Simple method for rapidly predicting content of resistant starch in rice

Abstract

The invention belongs to the technical field of analysis and detection of the content of resistant starch in rice, and particularly relates to a simple method for rapidly predicting the content of resistant starch in rice. The invention provides a simple method for rapidly predicting the content of resistant starch in rice. The simple method sequentially comprises the steps of measuring the physiological indexes of a polished rice sample to be measured, measuring the physiological indexes of cooked polished rice, predicting the content of resistant starch and the like. The content of the resistant starch is predicted by utilizing the correlation between the content of the resistant starch and the cooking characteristics of the rice, and the method is low in cost, simple in step, rapid in result obtaining and suitable for screening the resistant starch rice on a large scale. The method has a certain economic value, so that the method has a good application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of analysis and detection of resistant starch content in rice, and particularly relates to a simple method for quickly predicting the resistant starch content in rice. Background Art

[0002] Rice is an extremely important food crop. More than 60% of the population in my country and more than one-third of the world's population rely on rice as their staple food. The glycemic index (GI) value of rice varieties ranges from 48 to 93. Rice and its products are mainly digested by amylase in the stomach and small intestine, and the final product is glucose. Therefore, rice is considered to be a food with a high glycemic index (GI). Resistant starch (RS) is a general term for starch and starch degradation products that can avoid hydrolysis by pancreatic α-amylase and are not digested and absorbed in the small intestine of healthy people. It was named by Englyst in 1983.

[0003] As a special type of carbohydrate, resistant starch is gaining more and more attention in the food industry. It has a variety of physiological health benefits, including improving digestive health, promoting weight control and enhancing satiety, which makes it have a wide range of application prospects in the food industry. In addition, resistant starch can also be used to develop diet foods and treat type 2 diabetes, because it is not digested and absorbed in the small intestine, but can enter the large intestine and be fermented and utilized by intestinal flora, exerting a variety of physiological effects such as controlling blood sugar and blood lipids.

[0004] The industry research on resistant starch started late, but with the increasing awareness of health care, the market demand has increased and the industry has broad development space, which shows that resistant starch has great potential for application in the food industry. With the growth of the global resistant starch market, the demand for rapid prediction methods for this ingredient is also increasing. Market analysis shows that resistant starch is favored by consumers for its health benefits, which has driven the expansion of the market.

[0005] At present, the methods for determining the content of resistant starch mainly include in vivo determination and in vitro determination. The in vivo determination method determines the content of resistant starch by measuring the starch and its degradation products that are not absorbed by the human body, but it is costly and has certain risks. The in vitro determination method simulates the digestive conditions in the body and determines the content of starch that is not hydrolyzed by amylase in vitro.

[0006] In the in vitro assay, the method proposed by McCleary et al. was adopted as the official assay method (AOAC method 2002.02) because it is simple and reliable. This method involves incubating the sample at 37°C for 16 hours with α-amylase and amyloglucosidase (AMG). Through the combined action of the two enzymes, non-resistant starch is dissolved and hydrolyzed into glucose. After the incubation, ethanol is added to terminate the reaction, and resistant starch is separated by centrifugation.

[0007] In addition to the AOAC method, there are several other in vitro determination methods, such as the Englyst method, the Goni method, the Champ method, etc. The Englyst method is based on the definition of resistant starch as starch that is not hydrolyzed in the presence of pancreatic enzymes and saccharifying enzymes at pH 5.2 and 37°C for 120 minutes. The Goni method adds pepsin digestion to remove proteins before pancreatic α-amylase hydrolysis, and the Champ method uses pancreatic α-amylase and saccharifying enzymes to hydrolyze the sample at 37°C for 16 hours, and then precipitates with 80% ethanol and determines the RS content.

[0008] In summary, the existing methods for determining the resistant starch content in rice have technical defects such as high cost, complicated analysis process, long determination cycle, and difficulty in rapid screening of large batches of samples. Summary of the invention

[0009] The problem to be solved by the present invention is to provide a simple method for quickly predicting the resistant starch content of rice. The method predicts the resistant starch content of rice grains by utilizing the correlation between the resistant starch content of rice grains and the cooking characteristics of rice grains. The method has low cost, simple steps and fast results, and is suitable for large-scale screening of resistant starch rice.

[0010] In order to solve the above technical problems, the present invention provides a simple method for quickly predicting the content of resistant starch in rice, and its technical solution is as follows: A simple method for quickly predicting the resistant starch content of rice, wherein the rice is japonica rice, and the following steps are performed in sequence: 1) Measure the physiological parameters of polished rice samples to be tested Select an appropriate amount of polished rice with uniform size and no cracks from the polished rice sample to be tested, randomly divide it into no less than 5 portions with no less than 20 grains in each portion, measure the total weight of each portion, and measure it no less than 5 times respectively, and obtain no less than 5 parallel repeated results; 2) Measure the physiological parameters of polished rice after cooking The appropriate amount of polished rice with uniform size and no cracks selected in the first step is randomly divided into no less than 5 portions with no less than 20 grains in each portion, and the portions are respectively placed in centrifuge tubes, the centrifuge tubes are placed in an iron test tube rack, an appropriate amount of distilled water is added, and the mixture is allowed to stand for 12-20 minutes, and then placed in a boiling water bath for 12-20 minutes, the rice grains are taken out, placed on absorbent paper, and after standing for 12-20 minutes, the grain weight data of each sample is measured; 3) Prediction of resistant starch content After the samples were steamed according to the above steps, the water absorption of the samples was calculated. The formula for calculating the water absorption after steaming is: water absorption = (weight of rice grains after steaming - weight of rice grains before steaming) / weight of rice grains before steaming × 100%. The water absorption after steaming was calculated and substituted into the standard curve y = -0.1217x + 23.623, where y: RS predicted content, x: water absorption; According to the standard curve, when the water absorption is 153-200%, the RS range is 0-5%; when the water absorption is 153%, the RS value is 5%; when the water absorption is 80-153% and does not include 153%, the RS range is RS>5%.

[0011] In the above-mentioned simple method for quickly predicting the resistant starch content of rice, preferably, in step 1), the grain weight data of each repetition of rice is measured by a balance. It is also preferred that in step 1), a suitable amount of polished rice with uniform size and no cracks is selected from the polished rice sample to be tested, and the polished rice is randomly divided into 5 portions with 20 grains in each portion, and the total weight of each portion is measured, and the measurement is performed 5 times respectively to obtain 5 parallel repetition results.

[0012] The above-mentioned simple method for quickly predicting the resistant starch content of rice, preferably step 2) put 5 portions of 20 rice grains into 15mL centrifuge tubes, put the centrifuge tubes in an iron test tube rack, add 10mL of distilled water, let it stand for 15 minutes, and then put it in a boiling water bath for 15 minutes, take out the rice grains, put them on absorbent paper, let them stand for 15 minutes, and then measure the grain weight data of each sample.

[0013] The present invention also provides a simple method for quickly predicting the resistant starch content of rice, wherein the rice is indica rice, and the following steps are performed in sequence: 1) Measure the physiological parameters of the polished rice sample to be tested Select an appropriate amount of polished rice with uniform size and no cracks from the polished rice sample to be tested, randomly divide it into no less than 5 portions with no less than 20 grains in each portion, measure the total weight of each portion, and measure it no less than 5 times respectively, and obtain no less than 5 parallel repeated results; 2) Measurement of physiological parameters of polished rice after cooking The appropriate amount of polished rice with uniform size and no cracks selected in the first step is randomly divided into no less than 5 portions with no less than 20 grains in each portion, and the portions are respectively placed in centrifuge tubes, the centrifuge tubes are placed in an iron test tube rack, an appropriate amount of distilled water is added, and the mixture is allowed to stand for 12-20 minutes, and then placed in a boiling water bath for 12-20 minutes, the rice grains are taken out, placed on absorbent paper, and after standing for 12-20 minutes, the grain weight data of each sample is measured; Retrogradation of polished rice samples to be tested If the water absorption rate after the first two steps is between 90-120%, including both ends, the polished rice after steaming needs to be placed in a square dish and placed in a refrigerator at 4 degrees for 24 hours, and then randomly divided into groups of 20 and placed on absorbent paper. After standing for 15 minutes, the grain weight data of each group of samples after regeneration is measured, and the regeneration water loss rate is calculated, and the judgment is made in combination with the steaming water absorption rate; if the water absorption rate after the first two steps is not between 90-120%, excluding both ends, directly go to step 4) to predict the resistant starch content; 4) Prediction of resistant starch content After the samples are steamed according to the above steps, the water absorption of the samples is calculated. The formula for calculating the water absorption after steaming is: water absorption = (weight of rice grains after steaming - weight of rice grains before steaming) / weight of rice grains before steaming × 100%. The water absorption after steaming is calculated. According to the water absorption after steaming, the resistant starch content of the sample is divided into two preliminary prediction ranges of RS < 11% or RS > 11%. When the water absorption is between 120-250%, it is brought into the RS < 11% fitting curve; when the water absorption is between 60-90%, it is substituted into the RS > 11% standard curve to predict the resistant starch content. The standard curve is as follows: The fitting standard curve of RS<11% is: y = -0.0571x + 14.223, where Y: RS predicted content, X: water absorption; The fitting standard curve of RS>11% is: y = 0.1466x + 4.3208, where Y: RS predicted content, X: water absorption rate; When the water absorption rate is between 90-120%, including both ends, it is necessary to make a judgment in combination with the steaming and regeneration water loss rate. When the water absorption rate is between 90-120% and the steaming and regeneration water loss rate is greater than 9%, it is substituted into the RS<11% fitting standard curve, and finally the RS is obtained in the range of 5-11%; when the steaming and regeneration water loss rate is less than or equal to 9%, it is substituted into the RS>11% standard curve prediction, and finally the RS is obtained in the range of 11-22%; Regeneration water loss rate = (weight of 20 grains after steaming - weight of regeneration) / weight after cooking × 100%.

[0014] In the above-mentioned simple method for rapidly predicting the resistant starch content of rice, preferably, in step 1), the grain weight data of each repetition of rice is measured by a balance. Also preferably, in step 1), 100 grains of polished rice with uniform size and no cracks are selected from the polished rice sample to be tested, and the grains are randomly divided into 5 portions with 20 grains in each portion, and the total weight of each portion is measured, and the measurement is performed 5 times respectively to obtain 5 parallel repetition results.

[0015] The above-mentioned simple method for quickly predicting the resistant starch content of rice is preferably as follows: in step 2), 5 portions of 20 rice grains each are placed in 15 mL centrifuge tubes, the centrifuge tubes are placed in an iron test tube rack, 10 mL of distilled water is added, the rice grains are allowed to stand for 15 min, and then placed in a boiling water bath for 15 min; the rice grains are taken out, placed on absorbent paper, allowed to stand for 15 min, and then the grain weight data of each sample is measured.

[0016] The beneficial effects of the present invention are as follows: 1. Low cost. First, the common method requires the participation of a series of enzymes such as α-amylase and amyloglucosidase in the process of measuring the content of resistant starch, but the present method does not require the participation of any enzymes in the experimental process. Secondly, various expensive instruments and consumables are required in the process of determining the content of resistant starch using conventional methods, while the present method only requires an electric rice cooker and an electronic scale, and the determination method reduces the cost of determination from all aspects. 2. Simple steps. The steps of the conventional method for measuring resistant starch are relatively cumbersome, and the steps are roughly sample pretreatment, enzyme treatment, termination reaction, centrifugal washing, RS dissolution, neutralization and hydrolysis reaction, glucose determination, and result calculation. The steps of the present method for measuring the content of resistant starch are relatively simple. First, the sample is pretreated and ground into polished rice. Secondly, the polished rice is soaked for 15 minutes, and then put into boiling water and boiled for 15 minutes (cooked, that is, there is no white core in the middle of the rice grains). After cooking, the rice grains are dried on absorbent paper for 15 minutes and weighed. Finally, the water absorption rate is calculated, and the resistant starch content of the measured sample is predicted according to the water absorption rate combined with the standard curve. 3. Get results quickly. When determining the resistant starch content according to conventional methods, it is necessary to go through various enzyme treatments and various operation processes, and the measurement cycle is about 20 hours before the measurement results can be obtained. However, using this cooking method to predict the resistant starch content, the fastest japonica rice measurement cycle is only 1 hour. 4. Rapid batch screening, accurate prediction range. Some of the current conventional methods are still relatively difficult to achieve large-scale screening of resistant starch samples, but this method can quickly and accurately predict the range of resistant starch, and can achieve rapid screening of large batches of resistant starch samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 , 2 , 3 are standard curve models for predicting resistant starch content in japonica rice and indica rice, respectively, using samples with resistant starch content of 0.5%-22%, where: Figure 1 The standard curve model diagram for predicting the content of resistant starch in japonica rice is shown in Figure 2. According to the sample data of the japonica rice group, the fitting standard curve is y = -0.1217x + 23.623 (R 2 = 0.758)(y: RS predicted content, x: water absorption, R 2 : correlation coefficient); Figure 2 To predict the standard curve model diagram of resistant starch content in indica rice less than 11%, according to the sample data of indica rice group, the fitting standard curve when RS<11% is: y = -0.0571x + 14.223 (R 2 = 0.8022)(y: RS predicted content, x: water absorption, R 2 : correlation coefficient); Figure 3 This is the standard curve model diagram for predicting the resistant starch content in japonica rice greater than 11%. The RS>11% fitting standard curve is: y = 0.1466x + 4.3208 (R 2 = 0.9021) (y: RS predicted content, x: water absorption, R 2 : correlation coefficient); Figure 4 This is a flow chart for predicting the content of resistant starch. After the sample is steamed according to the technical method, the water absorption rate of the processed sample is calculated. When the water absorption rate of japonica rice is 153-200%, its RS range can be predicted to be 0-5%; when the water absorption rate is 80-153%, its RS range can be predicted to be RS>5%.

[0018] When measuring indica rice, first determine the water absorption rate according to the technical method. When the water absorption rate is between 120-250%, bring it into the standard curve of RS<11% for prediction, and finally get RS in the range of <5%; when the water absorption rate is between 60-90%, excluding the two end values, bring it into the standard curve of RS>11% for prediction; when the water absorption rate is between 90-120%, including the two end values, it is necessary to judge in combination with the steaming and regeneration water loss rate: when the water absorption rate is between 90-120% and the steaming and regeneration water loss rate is greater than 9%, bring it into the RS<11% fitting standard curve, and finally get RS content in the range of 5-11%; when the steaming and regeneration water loss rate is less than and equal to 9%, bring it into the standard curve of RS>11% for prediction, and RS is finally in the range of 11-22%; Retrogradation water loss rate = (weight of 20 grains after steaming - weight of regeneration) / weight after cooking × 100%. DETAILED DESCRIPTION

[0019] The present invention is further explained in detail below through the description of embodiments, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0020] Terminology explanation: Rice starch retrogradation refers to the process that occurs after rice is gelatinized. During the gelatinization process, the amylose is released and the amylopectin molecules are fully unfolded. During the storage process of the starch paste at a lower temperature, the free amylose and amylopectin recrystallize. This is the retrogradation of rice starch.

[0021] Rice retrogradation usually refers to the phenomenon that the taste and texture of rice deteriorates after it is cooked, refrigerated or frozen and then reheated. This process is also called "aging" or "reversion".

[0022] Specifically, after rice is cooked, its starch changes from an ordered structure to a disordered structure, which makes the rice soft and elastic. But over time, especially under low temperature conditions, the starch molecules will rearrange to form a more ordered structure, causing the rice to become hard and lose its original taste. This process is called "starch retrogradation" or "starch aging" in food science.

[0023] The simple method of the present invention was used to cooperate with Yazhou Bay Laboratory to measure RS content. The results of a series of materials measured by this method were consistent with those of the traditional AOAC method. For details, see the examples: Example 1 Determination of RS content using traditional AOAC method Instruments used: test tube, glass rod, rice polisher, sample grinder, 1 mm sieve, centrifuge, water bath, pH meter, magnetic stirrer, vortex oscillator, oscillating water bath Reagents: anhydrous ethanol, 50% ethanol, KOH solution, 1.2 M acetate buffer, sodium maleate buffer, 100 mM sodium acetate buffer, GOPOD reagent, α-pancreatic amylase solution, AMG enzyme Determination steps: 1. Sample preparation: Use a rice polisher to make polished rice for the sample to be tested, and use a grinder to grind it into rice flour that can pass through a 1 mm sample sieve. Weigh 100 mg of rice flour and add it to a centrifuge tube with a lid. Gently tap the test tube to concentrate the sample at the bottom, add 180 mL of distilled water, and cook in a boiling water bath for 20 min until the rice is edible.

[0024] 2. Digestion treatment: Take out the cooked sample from the centrifuge tube, cool it to room temperature, add 1 mL of freshly prepared α-amylase solution to the test tube, crush the rice flour block with a glass rod, and then use 3 mL of freshly prepared α-amylase solution to rinse the starch attached to the glass rod into the test tube, using a total of 4 mL of α-amylase solution.

[0025] 3. Oscillating incubation: Cover the lid tightly, mix well with a vortex oscillator, and place horizontally in an oscillating water bath with the long axis of the test tube parallel to the direction of movement. Oscillate continuously at a speed of 100 threads / min and incubate at 37°C for 16 hours.

[0026] 4. Terminate the reaction: Remove the test tube from the water bath, wipe off excess water with a paper towel, open the lid, add 4.0 mL of ethanol (99% v / v), and vortex with a vortexer to terminate the digestion reaction.

[0027] 5. Centrifugation: Centrifuge the mixture at 1500 g for 10 min (without covering) to separate the resistant starch (RS) precipitate.

[0028] 6. Wash the precipitate: Carefully pour out the supernatant, add 2 mL of 50% ethanol or 50% IMS to resuspend, vortex with a vortexer, add 6 mL of 50% IMS to mix, and centrifuge at 1500 g for 10 minutes. Carefully pour out the supernatant and repeat the washing and centrifugation steps at least twice. Carefully pour out the supernatant, turn the test tube over, and absorb the excess liquid with a paper towel.

[0029] 7. Dissolve the precipitate: Place the RS precipitate in an ice-water bath, add a small magnetic rotor and 2 mL of 2M KOH solution to the test tube to dissolve it, and use a magnetic stirrer to stir vigorously. Stir in an ice / water bath for 20 min to resuspend the floccules and dissolve the RS.

[0030] 8. Stirring water bath: Add 8 mL of 1.2M sodium acetate buffer (pH=3.8) to the test tube and stir with a magnetic stirrer. Immediately add 0.1 mL of AMG (3300 U / mL), mix well, and place in a 50℃ water bath.

[0031] 9. Incubation and centrifugation: Incubate for 30 min, mixing intermittently with a vortexer. For samples with RS content <10%, centrifuge directly at 1500 g for 10 min. Transfer 0.1 mL of the supernatant after centrifugation to a glass test tube (16×100 mm) in duplicate, add 3.0 mL of GOPOD reagent, and incubate at 50°C for 20 min.

[0032] 10. Absorbance determination: Measure the absorbance value relative to the blank reagent at 510 nm.

[0033] Collect the supernatant obtained by centrifugation in the initial incubation step 5 and the supernatant obtained in the two 50% ethanol washes in step 6 into a volumetric flask. Make up to 100 mL with 100 mM sodium acetate buffer (pH = 4.5). Mix well.

[0034] The solution was incubated in duplicate at 0.1 mL and 10 μL of diluted AMG solution (300 U / mL) was added, incubated at 50°C for 20 min, and 3.0 mL of GOPOD reagent was added, incubated at 50°C for 20 min.

[0035] 11. Prepare blank reagent: Prepare blank reagent: pipette 0.1 mL of 100 mM sodium acetate buffer (pH = 4.5) into a 16 × 100 mm glass test tube, add 3.0 mL of GOPOD reagent, and mix well.

[0036] Prepare D-glucose standard: pipette 0.1 mL of D-glucose (1 mg / mL) into a 16 × 100 mm glass test tube, add 3.0 mL of GOPOD reagent, mix well, and incubate at 50°C for 20 minutes to prepare D-glucose standard.

[0037] 12. Calculation: Calculate the resistant starch content, non-resistant starch content and total starch content in the sample (%) Resistant starch (g / 100g sample) (sample contains <10% RS) =⊿E×F×10.3 / 0.1×1 / 1000×100 / W×162 / 180 =⊿E×F / W×9.27 Non-resistant starch content (g / 100g sample) =⊿E×F×100 / 0.1×1 / 1000×100 / W×162 / 180 =⊿E×F / W×90 Total starch content = resistant starch content + non-resistant starch content ⊿E = absorbance value relative to blank reagent F = conversion from absorbance to micrograms. (In the GOPOD reaction, the absorbance of 100 μg of D-glucose is determined, and F = 100 (μg of D-glucose) divided by the GOPOD absorbance of 100 μg of D-glucose) 100 / 0.1 = volume correction (0.1 mL from 100 mL) 1 / 1000 = from micrograms to milligrams W = dry weight of the sample analyzed = weight × (100-water content) / 100 100 / W = RS percentage factor in sample weight 162 / 180 = Factor for conversion of free D-glucose obtained from the assay to anhydro-D-glucose present in starch 10.3 / 0.1 = volume correction (0.1 mL from 10.3 mL) for solutions containing 0-10% RS that were not diluted when incubating, giving a final volume of 10.3 mL.

[0038] The above traditional AOAC method was used to measure the modeling samples and verification samples. The RS content is as follows:

[0039]

[0040] Example 2 Determination of RS content using the rapid prediction method of the present invention Determination verification samples: Zhongkefa No. 5, Huantang No. 1 Instruments used: 15 ml test tube, electronic balance, rice cooker, iron test tube rack Firstly, 100 grains of crack-free whole polished rice were selected for Zhongkefa No. 5 and Huantang No. 1 respectively, and the measurements were repeated five times, with 20 grains of whole polished rice in each repeat. The weighings were performed on an electronic balance, and the average values ​​of the original polished rice weights of Zhongkefa No. 5 and Huantang No. 1 after five repeats were 0.4282 g and 0.3151 g, respectively.

[0041] Secondly, the above 100 grains of crack-free whole polished rice were divided into 5 replicates and placed in 5 15 ml test tubes, with 20 grains of whole polished rice in each test tube. The centrifuge tube was placed in an iron test tube rack, 10 mL of distilled water was added, and it was allowed to stand for 15 min, and then placed in a boiling water bath for 15 min. The rice grains were taken out, placed on absorbent paper, and after standing for 15 min, the grain weight data of each group of samples was measured. The average values ​​of the polished rice weights of Zhongkefa No. 5 and Huantang No. 1 after steaming were 1.1918 g and 0.6668 g, respectively.

[0042] Finally, according to the formula of steaming water absorption rate: steaming water absorption rate = (weight of 20 grains after steaming - original weight) / original weight × 100%, data analysis was conducted on Zhongkefa No. 5 and Huantang No. 1.

[0043] Zhongkefa No. 5: Steaming water absorption rate = (1.1918-0.4282) / 0.4282×100%=178.3% No. 1 slow sugar: water absorption rate during cooking = (0.6668-0.3151) / 0.3151×100%=111.62% According to data analysis, the cooking water absorption rate of Zhongkefa No. 5 is 178.30%, and the water absorption rate is in the range of 153-200%. According to the japonica rice standard curve, the RS range is 0-5%.

[0044] According to data analysis, the cooking water absorption rate of Huantang No. 1 is 111.62%, and the water absorption rate is in the range of 80-153%. According to the japonica rice standard curve, the RS range is RS>5%.

[0045] According to the conventional AOAC method, the actual RS contents of Zhongkefa No. 5 and Huantang No. 1 were 0.24% and 11.00%, respectively, which were consistent with the predicted range.

[0046]

[0047] Example 3 Determination of RS content using the rapid prediction method of the present invention Determination verification samples: Guichao rice, gSS3a / rs4 Instruments used: 15 ml test tube, electronic balance, rice cooker, iron test tube rack First, mix the Guichao rice and gSS3a / rs4 100 grains of crack-free whole polished rice were selected for each experiment, and the results were repeated five times, with 20 grains of whole polished rice each time. The results were weighed on an electronic balance. gSS3a / rs4 The means of five repeated measurements of the original polished rice weight were 0.4671 g and 0.3714 g, respectively.

[0048] Secondly, the 100 grains of crack-free whole polished rice were divided into 5 replicates and placed in 5 15 ml test tubes, with 20 grains of whole polished rice in each test tube. The centrifuge tubes were placed in an iron test tube rack, 10 mL of distilled water was added, and the mixture was allowed to stand for 15 min, and then placed in a boiling water bath for 15 min. The rice grains were taken out and placed on absorbent paper. After standing for 15 min, the grain weight data of each group of samples was measured. gSS3a / rs4 The average values ​​of the five repeated measurements of the polished rice weight after cooking were 1.4452 g and 1.1178 g, respectively.

[0049] Finally, according to the steaming water absorption formula: steaming water absorption = (weight of 20 grains after steaming - original weight) / original weight × 100% for Guichao rice and gSS3a / rs4 The boiling water absorption of the sample is calculated Guichao rice: Steaming water absorption rate = (1.4452-0.4671) / 0.4671×100%=209.40% gSS3a / rs4 : Cooking water absorption rate = (1.1178-0.3714) / 0.3714×100%=200.97% According to data analysis, the cooking water absorption rate of Guichao rice is 209.40%, and the water absorption rate is in the range of 120-250%. Based on the standard curve of indica rice RS < 11%, it is judged that the RS range is 0-5%.

[0050] According to data analysis, gSS3a / rs4 The steaming water absorption rate is 200.97%, and the water absorption rate is in the range of 120-250%. According to the standard curve of indica RS < 11%, the RS range is judged to be 0-5%.

[0051] According to the conventional AOAC method, the gSS3a / rs4 The actual RS contents are 1.08% and 1.73%, respectively, which are consistent with the predicted range.

[0052]

[0053] Example 4 Determination of RS content using the rapid prediction method of the present invention Determination of validation samples: rs5 and rs6 Instruments used: 15 ml test tube, electronic balance, rice cooker, iron test tube rack First, rs5 and rs6 100 grains of crack-free whole polished rice were selected for each experiment, and the experiment was repeated five times, with 20 grains of whole polished rice each time, and the rice was weighed on an electronic balance. rs5 and rs6 The means of five repeated measurements of the original polished rice weight were 0.4671 g and 0.3714 g, respectively.

[0054] Secondly, the 100 grains of crack-free whole polished rice were divided into 5 replicates and placed in 5 15 ml test tubes, with 20 grains of whole polished rice in each test tube. The centrifuge tubes were placed in an iron test tube rack, 10 mL of distilled water was added, and the mixture was allowed to stand for 15 min, and then placed in a boiling water bath for 15 min. The rice grains were taken out and placed on absorbent paper. After standing for 15 min, the grain weight data of each group of samples was measured. rs5 and rs6 The average values ​​of the five repeated measurements of the polished rice weight after cooking were 1.4452 g and 1.1178 g, respectively.

[0055] Finally, according to the formula: steaming water absorption rate = (weight of 20 grains after steaming - original weight) / original weight × 100% rs5 and rs6 The boiling water absorption of the samples was calculated.

[0056] rs5 : Steaming water absorption rate = (0.4837-0.2799) / 0.2799×100%=72.81% rs6 : Cooking water absorption rate = (0.5116g-0.2970) / 0.2970×100%=72.26% According to data analysis, rs5 The steaming water absorption rate is 72.81%, and the water absorption rate is in the range of 60-90%. The RS range is 11-22% directly based on the standard curve of indica rice RS>11%.

[0057] According to data analysis, rs6 The steaming water absorption rate is 72.26%, and the water absorption rate is in the range of 60-90%. According to the standard curve of indica rice RS>11%, it is judged that the RS range is 11-22%.

[0058] Determined according to conventional AOAC methodrs5 and rs6 The actual RS contents of the samples were 18.55% and 14.75%, respectively, which were consistent with the predicted range.

[0059]

[0060] Example 5 Determination of RS content using the rapid prediction method of the present invention Determination of validation samples: gSS3b / rs4 Instruments used: 15 ml test tube, electronic balance, rice cooker, 4 degree refrigerator, iron test tube rack First, gSS3b / rs4 The sample was 100 grains of crack-free whole polished rice, which was repeated five times, with 20 grains of whole polished rice each time, and weighed on an electronic balance. gSS3b / rs4 The mean of the original polished rice weight measured five times was 0.3561 g.

[0061] Secondly, the 100 grains of crack-free whole polished rice were divided into 5 replicates and placed in 5 15 ml test tubes, with 20 grains of whole polished rice in each test tube. The centrifuge tubes were placed in an iron test tube rack, 10 mL of distilled water was added, and the mixture was allowed to stand for 15 min, and then placed in a boiling water bath for 15 min. The rice grains were taken out and placed on absorbent paper. After standing for 15 min, the grain weight data of each group of samples was measured. gSS3b / rs4 The mean of the polished rice weight after cooking was 0.7540 g after five repeated measurements.

[0062] According to the formula: Steaming water absorption rate = (weight of 20 grains after steaming - original weight) / original weight × 100% gSS3b / rs4 The boiling water absorption of the samples was calculated.

[0063] gSS3b / rs4 : Cooking water absorption rate = (0.7540-0.3561) / 0.3561g×100%=111.74% According to data analysis, rs5 The cooking water absorption rate is 111.74%, and the water absorption rate is in the range of 90-120%. Therefore, it is necessary to judge the RS content in combination with the recovery water loss rate.

[0064] Finally, the cooked polished rice was placed in a square dish and placed in a refrigerator at 4 degrees for 24 hours. It was then randomly divided into groups of 20 grains and placed on absorbent paper. After standing for 15 minutes, the average grain weight of each group of samples was measured to be 0.6840 g.

[0065] According to the formula: water loss rate after regeneration = (weight of 20 grains after cooking - weight of regeneration) / weight after cooking × 100% gSS3b / rs4 The regeneration water loss rate of the sample was calculated.

[0066] gSS3b / rs4 :Regeneration water loss rate = (0.7540-0.6840) / 0.7540×100% = 9.28% In summary, gSS3b / rs4 The sample meets the requirements of water absorption of 90-120% and water loss after regeneration of more than 9%, so the RS range is 5-11%. gSS3b / rs4 The actual RS content is 7.84%, which is consistent with the predicted range.

[0067]

Claims

1. A simple method for quickly predicting the content of rice resistant starch, characterized in that: The rice is japonica rice, and the following steps are performed in sequence: 1) Measure the physiological parameters of polished rice samples to be tested Select an appropriate amount of polished rice with uniform size and no cracks from the polished rice sample to be tested, randomly divide it into no less than 5 portions with no less than 20 grains in each portion, measure the total weight of each portion, and measure it no less than 5 times respectively, and obtain no less than 5 parallel repeated results; 2) Measure the physiological parameters of polished rice after cooking The appropriate amount of polished rice with uniform size and no cracks selected in the first step is randomly divided into no less than 5 portions with no less than 20 grains in each portion, respectively placed in centrifuge tubes, added with appropriate amount of distilled water, left to stand for 12-20 min, then placed in a boiling water bath for 12-20 min, the rice grains are taken out, placed on absorbent paper, left to stand for 12-20 min, and then the grain weight data of each sample is measured; 3) Prediction of resistant starch content After the samples were steamed according to the above steps, the water absorption of the samples was calculated. The formula for calculating the water absorption after steaming is: water absorption = (weight of rice grains after steaming - weight of rice grains before steaming) / weight of rice grains before steaming × 100%. The water absorption after steaming was calculated and substituted into the standard curve y = -0.1217x + 23.623, where y: RS predicted content, x: water absorption; According to the standard curve, when the water absorption is 153-200%, the RS prediction range is 0-5%; when the water absorption is 153%, the RS value is 5%; when the water absorption is 80-153% and does not include 153%, the RS prediction range is >5%.

2. The simple method for rapidly predicting the content of resistant starch in rice according to claim 1, characterized in that: In step 1), the grain weight data of each replicate of rice was measured using a balance.

3. The simple method for rapidly predicting the content of resistant starch in rice according to claim 2, characterized in that: Step 1) 100 grains of polished rice with uniform size and no cracks are selected from the polished rice sample to be tested, and the grains are randomly divided into 5 portions with 20 grains in each portion. The total weight of each portion is measured 5 times, and the results are repeated 5 times.

4. The simple method for rapidly predicting the content of resistant starch in rice according to claim 3, characterized in that: Step 2) Place 5 portions of 20 grains of polished rice into 15 mL centrifuge tubes, add 10 mL of distilled water, let stand for 15 min, then place in a boiling water bath for 15 min, take out the rice grains, place them on absorbent paper, let stand for 15 min, and measure the grain weight of each sample.

5. A simple method for quickly predicting the content of rice resistant starch, characterized in that: The rice is indica rice, and the following steps are performed in sequence: 1) Measure the physiological parameters of polished rice samples to be tested Select an appropriate amount of polished rice with uniform size and no cracks from the polished rice sample to be tested, randomly divide it into no less than 5 portions with no less than 20 grains in each portion, measure the total weight of each portion, and measure it no less than 5 times respectively, and obtain no less than 5 parallel repeated results; 2) Measurement of physiological parameters of polished rice after cooking The appropriate amount of polished rice with uniform size and no cracks selected in the first step is randomly divided into no less than 5 portions with no less than 20 grains in each portion, respectively placed in centrifuge tubes, added with appropriate amount of distilled water, left to stand for 12-20 min, then placed in a boiling water bath for 12-20 min, the rice grains are taken out, placed on absorbent paper, left to stand for 12-20 min, and then the grain weight data of each sample is measured; 3) Retrogradation of polished rice samples to be tested If the water absorption rate after the first two steps is between 90% and 120%, including both ends, the polished rice after steaming needs to be placed in a square dish and placed in a refrigerator at 4 degrees for 24 hours, and then randomly divided into groups of 20 and placed on absorbent paper. After standing for 15 minutes, the grain weight data of each group of samples after regeneration is measured, and the regeneration water loss rate is calculated, and the judgment is made in combination with the steaming water absorption rate; if the water absorption rate after the first two steps is not between 90% and 120%, excluding both ends, directly proceed to step 4) to predict the resistant starch content; 4) Prediction of resistant starch content After the samples were steamed according to the above steps, the water absorption of the samples was calculated. The formula for calculating the water absorption after steaming is: water absorption = (weight of rice grains after steaming - weight of rice grains before steaming) / weight of rice grains before steaming × 100%. The water absorption after steaming was calculated. According to the water absorption after steaming, the resistant starch content of the samples was divided into two preliminary prediction ranges of RS < 11% or RS > 11%. When the water absorption was between 120-250%, it was brought into the RS < 11% fitting curve; when the water absorption was between 60-90%, it was substituted into the RS > 11% standard curve to predict the resistant starch content. The standard curve is as follows: The fitting standard curve of RS<11% is: y = -0.0571x + 14.223, where Y: RS predicted content, X: water absorption; The fitting standard curve of RS>11% is: y = 0.1466x + 4.3208, where Y: RS predicted content, X: water absorption rate; When the water absorption rate is between 90-120%, including both ends, it is necessary to judge in combination with the steaming and regeneration water loss rate. When the water absorption rate is between 90-120% and the steaming and regeneration water loss rate is greater than 9%, it is substituted into the RS<11% fitting standard curve, and finally the RS content is in the range of 5-11%; when the steaming and regeneration water loss rate is less than and equal to 9%, it is substituted into the RS>11% standard curve prediction, and finally the RS is in the range of 11-22%; Regeneration water loss rate = (weight of 20 grains after steaming - weight of regeneration) / weight after cooking × 100%.

6. The simple method for rapidly predicting the content of resistant starch in rice according to claim 5, characterized in that: In step 1), the rice grain weight data is measured using a balance.

7. The simple method for rapidly predicting the content of resistant starch in rice according to claim 6, characterized in that: Step 1) 100 grains of polished rice with uniform size and no cracks are selected from the polished rice sample to be tested, and the grains are randomly divided into 5 portions with 20 grains in each portion. The total weight of each portion is measured 5 times, and the results are repeated 5 times.

8. The simple method for rapidly predicting the content of resistant starch in rice according to claim 7, characterized in that: Step 2) Place 5 portions of 20 rice grains each into 15 mL centrifuge tubes, add 10 mL of distilled water, let stand for 15 min, then place in a boiling water bath for 15 min, take out the rice grains, place on absorbent paper, let stand for 15 min, and measure the grain weight data of each sample.

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