Compound recombinant rice and preparation method thereof

Abstract

The invention discloses compound recombinant rice and a preparation method thereof, and particularly relates to the technical field of recombinant rice. The compound recombinant rice comprises 35% of white rice, 35% of highland barley flour and 30% of corn flour. The preparation method of the compound recombinant rice comprises the following steps: S1, mixing and stirring 35% of white rice, 35% of highland barley flour and 30% of corn flour into a raw material; s2, adding a monoglyceride additive into the raw materials; s3, adjusting the moisture of the uniformly mixed raw materials to 34%; s4, feeding the raw materials subjected to moisture adjustment into a double-screw extruder for extrusion and granulation to obtain recombined rice; and S5, drying the prepared recombinant rice in a constant-temperature oven at 40 DEG C for 12 hours. According to the compound recombinant rice and the preparation method thereof provided by the invention, the physicochemical properties and digestion characteristics of coarse cereal recombinant rice can be influenced, and a theoretical reference is provided for developing the recombinant rice with low GI and good eating quality.

Description

Technical Field

[0001] The invention relates to the technical field of recombinant rice, and in particular to a compound recombinant rice and a preparation method thereof. Background Art

[0002] Rice plays a vital role as a staple food worldwide. However, the refined processing of rice inevitably leads to the loss of important nutrients, such as lipids, proteins, etc. In addition, the consumption of traditional rice requires about 30 minutes of steaming. In today's fast-paced society, people's demand for nutritionally balanced convenience foods is increasing. Reconstituted rice consists of milled rice, rice flour or other starch-based raw materials, which are crushed, conditioned, and then fed into an extruder for re-granulation. In addition, the starch gelatinizes during the extrusion process, allowing the reconstituted rice to be steamed faster.

[0003] The high-energy environment during the extrusion process will cause various reactions of biopolymers in the matrix, such as changes in protein conformation and destruction of starch crystal structure. These changes will affect the interaction between the raw material components, and then affect the structural characteristics, physicochemical properties and digestibility of the extrudate. There is still a gap between recombinant rice and ordinary white rice in edible quality, and there are problems such as large cooking loss rate, caking, and soft taste; at the same time, starch digestibility is improved, which is not good for people with high blood sugar. The digestibility of coarse grains is lower than that of polished white rice. The compounding of coarse grains when preparing recombinant rice can improve digestibility. At present, there are many studies on the optimization of recombinant rice extrusion process and improvement of edible quality, but there is still a lack of comprehensive research on the effects of coarse grain compounding on the physicochemical properties, edible quality and digestible characteristics of recombinant rice.

[0004] Therefore, the present invention systematically explored the effects of coarse grains on the physical and chemical properties, edible quality and digestive characteristics of recombinant rice, using ordinary white rice and white rice recombinant rice as controls. In particular, this study used a combination of in vitro digestion experiments and in vivo postprandial blood glucose experiments to comprehensively evaluate the effects of coarse grains on the digestive characteristics of recombinant rice. This study can provide a theoretical reference for the subsequent development of high-quality low-GI recombinant rice. Summary of the invention

[0005] In view of the above situation, in order to overcome the defects of the prior art, the present invention provides a composite recombinant rice and a preparation method thereof, which can affect the physicochemical properties and digestibility of coarse grain recombinant rice, and provide a theoretical reference for developing recombinant rice with low GI and good edible quality.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] Compound recombinant rice, including: 35% white rice, 35% highland barley flour and 30% corn flour.

[0008] The preparation method of compound recombinant rice comprises the following steps:

[0009] S1: 35% white rice, 35% highland barley flour and 30% corn flour are mixed and stirred into raw materials;

[0010] S2: adding monoglyceride additive to the raw material;

[0011] S3: adjusting the moisture content of the mixed raw materials to 34%;

[0012] S4: sending the raw materials after adjusting the moisture content into a twin-screw extruder for extrusion and granulation to obtain reconstituted rice;

[0013] S5: Place the prepared recombinant rice in a constant temperature oven at 40° C. and dry for 12 h.

[0014] Preferably, the monoglyceride additive is 0.4% by weight of the raw material.

[0015] Preferably, the screw diameter is 20 mm, the L / D ratio is 40:1, the die diameter is 1 mm, the tool speed is 1000 rpm, the screw speed is 150 rpm, and the feed rate is 5 kg / h.

[0016] Preferably, the barrel portion of the twin-screw extruder from the feeding zone to the extrusion zone is divided into five zones, zones I, II, III, IV, and V, with temperatures of 40°C, 50°C, 60°C, 80°C, and 40°C, respectively.

[0017] Preferably, the recombinant rice has a length of 3-5 mm and a diameter of 1.5-2 mm.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The starch, protein, and fat contents of extruded white rice and reconstituted rice were reduced, while the ash and dietary fiber contents were increased; the addition of coarse grains increased the protein and fat contents and reduced the starch content.

[0020] (2) The XRD pattern of ordinary white rice shows an A-type crystal structure, which has the largest relative crystallinity and short-range order. Different from the sharp V-type crystal structure of white rice, the multi-grain recombinant rice has other impurity peaks in addition to the larger V-type crystal peak, which improves the relative crystallinity and short-range order of starch to a certain extent.

[0021] (3) Extrusion destroys the microstructure of starch. Unlike the angular starch granules of ordinary white rice, the cross-section of reconstituted white rice is dense and uniform; the cross-section of reconstituted coarse grain rice still has starch granules with fuzzy boundaries.

[0022] (4) After extrusion, the hardness, elasticity, chewiness, cooking loss and rehydration ratio of the reconstituted rice increased, while the adhesion and iodine blue value decreased. The taste and flavor of the reconstituted rice were not as good as those of ordinary white rice. The addition of miscellaneous grains improved the smell, color, and rice grain integrity of the reconstituted rice, enriched the taste, and improved the sensory evaluation, but there was still a certain gap with ordinary white rice.

[0023] (5) In terms of digestibility, the RDF of extruded white rice reconstituted rice increased, RS decreased, and digestibility improved.

[0024] (6) The addition of grains reduced the RDF of recombinant rice, increased the SDF and RS, and decreased the eGI value; at the same time, it delayed the release of postprandial blood sugar to a certain extent and reduced the GI value.

[0025] (7) Considering the physicochemical properties, edible quality and digestive characteristics, it is crucial to improve the nutritional value of recombinant rice by adding coarse grains. Further research will systematically consider the effects of different extrusion processes (extrusion temperature, moisture content, screw speed, cutter speed, etc.) on the physicochemical properties and digestive characteristics of coarse grain recombinant rice, and provide a theoretical reference for the development of recombinant rice with low GI and good edible quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 are X-ray diffraction patterns at different meters;

[0027] Figure 2 Fourier transform infrared spectra (A-4000cm -1 -600cm -1 , B-1200cm -1 -800cm -1 );

[0028] Figure 3 Figures A1-C3, from left to right, are the microstructures of recombinant rice of coarse grains, recombinant white rice and ordinary white rice; A1-C1, magnified 500 times; A2-C2, magnified 2000 times; A3-C3, magnified 4000 times; D1-D3, the rice grain shaping properties of recombinant rice of coarse grains, recombinant white rice and ordinary white rice before steaming; F1-F3, the rice grain shaping properties of recombinant rice of coarse grains, recombinant white rice and ordinary white rice after steaming;

[0029] Figure 4 The starch digestion curves of recombinant coarse grain rice, recombinant white rice and ordinary white rice (A); the LOS / CPS kinetic model of recombinant coarse grain rice, recombinant white rice and ordinary white rice (BD);

[0030] Figure 5 These are the postprandial blood glucose response curves of reconstituted coarse grain rice, reconstituted white rice and ordinary white rice. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with the accompanying drawings and embodiments. The embodiments of the present invention include but are not limited to the following embodiments.

[0032] Compound recombinant rice, including: 35% white rice, 35% highland barley flour and 30% corn flour.

[0033] The preparation method of compound recombinant rice comprises the following steps:

[0034] S1: 35% white rice, 35% highland barley flour and 30% corn flour are mixed and stirred into raw materials;

[0035] S2: adding monoglyceride additive to the raw material, wherein the monoglyceride additive is 0.4% of the raw material mass;

[0036] S3: adjusting the moisture content of the mixed raw materials to 34%;

[0037] S4: The raw materials after adjusting the moisture content are then sent to a twin-screw extruder for extrusion granulation to obtain reconstituted rice, wherein the screw diameter is 20 mm, the L / D ratio is 40:1, the die diameter is 1 mm, the tool speed is 1000 rpm, the screw speed is 150 rpm, the feeding rate is 5 kg / h, and the barrel part of the twin-screw extruder from the feeding zone to the extrusion zone is divided into five zones, namely zones I, II, III, IV, and V, with temperatures of 40°C, 50°C, 60°C, 80°C, and 40°C, respectively. The reconstituted rice has a length of 3-5 and a diameter of 1.5-2 mm.

[0038] S5: Place the prepared recombinant rice in a constant temperature oven at 40° C. and dry for 12 h.

[0039] Screening of the proportion of ingredients in grain-compounded recombinant rice:

[0040] The blank recombinant rice was prepared using japonica rice flour as the raw material, and the coarse grain recombinant rice was prepared using a mixture of japonica rice flour, highland barley flour and corn flour in different proportions as the raw materials:

[0041] (1) Compound 1: 35% white rice + 15% highland barley flour + 50% corn flour;

[0042] (2) Compound 2: 35% white rice + 25% highland barley flour + 40% corn flour;

[0043] (3) Compound 3: 35% white rice + 35% highland barley flour + 30% corn flour;

[0044] (4) Compound 4: 35% white rice + 45% highland barley flour + 20% corn flour;

[0045] (5) Compound 5: 35% white rice + 55% highland barley flour + 10% corn flour.

[0046] The sensory evaluation results of recombinant rice prepared according to different proportions of grains are shown in Table 1. The total sensory score of compound 3 was the highest, and it was significantly better than other compounding schemes in color, rice grain integrity, hardness and taste (p < 0.05). In terms of color, it is related to the Maillard reaction and browning degree that occurred during the extrusion process. Because the corn flour content of compounds 1 and 2 is high, the Maillard reaction during the extrusion process makes the recombinant rice of grains too yellow, resulting in a low color score; because of the high content of highland barley flour in compound 5, the color is darker, resulting in a low color score. With the addition of highland barley flour, the scores of rice grain integrity and hardness are significantly reduced (p < 0.05), which may be due to the increase in fiber content, which leads to a decrease in rice moldability and an increase in rice hardness. In summary, compound 3 was selected to prepare recombinant rice of grains, and the various physical and chemical indicators of recombinant rice and ordinary white rice were compared and analyzed.

[0047] Table 1 Sensory evaluation of different grain blending schemes

[0048]

[0049] Effects of mixed grains on the physicochemical properties of recombinant rice

[0050] Basic ingredients

[0051] As shown in Table 2, the starch, protein and fat contents of ordinary white rice decreased after extrusion, while the ash and dietary fiber contents increased. The total starch content decreased by 2.87% after extrusion, of which the amylose content decreased by 1.26%. This is because the glycosidic bonds between starch molecules are broken during the extrusion process and degraded into small molecular sugars or other substances. Under high temperature and high pressure, amylose interacts with lipids to form a starch-lipid complex, which also corresponds to the reduction of amylose and fat content after extrusion. Compared with white rice recombinant rice, the ash and protein content of coarse grain recombinant rice increased, and the starch content decreased, which shows that the compounding of coarse grains changed the composition of the recombinant rice.

[0052] Table 2 Basic components of different rice

[0053]

[0054]

[0055] XRD analysis

[0056] like Figure 1As shown in the figure, ordinary white rice has characteristic diffraction peaks at 15.2°, 17.1°, 18.1°, and 23.1°, which is a typical A-type crystal structure; while the two recombinant rices have characteristic diffraction peaks at 13.0° and 20.0°. These crystal peaks are V-type crystal structures, which can be attributed to the starch-lipid complex formed by the combination of amylose and lipids during the extrusion process. During the extrusion process, the starch granules gradually gelatinize, resulting in the gradual disappearance of A-type crystals, the formation of a small amount of V-type crystals, and the decrease in relative crystallinity (as shown in Table 3). Compared with white rice recombinant rice, the V-type crystal peak of the coarse grain recombinant rice is larger, and there are other miscellaneous peaks, which shows that the addition of coarse grains is the reason for the increase in the relative crystallinity of the recombinant rice.

[0057] ATR-FTIR analysis

[0058] like Figure 2 As shown in A, at 3600cm -1 -3000cm -1 The spectral absorption peaks in the range can be attributed to the stretching vibration of the hydroxyl (-OH) group. In addition, the 2925cm -1 and 1645cm -1 The absorption peaks of the band indicate carbonyl C=O and CH 2 and CH 3 Asymmetric stretching vibration of the group. It is reported that at 1200cm -1 -800cm -1 ATR-FTIR spectroscopy in the wide range is very sensitive to short-range conformational changes in the starch molecular structure. -1 / 1022cm -1 The spectral absorption intensity ratio represents the ratio of the crystalline and amorphous regions, reflecting the change in starch conformation. Figure 2 The data shown in B show that the 1047cm -1 / 1022cm -1 The intensity ratio (0.83) was significantly higher than that of reconstituted rice (0.66) and white rice (0.50) (p < 0.05). It can be seen that the destruction of starch granule structure by extrusion led to a decrease in the order of reconstituted rice, while the addition of miscellaneous grains increased the short-range order of reconstituted rice starch, which is consistent with the results of XRD research.

[0059] like Figure 3As shown in the figure, a large number of complete starch granules with sharp edges and neat arrangement were observed on the cross-section of ordinary white rice. No complete starch granules were observed in the cross-section of coarse grain recombinant rice, and the boundaries were blurred, indicating that the starch granules were gelatinized during the extrusion process. The cross-section of white rice recombinant rice was smooth, dense and uniform, indicating that its starch granules were completely gelatinized. During the high temperature and high pressure extrusion process, more starch was leached and combined with the surface of the granules, and the surface of the granules gradually became smooth. These findings emphasize that extrusion treatment promotes the gelatinization of starch; it also shows that the addition of coarse grains hinders the gelatinization of recombinant rice starch.

[0060] Gelatinization degree

[0061] As shown in Table 3, the gelatinization degrees of recombinant rice, recombinant white rice and ordinary white rice are 82.62%, 95.20% and 20.87% respectively. The results show that the gelatinization degree of starch increases after extrusion treatment, while the addition of grains slows down the gelatinization of starch during extrusion, which is consistent with the observation results of microstructure.

[0062] Table 3 Physical and chemical properties of different rice

[0063]

[0064]

[0065] Gelatinization characteristics

[0066] Starch granules absorb water and expand under high-temperature extrusion, partially dissolve in water and produce viscosity. This process is called starch gelatinization. As shown in Table 3, the RVA characteristic values ​​of ordinary white rice are significantly higher than those of the two recombinant rices (p < 0.05). This is because the starch granules have swelled and broken under the action of extrusion, and the mutual friction is reduced after absorbing water, resulting in a decrease in viscosity. The peak viscosity is caused by the swelling of starch due to water absorption, and the friction of the dissolved material causes a sharp increase in the viscosity of the paste. The high temperature and high pressure during the extrusion process promote the expansion and dissolution of part of the starch, which reduces the expansion of the starch granules and reduces the peak viscosity. The disintegration value and regeneration value of the recombinant rice are much lower than those of ordinary white rice, which shows that its starch paste is thermally stable and not easy to age. The formation of starch-lipid complexes and short-chain branches during the extrusion process weakens the regeneration effect of starch.

[0067] Compared with white rice, the peak viscosity, maintained viscosity, final viscosity and disintegration value of multi-grain reconstituted rice are lower, which indicates that the addition of multi-grain further increases the thermal stability of starch paste. At the same time, the addition of multi-grain also increases the retrogradation value of starch granules. This indicates that the addition of multi-grain enhances the gel structure of starch paste, making reconstituted rice more prone to aging.

[0068] DSC analysis

[0069] As shown in Table 3, the endothermic peak of ordinary white rice is around 60°C and ΔH is 8.04 J / g. The endothermic peaks of coarse grain recombinant rice and white rice recombinant rice are both between 90°C and 100°C, and ΔH is 3.51 J / g and 0.69 J / g, respectively. The difference in gelatinization temperature may be related to the difference in the conformation and distribution of starch molecules and the internal arrangement of molecular components

[22] . ΔH is inversely proportional to the degree of gelatinization. ΔH is believed to reflect the energy change during the breaking of hydrogen bonds between starch molecules. Therefore, the destruction of starch granule structure during extrusion may be the reason for the reduction or even absence of ΔH in recombinant rice flour.

[0070] There was no significant difference in T0, Tp and Tc between recombinant rice containing whole grains and white rice. However, the addition of whole grains significantly increased the ΔH of starch from 0.69 J / g to 3.51 J / g (p<0.05), which may be related to the improvement of relative crystallinity and starch order.

[0071] Effects of adding coarse grains on the edible quality of recombinant rice

[0072] Texture characteristics

[0073] As shown in Table 4, the hardness of recombinant rice is higher than that of ordinary white rice, and its adhesion is lower than that of ordinary white rice. Hardness is related to the density of rice grains, which is determined by the maximum force required to compress the sample. The increase in the hardness of recombinant rice indicates that the internal structure of recombinant rice is dense and uniform, which may be the reason for its poor sensory quality. Adhesion is related to the force required for the mouth and teeth to peel off attached food. The decrease in adhesion indicates that recombinant rice is not as sticky as ordinary white rice. Compared with white rice, coarse grain recombinant rice is harder and less adhesive. This may be caused by the complex formed by the rich dietary fiber and protein in the coarse grain ingredients during the extrusion process.

[0074] Table 4 Edible quality data of different rice

[0075]

[0076]

[0077] Cooking characteristics

[0078] Cooking loss is mainly due to the dissolution of gelatinized starch, which is related to the network strength around the gelatinized starch. As shown in Table 4, the cooking loss rate of coarse grain reconstituted rice is the smallest, which indicates that less substances are dissolved in the coarse grain reconstituted rice during the cooking process. In addition, the iodine blue value is positively correlated with the amount of amylose dissolved during the cooking process. The iodine blue value of reconstituted rice is low because amylose-lipid complexes are generated during the extrusion process, resulting in a decrease in the amount of amylose dissolved during the cooking process. The iodine blue value of coarse grain reconstituted rice is even lower, which means that the addition of coarse grains reduces the amount of amylose dissolved in the reconstituted rice during the cooking process, and the rice has better formability ( Figure 3F1-F3), which is consistent with the research results of cooking loss rate. When passing through the die extrusion outlet, the pressure change causes cavities and gaps inside the reconstituted rice, which makes it easy for water to penetrate and become swollen; while the interior of ordinary white rice is relatively flat, so it is not easy to expand during the cooking process. The expansion rate and rehydration ratio of coarse grain reconstituted rice are lower than those of white rice reconstituted rice. This is because the addition of coarse grains strengthens the starch gel structure and limits the water absorption and expansion of reconstituted rice.

[0079] Sensory evaluation

[0080] Different samples before and after cooking Figure 3 D1-F3. As shown in Table 4, there are significant differences in the sensory scores of smell, color, gloss, palatability and taste between recombinant rice and ordinary white rice (p < 0.05). The color of white rice recombinant rice may be due to the partial degradation of starch molecules into reducing sugars during the extrusion process, and the Maillard reaction between the raw material components under high temperature and high pressure, resulting in lower color and gloss scores of recombinant rice. The integrity of recombinant rice grains is not as good as that of ordinary white rice, which may be related to its larger expansion rate. In addition, the recombinant rice is harder and has a low taste score. The taste of coarse grain recombinant rice is worse than that of white rice recombinant rice, which may be because the flavor of coarse grains enriches the taste of recombinant rice.

[0081] Effects of supplementation of coarse grains on digestibility of reconstituted rice

[0082] In vitro digestion

[0083] like Figure 4 As shown in A, the starch hydrolysis rate increased rapidly in the first 20 minutes, then the growth rate slowed down and stabilized at 120 minutes. As shown in Table 5, the C ∞ The C content of extruded white rice and reconstituted rice was 75.45%, 90.47% and 84.13% respectively. ∞ The C content of recombinant rice increased significantly (p < 0.05), which is because high temperature and high pressure destroyed the structure of starch granules, increased the contact area between the internal area and the enzyme during in vitro digestion, and promoted starch hydrolysis. ∞ The results showed that the content of starch in the extrusion process increased significantly (p < 0.05), which was because the addition of whole grains resulted in the generation of more starch-lipid complexes during the extrusion process, which hindered the contact between enzymes and starch during the digestion process.

[0084] The LOS and CPS kinetic model fitting of coarse grain recombinant rice, white rice recombinant rice and ordinary white rice is as follows Figure 4 BD. The LOS graphs all show discontinuity in the linear regression fit, indicating that the recombinant rice of coarse grains, the recombinant rice of white rice, and the ordinary white rice all have two digestible parts, RDF and SDF. 2startIt is located within 0 min from the end of the first digestion stage. This indicates that the digestion of multigrain recombinant rice, white rice recombinant rice and ordinary white rice follows a combination of parallel and sequential digestion modes.

[0085] As shown in Table 5, the digestibility parameters k1, k2, C1 of recombinant rice of grains, recombinant rice of white rice and recombinant rice of white rice are ∞ 、C2 ∞ and t 2start There were significant differences (p < 0.05). The k1 of recombinant rice was significantly higher than that of ordinary white rice, indicating that the digestion rate of RDF was significantly increased after extrusion (p < 0.05); the k2 of coarse grain recombinant rice was significantly lower than that of white rice recombinant rice and ordinary white rice, t2start was significantly advanced, and C2∞ was significantly increased (p < 0.05). This shows that the addition of coarse grains increases the SDF of recombinant rice. The RS of coarse grain recombinant rice, white rice recombinant rice and ordinary white rice were 24.55%, 9.53% and 15.87%, respectively; the estimated glycemic index (eGI) was 67.07, 83.53 and 75.46, respectively. These results show that extrusion changes the crystal type and crystallinity of starch and reduces the RS content. The increase in eGI of white rice recombinant rice can be attributed to the increase in RDF (C1 ∞ The addition of grains reduced the eGI of recombinant rice, which can be attributed to the reduction of RDF (C1 ∞ decrease), increase in SDF (C2 ∞ The increase in RS may be due to the interaction between the protein, lipid and dietary fiber in the grains and starch during the extrusion process to form complexes such as starch-lipid complexes. These complexes are classified as resistant starch type V (RS5), which changes the conformation of amylose, reduces the accessible enzyme binding sites on its surface, destroys the enzyme-starch binding mechanism during starch digestion, and reduces starch digestibility. At the same time, starch-lipid complexes may also delay the degradation of starch into small molecular oligosaccharides during extrusion.

[0086] Table 5 Digestion data of different rice

[0087]

[0088] Blood sugar response in the body

[0089] Considering the complexity of food matrix and gastrointestinal system, the blood glucose response in vivo more truly reflects the digestibility and absorption rate of food containing the same amount of carbohydrates. This study further investigated the postprandial blood glucose response of reconstituted rice, reconstituted white rice and ordinary white rice. Figure 5As shown. Blood glucose level reaches a peak within 20-30 minutes after a meal, which indicates that the rapidly digestible components of starch are rapidly hydrolyzed and absorbed. The blood glucose curve stabilizes after 120 minutes. As shown in Table 5, compared with white rice reconstituted rice and ordinary white rice, the peak time of coarse grain reconstituted rice is significantly advanced, and the peak concentration is significantly decreased (p < 0.05). This shows that the addition of coarse grains slows down the release of blood glucose from rice in the human body and reduces the blood glucose level after a meal.

[0090] Combined with the in vitro and in vivo digestion data in Table 5, it can be seen that the area under the blood glucose curve (IAUG) within 2 hours after a meal r ) is inversely proportional to RS, which also shows that the GI value measured by the in vivo blood glucose response is consistent with the eGI value during in vitro digestion, emphasizing the reliability of in vitro digestion of starch in predicting postprandial blood glucose response. The GI values ​​of reconstituted rice, white rice and ordinary white rice are 65.31, 82.88 and 77.10, respectively. Among them, reconstituted rice is a medium GI food, while reconstituted rice and ordinary white rice are high GI foods. These results also show that extrusion treatment improves the digestibility of white rice, while the addition of miscellaneous grains reduces the digestibility of reconstituted rice, which is consistent with the results of in vitro digestion experiments. During the extrusion process, the starch crystal structure undergoes a continuous order-disorder-reorder transformation through gelatinization and coagulation, and the addition of miscellaneous grains strengthens the interaction between starch and other components in the raw materials such as lipids and proteins, affecting the gelatinization and degradation of starch. Therefore, the addition of miscellaneous grains is the key to the significant differences in the digestibility and GI value of reconstituted rice.

[0091] This application selects the optimal ratio of mixed grains for preparing mixed grain recombinant rice through sensory evaluation, and then compares and analyzes the various physical and chemical indicators of white rice recombinant rice and ordinary white rice to explore the effects of mixed grains on the physical and chemical properties, edible quality and digestibility of extruded recombinant rice. The starch, protein and fat content of the extruded white rice recombinant rice is reduced, and the ash and dietary fiber content are increased; the addition of mixed grains increases the protein and fat content and reduces the starch content. The XRD diagram of ordinary white rice shows an A-type crystal structure with the largest relative crystallinity and short-range order; unlike the sharp V-shaped crystal structure of white rice recombinant rice, mixed grain recombinant rice has other impurity peaks in addition to the larger V-shaped crystal peak, which improves the relative crystallinity and short-range order of starch to a certain extent. Extrusion destroys the microstructure of starch. Unlike the angular starch granules of ordinary white rice, the cross-section of white rice recombinant rice is dense and uniform; the cross-section of mixed grain recombinant rice still has starch granules with blurred boundaries. After extrusion, the hardness, elasticity, chewiness, cooking loss and rehydration ratio of reconstituted rice increased, while the adhesion and iodine blue value decreased. The taste and flavor were not as good as those of ordinary white rice. The addition of grains improved the smell, color, and rice grain integrity of reconstituted rice, enriched the taste, and improved the sensory evaluation, but there was still a certain gap with ordinary white rice. In terms of digestive characteristics, the RDF of reconstituted white rice after extrusion increased, the RS decreased, and the digestibility improved. The addition of grains reduced the RDF of reconstituted rice, increased the SDF and RS, and decreased the eGI value. At the same time, it delayed the release of blood sugar after a meal to a certain extent, reducing the GI value.

[0092] The results show that the combination of whole grains is crucial to improving the nutritional value of recombinant rice from the aspects of physical and chemical properties, edible quality and digestion characteristics.

[0093] The determination of moisture content of basic components shall refer to GB 5009.3-2016; the determination of ash content shall refer to GB5009.4-2016; the determination of protein content shall refer to GB 5009.5-2016; the determination of fat content shall refer to GB 5009.6-2016; the determination of starch content shall refer to GB 5009.9-2016; the determination of amylose content shall refer to GB / T15683-2008; the determination of dietary fiber content shall refer to GB5009.88-2014. In the determination results of basic components, except for moisture content, the contents of other components are all dry basis contents.

[0094] X-ray diffraction (XRD) analysis was performed to determine the crystal structure of the sample powders using an X-ray diffractometer at 40 kV and 40 mA Cu-K-α radiation, and the relative intensity was recorded in the scattering range of (2θ) 5°–35° with a scanning rate of 0.05° / s.

[0095] Fourier transform infrared spectroscopy (ATR-FTIR) analysis was performed using an ATR-FTIR infrared spectrometer to measure the sample powder with a resolution of 4 cm -1 , scan 64 times / s, scanning range is 4000cm -1 -400cm -1 .

[0096] Microstructure, select the complete rice grains and cut them with a blade to obtain the cross section, and stick them on the copper stage with conductive double-sided tape. Then use an ion sputtering instrument to vacuum spray gold on the cross section. The working voltage of the electron microscope is 3kV, and the magnifications are 500 times, 2000 times and 4000 times respectively.

[0097] The gelatinization degree of the sample was determined by the saccharifying enzyme method.

[0098] Gelatinization properties: The gelatinization properties of the sample powder were determined using a rapid viscosity analyzer, and the RVA characteristic values ​​of starch during the gelatinization process were recorded.

[0099] DSC analysis: The sample powder (3 mg) was directly weighed into an aluminum crucible, mixed with deionized water at a ratio of 3:7 (w / w), sealed and equilibrated for 12 hours, and then placed in a differential scanning calorimeter and heated from 30°C to 100°C at 10°C / min. The endothermic enthalpy (ΔH), onset temperature (To), peak temperature (Tp), and end temperature (Tc) were recorded.

[0100] Texture characteristics: Take 3 cooked rice grains on the round table of the texture analyzer and compress them with a cylindrical probe with a diameter of 25 mm at a speed of 1.0 mm / s until the compression ratio reaches 50%.

[0101] Cooking characteristics: The cooking loss rate, rehydration ratio, expansion ratio and iodine blue value were determined according to the method of Dai Jiao et al. [6] with slight modifications.

[0102] Sensory evaluation: refer to GB / T 15682-2008 to conduct sensory evaluation on samples.

[0103] In vitro digestion

[0104] Weigh 200 mg of sample and add 10 mL of buffer (18 mmol / L acetic acid, 0.2 mol / L sodium acetate, 4 mmol / L CaCl 2 、0.49mmol / L MgCl 2, pH = 6.0), boil in boiling water for 30 minutes and then cool. Add 10mL of mixed enzyme solution (2U / mol α-amylase, 10U / mol amyloglucosidase), keep in a constant temperature water bath at 37°C and stir magnetically. Take equal amounts of the reaction solution at 0min, 5min, 10min, 15min, 20min, 30min, 45min, 60min, 90min, 120min and 180min, measure the amount of glucose released in the form of D-glucose (glucose determination kit), and convert it into the amount of digested starch molecules.

[0105] The logarithmic slope transformation model (LOS) is often used to identify starch components with different digestibility coefficients in a food system and is described by the following formula.

[0106]

[0107] In the formula, C ∞ - Hydrolysis rate of starch at the end of the digestion experiment, %; C t - The amount of starch digested at time t (min), %; C 0 -The amount of starch digested at time 0 min, %; k-The total digestion rate coefficient of starch.

[0108] Food systems in which rice or reconstituted rice may have a variety of digestible starch components [7] , can be analyzed with the help of parallel and sequential digestion kinetic model (CPS), the equation is shown below.

[0109]

[0110] Where C 1∞ - The maximum amount of starch that can be digested in an unlimited time (RDF) in the fast digestible fraction, %; C 2∞ - Slowly digestible starch fraction (SDF) The maximum amount of starch digested in an infinite time, %; k 1 - RDF digestion rate coefficient; k 2 -SDF digestion rate constant; t 2start - Time when SDF digestion starts, min.

[0111] k 1 , k 2 , C 1∞ , C 2∞ and t 2start The nonlinear least squares (NLLS) optimization was used in Microsoft Excel. The resistant starch content (RS) was calculated as follows.

[0112] RS=1-(C 0 -C 1∞ -C2∞ )#(3)

[0113] Taking white bread as a reference, the area under the starch hydrolysis curve was calculated by the integration method, and then the starch hydrolysis rate (HI) and expected glycemic index (eGI) were calculated as follows.

[0114]

[0115] eGI=39.71+59.4HI#(5)

[0116] Where: AUC s - Area under the sample hydrolysis curve; AUC w -Area under the hydrolysis curve for white bread.

[0117] Blood sugar response in the body

[0118] The human testing method was based on WS / T 652-2019, and the Medical Ethics Committee of Jiangnan University obtained a review certificate. Twelve subjects who had no sugar metabolism-related diseases and did not use drugs that affect sugar metabolism were recruited. The basic information of the subjects was recorded, and a consent form for the trial was issued and signed. The subjects were required to fast for 10 hours before the trial and measure their blood sugar with a Johnson & Johnson Steady Blood Glucose Meter.

[0119] Test fasting blood sugar twice within 5 minutes. Eat 250 mL of sugar water (50 g glucose) or cooked staple food with the same amount of carbohydrates with 250 mL of warm water. All foods should be eaten within 10 minutes. Take blood and record blood sugar values ​​at 15 minutes, 30 minutes, 45 minutes, 60 minutes, 90 minutes and 120 minutes after the meal. Calculate the GI value using the reference formula.

[0120]

[0121] Where: IAUC r - Area under the blood glucose response curve of the sample; IAUC g -Area under the glycemic response curve for glucose.

[0122] Data analysis

[0123] SPSS 21.0 statistical software was used to perform group mean variance analysis (ANOVA), and the results were presented as mean ± standard deviation. The significance of the difference between means was determined at the 0.05 significance level, and all experiments were performed 3 times.

Claims

1. A composite recombinant rice, characterized in that: include: 35% white rice, 35% barley flour and 30% corn flour.

2. A method for preparing a composite recombinant rice, applicable to the composite recombinant rice according to claim 1, characterized in that: The steps include: S1: 35% white rice, 35% highland barley flour and 30% corn flour are mixed and stirred into raw materials; S2: adding monoglyceride additive to the raw material; S3: adjusting the moisture content of the mixed raw materials to 34%; S4: sending the raw materials after adjusting the moisture content into a twin-screw extruder for extrusion and granulation to obtain reconstituted rice; S5: Place the prepared recombinant rice in a constant temperature oven at 40° C. and dry for 12 h.

3. The method for preparing the composite recombinant rice according to claim 2, characterized in that: The monoglyceride additive is 0.4% of the raw material mass.

4. The method for preparing the composite recombinant rice according to claim 2, characterized in that: The screw diameter is 20 mm, the L / D ratio is 40:1, the die diameter is 1 mm, the tool speed is 1000 rpm, the screw speed is 150 rpm, and the feed rate is 5 kg / h.

5. The method for preparing the composite recombinant rice according to claim 2, characterized in that: The barrel part of the twin-screw extruder from the feeding zone to the extrusion zone is divided into five zones, zones I, II, III, IV, and V, with temperatures of 40°C, 50°C, 60°C, 80°C, and 40°C respectively.

6. The method for preparing the composite recombinant rice according to claim 2, characterized in that: The recombinant rice has a length of 3-5 mm and a diameter of 1.5-2 mm.

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