Preparation process of rice resistant starch with high enzymolysis resistance

Abstract

The invention relates to a preparation process of rice resistant starch with high enzymolysis resistance. The preparation process comprises the following steps: extracting rice starch, performing acid hydrolysis treatment, performing hot pressing-cooling circulation modification, adding calcium ions for compounding, drying, grinding and sieving, thereby obtaining the rice resistant starch. The rice starch preparation process provided by the invention does not need additional enzyme, and is simple in production process, convenient to operate, good in enzymolysis resistance, high in safety controllability and suitable for large-scale production.

Description

Technical Field

[0001] The present invention relates to the field of food processing, and more specifically, to a preparation process of rice resistant starch. Background Art

[0002] Rice is an important cereal crop in China. It is not only the main food crop for the people, but also can be used as a raw material for the processing of downstream products such as brewing, syrup, rice noodles, and puffed rice foods. The most abundant component in rice is rice starch. However, in recent years, with the increase in per capita income level, people's dietary structure has changed greatly, and consumers' demand for healthy diets has been growing day by day. Relevant research has pointed out that excessive intake of rice starch will cause high glycemic load and other potential disease risks.

[0003] Resistant starch is a type of starch that is difficult to be digested by the small intestine but can be fermented by intestinal flora in the colon into short-chain fatty acids. If rice starch can be modified into resistant rice starch, it can reduce the blood sugar metabolism burden of consumers. Therefore, the development and popularization of the preparation process of rice resistant starch are of great significance for improving the healthy diet of the whole people.

[0004] Enzymolysis is an important process for starch to be absorbed in the human body. Starch will be hydrolyzed into monosaccharides and then further metabolized and absorbed. Therefore, improving the anti-enzymolysis ability of resistant starch can reduce the absorption burden of the human body. The enzymatic method is a commonly used means for starch modification. Compared with the use of enzyme additives, the present invention provides a safe and controllable preparation process of rice resistant starch that does not require external enzymes, has a simpler production process, more convenient operation, and better anti-enzymolysis ability. Its main modification means is to prepare it by repeated hot pressing and retrogradation treatment and then complexing with calcium ions.

[0005] Hot pressing and retrogradation are commonly used processes for preparing resistant starch. Due to the different powder properties of starches from different sources, there will be particularities in the specific implementation of the process. In Patent CN101427741A, the concentration of the starch milk to be treated is 30-40%. In fact, directly applying this starch milk concentration to the production of resistant starch from different sources is not appropriate. Relevant research has pointed out that when the starch milk concentration is too high, the viscosity becomes larger, which will make it difficult for the starch to fully expand, and is not conducive to the amylose molecules approaching each other, forming double helices and crystallization. There is a certain difference in the amylose content between rice starch and corn starch, and using the preparation process of corn resistant starch for rice resistant starch cannot obtain a product with high anti-enzymolysis property. In addition, relevant research has also pointed out that the hot pressing time will also affect the content of resistant starch. If the treatment time is short, the amylose molecules are not completely free; if the treatment time is long, the formation of resistant starch will be affected due to its excessive degradation.

[0006] The non-starch polysaccharide-metal ion coating described in Patent CN113575972A is actually a kind of "embedding" technology. Although the encapsulation of the non-starch polysaccharide-metal ion coating can reduce the contact between enzymes and starch granules, resulting in slow digestion, the addition of the coating actually changes the original properties of resistant starch, such as viscosity, gelatinization properties, taste, etc., affecting the usability. In addition, excessive intake of non-starch polysaccharides may also affect the digestion and absorption of other nutrients in the intestine, and even change the microbial flora in the intestine, posing a health hazard.

[0007] Furthermore, Wu Na et al. from Tianjin University of Science and Technology pointed out that the simultaneous addition of pectin and calcium ions would reduce the anti-enzymatic hydrolysis property of starch. The reason may be that when pectin binds to starch first, the hydroxyl groups in pectin form hydrogen bonds with starch, promoting the enhancement of starch's anti-enzymatic hydrolysis property. However, after adding calcium ions, pectin preferentially binds to calcium ions to form calcium pectate and dissociates from starch, resulting in a reduction in the original hydrogen bonds formed. Summary of the Invention

[0008] The purpose of the present invention is to provide a safe and controllable preparation process of rice resistant starch that does not require the addition of external enzymes, has a simpler production process, more convenient operation, and better anti-enzymatic hydrolysis ability, and is suitable for large-scale production. The highly anti-enzymatic hydrolysis rice resistant starch obtained by the present invention uses rice as the raw material, first extracts rice starch, modifies it to obtain RS3-type resistant starch, and then composites it with calcium ions.

[0009] To achieve the above purpose, the present invention provides the following technical solutions:

[0010] A preparation process of highly anti-enzymatic hydrolysis rice resistant starch (using rice as the raw material), comprising the following steps:

[0011] (1) Extraction;

[0012] (2) Acid hydrolysis;

[0013] (3) Heat pressing-cooling cycle modification treatment;

[0014] (4) Adding food-grade calcium ions for composite;

[0015] (5) Drying, grinding, and sieving to obtain rice resistant starch.

[0016] Preferably, the extraction step includes:

[0017] (a) Soaking the rice grains in a 0.30 - 0.45% (w / v) NaOH solution and refrigerating at 4°C for 20 ± 2 h;

[0018] (b) Draining the supernatant, grinding the rice grains into a slurry, and then passing through a 100-mesh sieve.

[0019] (c) Centrifuge the obtained starch slurry at 3000 g / min for 15 min;

[0020] (d) Remove the supernatant, add 2.5 - 3.5 times the volume of deionized water to the precipitate, centrifuge at 3000 g / min for 15 min, discard the supernatant, and repeat the water washing and centrifugation operations 3 times. Finally, add 3 times the volume of deionized water to the obtained precipitate and stir well;

[0021] (e) Adjust the pH of the starch solution obtained in (4) to 7.0 ± 0.1 with 1 mol / L HCl, then centrifuge at 3000 g / min for 15 min, and discard the supernatant for later use.

[0022] (f) Dry at 60 °C, grind into powder, and pass through a 100 - mesh sieve for later use.

[0023] Preferably, the acid hydrolysis step includes:

[0024] (1) Add 1.5 times (w / v) of 1.5 - 2.0 mol / L HCl solution to the prepared rice starch, stir evenly, and keep it at a constant temperature of 40 °C for 3 h;

[0025] (2) Adjust the pH of the above - mentioned solution to 6.5 ± 0.1 with 9 - 11% (w / v) NaOH solution, centrifuge at 1000 g / min for 5 min, discard the supernatant, and repeat the water washing and centrifugation operations 3 times, discard the supernatant for later use;

[0026] (3) Dry at 40 °C, grind into powder, and pass through a 100 - mesh sieve for later use.

[0027] Preferably, the hot - press - cooling cycle modification treatment step includes:

[0028] (1) Adjust the hydrolyzed rice starch and deionized water to make a slurry in a ratio of 1:5, and stir at a constant temperature of 85 °C for 25 - 35 min;

[0029] (2) Put the above - mentioned starch slurry into a high - pressure cooking pot and cook at 135 °C for 25 - 35 min;

[0030] (3) Refrigerate the starch slurry after high - temperature and high - pressure cooking at 4 °C for 20 ± 2 h;

[0031] (4) Repeat the hot - press - cooling and refrigeration steps 3 times;

[0032] (5) Filter the obtained starch slurry through a 100 - mesh sieve for later use.

[0033] Preferably, the step of complexing with food - grade calcium ions includes:

[0034] (1) The calcium ions mentioned include but are not limited to food - grade calcium chloride, calcium hydrogen phosphate, and calcium lactate;

[0035] (2) Add food-grade calcium salt to the starch slurry after heat pressing-cooling treatment and stir well. The addition ratio of calcium ions is 15-20% (calculated based on the dry starch basis).

[0036] (3) Treat the compounded starch slurry at 90-95 °C for 30 min, then at 115-125 °C for 20 min, and finally store it at 4 °C for 20 ± 2 h.

[0037] (4) Dry at 60 °C, grind into powder, and pass through a 100-mesh sieve to obtain the finished product.

[0038] Compared with the existing preparation process of rice resistant starch, the present invention can achieve at least one of the following beneficial effects:

[0039] 1. Without using enzyme additives, the production process is more natural and environmentally friendly.

[0040] 2. The rice resistant starch obtained by the preparation process of this patent has better anti-enzyme digestion ability compared with the enzyme method.

[0041] 3. The rice resistant starch obtained by the preparation process of this patent has a lower glycemic index (GI value) compared with the enzyme method. Description of the Drawings

[0042] In order to more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the embodiments of this specification. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0043] Figure 1 It is the process flow chart of the rice resistant starch of the present invention. Detailed Embodiments

[0044] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the drawings in the embodiments of this application. Obviously, the described embodiments are some, but not all, of the embodiments of this application. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of this application.

[0045] Anti - enzymatic hydrolysis detection method: Accurately weigh 1 g of starch and dissolve it in 30 mL of phosphate buffer (0.2 mol / L, pH 6.9). Heat it in a water bath at 95 °C for 30 min. After cooling to 25 °C, add 320 units of heat - resistant α - amylase, and enzymatically hydrolyze it with shaking in a water bath at 90 °C for 2 h. Then, terminate the enzymatic hydrolysis reaction with 5 mL of 1% (mass concentration) sulfuric acid. After centrifugation, wash the unhydrolyzed product with 80% ethanol. After centrifugation again, dry the precipitate in an oven at 80 °C until it reaches a constant weight.

[0046]

[0047] Glycemic index (GI value) detection method: Use a glucose oxidase - peroxidase kit for detection.

[0048] Example 1

[0049] The preparation process includes: extracting starch, acid hydrolysis, heat - pressing - cooling cycle modification treatment, adding food - grade calcium ions for complexation, drying, grinding, and sieving to obtain rice resistant starch.

[0050] The specific steps are as follows:

[0051] Extraction: Soak the rice grains in 0.30% (w / v) NaOH solution and refrigerate at 4 °C for 22 h. Drain the supernatant, grind the rice grains into a slurry, and then pass it through a 100 - mesh sieve. Centrifuge the slurry at 3000 g / min for 15 min, discard the supernatant, add 2.5 times the volume of deionized water to the precipitate, then centrifuge at 3000 g / min for 15 min and discard the supernatant. Repeat the water - washing and centrifugation operations 3 times. Finally, add 3 times the volume of deionized water to the obtained precipitate, stir well to obtain a starch solution. Adjust the pH of the starch solution to 6.9 with 1 mol / L HCl, then centrifuge at 3000 g / min for 15 min, discard the supernatant for later use, and obtain rice starch. Take a small amount of the sample, dry it at 60 °C, grind it into powder, and pass it through a 100 - mesh sieve for detection.

[0052] Acid hydrolysis: Add 1.5 times (w / v) of 1.5 mol / L HCl solution to the prepared rice starch, stir evenly, and keep it at a constant temperature of 40 °C for 3 h. Adjust the pH of the above - mentioned solution to 6.5 with 9% (w / v) NaOH solution, centrifuge at 1000 g / min for 5 min, discard the supernatant, and repeat the water - washing and centrifugation operations 3 times, discard the supernatant for later use. Take a small amount of the sample, dry it at 60 °C, grind it into powder, and pass it through a 100 - mesh sieve for detection.

[0053] Hot pressing - cooling cycle modification treatment: The rice starch after acid hydrolysis and deionized water were slurried at a ratio of 1:5 and stirred at a constant temperature of 85 °C for 25 min. The starch slurry was placed in a high - pressure steamer and steamed at 135 °C for 35 min. The starch slurry after high - temperature and high - pressure steaming was refrigerated at 4 °C for 20 h. The hot pressing - cooling refrigeration steps were repeated 3 times. A small amount of the sample was taken, dried at 60 °C, ground into powder, and passed through a 100 - mesh sieve for detection.

[0054] Compound: Food - grade calcium salt was added to the starch slurry after hot pressing - cooling cycle modification treatment and stirred evenly. The addition ratio of calcium ions was 20% (calculated based on the dry weight of starch). The compounded starch slurry was treated at 90 °C for 30 min, then at 115 °C for 20 min, and finally stored at 4 °C for 20 h. It was dried at 60 °C, ground into powder, and passed through a 100 - mesh sieve to obtain the finished product. The compound calcium ion used was food - grade calcium chloride.

[0055] Example 2

[0056] Extraction: The rice grains were soaked in 0.40% (w / v) NaOH solution and refrigerated at 4 °C for 20 h. The supernatant was drained, the rice grains were ground into a slurry, then passed through a 100 - mesh sieve. The obtained starch slurry was centrifuged at 3000 g / min for 15 min. The supernatant was removed, 3 times the volume of deionized water was added to the precipitate, and then centrifuged at 3000 g / min for 15 min and the supernatant was discarded. The washing and centrifugation operations were repeated 3 times. Finally, 3 times the volume of deionized water was added to the obtained precipitate and stirred well to obtain a starch solution. The starch solution was adjusted to pH 7.0 with 1 mol / L HCl, and then centrifuged at 3000 g / min for 15 min, and the supernatant was discarded for later use. It was dried at 60 °C, ground into powder, and passed through a 100 - mesh sieve for later use.

[0057] Acid hydrolysis: 1.5 times (w / v) of 1.8 mol / L HCl solution was added to the above - mentioned rice starch. After stirring evenly, it was placed at a constant temperature of 40 °C for 3 h. The pH of the above - mentioned solution was adjusted to 6.4 with 10% (w / v) NaOH solution, centrifuged at 1000 g / min for 5 min, and the supernatant was discarded. The washing and centrifugation operations were repeated 3 times, and the supernatant was discarded for later use.

[0058] Hot pressing - cooling cycle modification treatment: The hydrolyzed rice starch and deionized water were slurried at a ratio of 1:5 and stirred at a constant temperature of 85 °C for 30 min. The starch slurry was placed in a high - pressure steamer and steamed at 135 °C for 30 min. The starch slurry was refrigerated at 4 °C for 21 h, and the hot pressing - cooling refrigeration steps were repeated 3 times.

[0059] Compound: After adding food-grade calcium salt to the starch slurry after hot pressing-cooling treatment, stir well. The addition ratio of calcium ions is 18% (calculated based on the dry starch basis). Treat the compounded starch slurry at 93 °C for 30 min, then at 120 °C for 20 min, and finally store it at 4 °C for 21 h. Dry it at 60 °C, grind it into powder, and pass through a 100-mesh sieve to obtain the finished product. The calcium ions are food-grade calcium hydrogen phosphate.

[0060] Example 3

[0061] Acid hydrolysis: Take rice starch, add 1.5 times (w / v) of 2.0 mol / L HCl solution to it, stir well and keep it at a constant temperature of 40 °C for 3 h. Adjust the pH of the above solution to 6.6 with 10% (w / v) NaOH solution, centrifuge at 1000 g / min for 5 min to discard the supernatant, and repeat the water washing and centrifugation operations 3 times, discarding the supernatant for later use.

[0062] Hot pressing-cooling cycle modification treatment: Adjust the hydrolyzed rice starch and deionized water to make a slurry at a ratio of 1:5, and stir at a constant temperature of 85 °C for 35 min. Put the starch slurry into a high-pressure steamer and cook it at 135 °C for 25 min. The starch slurry after high-temperature and high-pressure cooking is refrigerated at 4 °C for 22 h, and repeat the hot pressing-cooling refrigeration steps 3 times.

[0063] Compound: After adding food-grade calcium salt to the starch slurry after hot pressing-cooling treatment, stir well. The addition ratio of calcium ions is 15% (calculated based on the dry starch basis). Treat the compounded starch slurry at 90 - 95 °C for 30 min, then at 115 - 125 °C for 20 min, and finally store it at 4 °C for 22 h. Dry it at 60 °C, grind it into powder, and pass through a 100-mesh sieve to obtain the finished product. The food-grade calcium salt is food-grade calcium lactate.

[0064] Comparative Example 1 Preparation of rice resistant starch by compound enzyme method

[0065] Referring to the process of CN 109988798A, a green preparation method of rice resistant starch, (1) Using rice starch as the raw material, prepare a suspension with a weight-volume fraction of 10% and adjust the pH of the suspension to 5.0; (2) Add 1300 - 1600 U / g of β-amylase to the suspension, oscillate and hydrolyze it in a 50 °C water bath for 2 hours, then inactivate the enzyme activity and adjust the pH of the enzyme hydrolysis solution to 5.0; (3) Add 1600 - 1800 U / g of glucosyltransferase to the enzyme hydrolysis solution, oscillate and enzymatically hydrolyze it in a 50 °C water bath for 4 - 12 hours, then inactivate the enzyme activity and adjust the pH value of the enzyme hydrolysis solution to 5.0; (4) Add 20 - 40 U / g of pullulanase to the enzyme hydrolysis solution, oscillate and enzymatically hydrolyze it in a 55 °C water bath for 12 hours, then inactivate the enzyme activity, and finally adjust the pH value of the enzyme hydrolysis solution to 7.0; (5) Add the enzyme hydrolysis solution to anhydrous ethanol and let it stand; (6) Centrifuge to collect the precipitate, and the obtained precipitate is frozen and dried to obtain the product.

[0066] The implementation purpose of Comparative Example 1 is to verify and compare the anti - enzymatic hydrolysis ability of conventional enzymatic hydrolysis of rice resistant starch and the non - enzymatic rice resistant starch of the present invention, aiming to illustrate that non - enzymatic rice resistant starch has better anti - enzymatic hydrolysis property than enzymatic rice resistant starch, and in the actual production process, enzymatic hydrolysis often has high requirements for equipment, and the addition of enzymes (proteins) will make the filtration of starch solution difficult.

[0067] Preparation of resistant starch using corn starch as raw material in Comparative Example 2

[0068] It is exactly the same as the steps in Example 1, with the only difference being that the starch extraction step is not required, and corn starch is directly used to prepare resistant starch, and the rest of the process is exactly the same.

[0069] Acid hydrolysis: (1) Take corn starch, add 1.5 times (w / v) of 1.5 mol / L HCl solution, stir evenly and keep it at a constant temperature of 40 °C for 3 h; (2) Adjust the pH of the above - mentioned solution to 6.5 ± 0.1 with 9% (w / v) NaOH solution, centrifuge at 1000 g / min for 5 min, discard the supernatant, and repeat the water - washing and centrifugation operation 3 times, discard the supernatant for later use; (3) Take a small amount of the sample, dry it at 60 °C, grind it into powder, and pass it through a 100 - mesh sieve for detection.

[0070] Thermal - pressing - cooling cycle modification: Add deionized water to the hydrolyzed corn starch, adjust the starch slurry concentration to 20%, stir at a constant temperature of 85 °C for 25 min; put the above - mentioned starch slurry into a high - pressure steamer and steam it at 135 °C for 35 min; refrigerate the starch slurry after high - temperature and high - pressure steaming at 4 °C for 20 h; repeat the thermal - pressing - cooling and refrigeration steps 3 times.

[0071] Compound: Add food - grade calcium salt to the starch slurry after thermal - pressing - cooling treatment and stir evenly, the calcium ion addition ratio is 20% (calculated based on the dry basis of starch); treat the compounded starch slurry at 90 - 95 °C for 30 min, then at 115 °C for 20 min, and finally store it at 4 °C for 20 h. Dry it at 60 °C, grind it into powder, and pass it through a 100 - mesh sieve to obtain the finished product.

[0072] The implementation purpose of Comparative Example 2 is to verify whether the starch slurry concentration of 30 - 40% commonly used in the thermal - pressing - cooling step in the production of corn resistant starch is applicable in the production of rice resistant starch. There are certain differences in the amylose content of rice starch and corn starch, and using the preparation process of corn resistant starch for rice resistant starch cannot obtain a product with high anti - enzymatic hydrolysis property.

[0073] Comparative Example 3

[0074] The extraction operation of rice starch is as follows: (1) Soak the rice grains in a 0.30 - 0.45% (w / v) NaOH solution and refrigerate at 4°C for 20 ± 2 h; (2) Drain the supernatant, grind the rice grains into a slurry, and then pass through a 100 - mesh sieve; (3) Centrifuge the obtained starch slurry at 3000 g / min for 15 min; (4) Remove the supernatant, add 2.5 - 3.5 times the volume of deionized water to the precipitate, centrifuge at 3000 g / min for 15 min, discard the supernatant, and repeat the water - washing and centrifugation operation 3 times. Finally, add 3 times the volume of deionized water to the obtained precipitate and stir well; (5) Adjust the pH of the starch solution obtained in (4) to 7.0 ± 0.1 with 1 mol / L HCl, then centrifuge at 3000 g / min for 15 min, and discard the supernatant for later use. (6) Dry at 60°C, grind into powder, and pass through a 100 - mesh sieve for later use.

[0075] The acid hydrolysis operation of rice starch is as follows: (1) Add 1.5 times (w / v) of a 1.5 - 2.0 mol / L HCl solution to the prepared rice starch, stir evenly, and keep it at a constant temperature of 40°C for 3 h; (2) Adjust the pH of the above - mentioned solution to 6.5 ± 0.1 with a 9 - 11% (w / v) NaOH solution, centrifuge at 1000 g / min for 5 min, discard the supernatant, and repeat the water - washing and centrifugation operation 3 times, discard the supernatant for later use; (3) Dry at 40°C, grind into powder, and pass through a 100 - mesh sieve for later use.

[0076] The hot - pressing - cooling cycle modification treatment is as follows: (1) Adjust the slurry of hydrolyzed rice starch and deionized water in a ratio of 1:5, and stir at a constant temperature of 85°C for 25 - 35 min; (2) Put the above - mentioned starch slurry into a high - pressure steamer and cook at 135°C for 25 - 35 min; (3) Refrigerate the starch slurry after high - temperature and high - pressure cooking at 4°C for 20 ± 2 h; (4) Repeat the hot - pressing - cooling and refrigeration steps 3 times; (5) Filter the obtained starch slurry through a 100 - mesh sieve for later use, dry at 60°C, grind into powder, and pass through a 100 - mesh sieve to obtain the finished product.

[0077] The purpose of Comparative Example 3 is to verify whether the addition of food - grade calcium ions of non - starch polysaccharides can effectively improve the anti - enzymatic hydrolysis property of rice resistant starch. The non - starch polysaccharide - metal ion coating described in Patent CN113575972A is actually a kind of "embedding" technology. Although the encapsulation of the non - starch polysaccharide - metal ion coating can reduce the contact between enzymes and starch granules, resulting in slow digestion, the addition of the coating actually changes the original properties of resistant starch, such as viscosity, gelatinization properties, taste, etc., affecting the usability.

[0078] Effect of the addition of food - grade potassium and calcium ions of non - starch polysaccharides on the anti - enzymatic hydrolysis property of rice resistant starch in Comparative Example 4

[0079] Extraction: (1) Soak the rice grains in a 0.30 - 0.45% (w / v) NaOH solution and refrigerate at 4°C for 20 ± 2 h; (2) Drain the supernatant, grind the rice grains into a slurry, and then pass through a 100 - mesh sieve; (3) Centrifuge the obtained starch slurry at 3000 g / min for 15 min; (4) Remove the supernatant, add 2.5 - 3.5 times the volume of deionized water to the precipitate, centrifuge at 3000 g / min for 15 min, discard the supernatant, and repeat the water - washing and centrifugation operations 3 times. Finally, add 3 times the volume of deionized water to the obtained precipitate and stir well; (5) Adjust the pH of the starch solution obtained in (4) to 7.0 ± 0.1 with 1 mol / L HCl, then centrifuge at 3000 g / min for 15 min, and discard the supernatant for later use. (6) Dry at 60°C, grind into powder, and pass through a 100 - mesh sieve for later use.

[0080] Acid hydrolysis: (1) Add 1.5 times (w / v) of a 1.5 - 2.0 mol / L HCl solution to the prepared rice starch, stir evenly, and keep at a constant temperature of 40°C for 3 h; (2) Adjust the pH of the above - mentioned solution to 6.5 ± 0.1 with a 9 - 11% (w / v) NaOH solution, centrifuge at 1000 g / min for 5 min, discard the supernatant, and repeat the water - washing and centrifugation operations 3 times, discard the supernatant for later use; (3) Dry at 40°C, grind into powder, and pass through a 100 - mesh sieve for later use.

[0081] Hot - press - cooling cycle modification treatment: (1) Adjust the slurry of hydrolyzed rice starch and deionized water in a ratio of 1:5, and stir at a constant temperature of 85°C for 25 - 35 min; (2) Put the above - mentioned starch slurry into a high - pressure steamer and steam at 135°C for 25 - 35 min; (3) Refrigerate the starch slurry after high - temperature and high - pressure steaming at 4°C for 20 ± 2 h; (4) Repeat the hot - press - cooling and refrigeration steps 3 times; (5) Filter the obtained starch slurry through a 100 - mesh sieve for later use.

[0082] Compound with food - grade potassium ions: (1) The potassium ions mentioned include but are not limited to food - grade potassium chloride, potassium bicarbonate, potassium carbonate, tripotassium phosphate, etc.; (2) Add food - grade potassium salt to the starch slurry after hot - press - cooling treatment and stir well. The addition ratio of potassium ions is 15 - 20% (calculated based on the dry basis of starch); (3) Treat the compounded starch slurry at 90 - 95°C for 30 min, then at 115 - 125°C for 20 min, and finally store at 4°C for 20 ± 2 h; (4) Dry at 60°C, grind into powder, and pass through a 100 - mesh sieve to obtain the finished product.

[0083] The purpose of Comparative Example 4 is to verify the effect of the addition of non - starch polysaccharide food - grade potassium and calcium ions on the anti - enzymatic hydrolysis property of rice resistant starch.

[0084] The influence of the co - compounding of pectin and calcium ions on the preparation process of resistant starch in Comparative Example 5

[0085] The extraction operation of rice starch is as follows: (1) Soak the rice grains in a 0.30 - 0.45% (w / v) NaOH solution and refrigerate at 4°C for 20 ± 2 h; (2) Drain the supernatant, grind the rice grains into a slurry, and then pass through a 100 - mesh sieve; (3) Centrifuge the obtained starch slurry at 3000 g / min for 15 min; (4) Remove the supernatant, add 2.5 - 3.5 times the volume of deionized water to the precipitate, then centrifuge at 3000 g / min for 15 min and discard the supernatant, and repeat the water - washing and centrifugation operations 3 times. Finally, add 3 times the volume of deionized water to the obtained precipitate and stir well; (5) Adjust the pH of the starch solution obtained in (4) to 7.0 ± 0.1 with 1 mol / L HCl, then centrifuge at 3000 g / min for 15 min and discard the supernatant for later use. (6) Dry at 60°C, grind into powder, and pass through a 100 - mesh sieve for later use.

[0086] The acid hydrolysis operation of rice starch is as follows: (1) Add 1.5 times (w / v) of a 1.5 - 2.0 mol / L HCl solution to the prepared rice starch, stir evenly, and keep it at a constant temperature of 40°C for 3 h; (2) Adjust the pH of the above - mentioned solution to 6.5 ± 0.1 with a 9 - 11% (w / v) NaOH solution, centrifuge at 1000 g / min for 5 min and discard the supernatant, and repeat the water - washing and centrifugation operations 3 times, discard the supernatant for later use; (3) Dry at 40°C, grind into powder, and pass through a 100 - mesh sieve for later use.

[0087] The hot - press - cooling cycle modification treatment is as follows: (1) Adjust the slurry of hydrolyzed rice starch and deionized water in a ratio of 1:5, and stir at a constant temperature of 85°C for 25 - 35 min; (2) Put the above - mentioned starch slurry into a high - pressure steamer and cook at 135°C for 25 - 35 min; (3) Refrigerate the starch slurry after high - temperature and high - pressure cooking at 4°C for 20 ± 2 h; (4) Repeat the hot - press - cooling and refrigeration steps 3 times; (5) Filter the obtained starch slurry through a 100 - mesh sieve for later use.

[0088] The compounding with pectin and food - grade calcium ions is as follows: (1) The calcium ions include but are not limited to food - grade calcium chloride, calcium hydrogen phosphate, and calcium lactate; (2) The pectin is low - methoxyl pectin; (3) Add 3 - 5% of low - methoxyl pectin (calculated based on the dry starch basis) and 15 - 20% of calcium ions (calculated based on the dry starch basis) to the starch slurry after hot - press - cooling treatment, and stir well; (4) Treat the compounded starch slurry at 90 - 95°C for 30 min, then at 115 - 125°C for 20 min, and finally store at 4°C for 20 ± 2 h; (4) Dry at 60°C, grind into powder, and pass through a 100 - mesh sieve to obtain the finished product.

[0089] The purpose of the implementation of Comparative Example 5 is to verify whether the simultaneous addition of pectin and calcium ions plays a synergistic promoting role or an antagonistic role in the process preparation of rice resistant starch.

[0090] Example 4 Detection of Resistant Starch Performance

[0091] The glycemic index and anti - enzymatic hydrolysis properties of the resistant starch in Examples 1 - 3 and the comparative examples were detected, and the detection results are shown in Table 1:

[0092] Table 1

[0093] Sample Anti - enzymatic hydrolysis property (%) Blood glucose growth index (GI, %) Example 1 48.64±0.20 48.43±0.15 Example 2 49.85±0.19 46.89±0.22 Example 3 50.32±0.27 45.71±0.16 Comparative Example 1 32.16±0.24 69.18±0.18 Comparative Example 2 39.51±0.26 55.96±0.20 Comparative Example 3 34.65±0.25 63.21±0.17 Comparative Example 4 42.33±0.22 51.05±0.16 Comparative Example 5 39.58±0.21 54.87±0.31

[0094] It can be seen from the three groups of examples that the rice resistant starch prepared by applying the process of the present invention has a lower glycemic index and better performance in anti - enzymatic hydrolysis compared with the rice resistant starch prepared in other comparative examples.

[0095] The specific embodiments described above have further detailed the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above are only specific embodiments of the present application and are not used to limit the protection scope of the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A rice resistant starch, characterized in that: The enzymolysis resistance of the rice resistant starch is not higher than 51.0%, and the glycemic index is not higher than 49.0%.

2. A process for preparing rice resistant starch, characterized in that: The following steps are involved: (1) Extraction; (2) Acid hydrolysis; (3) Hot pressing-cooling cycle modification treatment; (4) adding food-grade calcium ions for compounding; (5) After drying, grinding and sieving, rice resistant starch is obtained.

3. The preparation process according to claim 2, characterized in that: The extraction step comprises: (a) soaking rice grains in 0.30-0.45% (w / v) NaOH solution and refrigerating at 4°C for 20±2h; (b) draining the supernatant, grinding the rice grains into a slurry, and then passing the slurry through a 100-mesh sieve; (c) centrifuging the starch slurry obtained above at 3000 g / min for 15 min; (d) removing the supernatant, adding 2.5-3.5 times the volume of deionized water to the precipitate, centrifuging at 3000 g / min for 15 min, discarding the supernatant, and repeating the water washing and centrifugation operation three times. Finally, adding 3 times the volume of deionized water to the precipitate obtained, and stirring thoroughly; (e) adjusting the pH of the starch solution obtained in step (d) to 7.0±0.1 with 1 mol / L HCl, and then centrifuging at 3000 g / min for 15 min, and discarding the supernatant for later use; (f) Dry at 60°C, grind into powder, and pass through a 100-mesh sieve for later use.

4. The preparation process according to claim 2 or 3, characterized in that: The acid hydrolysis step comprises: (a) adding 1.5 times (w / v) 1.5-2.0 mol / L HCl solution to the prepared rice starch, stirring evenly and then placing at a constant temperature of 40° C. for 3 h; (b) adjusting the pH of the solution to 6.5±0.1 with 9-11% (w / v) NaOH solution, centrifuging at 1000 g / min for 5 min, discarding the supernatant, and repeating the water washing and centrifugation operation for 3 times, and discarding the supernatant for later use; (c) Dry at 40°C, grind into powder, and pass through a 100-mesh sieve for later use.

5. The preparation process according to any one of claims 2 to 4, characterized in that: The hot pressing-cooling cycle modification treatment step comprises: (a) preparing a slurry of hydrolyzed rice starch and deionized water in a ratio of 1:5, and stirring at a constant temperature of 85° C. for 25 to 35 minutes; (b) placing the starch slurry in a high pressure cooking pot at 135° C. and cooking for 25 to 35 minutes; (c) The starch slurry after high temperature and high pressure cooking is refrigerated at 4°C for 20±2h; (d) repeating the hot pressing-cooling and refrigeration steps three times; (e) The starch slurry obtained above was filtered through a 100-mesh sieve and then set aside.

6. The preparation process according to any one of claims 2 to 5, characterized in that: The step of compounding with food-grade calcium ions comprises: (a) The calcium ions include but are not limited to food grade calcium chloride, calcium hydrogen phosphate and calcium lactate; (b) adding food-grade calcium salt to the starch slurry after the hot pressing-cooling treatment and stirring the mixture thoroughly, wherein the calcium ion addition ratio is 15-20% (calculated on a starch dry basis); (c) treating the prepared starch slurry at 90-95°C for 30 min, then treating it at 115-125°C for 20 min, and finally storing it at 4°C for 20±2 h; (d) Dry at 60°C, grind into powder, and pass through a 100-mesh sieve to obtain the finished product.

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