A simple method for rapid prediction of resistant starch content in rice

Abstract

The present invention belongs to the technical field of analysis and detection of resistant starch content in rice, and specifically relates to a simple method for rapidly predicting the resistant starch content in rice. The simple method for rapidly predicting the resistant starch content in rice provided by the present invention successively performs steps such as measuring the physiological indexes of the rice samples to be measured, measuring the physiological indexes of the polished rice after cooking, and predicting the resistant starch content. By using the correlation between the resistant starch content and the cooking characteristics of rice to predict the resistant starch content, this method has low cost, simple steps and rapid result acquisition, and is suitable for large-scale screening of resistant starch rice. It has certain economic value and thus has a good application prospect.

Description

Technical Field

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

[0002] Rice is an extremely important food crop. More than 60% of the population in China takes rice as the staple food, and more than 1 / 3 of the global population takes rice as the staple food. The glycemic index (GI) value of rice varieties varies from 48 to 93. Rice and its products are mainly digested by the enzymatic hydrolysis of amylase in the stomach and small intestine, and the final product is glucose. Therefore, rice is considered a high-glycemic-index (Glycemic index, GI) food; 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, and was named by Englyst in 1983.

[0003] As a special type of carbohydrate, resistant starch has been attracting increasing attention in the food industry. It has a variety of physiological and health benefits, including improving digestive system health, promoting weight control, and enhancing satiety. These characteristics make it have broad application prospects in the food industry. In addition, resistant starch can also be used to develop weight-loss foods and dietary therapies for treating type 2 diabetes, because it is not digested and absorbed in the small intestine and can enter the large intestine to be fermented and utilized by intestinal flora, exerting various physiological effects such as controlling blood sugar and blood lipids.

[0004] The industrial research on resistant starch started relatively late, but with the enhancement of health awareness and the increase in market demand, the industry has broad development space, indicating that the application potential of resistant starch in the food industry is huge. With the growth of the global resistant starch market, the demand for rapid prediction methods for this component is also increasing simultaneously. Market analysis shows that resistant starch is favored by consumers due to its health benefits, driving the expansion of the market.

[0005] Currently, the methods for determining the resistant starch content mainly include two categories: in vivo determination methods and in vitro determination methods. In vivo determination methods determine the resistant starch content by measuring the unabsorbed starch and its degradation products in the human body, but the cost is high and there are certain risks. In vitro determination methods simulate the in vivo digestion conditions and measure the starch content that is not hydrolyzed by amylase in vitro.

[0006] Among the in vitro determination methods, the method proposed by McCleary et al. has been adopted as the official determination method (AOAC method 2002.02) because it is simple and reliable. This method involves incubating the sample with α-amylase and amyloglucosidase (AMG) at 37°C for 16 hours. 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 the resistant starch is separated by centrifugation.

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

[0008] To sum up, the existing methods for measuring the resistant starch content in rice have technical defects such as high cost, cumbersome analysis process, long measurement cycle, and difficulty in realizing rapid screening of a large number of samples. Summary of the Invention

[0009] The problem to be solved by the present invention is to provide a simple method for rapidly predicting the resistant starch content in rice. This method predicts the resistant starch content in rice grains by using the correlation between the resistant starch content and the cooking characteristics of rice grains. This method has low cost, simple steps and rapid results, and is suitable for rapid screening of resistant starch rice in large quantities.

[0010] To solve the above technical problems, the present invention provides a simple method for rapidly predicting the resistant starch content in rice, and its technical solution is as follows:

[0011] A simple method for rapidly predicting the resistant starch content in rice, the rice is japonica rice, and the following steps are carried out in sequence:

[0012] 1) Measure the physiological indexes of the polished rice sample to be tested

[0013] 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 at least 5 portions with each portion having at least 20 grains, measure the total weight of each portion, and measure at least 5 times respectively to obtain at least 5 parallel repeated results;

[0014] 2) Measure the physiological indexes of the polished rice to be tested after cooking

[0015] Take the appropriate amount of polished rice with uniform size and no cracks selected in the first step, randomly divide it into at least 5 portions with each portion having at least 20 grains, put them into centrifuge tubes respectively, place the centrifuge tubes on an iron test tube rack, add an appropriate amount of distilled water, let it stand for 12 - 20 min, then place it in a boiling water bath for 12 - 20 min, take out the rice grains, place them on absorbent paper, and after standing for 12 - 20 min, measure the grain weight data of each sample;

[0016] 3) Prediction of resistant starch content

[0017] After cooking the sample according to the above steps, calculate the water absorption rate of the sample. The formula for calculating the water absorption rate after cooking is: Water absorption rate = (weight of rice grains after cooking - weight of rice grains before cooking) / weight of rice grains before cooking × 100%. Calculate the water absorption rate after cooking and substitute it into the standard curve y = -0.1217x + 23.623, where y is the predicted RS content and x is the water absorption rate. According to the standard curve, when the water absorption rate is 153 - 200%, the RS range is 0 - 5%; when the water absorption rate is 153%, the RS value is 5%; when the water absorption rate is 80 - 153% and does not include 153%, the RS range is RS > 5%.

[0018] The above simple method for quickly predicting the resistant starch content of rice preferably measures the grain weight data of each repeat of the rice with a balance in step 1). It also preferably selects an appropriate amount of polished rice with uniform size and no cracks from the polished rice samples to be tested, randomly divides them into 5 equal parts with 20 grains in each part, measures the total weight of each part, and measures 5 times respectively to obtain 5 parallel repeated results.

[0019] The above simple method for quickly predicting the resistant starch content of rice preferably puts 5 equal parts with 20 grains in each part into 15 mL centrifuge tubes respectively, places the centrifuge tubes in an iron test tube rack, adds 10 mL of distilled water, stands for 15 min, then places them in a boiling water bath for 15 min, takes out the rice grains, places them on absorbent paper, and measures the grain weight data of each sample after standing for 15 min.

[0020] The present invention also provides a simple method for quickly predicting the resistant starch content of rice. The rice is indica rice, and the following steps are carried out in sequence:

[0021] 1) Measure the physiological indexes of the polished rice samples to be tested

[0022] Select an appropriate amount of polished rice with uniform size and no cracks from the polished rice samples to be tested, randomly divide them into no less than 5 equal parts with no less than 20 grains in each part, measure the total weight of each part, and measure no less than 5 times respectively to obtain no less than 5 parallel repeated results;

[0023] 2) Measure the physiological indexes of the polished rice after cooking

[0024] Put the appropriate amount of polished rice with uniform size and no cracks selected in the first step, randomly divide them into no less than 5 equal parts with no less than 20 grains in each part, put them into centrifuge tubes respectively, place the centrifuge tubes in an iron test tube rack, add an appropriate amount of distilled water, stand for 12 - 20 min, then place them in a boiling water bath for 12 - 20 min, take out the rice grains, place them on absorbent paper, and measure the grain weight data of each sample after standing for 12 - 20 min;

[0025] Retrogradation of polished rice samples to be measured

[0026] If the water absorption rate is between 90 - 120% (including both ends) after the first two steps, then the cooked polished rice should be placed in a square dish and stored in a 4°C refrigerator for 24 hours. Then, it should be randomly divided into groups of 20 grains and placed on blotting paper. After standing for 15 minutes, measure the weight data of each group of samples after retrogradation, calculate the retrogradation water loss rate, and make a judgment in combination with the cooking water absorption rate. If the water absorption rate is not between 90 - 120% (excluding both ends) after the first two steps, directly proceed to step 4) for predicting the resistant starch content;

[0027] 4) Prediction of resistant starch content

[0028] After cooking the sample according to the above steps, calculate the water absorption rate of the sample. The formula for calculating the water absorption rate after cooking is: Water absorption rate = (weight of cooked rice grains - weight of uncooked rice grains) / weight of uncooked rice grains × 100%. Calculate the water absorption rate after cooking. According to the water absorption rate after cooking, divide the resistant starch content of the sample into two preliminary prediction ranges: RS < 11% or RS > 11%. When the water absorption rate is between 120 - 250%, substitute it into the RS < 11% fitting curve; when the water absorption rate is between 60 - 90%, substitute it into the RS > 11% standard curve to predict the resistant starch content. The standard curves are as follows:

[0029] The RS < 11% fitting standard curve is: y = -0.0571x + 14.223, where Y: predicted RS content, X: water absorption rate;

[0030] The RS > 11% fitting standard curve is: y = 0.1466x + 4.3208, where Y: predicted RS content, X: water absorption rate;

[0031] When the water absorption rate is between 90 - 120% (including both ends), it is necessary to make a judgment in combination with the cooking retrogradation water loss rate. When the water absorption rate is between 90 - 120% and the cooking retrogradation water loss rate is greater than 9%, substitute it into the RS < 11% fitting standard curve, and finally obtain that RS is in the range of 5 - 11%; when the cooking retrogradation water loss rate is less than or equal to 9%, substitute it into the RS > 11% standard curve for prediction, and finally obtain that RS is in the range of 11 - 22%; Retrogradation water loss rate = (weight of 20 cooked grains - weight after retrogradation) / weight of cooked grains × 100%.

[0032] The above - mentioned simple method for quickly predicting the resistant starch content of rice preferably uses an analytical balance to measure the weight data of each replicate of the rice in step 1). It also preferably selects 100 polished rice grains with uniform size and no cracks from the polished rice samples to be measured in step 1), randomly divide them into 5 equal parts with 20 grains in each part, measure the total weight of each part, and measure 5 times respectively to obtain 5 parallel repeated results.

[0033] The above-mentioned simple method for quickly predicting the resistant starch content of rice preferably includes, in step 2), putting 5 portions, each portion having 20 grains, into 15 mL centrifuge tubes respectively, placing the centrifuge tubes in an iron test tube rack, adding 10 mL of distilled water, standing for 15 min, and then placing them in a boiling water bath for 15 min; taking out the rice grains, placing them on absorbent paper, standing for 15 min, and then measuring the weight data of each sample of rice grains.

[0034] Advantages of the present invention: 1. Low cost. First, in the process of measuring the resistant starch content by the ordinary method, a series of enzymes such as α-amylase and amyloglucosidase are required, but this method does not require any enzymes in the experiment process. Second, various expensive instruments and consumables are required in the process of measuring the resistant starch content by the conventional method, while this method only requires a rice cooker and an electronic scale, and this measurement method reduces the measurement cost in all aspects. 2. Simple steps. At present, the steps of the conventional method for measuring resistant starch are relatively cumbersome. The steps are generally sample pretreatment, enzyme treatment, termination of reaction, centrifugal washing, RS dissolution, neutralization hydrolysis reaction, glucose determination, and result calculation. However, the steps of this method for measuring the resistant starch content are relatively simple. First, the sample is pretreated by grinding it into polished rice. Second, the polished rice is soaked for 15 minutes and then put into boiling water and boiled for 15 minutes (cooked means 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, and 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. Quick result acquisition. When measuring the resistant starch content by the conventional method, it takes about 20 hours of measurement cycle after various enzyme treatments and various operation processes to obtain the measurement result. However, by this steaming method to predict the resistant starch content, the measurement cycle of japonica rice is only 1 hour at the fastest. 4. Quick batch screening and accurate prediction range. At present, it is still relatively difficult to achieve large-scale screening of resistant starch samples by some conventional methods, but this method can quickly and accurately predict the range of resistant starch and can realize the quick screening of a large number of resistant starch samples. Description of the Drawings

[0035] Figure 1 、 2 Figures 1 and 3 are standard curve models for predicting the resistant starch content of japonica rice and indica rice established by using samples with a resistant starch content of 0.5% - 22%, where:

[0036] Figure 1 is the standard curve model diagram for predicting the resistant starch content of japonica rice, and according to the sample data of the japonica rice group, the fitted standard curve is y = -0.1217x + 23.623 (R 2 = 0.758) (y: predicted content of RS, x: water absorption rate, R 2: correlation coefficient);

[0037] Figure 2 It is a standard curve model diagram for predicting that the resistant starch content in indica rice is less than 11%. According to the sample data of the indica rice group, when RS < 11%, the fitted standard curve is: y = -0.0571x + 14.223 (R 2 = 0.8022) (y: predicted content of RS, x: water absorption rate, R 2 : correlation coefficient);

[0038] Figure 3 It is a standard curve model diagram for predicting that the resistant starch content in japonica rice is greater than 11%. When RS > 11%, the fitted standard curve is: y = 0.1466x + 4.3208 (R 2 = 0.9021) (y: predicted content of RS, x: water absorption rate, R 2 : correlation coefficient);

[0039] Figure 4 It is a flow chart for predicting the resistant starch content. After the sample is cooked according to the technical method, the water absorption rate of the treated 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%.

[0040] When measuring indica rice, first measure the water absorption rate according to the technical method. When the water absorption rate is between 120 - 250%, substitute it into the standard curve for RS < 11% for prediction, and finally obtain that RS is in the range of < 5%; when the water absorption rate is between 60 - 90% (excluding both end values), substitute it into the standard curve for RS > 11% for prediction; when the water absorption rate is between 90 - 120% (including both end values), it is necessary to combine the cooking and retrogradation water loss rate to judge: when the water absorption rate is between 90 - 120% and the cooking and retrogradation water loss rate is greater than 9%, then substitute it into the fitted standard curve for RS < 11%, and finally obtain that the RS content is in the range of 5 - 11%; when the cooking and retrogradation water loss rate is less than or equal to 9%, substitute it into the standard curve for RS > 11% for prediction, then RS is finally in the range of 11 - 22%; the retrogradation water loss rate = (weight of 20 grains after cooking - weight after retrogradation) / weight after cooking × 100%. Detailed implementation mode

[0041] The present invention will be further described in detail below through the description of embodiments to help those skilled in the art have a more complete, accurate and in - depth understanding of the inventive concept and technical solution of the present invention.

[0042] Terminology explanation: Retrogradation of rice starch refers to the phenomenon that after rice is gelatinized, amylose is released during the gelatinization process, the amylopectin molecules are fully unfolded, and during the process of cooling and storage of the starch paste, the free amylose and amylopectin recrystallize, which is the retrogradation of rice starch.

[0043] Rice retrogradation usually refers to the phenomenon that the taste and texture of cooked rice deteriorate during the process of refrigeration or freezing and subsequent reheating. This process is also called "aging" or "regaining hardness".

[0044] Specifically, after rice is cooked, its starch changes from an ordered structure to a disordered structure, which makes the cooked rice soft and elastic. However, over time, especially under low-temperature conditions, the starch molecules will rearrange to form a more ordered structure, resulting in the hardening of the cooked rice and the loss of its original taste. This process is called "starch retrogradation" or "starch aging" in food science.

[0045] Using the simple method of the present invention to cooperate with Yazhou Bay Laboratory to measure the RS content, the results of a series of materials measured by this method are within the same range as those measured by the traditional AOAC method. For details, see the examples:

[0046] Example 1: Measuring the RS content using the traditional AOAC method

[0047] Instruments used: test tubes, glass rods, polished rice machines, grinding machines, 1 mm sieves, centrifuges, water baths, pH meters, magnetic stirrers, vortex oscillators, oscillating water baths

[0048] Reagents: anhydrous ethanol, 50% ethanol, KOH solution, 1.2 M acetate buffer solution, maleate buffer solution, 100 mM sodium acetate buffer solution, GOPOD reagent, α-amylase solution, AMG enzyme

[0049] Measurement steps:

[0050] 1. Sample preparation: Use a polished rice machine to make the sample to be tested into polished rice, and use a grinding instrument to grind it into rice flour that can pass through a 1 mm sample sieve. Weigh 100 mg of rice flour, add it to a centrifuge tube with a lid, gently tap the test tube to make the sample concentrate at the bottom, add 180 mL of distilled water, and cook in a boiling water bath for 20 min until the cooked rice is edible.

[0051] 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, use a glass rod to crush the rice flour block, and then use 3 mL of freshly prepared α-amylase solution to wash the starch attached to the glass rod into the test tube. A total of 4 mL of α-amylase solution is used.

[0052] 3. Oscillatory Incubation: Close the lid tightly, mix well with a vortex oscillator, place it horizontally in an oscillating water bath with the long axis of the test tube parallel to the direction of movement. Incubate continuously with linear oscillation at a speed of 100 strokes / min for 16 hours at 37°C precisely.

[0053] 4. Terminate the Reaction: Remove the test tube from the water bath and wipe off the excess water with a tissue. Open the lid and add 4.0 mL of ethanol (99% v / v), vortex with a vortex mixer to terminate the digestion reaction.

[0054] 5. Centrifugal Separation: Centrifuge the mixture at 1500 g for 10 minutes (without the lid) to separate the resistant starch (RS) precipitate.

[0055] 6. Wash the Precipitate: Carefully pour out the supernatant, add 2 mL of 50% ethanol or 50% IMS to resuspend, vortex with a vortex mixer, then 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, invert the test tube, and absorb the excess liquid with a tissue.

[0056] 7. Dissolve the Precipitate: Place the RS precipitate in an ice-water bath, add a magnetic stir bar and 2 mL of 2M KOH solution to the test tube to dissolve it, and stir vigorously with a magnetic stirrer for 20 minutes in the ice / water bath state to resuspend the floccules and dissolve the RS.

[0057] 8. Stir in the 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 it in a 50°C water bath.

[0058] 9. Incubate and Centrifuge: Incubate for 30 minutes, and mix intermittently with a vortex mixer during this period. For samples with an RS content < 10%, centrifuge directly at 1500 g for 10 minutes. Transfer the centrifuged supernatant to a glass test tube (16×100 mm) in 0.1 mL units, in duplicate, add 3.0 mL of GOPOD reagent, and incubate at 50°C for 20 minutes.

[0059] 10. Absorbance Measurement: Measure the absorbance value at 510 nm relative to the blank reagent.

[0060] Collect the supernatant obtained by centrifugation in step 5 of the initial incubation and the supernatants obtained in the two 50% ethanol washing steps in step 6 into a volumetric flask. Dilute to 100 mL with 100 mM sodium acetate buffer (pH = 4.5). Mix well.

[0061] Incubate the solution in 0.1 mL aliquots (in duplicate) and add 10 μL of diluted AMG solution (300 U / mL). Incubate at 50 °C for 20 minutes, add 3.0 mL of GOPOD reagent, and incubate at 50 °C for 20 minutes.

[0062] 11. Preparation of blank reagent:

[0063] Prepare the 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.

[0064] 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 the D-glucose standard.

[0065] 12. Calculation: Calculate the resistant starch content, non-resistant starch content, and total starch content (%) in the sample.

[0066] Resistant starch (g / 100 g sample) (sample contains <10% RS)

[0067] = ΔE × F × 10.3 / 0.1 × 1 / 1000 × 100 / W × 162 / 180

[0068] = ΔE × F / W × 9.27

[0069] Non-resistant starch content (g / 100 g sample)

[0070] = ΔE × F × 100 / 0.1 × 1 / 1000 × 100 / W × 162 / 180

[0071] = ΔE × F / W × 90

[0072] Total starch content = Resistant starch content + Non-resistant starch content

[0073] ΔE = Absorbance value relative to the blank reagent

[0074] F = Conversion from absorbance value to micrograms. (The absorbance value of 100 μg D-glucose in the GOPOD reaction is determined, F = 100 (μg number of D-glucose) divided by the GOPOD absorbance value of this 100 μg D-glucose)

[0075] 100 / 0.1 = Volume correction (taking 0.1 mL from 100 mL)

[0076] 1 / 1000 = Conversion from micrograms to milligrams

[0077] W = Dry weight of the analysis sample = Weight × (100 - Water content) / 100

[0078] 100 / W = Percentage factor of RS in the sample weight

[0079] 162 / 180 = Factor for converting free D - glucose obtained from the determination to anhydro - D - glucose present in starch

[0080] 10.3 / 0.1 = Volume correction (taking 0.1 mL from 10.3 mL). For samples containing 0 - 10% RS, when incubating the solution, it is not diluted, and the final volume is 10.3 mL.

[0081] The modeling samples and validation samples were determined using the above - mentioned traditional AOAC method, and the RS contents are as follows in the table:

[0082]

[0083]

[0084] Example 2 Determining the RS content using the rapid prediction method of the present invention

[0085] Determining validation samples: Zhongkefa No. 5, Huantang No. 1

[0086] Instruments used: 15 ml test tubes, electronic balance, rice cooker, iron test tube rack

[0087] First, select 100 intact paddy rice grains without cracks from Zhongkefa No. 5 and Huantang No. 1 respectively, and divide them into five replicates, with 20 intact paddy rice grains in each replicate. Weigh them on an electronic balance. The average values of the original paddy rice weights of Zhongkefa No. 5 and Huantang No. 1 measured in five replicates are 0.4282 g and 0.3151 g respectively.

[0088] Secondly, put the above - mentioned 100 intact paddy rice grains without cracks into five replicates and place them into five 15 ml test tubes respectively, with 20 intact paddy rice grains in each test tube. Place the centrifuge tubes in an iron test tube rack, add 10 mL of distilled water, let it stand for 15 min, and then place it in a boiling water bath for 15 min. Take out the rice grains, place them on absorbent paper, and after standing for 15 min, measure the weight data of each group of sample grains. The average values of the cooked paddy rice weights of Zhongkefa No. 5 and Huantang No. 1 measured in five replicates are 1.1918 g and 0.6668 g respectively.

[0089] Finally, conduct data analysis on Zhongkefa No. 5 and Huantang No. 1 according to the formula for cooking water absorption rate: Cooking water absorption rate = (Weight of 20 grains after cooking - Original weight) / Original weight × 100%

[0090] Zhongkefa 5: Cooking water absorption rate = (1.1918 - 0.4282) / 0.4282 × 100% = 178.3%

[0091] Huantang No. 1: Cooking water absorption rate = (0.6668 - 0.3151) / 0.3151 × 100% = 111.62%

[0092] According to data analysis, the cooking water absorption rate of Zhongkefa 5 is 178.30%. The water absorption rate is in the range of 153 - 200%. According to the japonica rice standard curve, the RS range is judged to be 0 - 5%.

[0093] According to data analysis, the cooking water absorption rate of Huantang No. 1 is 111.62%. The water absorption rate is in the range of 80 - 153%. According to the japonica rice standard curve, the RS range is judged to be RS > 5%.

[0094] According to the conventional AOAC method, the actual RS contents of Zhongkefa 5 and Huantang No. 1 are 0.24% and 11.00% respectively, which are in line with the predicted range.

[0095]

[0096] Example 3 uses the rapid prediction method of the present invention to determine the RS content

[0097] Determine the verification samples: Guichao rice, gSS3a / rs4

[0098] Instruments used: 15 ml test tubes, electronic balance, rice cooker, iron test tube rack

[0099] First, for Guichao rice and gSS3a / rs4 Select 100 intact milled rice grains without cracks, and divide them into five replicates, with 20 intact milled rice grains in each replicate. Weigh them on an electronic balance. The average values of the original milled rice weights of Guichao rice and gSS3a / rs4 for the five replicates are 0.4671 g and 0.3714 g respectively.

[0100] Secondly, put the above 100 intact milled rice grains without cracks into 5 replicates and place them in 5 15 ml test tubes, with 20 intact milled rice grains in each test tube. Place the centrifuge tubes in an iron test tube rack, add 10 mL of distilled water, let it stand for 15 min, and then place it in a boiling water bath for 15 min. Take out the cooked rice grains, place them on absorbent paper, let it stand for 15 min, and then measure the weight data of each group of sample grains. The average values of the cooked milled rice weights of Guichao rice and gSS3a / rs4 for the five replicates are 1.4452 g and 1.1178 g respectively.

[0101] Finally, according to the formula for cooking water absorption rate: cooking water absorption rate = (weight of 20 grains after cooking - original weight) / original weight × 100%, the cooking water absorption rates of Guichao rice and gSS3a / rs4 the sample were calculated

[0102] Guichao rice: cooking water absorption rate = (1.4452 - 0.4671) / 0.4671 × 100% = 209.40%

[0103] gSS3a / rs4 : cooking water absorption rate = (1.1178 - 0.3714) / 0.3714 × 100% = 200.97%

[0104] According to the 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%. Directly according to the standard curve of indica rice with RS < 11%, the RS range is judged to be 0 - 5%.

[0105] According to the data analysis, gSS3a / rs4 the cooking water absorption rate is 200.97%, and the water absorption rate is in the range of 120 - 250%. Directly according to the standard curve of indica RS < 11%, the RS range is judged to be 0 - 5%.

[0106] According to the conventional AOAC method, the actual RS contents of Guichao rice and

[0107] gSS3a / rs4

[0108] are 1.08% and 1.73% respectively, which are in line with the predicted range.

[0109]

[0110] Example 4 uses the rapid prediction method of the present invention to determine the RS content

[0111] Determine the verification samples: rs5 and rs6

[0112] Instruments used: 15 ml test tubes, electronic balance, rice cooker, iron test tube rack

[0113] First, for rs5 and rs6 100 whole milled rice grains without cracks were selected respectively, and divided into five replicates, with 20 whole milled rice grains in each replicate. They were weighed on an electronic balance, rs5 and rs6 The average values of the original milled rice weights measured five times for the replicates are 0.4671 g and 0.3714 g respectively.

[0114] Secondly, the above 100 crack-free head rice grains were divided into 5 replicates and placed into 5 test tubes of 15 ml respectively, with 20 head rice grains in each test tube. The centrifuge tubes were placed in an iron test tube rack, 10 mL of distilled water was added, and they were left standing for 15 min, then placed in a boiling water bath for 15 min. The cooked rice grains were taken out, placed on absorbent paper, and after standing for 15 min, the weight data of each group of samples were measured. rs5 and rs6 The average values of the weight of the cooked polished rice measured five times were 1.4452 g and 1.1178 g respectively.

[0115] Finally, according to the formula: cooking water absorption rate = (weight of 20 grains after cooking - original weight) / original weight × 100%, rs5 and rs6 the cooking water absorption rates of the samples were calculated.

[0116] rs5 : cooking water absorption rate = (0.4837 - 0.2799) / 0.2799 × 100% = 72.81%

[0117] rs6 : cooking water absorption rate = (0.5116 g - 0.2970) / 0.2970 × 100% = 72.26%

[0118] According to the data analysis, rs5 the cooking water absorption rate of

[0119] According to the data analysis, rs6 the cooking water absorption rate of

[0120] was 72.81%, and the water absorption rate was in the range of 60 - 90%. Directly according to the standard curve of indica rice RS > 11%, the RS range was judged to be 11 - 22%. rs5 and rs6 the actual RS contents of

[0121]

[0122] Example 5 used the rapid prediction method of the present invention to determine the RS content

[0123] Determination of verification samples: gSS3b / rs4

[0124] Instruments used: 15 ml test tubes, electronic balance, rice cooker, 4-degree refrigerator, iron test tube rack

[0125] First,gSS3b / rs4 For sample selection, 100 crack-free head rice grains were divided into five replicates, with 20 head rice grains in each replicate, and weighed on an electronic balance. gSS3b / rs4 The average value of the original head rice weight measured five times in replicates was 0.3561 g.

[0126] Secondly, the above-mentioned 100 crack-free head rice grains were divided into 5 replicates and placed into 5 15-ml test tubes, with 20 head rice grains in each test tube. The centrifuge tubes were placed in an iron test tube rack, 10 mL of distilled water was added, and they were left standing for 15 min, then placed in a boiling water bath for 15 min. The cooked rice grains were taken out, placed on absorbent paper, and after standing for 15 min, the weight data of each group of samples were measured. gSS3b / rs4 The average value of the cooked head rice weight measured five times in replicates was 0.7540 g.

[0127] Then, according to the formula: cooking water absorption rate = (weight of 20 grains after cooking - original weight) / original weight × 100%, the gSS3b / rs4 cooking water absorption rate of the sample was calculated.

[0128] gSS3b / rs4 : cooking water absorption rate = (0.7540 - 0.3561) / 0.3561 g × 100% = 111.74%

[0129] According to the data analysis, rs5 the cooking water absorption rate of the sample was 111.74%, and the water absorption rate was in the range of 90 - 120%. Therefore, it was necessary to combine the retrogradation water loss rate to judge the RS content.

[0130] Finally, the cooked head rice was placed in a square dish and stored in a 4-degree refrigerator for 24 hours, then randomly divided into groups of 20 grains and placed on absorbent paper. After standing for 15 min, the average weight of each group of samples was measured to be 0.6840 g.

[0131] Then, according to the formula: retrogradation water loss rate = (weight of 20 grains after cooking - weight after retrogradation) / weight after cooking × 100%, the gSS3b / rs4 retrogradation water loss rate of the sample was calculated.

[0132] gSS3b / rs4 : retrogradation water loss rate = (0.7540 - 0.6840) / 0.7540 × 100% = 9.28%

[0133] In summary,

[0134] gSS3b / rs4

[0135] The sample simultaneously met the requirements of a water absorption rate of 90 - 120% and a retrogradation water loss rate greater than 9%. Therefore, it was judged that the RS range was 5 - 11%. Determined according to the conventional AOAC method

[0136] gSS3b / rs4

[0137] The actual RS content is 7.84%, which is in line with the predicted range.

[0138]

Claims

1. A simple method for quickly predicting the resistant starch content of rice, characterized in that, The rice is indica rice, and the following steps are carried out in sequence: 1) Measure the physiological indexes of the polished rice samples to be tested Select an appropriate amount of polished rice with uniform size and no cracks from the polished rice samples to be tested, randomly divide them into at least 5 portions with each portion containing at least 20 grains, measure the total weight of each portion, and measure at least 5 times respectively to obtain at least 5 parallel repeated results; 2) Measure the physiological indexes of the polished rice after cooking Take the appropriate amount of polished rice with uniform size and no cracks selected in the first step, randomly divide it into at least 5 portions with each portion containing at least 20 grains, put them into centrifuge tubes respectively, add an appropriate amount of distilled water, let it stand for 12 - 20 min, then place it in a boiling water bath for 12 - 20 min, take out the rice grains, place them on absorbent paper, after standing for 12 - 20 min, measure the grain weight data of each sample; If the water absorption rate is between 90% - 120% (including the two end values) after the first two steps, then place the cooked polished rice in a square dish and put it in a 4 - degree refrigerator for 24 hours, then randomly divide it into groups of 20 grains and place them on absorbent paper, after standing for 15 min, measure the grain weight data of each group of samples after retrogradation, calculate the retrogradation water loss rate, and make a judgment in combination with the cooking water absorption rate; if the water absorption rate is not between 90 - 120% (excluding the two end values) after the first two steps, directly enter step 4) to predict the resistant starch content; 4) Prediction of resistant starch content After cooking the samples according to the above steps, calculate the water absorption rate of the samples. The formula for calculating the water absorption rate after cooking is: Water absorption rate = (weight of the rice grains after cooking - weight of the rice grains before cooking) / weight of the rice grains before cooking × 100%, and calculate the water absorption rate after cooking; according to the water absorption rate after cooking, divide the resistant starch content of the samples into two preliminary prediction ranges of RS < 11% or RS > 11%. When the water absorption rate is between 120 - 250%, substitute it into the RS < 11% fitting curve; when the water absorption rate is between 60 - 90%, substitute it into the RS > 11% standard curve to predict the resistant starch content. The standard curves are as follows: The RS < 11% fitting standard curve is: y = -0.0571x + 14.223, where Y: predicted RS content, X: water absorption rate; The RS > 11% fitting standard curve is: y = 0.1466x + 4.3208, where Y: predicted RS content, X: water absorption rate; When the water absorption rate is between 90 - 120% (including the two end values), it is necessary to make a judgment in combination with the cooking retrogradation water loss rate. When the water absorption rate is between 90 - 120% and the cooking retrogradation water loss rate is greater than 9%, then substitute it into the RS < 11% fitting standard curve, and finally obtain the RS content in the range of 5 - 11%; when the cooking retrogradation water loss rate is less than or equal to 9%, substitute it into the RS > 11% standard curve for prediction, and finally obtain the RS in the range of 11 - 22%; Retrogradation water loss rate = (weight of 20 grains after cooking - weight after retrogradation) / weight after cooking × 100%.

2. The simple method for rapidly predicting the resistant starch content of rice according to claim 1, characterized in that In step 1), a balance is used to measure the rice grain weight data.

3. The simple method for rapidly predicting the resistant starch content of rice according to claim 2, characterized in that, Step 1) Select 100 grains of polished rice with uniform size and no cracks from the polished rice sample to be tested, randomly divide them into 5 equal parts with 20 grains in each part, measure the total weight of each part, and measure 5 times respectively to obtain 5 parallel repeated results.

4. The simple method for quickly predicting the resistant starch content of rice according to claim 3, characterized in that, Step 2) Put 5 parts with 20 grains in each part into 15 mL centrifuge tubes respectively, add 10 mL of distilled water, let it stand for 15 min, then place it in a boiling water bath for 15 min, take out the rice grains, place them on absorbent paper, and after standing for 15 min, measure the grain weight data of each sample.

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