Method for producing colored low-digestion extruded recombinant rice by forming starch-polyphenol complex through one-step method

Abstract

The invention discloses a method for producing colored low-digestion extruded recombinant rice by forming a starch-polyphenol complex through a one-step method, and relates to the technical field of food processing, and the method comprises the following steps: preparing a natural eutectic solvent; colored polyphenol is added, crystalline polyphenol is dissociated by adjusting a natural eutectic solvent-polyphenol interaction mode, and free polyphenol is formed; the method comprises the following steps: taking crushed by-product broken rice as a main base material, mixing the main base material with a natural eutectic solvent-free polyphenol solution, and enabling free polyphenol to enter a spiral inner cavity of starch through self-assembly driving to form a starch-polyphenol complex; tempering, extruding, forming and granulating; and cooling, crystallizing and drying to obtain the product. The preparation method has the beneficial effects that crystalline polyphenol is dissociated through dipole-dipole interaction and hydrogen bond interaction of a natural eutectic solvent, so that free polyphenol directionally enters a spiral cavity of an amylose molecule to be complexed and then is self-assembled to form a starch-polyphenol complex, the solubility, uniformity and stability of colored polyphenol can be effectively improved, and the preparation method is suitable for industrial production. The degradation in the processing and digestion processes is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, and in particular to a method for producing colored low-digestible extruded recombinant rice by forming a starch-polyphenol complex in one step. Background Art

[0002] With the acceleration of people's pace of life, changes in dietary composition and lifestyle, the proportion of metabolic syndromes related to insulin resistance such as diabetes continues to increase. These metabolic syndromes are closely related to the hyperglycemic response caused by long-term intake of refined rice and flour products with high content of rapidly digestible starch. The preparation of polyphenol-fortified recombinant rice through extrusion processing can improve the daily staple food structure without changing people's eating habits, effectively prevent the occurrence of the above-mentioned metabolic syndrome, and even have a therapeutic function for early patients. The difficulty of re-granulating fortified recombinant rice, the low solubility and poor stability of the fortifying factors are the key issues restricting the extruded recombinant rice fortified with polyphenols.

[0003] Nutritionally fortified extruded recombinant rice is an engineered recombinant rice that is similar in appearance to polished white rice after being finely ground into broken rice and mixed with a fortifier, and then subjected to processes such as extruder conditioning, recombining, granulating, aging, and drying. At present, scholars at home and abroad mainly conduct in-depth research on the process optimization, nutritional fortification, and quality improvement of extruded recombinant rice, but there are few reports on the digestibility of extruded recombinant rice. In existing related studies, nutritionally compatible textured recombinant rice is usually prepared by extruding and recombining with raw materials and auxiliary materials with blood sugar-lowering functions, and its digestive characteristics are studied. For example, Liu Chengmei (2020) and others found that the addition of 20% high-amylose corn starch, oat dietary fiber, and rice protein had no significant effect on the glycemic index (GI) of textured recombinant rice. Wang Xian (2018) and others showed that the addition of inulin and oat bran at 50% and the addition of soybean polysaccharides greater than 35% would have a significant effect on the glycemic index of nutritionally compounded recombinant rice, but the edible quality would deteriorate. It can be seen from this that the amount of hypoglycemic functional auxiliary materials required to significantly reduce the digestibility of extruded recombinant rice by the mutual blending method is large, while increasing the amount of auxiliary materials will make the granulation of extruded recombinant rice difficult and the quality will deteriorate.

[0004] In order to solve this technical problem, the applicant tried to mix broken rice powder and polyphenolic compounds, and then used a twin screw to process the above-mentioned mixture, rotary cutting, granulation and molding, and prepared a low digestibility nano-based extruded recombinant rice. Although this method can improve the digestibility of recombinant rice to a certain extent, directly adding polyphenolic compounds to the broken rice powder not only makes the polyphenolic compounds easy to degrade during processing and digestion, but also has low loading and poor stability, so that the effect of directly adding polyphenolic compounds to reduce the digestibility of extruded recombinant rice is limited. And because the solubility of polyphenolic compounds is low, it is difficult to directly form a complex with broken rice powder. In order to improve the binding property of the two, the prior art is to first make the polyphenolic compounds into nano form or use alkali or organic reagent to first treat the polyphenolic compounds, and then mix the treated polyphenolic compounds with broken rice powder, that is, to form a complex, multiple processing steps are required, resulting in a cumbersome preparation process. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the existing direct addition of polyphenol strengthening factors, break through the key technology of regulating starch-polyphenol complexes in a solute-solvent interaction mode, and provide a one-step method for forming a starch-polyphenol complex to produce colored low-digestible extruded recombinant rice, aiming at the problems of low digestibility of existing extruded recombinant rice, low solubility of polyphenol strengthening factors, poor stability, low bioavailability, etc.

[0006] Common natural pigments currently available on the market include beetroot red, anthocyanins, gardenia yellow, carotene, curcumin, etc. Most of these natural pigments are polyphenols. Natural polyphenols have biological activities such as antioxidant, hypoglycemic, hypolipidemic, antibacterial and anti-inflammatory, and anti-tumor. More and more evidence shows that long-term and moderate intake will have a beneficial effect on chronic diseases such as cancer, cardiovascular disease, type 2 diabetes, and cognitive impairment. Using polyphenol hypoglycemic functional factors as nutritional enhancers to regulate the digestibility of extruded recombinant rice can adjust the color of extruded recombinant rice, reduce the digestibility of extruded recombinant rice, and can also relieve chronic diseases through long-term and moderate intake. However, the directly added polyphenol extract has a low dissolution load and poor stability, and is easily degraded during processing and digestion, resulting in limited effect of directly adding colored polyphenol extracts to reduce the digestibility of extruded recombinant rice.

[0007] Since most colored polyphenol compounds are crystalline, their spatial structure is large and their water solubility is poor, making it difficult for them to form complexes with starch. Instead, they interact with starch molecules through hydrogen bonds, CH-π bonds and van der Waals forces to form type VII non-inclusion complexes, which are interspersed between starch helices in the form of "cross-linking agents-like". This does not fundamentally solve the problems of low solubility loading capacity of polyphenols, poor stability, and easy degradation during processing and digestion.

[0008] The technical solution adopted by the present invention to solve the technical problem is: a method for producing colored low digestibility extruded recombinant rice by forming a starch-polyphenol complex in one step. A natural low eutectic solvent is used as a medium for forming the starch-polyphenol complex, and the crystalline polyphenol is dissociated by adjusting the natural low eutectic solvent-polyphenol interaction mode, that is, the crystalline polyphenol is dissociated by the natural low eutectic solvent dipole-dipole interaction and hydrogen bond interaction, so that the free polyphenol enters the spiral cavity of the straight-chain starch molecule for complexation, and forms a similar starch-polyphenol complex. The main process steps are: using broken rice flour as a base material, heating and dissolving a natural low eutectic solvent containing colored polyphenols, and preparing a colored low digestibility extruded recombinant rice rich in starch-polyphenol complex through material modulation self-assembly, extrusion melting, rotary cutting granulation, cooling crystallization, and drying, breaking through the key technology of solute-solvent interaction mode regulation to form a starch-colored polyphenol complex in one step, and providing new ideas and new ways for the innovation of colored low digestibility extruded recombinant rice.

[0009] The technical solution of the present invention is as follows:

[0010] The first aspect of the present invention provides a one-step method for forming a starch-polyphenol complex to produce colored low-digestible extruded recombinant rice, comprising the following steps:

[0011] S1. preparing a natural low eutectic solvent from a hydrogen bond donor and a hydrogen bond acceptor, wherein the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1-6:12;

[0012] S2, adding colored polyphenols to the natural deep eutectic solvent of step S1, mixing evenly, and dissociating crystalline polyphenols by adjusting the natural deep eutectic solvent-polyphenol interaction mode to obtain a natural deep eutectic solvent-free polyphenol solution;

[0013] S3, crushing broken rice, a byproduct of rice processing, as the main base material, adding the natural low eutectic solvent-free polyphenol solution of step S2, stirring and mixing evenly, and the natural low eutectic solvent-free polyphenol solution self-assembles and drives into the inner cavity of the starch spiral to form a starch-polyphenol complex;

[0014] S4, subjecting the starch-polyphenol complex of step S3 to tempering, extrusion, molding and granulation;

[0015] S5, cooling, crystallizing and drying to obtain colored low-digestible extruded recombinant rice.

[0016] Optionally, in step S1, the method for preparing the natural low eutectic solvent comprises: preparing the natural low eutectic solvent by heating and melting a hydrogen bond donor and a hydrogen bond acceptor at 60-90°C.

[0017] Optionally, in step S1, an organic acid and choline chloride in a molar ratio of 1-6:12 are heated and melted at 60-90°C to prepare the product.

[0018] Optionally, in step S2, the colored polyphenols include one or more of capsanthin, anthocyanin, gardenia yellow, carotene, and curcumin.

[0019] Optionally, in step S2, colored polyphenols are added to the natural low eutectic solvent of step S1, and mixed and stirred for 3 to 5 hours using a magnetic stirrer, wherein the mass ratio of colored polyphenols to natural low eutectic solvent is 0.0001:10-20.

[0020] Optionally, in step S3, the particle size of broken rice, a by-product of rice processing, after crushing is less than 0.25 mm, and the amount of colored polyphenols added to each 1 kg of broken rice powder is 5-100 mg.

[0021] Optionally, in step S3, the broken rice flour and the colored free polyphenol solution are mixed in a mixer for 1 to 3 hours.

[0022] Optionally, in step S4, the feeding rate is 10-30kg / min, the water addition amount is 25%, the temperature of the extrusion material mixing preheating zone is 70-80°C, the temperature of the extrusion conveying zone is 80-90°C, the temperature of the pre-gelatinization zone is 90-103°C, the temperature of the gelatinization shear zone is 103-113°C, the temperature of the melting zone is 88-98°C, and the temperature of the die molding zone is 70-80°C; the screw speed is 40-60rpm, and then the rotary cutting granulation is performed, and the cutter speed is 110-130rpm.

[0023] Optionally, in step S5, the material processed in step S4 is placed in a constant temperature and humidity environment at 4-10°C and 50-80% humidity for cooling and recrystallization for 4-6 hours; then dried at 45-55°C until the moisture content is between 11-13%, thereby obtaining colored low-digestibility extruded recombinant rice.

[0024] The second aspect of the present invention provides a colored low-digestibility extruded recombinant rice, which is prepared by the above method.

[0025] The colored low-digestible extruded recombinant rice prepared by the present invention has good color and low digestibility due to the presence of colored polyphenols, is not easy to increase blood sugar, and is suitable for consumption by groups with high blood sugar. In addition, since natural polyphenols have biological activities such as antioxidant, hypoglycemic, hypolipidemic, antibacterial, anti-inflammatory and anti-tumor properties, the colored low-digestible extruded recombinant rice of the present invention has higher nutritional value than ordinary rice.

[0026] Since most colored polyphenol compounds are crystalline, their spatial structure volume is large and their water solubility is poor, which makes it difficult to form a complex with starch. In order to solve this problem, the existing technology is to make polyphenols into nano-forms to interact with starch molecules through hydrogen bonds, CH-π bonds and van der Waals forces to form non-inclusion complexes, and intercalate between starch helices in the form of "cross-linking agents". This method does not fundamentally solve the problem of low solubility loading capacity of polyphenols, poor stability, and easy degradation during processing and digestion.

[0027] The principle of the present invention is that the natural deep eutectic solvent has a very strong hydrogen bond network structure and can dissolve polyphenols and amylose. The crystalline polyphenols are dissociated through the dipole-dipole interaction and hydrogen bond interaction of the natural deep eutectic solvent, so that the free polyphenols are directed into the helical cavity of the amylose molecule for complexation, and then self-assembled to form a starch-polyphenol complex, which can effectively improve the solubility, uniformity and stability of the colored polyphenols and avoid degradation during processing and digestion.

[0028] The present invention uses a natural low eutectic solvent as a medium for forming a starch-polyphenol complex, and dissociates crystalline polyphenols by adjusting the natural low eutectic solvent-polyphenol interaction mode. Specifically, the present invention adjusts the natural low eutectic solvent-polyphenol interaction mode by the ratio of hydrogen bond donors to hydrogen bond acceptors. The applicant has found through research that the ratio of hydrogen bond donors to hydrogen bond acceptors will affect the interaction mode between the natural low eutectic solvent and polyphenols. When the ratio of the two is too high or too low, it will lead to the inability to dissociate crystalline polyphenols. In addition, the applicant has also found that the ratio of natural low eutectic solvent to polyphenols will also affect whether free polyphenols can be directed to enter the helical cavity of amylose molecules for complexation. When the mass ratio of colored polyphenols to natural low eutectic solvents is 0.0001:10-20, free polyphenols can be directed to enter the helical cavity of amylose molecules for complexation. This is because the helical structure of amylose molecules is a hydrophobic inner cavity, and the free polyphenols are spontaneously driven into the cavity by hydrophobic interactions. Therefore, the ratio of hydrogen bond donors to hydrogen bond acceptors and the ratio of colored polyphenols to natural deep eutectic solvents are key influencing factors of the present invention.

[0029] The present invention has at least one of the following beneficial effects:

[0030] The present invention uses a natural low eutectic solvent as a medium and directly mixes it with colored polyphenols and broken rice powder to self-assemble into a starch-polyphenol complex, that is, the starch-polyphenol complex can be formed in one step. Compared with the prior art which requires multiple processing steps such as pre-treatment of polyphenols and then mixing with broken rice powder, the preparation method of the present invention is simpler.

[0031] The starch-polyphenol complex formed by the invention belongs to the fifth type of resistant starch, and the polyphenol can inhibit the activity of digestive enzymes, thereby significantly reducing the digestibility of recombinant rice. Furthermore, the use of colored polyphenols as a nutritional enhancer to regulate the extruded recombinant rice can not only reduce the digestibility of the extruded recombinant rice, but also adjust the color of the extruded recombinant rice, thereby making the color of the extruded recombinant rice richer and improving the appetite of consumers. In addition, natural polyphenols have biological activities such as antioxidant, hypoglycemic, hypolipidemic, antibacterial and anti-inflammatory, and anti-tumor properties. The extruded recombinant rice is made of natural polyphenols and broken rice, thereby greatly improving the nutritional value of the extruded recombinant rice. Therefore, the production method of the invention has high feasibility and is easy to industrialize, and has significant effects on ensuring the sensory quality of the extruded recombinant rice, improving the color of the extruded recombinant rice, reducing the glycemic index of the recombinant rice, and realizing high-value utilization of the broken rice. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The X-ray diffraction patterns of the extruded recombinant rice prepared in Examples 1 to 3 and Comparative Examples 1 to 5 are shown.

[0033] Figure 2 The thermal property measurement diagram of the extruded recombinant rice prepared in Examples 1 to 3 and Comparative Examples 1 to 5. DETAILED DESCRIPTION

[0034] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] The present invention is further described in detail below with specific examples, but the present invention is not limited to the following specific examples.

[0036] Example 1

[0037] (1) mixing lactic acid and choline chloride in a molar ratio of 1:6, and heating at 80° C. until a clear and transparent liquid is formed to obtain a natural deep eutectic solvent;

[0038] (2) adding anthocyanidins to the prepared natural deep eutectic solvent, mixing and stirring with a magnetic stirrer for 4 hours to obtain a colored free polyphenol solution; wherein the mass ratio of anthocyanidins to the natural deep eutectic solvent is 0.0001:10;

[0039] (3) crushing the broken rice with a grinder and passing it through a 60-mesh sieve, weighing 6 kg of the broken rice powder and adding it to a mixer, slowly adding the colored free polyphenol solution of step (2), stirring and mixing in the mixer, standing, and self-assembly driving to form a starch-polyphenol complex; wherein the amount of polyphenol added per 1 kg of the broken rice powder is 10 mg;

[0040] (4) Pour the mixed raw materials into the feeder of the extruder at a feeding rate of 10 kg / h. Using extrusion reorganization technology, the temperatures of the mixing preheating zone, extrusion conveying zone, pre-gelatinization zone, shear gelatinization zone, melting zone, and die zone are set to 75°C, 85°C, 98°C, 108°C, 93°C, and 75°C respectively, and the screw speed is 60 rpm, and then cut and molded at 120 rpm;

[0041] (5) The prepared sample was placed in a constant temperature and humidity environment at 4°C and 50-60% humidity for cooling and recrystallization for 6 hours, and then dried at 45°C to a moisture content of 11-13%, and the product was packaged.

[0042] Example 2

[0043] (1) mixing lactic acid and choline chloride in a molar ratio of 1:8, and heating at 80° C. until a clear and transparent liquid is formed to obtain a natural deep eutectic solvent;

[0044] (2) adding carotene to the prepared natural deep eutectic solvent, mixing and stirring with a magnetic stirrer for 4 hours to obtain a colored free polyphenol solution; wherein the mass ratio of carotene to the natural deep eutectic solvent is 0.0001:15;

[0045] (3) crushing the broken rice with a grinder and passing it through a 60-mesh sieve, weighing 6 kg of the broken rice powder and adding it to a mixer, slowly adding the colored free polyphenol solution of step (2), stirring and mixing in the mixer, standing, and self-assembly driving to form a starch-polyphenol complex; wherein the amount of polyphenols added per 1 kg of the broken rice powder is 50 mg;

[0046] (4) Pour the mixed raw materials into the feeder of the extruder at a feeding rate of 10 kg / h. Using extrusion reorganization technology, the temperatures of the mixing preheating zone, extrusion conveying zone, pre-gelatinization zone, shear gelatinization zone, melting zone, and die zone are set to 75°C, 85°C, 98°C, 108°C, 93°C, and 75°C respectively, and the screw speed is 60 rpm, and then cut and molded at 120 rpm;

[0047] (5) The prepared sample was placed in a constant temperature and humidity environment at 60° C. and 60-70% humidity for cooling and recrystallization for 6 h, and then dried at 50° C. to a moisture content of 11-13%, and packaged to obtain the product.

[0048] Example 3

[0049] (1) mixing lactic acid and choline chloride in a molar ratio of 1:10, and heating at 80° C. until a clear and transparent liquid is formed to obtain a natural deep eutectic solvent;

[0050] (2) adding curcumin to the prepared natural deep eutectic solvent, mixing and stirring with a magnetic stirrer for 4 hours to obtain a colored free polyphenol solution; wherein the mass ratio of curcumin to the natural deep eutectic solvent is 0.0001:20;

[0051] (3) crushing the broken rice with a grinder and passing it through a 60-mesh sieve, weighing 6 kg of the broken rice powder and adding it to a mixer, slowly adding the colored free polyphenol solution of step (2), stirring and mixing in the mixer, standing, and self-assembly driving to form a starch-polyphenol complex; wherein the amount of polyphenol added per 1 kg of the broken rice powder is 100 mg;

[0052] (4) Pour the mixed raw materials into the feeder of the extruder at a feeding rate of 10 kg / h. Using extrusion reorganization technology, the temperatures of the mixing preheating zone, extrusion conveying zone, pre-gelatinization zone, shear gelatinization zone, melting zone, and die zone are set to 75°C, 85°C, 98°C, 108°C, 93°C, and 75°C respectively, and the screw speed is 60 rpm, and then cut and molded at 120 rpm;

[0053] (5) The prepared sample was placed in a constant temperature and humidity environment at 8° C. and 70-80% humidity for cooling and recrystallization for 6 h, and then dried at 55° C. to a moisture content of 11-13%, and packaged to obtain the product.

[0054] Comparative Example 1

[0055] The difference from Example 1 is that no natural low eutectic solvent is added. Specifically, steps (1), (2) and (3) are changed to "crush the broken rice with a grinder and pass it through a 60-mesh sieve, weigh 6 kg of broken rice powder and add it to a mixer, slowly add anthocyanins and water, stir and mix them in the mixer, and let it stand to obtain a mixture; wherein the amount of polyphenols added to each 1 kg of broken rice powder is 10 mg and the amount of water added is 1.2 kg".

[0056] The other steps are the same as those in Example 1.

[0057] Comparative Example 2

[0058] The difference from Example 1 is that in step (1), the mass ratio of curcumin to natural deep eutectic solvent is 0.0001:5.

[0059] The other steps are the same as those in Example 1.

[0060] Comparative Example 3

[0061] The difference from Example 1 is that in step (1), the mass ratio of curcumin to natural deep eutectic solvent is 0.0001:25.

[0062] The other steps are the same as those in Example 1.

[0063] Comparative Example 4

[0064] The difference from Example 1 is that in step (1), lactic acid and choline chloride are mixed in a molar ratio of 1:1.

[0065] The other steps are the same as those in Example 1.

[0066] Comparative Example 5

[0067] The difference from Example 1 is that in step (1), lactic acid and choline chloride are mixed in a molar ratio of 1:15.

[0068] The other steps are the same as those in Example 1.

[0069] Test results and analysis

[0070] The crystal structure, digestibility, estimated glycemic index and thermal properties of the extruded recombinant rice prepared in Examples 1 to 3 and Comparative Examples 1 to 5 were tested. The testing method is as follows:

[0071] (1) Crystal structure determination:

[0072] The crystal structure of the extruded recombinant rice was determined by X-ray diffractometer. The specific determination method is: using the copper target of the X-ray diffractometer under the conditions of 40kV and 40mA, a CuKα ray with a wavelength of 0.1546nm was generated. The diffraction scanning range was 5° to 40° (2θ), the step length was 0.02°, and the scanning rate was 6° / min.

[0073] The results are as follows Figure 1 shown.

[0074] (2) Determination of digestion characteristics:

[0075] From Examples 1 to 3 and Comparative Examples 1 to 5, 200 mg of the steamed sample (based on the dry basis of total starch) was weighed in a 50 mL centrifuge tube, 15 mL of sodium acetate buffer solution (0.2 M, pH 5.2) was added, 200 μL of mixed enzyme solution (360 U / mL a-amylase and 396 U / mL amyloglucosidase) was added after balancing at 37 ° C for 10 min, and the mixture was placed in a 37 ° C constant temperature water bath with a constant temperature oscillation of 300 rpm, 200 μL of enzymolysis solution was taken out at 0, 20, 40, 60, 90, 120 and 180 min, and the reaction was terminated by adding 800 μL of anhydrous ethanol in a 2 mL centrifuge tube, and the amount of glucose generated in the digestive solution was analyzed and determined at 510 nm by GOPOD reagent. The specific calculation formula is as follows, and the results are shown in Table 1.

[0076]

[0077] Among them, RDS, SDS, RS are the fast-digestible starch content, slowly digestible starch content, and resistant starch content, respectively; G0, G20, and G120 are the release amounts of glucose at 0, 20, and 120 min; TS is the total starch mass in the sample; and 0.9 is the molar mass conversion ratio of glucose to starch.

[0078] The starch hydrolysis rate (%) was calculated according to the following formula:

[0079]

[0080] Where S h is the amount of starch hydrolyzed; TS is the amount of starch in the starting material; G h is the amount of glucose produced by hydrolysis; 0.9 is the molar mass conversion ratio of glucose to starch.

[0081] (3) Estimated glycemic index ( e GI) determination:

[0082] The hydrolysis rate curve of starch in the modified extruded recombinant rice was drawn based on the hydrolysis rate of starch at different time points. The digestion kinetic parameters of the sample were obtained by fitting the hydrolysis rate curve of starch in the modified extruded recombinant rice through the first-order kinetic equation, and the formula is as follows:

[0083] C t =C∞(1-e -kt )

[0084] Where, Ct (%) is the hydrolysis rate of starch at time t (min); C∞ (%) is the final hydrolysis rate of starch; k (min- 1 ) is the first-order rate constant for in vitro digestion of starch and t is the digestion time.

[0085] The area under the hydrolysis curve (AUC) is given by the following formula:

[0086]

[0087] Where, C∞(%) is the final hydrolysis rate of starch, t f is the final reaction time (180 min), k (min- 1 ) is the first-order rate constant of starch digestion in vitro, t0 is the initial reaction time (0 min);

[0088] The hydrolysis index (HI) is obtained by the following formula:

[0089]

[0090] Taking white bread as the standard, its glycemic index (GI) is set at 100. The calculation formula for predicting GI from HI is as follows:

[0091] eGI=8.198+0.862×HI

[0092] The results are shown in Table 1.

[0093] (4) Determination of thermal properties

[0094] The thermal properties of recombinant rice were analyzed using a differential scanning calorimeter. 2-3 mg of recombinant rice was accurately weighed and placed in an aluminum crucible and mixed with three times the mass of deionized water. The crucible was then sealed and equilibrated for 16 hours. Using an empty crucible as a blank, the sample was heated from 20°C to 140°C at a rate of 10°C / min and the DSC curve of the sample was recorded.

[0095] The results are as follows Figure 2 shown.

[0096] Table 1 Digestion characteristics and GI values ​​of different samples

[0097]

[0098] As can be seen from Table 1, compared with Comparative Examples 1 to 5, the recombinant rice prepared in Examples 1 to 3 has a significantly reduced fast digestible content and a significantly increased resistant starch, and the estimated glycemic index (eGI) is significantly reduced, indicating that the method of the present invention can significantly reduce its digestibility and is not easy to increase blood sugar. In Comparative Example 1, since no natural deep eutectic solvent was added, the polyphenols and starch were compounded in a non-inclusion form, resulting in a significant increase in the eGI value, that is, improved digestibility; Comparative Example 2 is too little natural deep eutectic solvent, resulting in a significant increase in the eGI value, that is, improved digestibility; Comparative Example 3 is too much natural deep eutectic solvent, which also leads to a significant increase in the eGI value, that is, improved digestibility; Comparative Examples 4 to 5 are changes in the ratio of lactic acid and choline chloride, resulting in insufficient interaction between hydrogen bond donors and hydrogen bond acceptors to form a natural deep eutectic solvent, but a mixture of the two. This complex system is not conducive to the formation of an ordered V-type inclusion complex, and is easy to destroy the crystalline structure of starch, resulting in a significant increase in the eGI value, that is, improved digestibility.

[0099] like Figure 1As shown, as a control group, comparative example 1 did not add a natural low eutectic solvent, the binding effect of polyphenols and starch was poor, and no V-type diffraction peak appeared, indicating that the free polyphenols and starch were compounded in a non-inclusion form, which resulted in a high content of rapidly digestible starch and a high GI value, and were not suitable for consumption by diabetic patients. Examples 1, 2, and 3 showed sharp V-type diffraction peaks at 13° and 20°, which represented the inclusion structure of free polyphenols entering the spiral cavity of starch. The formation of this stable inclusion complex resulted in a higher resistant starch content and a lower GI value. The texture characteristics of Examples 2 and 3 were similar to those of Example 1, significantly reducing the rapidly digestible content and significantly increasing the resistant starch content. Example 3 had the most uniform color and the lowest digestibility. Due to the low and high addition amount of natural deep eutectic solvent, the diffraction peak intensity of Comparative Examples 2 and 3 decreased, and no characteristic diffraction peak of V-type crystal was observed. This may be because the addition amount of natural deep eutectic solvent was too low and too high, which resulted in the inability of free polyphenols to enter the helical cavity of amylose molecules for complexation and form characteristic diffraction peaks of V-type crystals, indicating that inappropriate addition amount of natural deep eutectic solvent resulted in high digestibility and GI value. As shown in the diffuse X-ray diffraction peak results of Comparative Examples 4 and 5, when the hydrogen bond acceptor and the hydrogen bond donor were mixed in an incorrect ratio, it was difficult to form an effective natural deep eutectic solvent, so that the association between polyphenols and starch existed in the form of non-inclusion complex between helices, further resulting in improved digestibility of recombinant rice. This is because the ratio of hydrogen bond donors to hydrogen bond acceptors affects the interaction mode between natural deep eutectic solvents and polyphenols. When the ratio of the two is too high or too low, the interaction mode between natural deep eutectic solvents and polyphenols is affected, resulting in the inability to dissociate crystalline polyphenols. It can be seen that compared with the comparative example and the embodiment, the extruded recombinant rice of the present invention can improve its color, significantly reduce starch digestibility, and ensure its texture characteristics.

[0100] like Figure 2As shown, compared with Comparative Examples 1 to 5, the endothermic peaks of the recombinant rice prepared in Examples 1 to 3 are all in a higher temperature range. This is because the embodiments dissociate the crystalline polyphenols through the dipole-dipole interaction and hydrogen bond interaction of the natural low eutectic solvent, so that the free polyphenols enter the helical cavity of the amylose molecule for complexation to form a V-type inclusion complex, thereby improving the thermal stability of the recombinant rice. Comparative Example 1 did not add a natural low eutectic solvent, and the binding effect of polyphenols and starch was poor, and the non-inclusion complex formed was relatively unstable. In addition, the endothermic peaks of Comparative Examples 2 to 5 are similar, and all show a lower gelatinization temperature. This shows that if the amount of natural deep eutectic solvent added is inappropriate or the proportion of components is incorrect, it is difficult to promote the formation of stable polyphenol-starch inclusion complexes. This is because the ratio of hydrogen bond donors to hydrogen bond acceptors will affect the interaction mode between the natural deep eutectic solvent and polyphenols. When the ratio of the two is too high or too low, the interaction mode of the natural deep eutectic solvent-polyphenol is affected, resulting in the inability to dissociate crystalline polyphenols; and if the amount of natural deep eutectic solvent added is too low or too high, the free polyphenols will be unable to enter the helical cavity of the amylose molecule for complexation.

[0101] In summary, when no natural deep eutectic solvent is added, the amount of natural deep eutectic solvent added increases or decreases, and the ratio of lactic acid to choline chloride increases or decreases, the crystalline structure of starch will be affected or destroyed, resulting in the failure to form a V-type complex, which ultimately leads to increased digestibility and GI value of the reconstructed rice, making it unsuitable for consumption by diabetic patients.

[0102] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for producing colored low-digestible extruded recombinant rice by forming a starch-polyphenol complex in one step, characterized in that: The following steps are involved: S1. preparing a natural low eutectic solvent from a hydrogen bond donor and a hydrogen bond acceptor, wherein the molar ratio of the hydrogen bond donor to the hydrogen bond acceptor is 1-6:12; S2, adding colored polyphenols to the natural deep eutectic solvent of step S1, mixing evenly, and dissociating crystalline polyphenols by adjusting the natural deep eutectic solvent-polyphenol interaction mode to obtain a natural deep eutectic solvent-free polyphenol solution; S3, crushing broken rice, a byproduct of rice processing, as the main base material, adding the natural low eutectic solvent-free polyphenol solution of step S2, stirring and mixing evenly, and the natural low eutectic solvent-free polyphenol solution self-assembles and drives into the inner cavity of the starch spiral to form a starch-polyphenol complex; S4, subjecting the starch-polyphenol complex of step S3 to tempering, extrusion, molding and granulation; S5, cooling, crystallizing and drying to obtain colored low-digestible extruded recombinant rice.

2. The method according to claim 1, characterized in that In step S1, the method for preparing the natural low eutectic solvent comprises: preparing the natural low eutectic solvent by heating and melting a hydrogen bond donor and a hydrogen bond acceptor at 60-90°C.

3. The method according to claim 1, characterized in that In step S1, an organic acid and choline chloride in a molar ratio of 1-6:12 are heated and melted at 60-90°C to prepare the product.

4. The method according to claim 1, characterized in that: In step S2, the colored polyphenols include one or more of capsanthin, anthocyanin, gardenia yellow, carotene, and curcumin.

5. The method according to claim 1, characterized in that: In step S2, colored polyphenols are added to the natural low eutectic solvent of step S1, and mixed and stirred for 3 to 5 hours using a magnetic stirrer, wherein the mass ratio of colored polyphenols to natural low eutectic solvent is 0.0001:10-20.

6. The method according to claim 1, characterized in that In step S3, the particle size of the broken rice, a by-product of rice processing, after being crushed is less than 0.25 mm, and the amount of colored polyphenols added to each 1 kg of broken rice powder is 5-100 mg.

7. The method according to claim 1, characterized in that In step S3, the broken rice flour and the colored free polyphenol solution are mixed in a mixer for 1 to 3 hours.

8. The method according to claim 1, characterized in that: In step S4, the feeding speed is 10-30kg / min, the water addition amount is 25%, the temperature of the extrusion material mixing preheating zone is 70-80°C, the temperature of the extrusion conveying zone is 80-90°C, the temperature of the pre-gelatinization zone is 90-103°C, the temperature of the gelatinization shearing zone is 103-113°C, the temperature of the melting zone is 88-98°C, and the temperature of the die head molding zone is 70-80°C; the screw speed is 40-60rpm, and then the rotary cutting granulation molding is performed, and the cutter speed is 110-130rpm.

9. The method according to claim 1, characterized in that: In step S5, the material treated in step S4 is placed in a constant temperature and humidity environment at 4-10° C. and 50-80% humidity for cooling and recrystallization for 4-6 hours; then dried at 45-55° C. until the moisture content is between 11-13%, thereby obtaining colored low-digestibility extruded recombinant rice.

10. Colored low digestibility extruded recombinant rice, characterized in that: The method is prepared by any one of claims 1 to 9.

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