material in Example 1 was replaced by linoleic acid alone, and the other steps and parameters were consistent with Example 1.

[0048] Comparative Example 3:

[0049] The zone temperatures of the twin-screw extruder in Example 2 were set to 60° C. in the feeding zone, 110° C. in the mixing zone, 130° C. in the reaction zone, and 80° C. in the homogenizing zone. Other steps and parameters were consistent with those in Example 2.

[0050] Comparative Example 4:

[0051] Mix rice flour with RS 3Resistant starch, chickpea flour, highland barley flour, soy protein, and mono- and diglycerol fatty acid esters were mixed uniformly in a weight ratio of 55:15:10:10:10:1, and a certain amount of water was added to the final mixture according to the water content of 32%. The recombinant rice was obtained under the conditions of setting the partition temperatures of the twin-screw extruder to 80°C for the feeding zone, 120°C for the mixing zone, 145°C for the reaction zone, 95°C for the homogenization zone, and a screw speed of 45r / min. The recombinant rice was then cooled in a gradient from 90 to 70 to 50°C, and dried at 45°C to constant weight after cooling.

[0052] Comparative Example 5:

[0053] Shanghai soft 1212 original rice.

[0054] Result test example:

[0055] (1) Cooking characteristics

[0056] The cooking characteristics of rice can be characterized by two key indicators: water absorption reflects the water absorption capacity of rice grains during the cooking process, which is specifically expressed as the percentage of mass increase; solid loss indicates the various nutrients such as amylose and soluble protein leached during the cooking process, and can also reflect the degree of interaction between the nutrients in rice. As shown in Table 2, Example 2 has a lower solid loss, which is not significantly different from natural rice. The main reason may be that the setting of appropriate extrusion puffing temperature can make the helix of amylose unfold better, and the reasonable ratio of lauric acid and linoleic acid can form a more stable structure of starch fatty acid complex, and the prepared recombinant rice starch has a higher degree of gelatinization and cross-linking. In Comparative Example 1, when lauric acid is used alone, the content of starch fatty acid complex in the prepared recombinant rice is high, but the structural stability is worse than that of Examples 1 to 3. In Comparative Example 2, when linoleic acid is used alone, the content of starch fatty acid complex in the prepared recombinant rice is reduced, and the stability of the cross-linked structure is also reduced. In Comparative Example 3, the recombinant rice starch prepared by extrusion at a lower temperature has a low degree of gelatinization and cross-linking. During the cooking process, the recombinant rice material is easily dissolved, resulting in a large increase in solid loss. In Comparative Example 4, RS 3 The water absorption rate of the prepared reconstituted rice is greatly reduced, which directly leads to the hard taste of the rice when steamed later.

[0057] Table 2 Cooking characteristics of reconstituted rice

[0058]

[0059]

[0060] (2) Sensory evaluation

[0061] Table 3 shows the sensory evaluation results of the four groups of recombinant rice, and the samples were comprehensively evaluated from the perspectives of smell, appearance structure, palatability, taste and cold rice texture. As shown in Table 3, the recombinant rice samples all scored low in terms of smell, which may be due to the fact that the flavor substances in the material are easily volatilized after high temperature and high pressure treatment during the extrusion process, resulting in a weaker overall smell of the recombinant rice. The integrity, stickiness and hardness of the rice grains containing resistant starch were improved, and the rice grains had a good taste and taste. Compared with the addition of RS 3 Compared with Comparative Example 4, the 5 The reconstituted rice has better elasticity and lower hardness.

[0062] Table 3 Sensory evaluation results of recombinant rice

[0063]

[0064] (3) Texture characteristics

[0065] Texture characteristics are important indicators for evaluating food quality and consumer acceptance. Its core parameters include hardness, elasticity, viscosity, etc., which not only reflect the physical properties of food, but are also closely related to the taste experience when eating. As shown in Table 4, the addition of RS 3 The reconstituted rice prepared with resistant starch has the highest hardness. 5 The hardness of the reconstituted rice with resistant starch is much smaller, and is closer to that of ordinary rice on the market. The stickiness reflects the property of the rice grains sticking to the contact surfaces such as teeth, palate, and tongue in the mouth when chewing rice, and the stickiness of Example 2 is significantly lower than that of the other samples.

[0066] Table 4 Texture characteristics of recombinant rice

[0067]

[0068] (4) Predicted glycemic index (eGI)

[0069] As shown in Table 5, the present invention prepares 5 The recombinant rice samples can effectively reduce the predicted glycemic index. Among them, the recombinant rice with a ratio of lauric acid to linoleic acid of 4:6 has the lowest eGI value. The main reason may be that during the extrusion process, the 4:6 lauric acid to linoleic acid can better form a complex with starch, making the starch crystals arranged in an orderly manner, thereby improving the resistance to enzymatic hydrolysis and effectively reducing the eGI value. At the same time, compared with the addition of RS 3 Compared with Comparative Example 4, Example 2 has a similar predicted glycemic index and a comparable ability to reduce postprandial blood sugar.

[0070] Table 5 Predicted glycemic index (eGI)

[0071]

[0072] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for preparing low GI recombinant rice, characterized in that: The following steps are involved: S1. Mix lauric acid and linoleic acid in a mass ratio of 2-4:6-8 to obtain a fatty acid raw material; S2, mixing rice flour, fatty acid raw material, chickpea flour, highland barley flour, soy protein, and mono- and di-glycerol fatty acid esters in a weight ratio of 50-60:10-20:5-15:5-15:5-15:1 to obtain a mixed material; S3, water content 30-35%, add water to the mixed material; S4, setting the zone temperatures of the twin-screw extruder to 75-85° C. for the feeding zone, 115-125° C. for the mixing zone, 140-150° C. for the reaction zone, and 90-100° C. for the homogenizing zone, respectively, adding the material to which water was added in step S3, and cooling and drying after extrusion to obtain the low GI recombinant rice.

2. The preparation method according to claim 1, characterized in that: The rice flour is obtained by grinding rice and passing the rice through a sieve of 80 to 200 meshes.

3. The preparation method according to claim 1, characterized in that: In step S4, the screw speed during extrusion is 40 to 50 r / min.

4. The preparation method according to claim 1, characterized in that: The cooling is performed in a gradient from 85 to 95°C → 65 to 75°C → 45 to 55°C.

5. The preparation method according to claim 1, characterized in that: The drying step is drying at 40-50° C. to a constant weight.

6. A low GI recombinant rice prepared by the method according to any one of claims 1 to 5.

7. Use of the low GI recombinant rice according to claim 6 in the preparation of low GI products.

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