Slowly digestible rice and screening method and application of special rice for slowly digestible rice

Abstract

The invention relates to slowly digestible rice and a screening method and application of special rice thereof. The endosperm of the slowly digestible rice comprises the following components: less than or equal to 80% of starch, more than or equal to 30% of amylose, more than or equal to 6% of resistant starch, more than or equal to 7% of protein, more than or equal to 1.5% of fat and more than or equal to 10 * 10 < 6 > g / mol of amylose. The method comprises the following steps: preliminarily screening a rice variety which has a slow digestion characteristic and is relatively good in eating quality of prepared rice through physicochemical index analysis, establishing a slow digestion rice screening model, predicting the quality characteristics of rice by combining a molecular marker technology of genetic information, screening out a slow digestion rice variety, and screening out the slow digestion rice variety. The number of samples needing a molecular marker technology of genetic information is greatly reduced, the cost of molecular marker screening is reduced, and it can be ensured that the screened variety has good nutritional characteristics and sensory quality in practical application. The method can accurately, stably and quickly breed the slowly digestible rice, and is applied to actual production, such as extruded coarse cereal rice, instant coarse cereal rice and the like.

Description

Technical Field

[0001] The invention relates to the technical field of agriculture, and in particular to a screening method and application of slow-digestible rice and special rice thereof. Background Art

[0002] my country is a major rice-growing country and a major rice-consuming country. About one-half of the residents use rice, a product of primary processing of rice, as their staple food. Rice-based foods are easy to digest, have low allergenicity, and have a rich taste, and are well-loved by residents, occupying an important position in the residents' dietary structure. However, the drastic fluctuations in blood sugar caused by the human body's intake of rice-based foods are not conducive to health. Relevant studies have shown that high blood sugar levels after long-term consumption of refined white rice are positively correlated with the prevalence of metabolic diseases such as type 2 diabetes and obesity. As people's health awareness increases, consumers tend to choose rice with slow digestion characteristics and relatively gentle blood sugar fluctuations after consumption. Establishing corresponding slow-digestible rice and rice screening methods will help develop slow-digestible rice products to meet the consumption needs of specific groups of people.

[0003] There have been some studies on the screening of slow-digestible rice and rice, which are mainly divided into physical and chemical index screening method and genetic information molecular marker method. The physical and chemical index screening method mainly involves the index of amylose content. Generally speaking, amylose content and rice digestion rate are negatively correlated, but other physical and chemical properties of rice, such as gel properties and edible quality of rice, are often ignored. While screening out slow-digestible rice, it may cause poor actual processing and application of rice, and the accuracy of screening out rice varieties also needs to be studied; genetic information molecular marker technology can conduct more accurate genetic analysis, thereby screening out slow-digestible rice varieties with specific genetic backgrounds, but molecular marker technology is relatively complex and costly, and it cannot infer whether rice is suitable for actual processing and production.

[0004] How to quickly and accurately screen out slowly digestible rice and paddy rice and ensure that the screened varieties can be well applied in actual production is of great significance to improving the dietary structure of residents and preventing and improving various chronic diseases including diabetes. Summary of the invention In order to solve the above problems, the present invention provides a screening method and application of slow-digestible rice and special rice thereof.

[0005] The solution of the present invention: Composition of slowly digestible rice endosperm: starch content ≤ 80% (dry basis), amylose content ≥ 30% (total starch content), resistant starch content ≥ 6% (dry basis), protein content ≥ 7% (dry basis), fat content ≥ 1.5% (dry basis), molecular weight of amylose ≥ 10×10 6 g / mol.

[0006] Preferably, the slow-digestible rice gel has the following quality characteristics: 400~800g; viscosity: -30~-80g; elasticity: 0.90~1; cohesion: 0.60~0.85; digestion rate constant: 4.0~6.5min −1 A method for screening slow-digestible rice, the method comprising the following steps: S1 collects rice from different sources, prepares it into polished rice after rice grain processing, and analyzes its quality characteristics, including the composition of rice endosperm, the gel properties of rice endosperm, and the sensory quality and digestibility of the cooked rice.

[0007] S2 determined the characteristics of the slow-digestible rice varieties through correlation analysis and regression analysis, that is, the digestion rate constant range of the cooked rice was 4.0~6.5min −1 , and establish a rice variety screening model; S3 uses molecular marker technology of genetic information, including DNA typing analysis, nucleotide polymorphism analysis, and molecular markers to screen out slow-digesting and high-quality rice varieties.

[0008] Preferably, in step S1, the rice components include starch, protein or fat; the endosperm gel properties include hardness, viscosity, elasticity or cohesion; and the sensory qualities of the rice include aroma, mouthfeel or taste.

[0009] Preferably, in step S1, the components of the slowly digestible rice endosperm are as follows: starch content ≤ 80% (dry basis), amylose content ≥ 30% (total starch content), resistant starch content ≥ 6% (dry basis), protein content ≥ 7% (dry basis), fat content ≥ 1.5% (dry basis), molecular weight of amylose ≥ 10×10 6 g / mol.

[0010] Preferably, the slow digestible rice gel has the following quality characteristics: 400-800 g; viscosity: -30--80 g; elasticity: 0.90-1; cohesion: 0.60-0.85; digestion rate constant: 4.0-6.5 min −1 .

[0011] Preferably, the data analysis in step S2 includes correlation analysis, principal component analysis, and regression analysis.

[0012] The slowly digestible rice or the slowly digestible rice special rice obtained by the screening method is used for processing coarse grain rice. Preferably, in step (1), a variety with wide ecological adaptability, good high and stable yield performance, and strong stress resistance is selected; the screening indicators of rice endosperm quality include starch content, fat content, protein content, and iodine blue value; the gel properties of rice endosperm include hardness, viscosity, elasticity, and cohesion. In step (3), the molecular marker technology selects MNP molecular markers.

[0013] Beneficial effects of the present invention: The present invention first preliminarily screens out rice varieties with slow digestion characteristics and better edible quality of rice prepared by physical and chemical index analysis, establishes a slow digestion rice screening model, and then predicts the quality characteristics of rice by combining molecular marker technology with genetic information to screen out slow digestion rice varieties, greatly reducing the number of samples that need to be subjected to molecular marker technology of genetic information, reducing the cost of molecular marker screening, and ensuring that the screened varieties have good nutritional characteristics and sensory quality in practical applications. The present invention can accurately, stably and quickly breed slow digestion rice, and apply it to practical production, such as extruded grain rice, instant grain rice, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Flow chart of the present invention; Figure 2 Flowchart of mutation detection information analysis; Figure 3 Distribution map of each variant site on the genome; Figure 4 Sequencing depth distribution diagram; Figure 5 Chromosome base content distribution map; Figure 6 Glucose blood sugar response graph; Figure 7 Blood sugar response graph of rice. DETAILED DESCRIPTION The present invention is described in further detail below in conjunction with the accompanying drawings and Examples, but embodiments of the present invention are not limited thereto. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art. The test methods for which specific experimental conditions are not specified in the following examples are usually carried out according to conventional experimental conditions or according to the experimental conditions recommended by the manufacturer. Unless otherwise specified, reagents and raw materials used in the present invention can be obtained by commercial means or conventional methods.

[0015] Preparation method of rice endosperm: After using a sieve to remove impurities in the rice, the collected rice is processed with a laboratory small rice husker to remove the husk to obtain brown rice, which is then processed with a laboratory small rice polishing machine to remove the bran layer and germ on the surface of the brown rice to obtain the rice endosperm. The rice endosperm with no abnormal color, full grains, and no diseases and insect pests is manually selected for subsequent experiments.

[0016] Determination of textural properties of rice gel: The rice gel was cut into samples with a diameter of 30 mm and a height of 15 mm and measured using the TPA double compression mode with a pre-test speed of 1 mm / s, a test speed of 1 mm / s, a post-test speed of 1 mm / s, and a compression ratio of 50% to obtain hardness, viscosity, elasticity, and cohesion.

[0017] Rice sensory evaluation table: Table 1 Sensory evaluation table of rice

[0018] Determination of digestibility of rice Weigh a certain mass of sample (converted to 90 mg starch dry weight) into a centrifuge tube, add 6.0 mL of distilled water and 10.0 mL of sodium acetate buffer (pH 6.0), put it into a stirring rotor, and balance it in a 37 ℃ water bath for 5 min. At the same time, the prepared mixed enzyme solution (i.e., 5.0 mL of pH 6.0 sodium acetate buffer containing 210 U α-amylase and 210 U glucosidase, incubated in a 37 ℃ water bath for 10 min, centrifuged at 4000 r / min for 5 min to take the supernatant) was incubated in a 37 ℃ water bath for 5 min. After the solution was balanced to 37 °C, 5.0 mL of mixed enzyme solution was added to the test sample solution, and 0.1 mL of digestion solution was immediately taken into a centrifuge tube containing 0.9 mL of anhydrous ethanol, which was recorded as the 0 min point. Then, the same volume of digestion solution was taken into a centrifuge tube containing anhydrous ethanol to inactivate the enzyme at 5 min, 10 min, 20 min, 30 min, 45 min, 60 min, 90 min, and 120 min. The starch digestion solution after enzyme inactivation was centrifuged at 4000 r / min for 10 min, 0.1 mL of supernatant was taken into a centrifuge tube, and 3.0 mL of glucose reagent was added. Then 0.1 mL of glucose standard solution and 0.1 mL of anhydrous ethanol were taken and added to 3.0 mL of glucose reagent. After each test tube was balanced in a 37 °C constant temperature water bath for 10 min, the absorbance values ​​of other tubes were measured after blank calibration, and the glucose concentration of each tube was calculated. The starch digestibility was calculated according to the method in the literature (Zou et al 2015). RDS is the amount of glucose released within 20 min of digestion, SDS is the portion of starch digested and hydrolyzed within 20-120 min of digestion, and RS is the portion of starch that remains undigested after 120 min. At the same time, the data from the starch digestion experiment were fitted and analyzed to obtain the characteristic parameters of digestion kinetics. The hydrolysis process of starch conforms to the first-order reaction kinetic equation (Formula 1) and the LOS conversion function (the logarithm of the slop; Formula 2) for further explanation.

[0019]

[0020] Where Ct (%) represents the amount of starch digested in a given time; C∞ (%) represents the estimated percentage of starch digestion at the end of digestion; k (min-1) represents the starch digestion rate constant (k). The starch digestion rate constant (k) was obtained based on the fitting results of the nonlinear curve.

[0021] Example 1 Sample collection and preparation, including varieties with broad ecological adaptability, good high-yield and stable yield performance, and strong stress resistance, including collecting rice samples of different varieties of indica rice varieties and preparing slowly digestible rice.

[0022] Table 2 Main components of rice endosperm (dry basis)

[0023] Table 3 Gel properties of rice endosperm

[0024] The sensory evaluation results of slow-digestible rice are shown in Table 4.

[0025] Table 4 Sensory quality and digestion rate of rice made from slow digestible rice

[0026] The correlation analysis between basic components of rice and sensory quality of cooked rice is shown in Table 5. Table 5 Correlation analysis between basic components of rice endosperm and sensory quality and digestibility of rice (r / α )

[0027] The mathematical model for predicting the digestion rate of rice based on the endosperm amylose content is shown in Formula 1 (p=0.04). As can be seen from Formula 1, rice with a higher amylose content has a slower digestion rate.

[0028] Prediction model of rice digestion speed: y 5 =7.085-2.805x 4 (5.14 / 0.04)(1) As shown in Tables 2-5, the total score of rice sensory evaluation is positively correlated with the content of amylose in rice endosperm, the hardness of rice endosperm gel and viscosity, and negatively correlated with cohesion; the digestion rate of rice is negatively correlated with the content of amylose. By analyzing the relationship between the basic indicators of rice and the sensory quality of rice and the digestion rate, the slow digestion rice can be screened while ensuring the quality of the rice after it is processed and eaten. The digestion rate determined by the in vitro digestion simulation experiment can reflect the digestion and absorption of rice in the human body and the blood sugar level that may be caused after consumption. Therefore, the rice varieties with slow digestion characteristics are screened based on the digestion rate, and the endosperm component characteristics of the slow digestion rice are determined in combination with the physical and chemical properties of the cultivated slow digestion rice.

[0029] Example 3 The genetic information of the slow-digestible rice Chuwang 2 was analyzed, including DNA series analysis, nucleotide polymorphism analysis, and molecular markers, to determine the genetic characteristics of the variety.

[0030] By analyzing the genetic information of Chuwang 2 and comparing it with the rice reference genome sequence, the high contrast ratio and sequencing depth indicate that the quality and coverage of the sequencing data are good, providing a reliable basis for subsequent genetic analysis. There are a large number of genetic variations in the Chuwang 2 genome, including a large number of SNPs, InDels and SV variations, which have an important impact on the physical and chemical properties of rice, such as digestibility and edible quality.

[0031] Example 4 Using Chuwang 2 rice variety as raw material, its genetic information, the content of key components in rice endosperm and the sensory quality of rice were tested. The results are shown in Table 6.

[0032] Among them, the molecular weight of amylose is determined by GPC-MALLS-RI: Weigh 5 mg of purified starch, add 5 mL of mobile phase DMSO, heat at 80℃ to dissolve for 3 h, and load the sample. The loading conditions are column temperature 60℃; injection volume 200 μl; mobile phase is DMSO containing 0.5% LiBr; flow rate 0.3 ml / min; gel exclusion chromatography columns use Ohpak SB-805 HQ (300×8 mm) and Ohpak SB-804 HQ (300×8 mm) connected in series.

[0033] The resistant starch content was determined by the spectrophotometric method specified in NY / T 2638-2014 for the determination of resistant starch in rice and its products. Table 6 Genetic information, endosperm content, gel properties and sensory quality of rice of Chuwang 2 rice

[0034] Blood glucose response of glucose and rice as shown in Table 6 Figure 6-7 It can be seen that Chuwang No. 2 rice has good sensory quality, a slow digestion rate, can significantly reduce the peak blood sugar level, and blood sugar fluctuations are relatively smooth.

[0035] Example 5 Effect of Mixing Ratio on Digestion Rate and Sensory Quality of Rice Rice, natural multi-grain rice and extruded multi-grain rice were stirred and mixed in a certain proportion and then steamed to measure the digestibility and sensory quality of the mixed rice, as shown in Table 7.

[0036] Table 7 Effect of mixing ratio on digestion rate and sensory quality of rice

[0037] It can be seen from Table 7 that the compounding of rice, natural multi-grain rice and extruded multi-grain rice can reduce the digestion rate of rice. The digestibility of rice without adding rice and only compounded with natural multi-grain rice and extruded multi-grain rice is the lowest, but at the same time the sensory quality of the rice is not good. Appropriately compounding rice with natural multi-grain rice and extruded multi-grain rice can slow down the digestion rate of rice while maintaining good sensory quality.

[0038] The technical solution of the present invention is explained through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above specific embodiments to be implemented. Any improvements made by technicians in the relevant field based on the present invention, or equivalent replacement of the materials selected by the present invention, etc., fall within the scope of protection of the patent.

Claims

1. A slow digestible rice, characterized in that: Composition of slowly digestible rice endosperm: starch content ≤ 80%, amylose content ≥ 30%, resistant starch content ≥ 6%, protein content ≥ 7%, fat content ≥ 1.5%, molecular weight of amylose ≥ 10×10 6 g / mol.

2. The slow-digestible rice according to claim 1, characterized in that: The quality characteristics of the slow digestible rice gel include: 400~800g; viscosity: -30~-80g; elasticity: 0.90~1; cohesion: 0.60~0.85; digestion rate constant: 4.0~6.5min −1 .

3. A method for screening slow-digestible rice, characterized in that: The method comprises the following steps: S1 collects rice from different sources, prepares polished rice after rice grain processing, and analyzes its quality characteristics, including the composition of rice endosperm, the gel properties of rice endosperm, and the sensory quality and digestibility of cooked rice; S2 determined the characteristics of slow-digestible rice varieties through correlation analysis and regression analysis, that is, the digestion rate constant range of cooked rice was 4.5~8min −1 , and establish a rice variety screening model; S3 uses molecular marker technology of genetic information, including DNA typing analysis, nucleotide polymorphism analysis, and molecular markers to screen out slow-digesting and high-quality rice varieties.

4. The method for screening the slow-digestible rice according to claim 3, characterized in that: In step S1, the rice components include starch, protein or fat; the endosperm gel properties include hardness, viscosity, elasticity or cohesion; and the sensory qualities of the rice include aroma, mouthfeel or taste.

5. The method for screening the slow-digestible rice according to claim 3, characterized in that: In step S1, the components of the slowly digestible rice endosperm are as follows: starch content ≤ 80%, amylose content ≥ 30%, resistant starch content ≥ 6%, protein content ≥ 7%, fat content ≥ 1.5%; the molecular weight of amylose ≥ 10×10 6 g / mol.

6. The method for screening the slow-digestible rice according to claim 3, characterized in that: Step S1, slow digestible rice gel quality characteristics: 400~800g； Viscosity: -30~-80g; Elasticity: 0.90~1; Cohesion: 0.60~0.85; Digestion rate constant: 4.0~6.5min −1 .

7. The method for screening the slow-digestible rice according to claim 3, characterized in that: In step S3, the molecular marker technology selects MNP molecular markers.

8. The slowly digestible rice obtained by the screening method of the slowly digestible rice or the rice specifically for slowly digestible rice according to any one of claims 1 to 7 is used for processing miscellaneous grain rice.

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