Anti-digestion starch-based product and preparation method thereof

Abstract

The invention relates to the technical field of food, and discloses an anti-digestion starch-based product and a preparation method thereof. The method comprises the following steps: mixing starch and water-soluble hemicellulose to obtain a mixture, heating the mixture to 40-60 DEG C for the first time, then heating to 75-155 DEG C for the second time, keeping constant temperature, and then cooling; wherein the heating rate of the second heating is 3-8 DEG C / min. After the food containing the digestion-resistant starch-based product provided by the invention is eaten, the starch digestibility is lower, and the blood sugar level is more favorably controlled.

Description

Technical Field

[0001] The invention relates to the technical field of food, and in particular to a digestion-resistant starch-based product and a preparation method thereof. Background Art

[0002] Diabetes is a metabolic disease characterized by high blood sugar, and large fluctuations in blood sugar after meals are an important cause of diabetes. There are also some functional food ingredients on the market that can control blood sugar levels. These ingredients are added to conventional starch foods instead of ordinary starch. After eating foods containing this ingredient, the starch digestibility can be reduced to a certain extent, thereby controlling blood sugar levels. However, the starch digestibility of this raw material currently available on the market still has significant room for improvement after application, and the level of blood sugar increase after consumption is still high. Therefore, it is also necessary to develop food additives with lower starch digestibility after application. Summary of the invention

[0003] The purpose of the present invention is to overcome the above-mentioned problems existing in the prior art and to provide a digestion-resistant starch-based product and a preparation method thereof. After eating food containing the digestion-resistant starch-based product provided by the present invention, the starch digestibility is lower, which is more conducive to controlling blood sugar levels.

[0004] In order to achieve the above object, the present invention provides a method for preparing a digestion-resistant starch-based product, the method comprising: mixing starch and water-soluble hemicellulose to obtain a mixture, heating the mixture to 40-60° C. for the first time, then heating the mixture to 75-155° C. for the second time, maintaining the constant temperature, and then cooling the mixture;

[0005] The second heating rate is 3-8°C / min.

[0006] A second aspect of the present invention provides a digestion-resistant starch-based product prepared by the method described above.

[0007] Compared with foods that do not contain resistant starch products, or foods that contain resistant starch products already available on the market, the starch digestibility of foods containing the resistant starch-based products provided by the present invention is significantly lower. In addition, the products provided by the present invention are prepared with safe raw materials, and are therefore healthier and more suitable for use in food production. DETAILED DESCRIPTION

[0008] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0009] In a first aspect, the present invention provides a method for preparing a digestion-resistant starch-based product, the method comprising: mixing starch and water-soluble hemicellulose to obtain a mixture, first heating the mixture to 40-60°C (for example, 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, and a range formed by any two of the above values ​​and a value within the range), then second heating the mixture to 75-155°C, maintaining a constant temperature, and then cooling the mixture;

[0010] The second heating rate is 3-8°C / min.

[0011] The inventors of the present invention have found in their research that when water-soluble hemicellulose and starch are treated in the above manner, the obtained product can be used in food processing to obtain food with significantly lower starch digestibility after consumption, thereby better controlling the degree of increase in blood sugar. In addition, the above-mentioned preparation raw materials are safe, so the digestion-resistant starch-based product provided by the present invention is healthier and more suitable for use in food production.

[0012] Preferably, the heating rate of the first heating is higher than the heating rate of the second heating.

[0013] Preferably, the heating rate of the first heating is 18-26 (for example, it can be 18, 19, 20, 21, 22, 23, 24, 25, 26 and a range formed by any two of the above values ​​and a value within the range) °C / min.

[0014] Preferably, the heating rate of the second heating is 4.8-6.2 (for example, it can be 4.8, 5, 5.2, 5.4, 5.6, 5.8, 6, 6.2, and a range formed by any two of the above values, and a value within the range) °C / min.

[0015] The inventors of the present invention have found in their research that when the mixed liquid undergoes the process as described above, the resulting digestion-resistant starch-based product can better reduce the starch digestibility.

[0016] According to the present invention, preferably, the second temperature is raised to 85-150 (for example, it can be 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150 and the range formed by any two of the above values ​​and the values ​​within the range) °C.

[0017] It is understandable that in general households or restaurants, the cooking temperature is 85-100°C, and in the production of food industry, such as the production of pre-prepared dishes, the products are generally sterilized at 140-150°C. The inventors of the present invention have found that by using the method of the present invention, when the constant temperature (i.e., the target temperature of the second heating) is 80-150°C, a product with good digestion resistance can be obtained. Therefore, the method provided by the present invention is applicable to daily life or the food industry.

[0018] According to the present invention, preferably, the constant temperature time is 2-10 min, more preferably 4.5-6.5 (for example, it can be 4.5, 5, 5.5, 6, 6.5) min.

[0019] According to the present invention, preferably, the cooling method includes: first cooling the mixture to 40-60°C (for example, it can be 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 56°C, 58°C, 60°C and values ​​within the range formed by any two of the above values) at a cooling rate of 3.5-7.5 (for example, it can be 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5 and values ​​within the range formed by any two of the above values) °C / min, keeping warm for 1.5-3.5 (for example, it can be 1.5, 2, 2.5, 3, 3.5 and values ​​within the range formed by any two of the above values) min, and then naturally cooling the mixture to room temperature.

[0020] More preferably, the cooling rate of the first cooling is 4.8-6.2 (for example, it can be 4.8, 5, 5.2, 5.4, 5.6, 5.8, 6, 6.2, and a range formed by any two of the above values, and a value within the range) °C / min.

[0021] The inventors of the present invention have found that the specific heating, constant temperature and cooling processes as described above can further ensure that the prepared digestion-resistant starch-based product has good digestion resistance. In order to make the temperature or material conditions at various locations in the mixture more uniform, the above process can be carried out under stirring, for example, the stirring speed of the first 10s of the first heating process can be 900-980rpm, and the stirring speed of the remaining first heating process, the second heating process, the constant temperature process and the first cooling process can be 140-180rpm, and stirring is not required during the natural cooling process.

[0022] It is understood that the starch and the water-soluble hemicellulose are mixed in the presence of a dispersant, which is generally water. The starch, water and the water-soluble hemicellulose can be mixed and then allowed to stand at room temperature for 8-15 minutes to stabilize the mixture before subsequent heat treatment.

[0023] According to the present invention, preferably, the mass ratio of starch to water-soluble hemicellulose is (7-16): 1, more preferably (9.5-12.5): 1. The inventors of the present invention further found in the study that when the above range is met, the digestion resistance of the prepared product can be further guaranteed, and the color of the product can be fully guaranteed to be light amber, and when used for processing products, a better appearance can be obtained.

[0024] According to the present invention, preferably, in starch, the mass of amylose accounts for more than 58wt% of the total mass of starch, and more preferably is 60-78 (for example, it can be 60, 62, 64, 66, 68, 70, 72, 74, 76, 78 and the range formed by any two of the above values ​​and the values ​​within the range) wt%.

[0025] Preferably, the weight average molecular weight of starch is (9×10 5 )-(9×10 7 )g / mol.

[0026] According to the present invention, preferably, in the mixture, the mass content of starch is 7-9.3 (for example, it can be 7, 7.2, 7.5, 7.8, 8, 8.2, 8.5, 8.8, 9, 9.3 and the range formed by any two of the above values ​​and the value within the range) wt%.

[0027] When the above conditions are met, the digestion resistance of the prepared product can be further guaranteed.

[0028] According to the present invention, preferably, the weight average molecular weight of the water-soluble hemicellulose is (3-9)×10 5 Da, the molecular weight distribution index is 1-140 (for example, it can be 1, 2, 10, 20, 40, 60, 80, 100, 120, 130, 140 and the range formed by any two of the above values ​​and the value within the range). The molecular weight distribution index is Mw / Mn, the ratio of the weight average molecular weight to the number average molecular weight.

[0029] It can be understood that hemicellulose is a type of heteropolysaccharide. Different raw material sources lead to differences in the components of hemicellulose. Its monosaccharide composition can include D-xylose, L-arabinopyranose, D-glucose, D-galactose, D-mannose and a small amount of uronic acid. According to the different monosaccharide compositions, hemicellulose generally includes galactans (mainly arabinogalactose), xyloglucans (with glucan as the main chain, connected by β-1,4 glycosidic bonds, and a large number of xylose side chains connected to the 6th position of the glycosidic bond), mannans (mainly mannose chain molecules connected by β-1,4 glycosidic bonds), and xylans (with xylan as the main chain, connected by β-1,4 glycosidic bonds, which can be extracted from a variety of plants, such as grass plants). Water-soluble hemicellulose is also a polymer composed of different types of monosaccharides (such as xylose, arabinose and galactose, etc.). The monosaccharides obtained by hydrolyzing the water-soluble hemicellulose have a composition and content that are not particularly limited and are related to the composition of the water-soluble hemicellulose itself.

[0030] According to a particularly preferred embodiment of the present invention, the method for preparing the water-soluble hemicellulose comprises:

[0031] (1) subjecting a material liquid containing corn bran to a first enzymatic hydrolysis in the presence of α-amylase; subjecting the material after the first enzymatic hydrolysis to a second enzymatic hydrolysis in the presence of alkaline protease, and performing a first solid-liquid separation after inactivating the enzyme;

[0032] (2) mixing the solid phase obtained in step (1) with an alkali to obtain an alkali-containing mixed liquid, and subjecting the mixed liquid to an alkali treatment; subjecting the alkali-treated material to a second solid-liquid separation, and taking a supernatant;

[0033] (3) The supernatant is mixed with an organic reagent to obtain a precipitate.

[0034] Among them, the obtained precipitate is water-soluble hemicellulose. The water-soluble hemicellulose prepared by the above method can further ensure that a digestion-resistant starch-based product with a lower starch digestibility after use is obtained, and can also meet the above requirements of weight average molecular weight and molecular weight distribution index. In addition, the hemicellulose obtained by using gramineous plants as raw materials is xylan (mainly 4-O-methyl glucuronic acid arabinoxylan, and xylan is the main chain, connected by β-1,4 glycosidic bonds). After the water-soluble hemicellulose prepared in this way is hydrolyzed, monosaccharides such as xylose, arabinose, galactose and glucose can be obtained, and the amount of xylose can account for 45-60wt% of the total monosaccharide amount, and the amount of arabinose can account for 30-40wt% of the total monosaccharide amount. It can also contain galactose and glucose, and the amount of the two is not particularly limited, such as the amount of galactose can account for 5-12wt% of the total monosaccharide amount, and the amount of glucose can account for 2-7wt% of the total monosaccharide amount.

[0035] According to the present invention, preferably, in step (1), in the slurry containing corn bran, the average particle size of corn bran is 0.01-0.6 mm, preferably 0.05-0.4 mm (for example, it can be 0.05 mm, 0.1 mm, 0.15 mm, 0.18 mm, 0.2 mm, 0.23 mm, 0.25 mm, 0.28 mm, 0.3 mm, 0.4 mm, and the range formed by any two of the above values ​​and the value within the range).

[0036] According to the present invention, preferably, in step (1), the weight content of corn bran in the corn bran-containing liquid is 4-11 (for example, it can be 4, 5, 6, 6.25, 6.5, 6.8, 7, 7.5, 7.8, 8, 8.2, 8.5, 9, 10, 11 and the range formed by any two of the above values ​​and the values ​​within the range) weight %.

[0037] It can be understood that the feed liquid containing corn bran is a material obtained by mixing corn bran and water. The corn bran can be washed, decolorized (sodium hypochlorite solution can be mixed with corn bran for decolorization, and the amount of sodium hypochlorite used can be 30-50g relative to 100g of corn bran; then centrifuged, and the solid phase is taken for subsequent operations), dried, and crushed to the above degree, and then mixed with water to obtain a feed liquid with the above corn bran content.

[0038] According to the present invention, preferably, in step (1), relative to 100g of corn bran, the amount of α-amylase used is 40000-80000U (for example, it can be 40000U, 50000U, 60000U, 70000U, 80000U, and the range formed by any two of the above values, and the value within the range), and the amount of alkaline protease used is 180000-500000U (for example, it can be 180000U, 200000U, 300000U, 400000U, 500000U, and the value within the range formed by any two of the above values, and the value within the range).

[0039] The enzyme activity of α-amylase is defined as the amount of enzyme that releases 1 mg of reducing sugar from a 2 wt% soluble starch solution per hour at a temperature of 60°C and a pH of 5.6, which is defined as 1 enzyme activity unit (U).

[0040] The enzyme activity of alkaline protease is defined as the amount of enzyme that produces 1 mg of tyrosine within 1 min at a temperature of 40°C and a pH of 11, which is defined as 1 enzyme activity unit (U).

[0041] According to the present invention, preferably, in step (1), the conditions of the first enzymolysis include: a temperature of 48-62°C (for example, 48°C, 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 62°C and the range formed by any two of the above values ​​and the values ​​within the range), a time of 1.3-2.8h, and a pH of 6-6.8 (for example, 6, 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.8 and the range formed by any two of the above values ​​and the values ​​within the range). The obtained corn bran-containing liquid can be adjusted to the above pH range, and then α-amylase is added.

[0042] According to the present invention, preferably, in step (1), the conditions of the second enzymolysis include: a temperature of 48-62°C (for example, 48°C, 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 62°C and the range formed by any two of the above values ​​and the values ​​within the range), a time of 1.3-2.8h, and a pH of 8.6-9.5 (for example, 8.6, 8.8, 8.9, 9, 9.1, 9.2, 9.3, 9.5 and the range formed by any two of the above values ​​and the values ​​within the range). The material after the first enzymolysis can be adjusted to the above pH range, and then alkaline protease is added.

[0043] The method of inactivating the enzyme may be: after the second enzymolysis, placing the material in a boiling water bath to inactivate the enzyme for 5-10 minutes.

[0044] The first solid-liquid separation can be centrifugation, and the centrifugal speed can be 3000-5000rpm (for example, it can be 3000rpm, 3200rpm, 3500rpm, 3800rpm, 4000rpm, 4200rpm, 4500rpm, 4800rpm, 5000rpm and the range formed by any two of the above values ​​and the value within the range), and the time can be 4-6min (for example, it can be 4min, 5min, 6min and the range formed by any two of the above values ​​and the value within the range).

[0045] According to the present invention, preferably, in step (2), in the alkali-containing mixed solution, the mass concentration of the alkali is 1.8-7.5wt%, more preferably 2.4-6.6 (for example, it can be 2.4, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 6.6 and the range formed by any two of the above values ​​and the value within the range) wt%. The alkali can be selected from inorganic bases, such as KOH and / or NaOH, and can be used in the form of its aqueous solution.

[0046] According to the present invention, preferably, in step (2), the conditions for the alkali treatment include: a temperature of 70-90°C (for example, it can be 70°C, 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 90°C and a range formed by any two of the above values ​​and values ​​within the range), and a time of 1-3h.

[0047] Wherein, the specific mode of the second solid-liquid separation is not particularly limited, for example, it can be filtration or centrifugation. The centrifugal conditions may include a rotation speed of 3000-5000rpm (for example, it can be 3000rpm, 3200rpm, 3500rpm, 3800rpm, 4000rpm, 4200rpm, 4500rpm, 4800rpm, 5000rpm and the range formed by any two of the above values ​​and the value within the range), and a time of 4-6min (for example, it can be 4min, 5min, 6min and the range formed by any two of the above values ​​and the value within the range).

[0048] According to the present invention, preferably, before mixing the supernatant and the organic reagent, the method further comprises: adjusting the pH of the supernatant to 5.8-7.2, and concentrating and dialyzing the supernatant in sequence. The pH of the supernatant can be adjusted using glacial acetic acid or sodium hydroxide.

[0049] According to the present invention, preferably, the specific method of concentration is: rotary evaporation concentration at 38-66°C (for example, it can be 38°C, 40°C, 42°C, 45°C, 48°C, 50°C, 52°C, 55°C, 58°C, 60°C, 62°C, 65°C, 66°C and the range formed by any two of the above values ​​and the values ​​within the range) and a stirring speed of 50-100rpm.

[0050] According to the present invention, preferably, the specific method of the dialysis is: the concentrated supernatant is dialyzed for 5-14 hours at room temperature using a dialysis bag with a molecular weight cutoff of 400-3200Da (for example, 400Da, 500Da, 800Da, 1000Da, 1500Da, 2000Da, 2500Da, 3000Da, 3200Da, and a range formed by any two of the above values ​​and a value within the range). In this way, impurities such as sodium ions and acetate ions in the supernatant can be fully removed. The portion that does not pass through the dialysis bag is taken for subsequent mixing with the organic reagent.

[0051] According to the present invention, preferably, the organic reagent is selected from at least one of ethanol and acetone. The ethanol can be used in the form of anhydrous ethanol or an ethanol-water solution with an ethanol concentration of 70-95wt% (e.g., 75wt%, 95wt%), more preferably anhydrous ethanol. In the case of selecting ethanol, both the extraction effect and the cost can be taken into account at the same time.

[0052] According to the present invention, preferably, in step (3), the volume ratio of the supernatant to the organic reagent is 1:(1.8-4.2).

[0053] According to the present invention, preferably, in step (3), after the supernatant and the organic reagent are mixed, the method further comprises: subjecting the material to a third solid-liquid separation. The third solid-liquid separation may be carried out by centrifugation, the speed may be 3000-5000 rpm, and the time may be 4-6 min.

[0054] The obtained precipitate can also be dried, and the drying method can be freeze-drying. The specific operating conditions may include: vacuum condition of 0Pa<vacuum degree<20Pa, and the freeze-drying time can be 18-36h (for example, it can be 18h, 20h, 24h, 28h, 30h, 32h, 36h).

[0055] In the second aspect, the present invention provides a digestion-resistant starch-based product prepared by the method described above. Through texture property analysis, it was found that compared with corn starch gel that has not undergone resistance processing, the digestion-resistant starch-based product prepared by the present invention has stronger elasticity, smaller hardness, and better taste. Among them, the hardness of the digestion-resistant starch-based product prepared by the present invention can be 1.0-30N, the adhesion can be 0.50-4.74mJ, the elasticity can be 1-10mm, the chewiness can be 2-10mJ, and the peak viscosity can be 10-2000cP. The above-mentioned texture property analysis is carried out under the following conditions: the test probe is a cylindrical probe P / 5 with a diameter of 2cm, the probe test rate is 30mm / s, the deformation is 50%, and the trigger force is 1N. Compared with corn starch gel that has not undergone resistance processing, the starch digestibility can be reduced by 5-20% compared with the original starch digestibility.

[0056] The method of using the digestion-resistant starch-based product prepared by the present invention is not particularly limited, and can be used in a similar way to the existing digestion-resistant starch products. Generally, in the preparation of food, it replaces a part of conventional starch (such as wheat starch, corn starch, etc., which can be replaced with equal mass), so as to exert the ability to inhibit starch digestion. The digestion-resistant starch-based product prepared by the method provided by the present invention has significantly improved texture properties (such as elasticity, adhesion, elasticity, chewiness, peak viscosity), and significantly reduced digestion properties. In addition, the obtained digestion-resistant starch-based product can also be obtained by other post-treatments, such as freeze-drying (such as freeze-drying for 18-36h under a vacuum condition of 0Pa<vacuum degree<20Pa), to obtain a dry powder. When used, the dry powder can be mixed with water in proportion to form a food to supplement dietary fiber and provide energy. Compared with conventional starch or starch gel products already available on the market, the digestion rate of starch after use of the digestion-resistant starch-based product provided by the present invention is lower, and it has more advantages.

[0057] The present invention will be described in detail below through preparation examples and examples.

[0058] In the following preparation examples, α-amylase was purchased from Roan, product number 9000-90-92;

[0059] Alkaline protease was purchased from Roan, catalog number 9068-59-1;

[0060] For the product prepared in the preparation example, the monosaccharide composition and content of the sample were analyzed by PMP pre-column derivatization HPLC method (Huang Xiaolan, He Xufeng, Yang Qin, et al. Determination of monosaccharide composition of Radix Glehniae polysaccharides by PMP pre-column derivatization HPLC method [J]. Food and Fermentation Industries, 2020, 46(07): 250-256. DOI: 10.13995 / j.cnki.11-1802 / ts.022499.) and confirmed to be water-soluble hemicellulose.

[0061] The weight average molecular weight and number average molecular weight were determined using a GPC-20A gel permeation chromatograph, and narrow distribution PEO or Pullula polysaccharide standards were used as standard curves. Chromatographic column: TSKgel GMPWXL aqueous gel chromatographic column; mobile phase: 0.1NNaNO 3 +0.06% NaN 3 Aqueous solution; Flow rate: 0.6 mL / min; Test column temperature: 35°C; Detector: RID-20A differential refractometer.

[0062] In the following preparation examples, the decolorization method is to use a sodium hypochlorite solution for decolorization, wherein the amount of sodium hypochlorite used is 40 g relative to 100 g of bran. After decolorization, centrifugation is performed, and the solid phase is taken for subsequent operations.

[0063] Preparation Example 1

[0064] The corn bran is washed, decolorized, dried, and then crushed to an average particle size of 0.18 mm, and then mixed with water to obtain a feed liquid with a weight content of corn bran of 6.25% by weight.

[0065] The pH of the feed liquid was adjusted to 6.2, and α-amylase was added to the feed liquid so that the amount of α-amylase used was 60000 U relative to 100 g of corn bran. The reaction was carried out at 55° C. for 2 h to obtain a material after the first enzymolysis.

[0066] The pH of the material after the first enzymolysis was adjusted to 9, and alkaline protease was added to the material solution so that the amount of alkaline protease used was 385000 U relative to 100 g of corn bran. The reaction was carried out at 55° C. for 2 h to obtain the material after the second enzymolysis.

[0067] The material after the second enzymatic hydrolysis was then placed in a boiling water bath to inactivate the enzyme for 8 minutes, and then centrifuged at 5000 rpm for 4 minutes to obtain a solid phase, which was the corn bran treated in step (1).

[0068] (2) Mixing the corn bran treated in step (1) with a NaOH solution to obtain an alkali-containing mixed solution having a NaOH mass concentration of 5 wt%, and reacting the mixture at 80° C. for 2 h.

[0069] The alkali-treated material was centrifuged at 4000 rpm for 5 min, and the supernatant was collected.

[0070] The pH of the supernatant was adjusted to 6.3 with glacial acetic acid, and then concentrated by rotary evaporation at 50°C and 90 rpm. The concentrated supernatant was then placed in a dialysis bag with a molecular weight cutoff of 1000 Da and dialyzed at room temperature for 8 h.

[0071] (3) The liquid that did not pass through the dialysis bag was mixed with anhydrous ethanol in a volume ratio of 1:3, and centrifuged at 4000 rpm for 5 min to obtain a precipitate.

[0072] The precipitate was freeze-dried under a vacuum of 8 Pa for 24 h. The weight average molecular weight of the prepared water-soluble hemicellulose was 7.7×10 5 Da, Mw / Mn is 2. After hydrolysis by PMP pre-column derivatization HPLC method, xylose accounts for 50.62wt% of the total monosaccharides, arabinose accounts for 36.5wt% of the total monosaccharides, galactose accounts for 7.4wt% of the total monosaccharides, and glucose accounts for 3.1wt% of the total monosaccharides.

[0073] Preparation Example 2

[0074] The corn bran is washed, decolorized, dried, and then crushed to an average particle size of 0.25 mm, and then mixed with water to obtain a feed liquid with a weight content of corn bran of 8 weight%.

[0075] The pH of the feed liquid was adjusted to 6.5, and α-amylase was added to the feed liquid so that the amount of α-amylase used was 50000 U relative to 100 g of corn bran. The reaction was carried out at 60° C. for 2.5 h to obtain a material after the first enzymolysis.

[0076] The pH of the material after the first enzymolysis was adjusted to 9.3, and alkaline protease was added to the material solution so that the amount of alkaline protease used was 250000 U relative to 100 g of corn bran. The reaction was carried out at 60° C. for 2.5 hours to obtain the material after the second enzymolysis.

[0077] The material after the second enzymatic hydrolysis is then placed in a boiling water bath to inactivate the enzyme for 10 minutes, and then centrifuged at 4000 rpm for 5 minutes to obtain a solid phase, which is the corn bran treated in step (1).

[0078] (2) Mixing the corn bran treated in step (1) with a NaOH solution to obtain an alkaline mixed solution having a NaOH mass concentration of 2.5 wt%, and reacting the mixture at 76° C. for 2.5 h.

[0079] The alkali-treated material was centrifuged at 4000 rpm for 5 min, and the supernatant was collected.

[0080] The pH of the supernatant was adjusted to 6.6 with glacial acetic acid, and then concentrated by rotary evaporation at 45°C and 80 rpm. The concentrated supernatant was then placed in a dialysis bag with a molecular weight cutoff of 2000 Da and dialyzed at room temperature for 10 hours.

[0081] (3) The liquid that did not pass through the dialysis bag was mixed with anhydrous ethanol in a volume ratio of 1:4 and centrifuged at 4000 rpm for 5 min to obtain a precipitate.

[0082] The precipitate was freeze-dried under a vacuum of 15 Pa for 24 h. The weight average molecular weight of the prepared water-soluble hemicellulose was 6.7×10 5 Da, Mw / Mn is 120. After hydrolysis by PMP pre-column derivatization HPLC method, xylose accounts for 49.40wt% of the total monosaccharides, arabinose accounts for 35.6wt% of the total monosaccharides, galactose accounts for 7.2wt% of the total monosaccharides, and glucose accounts for 2.7wt% of the total monosaccharides.

[0083] The following examples were carried out in an RVA (Rapid Visco Analyzer).

[0084] Example 1

[0085] Take the weight average molecular weight (8.5×10 6 g / mol) of starch (the mass of amylose accounts for 70wt% of the total mass of starch), water, and the water-soluble hemicellulose obtained in Preparation Example 1 are mixed, the mass ratio of starch to water-soluble hemicellulose is 11:1, and the mass content of starch in the obtained mixed solution is 8wt%. The mixed solution is allowed to stand at room temperature for 10 minutes.

[0086] The mixed solution was first heated to 50°C at a heating rate of 23°C / min; then the mixed solution was second heated to 95°C at a heating rate of 5.3°C / min, and the temperature was kept constant for 5 minutes. Then the temperature of the mixed solution was first cooled to 50°C at a cooling rate of 5.3°C / min, and kept warm for 1 minute. In the above process, the stirring speed was 960rpm for the first 10s of the heating process, and the stirring speed was 160rpm for the remaining heating process, the constant temperature process of 95°C and the first cooling process. Then the mixed solution was naturally cooled to room temperature within 2 hours (without stirring). A digestion-resistant starch-based product was obtained.

[0087] Example 2

[0088] Take the weight average molecular weight (3.99×10 6 g / mol) of starch (the mass of amylose accounts for 75wt% of the total mass of starch), water, and the water-soluble hemicellulose obtained in Preparation Example 1 were mixed, the mass ratio of starch to water-soluble hemicellulose was 11.5:1, and the mass content of starch in the obtained mixed solution was 8.5wt%. The mixed solution was allowed to stand at room temperature for 12 minutes.

[0089] The mixed solution was first heated to 53°C at a heating rate of 25°C / min; then the mixed solution was second heated to 140°C at a heating rate of 5.6°C / min, and the temperature was kept constant for 5.3 minutes. Then the temperature of the mixed solution was first cooled to 53°C at a cooling rate of 5.6°C / min, and kept warm for 2 minutes. In the above process, the stirring speed of the first 10s of the heating process was 920rpm, and the stirring speed of the remaining heating process, the constant temperature process of 140°C and the first cooling process was 150rpm, and then the mixed solution was naturally cooled to room temperature (without stirring) within 2 hours. A digestion-resistant starch-based product was obtained.

[0090] Example 3

[0091] Take the weight average molecular weight (1.0×10 7 g / mol) of starch (the mass of amylose accounts for 68wt% of the total mass of starch), water, and the water-soluble hemicellulose obtained in Preparation Example 1 were mixed, the mass ratio of starch to water-soluble hemicellulose was 10.2:1, and the mass content of starch in the obtained mixed solution was 8.7wt%. The mixed solution was allowed to stand at room temperature for 8 minutes.

[0092] The mixed solution was first heated to 48°C at a heating rate of 22°C / min; then the mixed solution was heated to 100°C for the second time at a heating rate of 5.8°C / min, and the temperature was kept constant for 4.8 minutes. Then the temperature of the mixed solution was first cooled to 48°C at a cooling rate of 5.8°C / min, and kept warm for 3 minutes. In the above process, the stirring speed was 940 rpm for the first 10 seconds of the heating process, and the stirring speed was 170 rpm for the remaining heating process, the constant temperature process of 100°C and the first cooling process. Then the mixed solution was naturally cooled to room temperature within 2 hours (without stirring). A digestion-resistant starch-based product was obtained.

[0093] Example 4

[0094] The method of Example 1 was followed, except that the water-soluble hemicellulose obtained in Preparation Example 1 was replaced by the water-soluble hemicellulose obtained in Preparation Example 2.

[0095] Example 5

[0096] The method of Example 1 was followed, except that the mass ratio of starch to water-soluble hemicellulose was 15:1, and the total mass amount of starch and water-soluble hemicellulose was consistent with that in Example 1.

[0097] Example 6

[0098] The method of Example 1 was followed, except that the mass content of starch in the mixed solution was 10 wt %. The mass ratio of starch to water-soluble hemicellulose was the same as that in Example 1.

[0099] Example 7

[0100] The method of Example 1 was followed, except that in the mixed solution, the water-soluble hemicellulose was purchased from Shaanxi Baicao Xintian Power Factory, the model was 95 type sugar powder, and its weight average molecular weight was 1.0×10 3 Da, Mw / Mn is 1.51.

[0101] Example 8

[0102] The method of Example 1 is followed, except that the second heating rate is 3° C. / min. The first cooling rate is 3° C. / min.

[0103] Example 9

[0104] The method of Example 1 was followed, except that after the temperature was raised to 95° C., the temperature was maintained constant for 7 minutes.

[0105] Example 10

[0106] The method of Example 1 was followed, except that the mixed solution was heated directly from room temperature to 95° C. at a heating rate of 23° C. / min.

[0107] Embodiment 11

[0108] The method of Example 1 was followed, except that after the constant temperature at 95° C. was completed, the mixed solution was directly cooled naturally to room temperature.

[0109] Comparative Example 1

[0110] The method of Example 1 was followed, except that the mixed solution was heated directly from room temperature to 140°C at a heating rate of 30°C / min, the temperature was maintained at that constant for 1 min, and the mass ratio of starch to water-soluble hemicellulose was 20:1.

[0111] Comparative Example 2

[0112] The method of Example 1 is followed, except that the mixed solution is heated directly from room temperature to 80°C at a heating rate of 30°C / min, and the second heating rate is 3°C / min to 140°C, and the constant temperature is maintained for 20 minutes, and the mass of straight-chain starch in the starch accounts for 30wt% of the total mass of the starch.

[0113] Test Example 1

[0114] The digestion-resistant starch-based product provided by the present invention is used to replace a portion of conventional starch when preparing starch food, thereby exerting the ability to inhibit starch digestion. The following experiment illustrates the inhibition of starch digestion by the digestion-resistant starch-based product provided by the present invention when used.

[0115] Rapidly digestible starch: refers to the starch that is digested and absorbed in the small intestine within 20 minutes. Rapidly digestible starch % refers to the percentage of this part of starch in the total amount of starch, reflecting the starch digestibility within 0-20 minutes.

[0116] Slowly digestible starch: refers to the starch that is digested and absorbed in the small intestine within 20-120 minutes. Slowly digestible starch % refers to the percentage of this part of starch in the total amount of starch, reflecting the starch digestibility within 20-120 minutes.

[0117] Resistant starch: starch that cannot be digested and absorbed within 120 minutes. This part will not be digested and absorbed in the small intestine, but can reach the colon and be fermented by colonic microorganisms, and then play an effective physiological role. Resistant starch % refers to the percentage of this part of starch in the total amount of starch.

[0118] The digestion-resistant starch-based products prepared in the examples and comparative examples were taken and the starch content therein was measured using a total starch assay kit (AA / AMG) from Megazyme, Ireland, USA, which is the total starch content.

[0119] The following experiments were conducted using 50 mg dry weight of conventional wheat starch and the digestion-resistant starch-based products prepared in the examples and comparative examples (in an amount such that the dry weight of starch was also 50 mg):

[0120] Disperse the digestion-resistant starch-based product (or conventional wheat starch) in 2 mL of distilled water, add 8 mL of enzyme solution (containing 0.33 mg of pancreatin and 16.67 μL of amyloglucosidase) in sodium acetate buffer (0.2 M, pH 6.0) at 37°C. Stir at 37°C and 300 rpm, and take 0.1 mL at 0, 20, and 120 min and mix with 0.9 mL of anhydrous ethanol to stop the enzymatic reaction.

[0121] For the above liquids after stopping the enzymatic reaction, the digested starch content was obtained by using the total starch assay kit (AA / AMG) and the glucose content assay kit (GOPOD Format) of Megazyme, Ireland, USA. The ratio of the digested starch content measured at each time to the total starch content is the rapidly digestible starch % and the slowly digestible starch %. The resistant starch % is deducted from the slowly digestible starch % from 100%.

[0122] The results are shown in Table 1.

[0123] Table 1

[0124]

[0125] It can be understood that the higher the percentage of resistant starch in the total amount of starch, the lower the starch digestibility when it is used in food, and the better the digestion resistance. Whether it is partially replacing conventional starch or completely replacing conventional starch, the higher the resistant starch content, the better the digestion resistance is.

[0126] From the results in Table 1, it can be seen that the digestion-resistant starch-based product prepared by the method (embodiment) of the present invention has a good digestion-resistant effect. It can be seen that the digestion-resistant starch-based products of Examples 1-4 have a better digestion-resistant effect than the digestion-resistant starch-based products of Examples 5-11. It shows that when the preferred water-soluble hemicellulose and the preferred preparation conditions of the digestion-resistant starch-based product of the present invention are adopted, the resistance effect will be better. The digestion-resistant starch-based product of the present invention can completely replace ordinary wheat starch, can significantly reduce the fast digestion rate, and can increase the slow digestion rate.

[0127] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing a digestion-resistant starch-based product, characterized in that: The method comprises: mixing starch and water-soluble hemicellulose to obtain a mixture, heating the mixture to 40-60°C for the first time, then heating the mixture to 75-155°C for the second time, maintaining the constant temperature, and then cooling the mixture; The second heating rate is 3-8°C / min.

2. The method according to claim 1, wherein: The heating rate of the first heating is higher than the heating rate of the second heating; And / or, the heating rate of the first heating is 18-26°C / min; And / or, the heating rate of the second heating is 4.8-6.2°C / min.

3. The method according to claim 1 or 2, wherein: Second, heat up to 85-150°C; And / or, the constant temperature time is 2-10 min, preferably 4.5-6.5 min.

4. The method according to claim 1 or 2, wherein: The cooling method includes: first cooling the mixture to 40-60°C at a cooling rate of 3.5-7.5°C / min, keeping the temperature for 1.5-3.5min, and then naturally cooling the mixture to room temperature; Preferably, the first cooling rate is 4.8-6.2°C / min.

5. The method according to claim 1 or 2, wherein: The mass ratio of starch to water-soluble hemicellulose is (7-16):1, preferably (9.5-12.5):1; and / or, in the starch, the mass of the amylose accounts for more than 58wt% of the total mass of the starch, preferably 60-78wt%; And / or, the weight average molecular weight of starch is (9×10 5 )-(9×10 7 )g / mol; and / or, in the mixture, the mass content of starch is 7-9.3wt%; and / or, the weight average molecular weight of the water-soluble hemicellulose is (3-9)×10 5 Da, molecular weight distribution index is 1-140.

6. The method according to claim 1 or 2, wherein: The preparation method of the water-soluble hemicellulose comprises: (1) subjecting a material liquid containing corn bran to a first enzymatic hydrolysis in the presence of α-amylase; subjecting the material after the first enzymatic hydrolysis to a second enzymatic hydrolysis in the presence of alkaline protease, and performing a first solid-liquid separation after inactivating the enzyme; (2) mixing the solid phase obtained in step (1) with an alkali to obtain an alkali-containing mixed liquid, and subjecting the mixed liquid to an alkali treatment; subjecting the alkali-treated material to a second solid-liquid separation, and taking a supernatant; (3) The supernatant is mixed with an organic reagent to obtain a precipitate.

7. The method according to claim 6, wherein: In step (1), in the feed liquid containing corn bran, the average particle size of corn bran is 0.01-0.6 mm, preferably 0.05-0.4 mm; And / or, in step (1), the weight content of corn bran in the corn bran-containing liquid is 4-11 weight %; And / or, in step (1), relative to 100g of corn bran, the amount of α-amylase used is 40000-80000U, and the amount of alkaline protease used is 180000-500000U; And / or, in step (1), the conditions of the first enzymatic hydrolysis include: temperature of 48-62°C, time of 1.3-2.8h, pH of 6-6.8; And / or, in step (1), the conditions of the second enzymatic hydrolysis include: temperature of 48-62°C, time of 1.3-2.8h, pH of 8.6-9.5; And / or, in step (2), the mass concentration of the alkali in the alkali-containing mixed solution is 1.8-7.5wt%, preferably 2.4-6.6wt%; And / or, in step (2), the conditions of the alkali treatment include: temperature of 70-90° C. and time of 1-3 h.

8. The method according to claim 6, wherein: Before mixing the supernatant and the organic reagent, the method further comprises: adjusting the pH of the supernatant to 5.8-7.2, and sequentially concentrating and dialyzing the supernatant; Preferably, the specific method of concentration is: rotary evaporation concentration at 38-66°C and a stirring speed of 50-100 rpm; Preferably, the specific method of dialysis is: dialyzing the concentrated supernatant for 5-14 hours at room temperature using a dialysis bag with a molecular weight cutoff of 400-3200Da.

9. The method according to claim 6 or 8, wherein: The organic reagent is selected from at least one of ethanol and acetone; and / or, in step (3), the volume ratio of the supernatant to the organic reagent is 1:(1.8-4.2); And / or, in step (3), after mixing the supernatant and the organic reagent, the method further comprises: performing a third solid-liquid separation on the material.

10. A digestion-resistant starch-based product prepared by the method of any one of claims 1 to 9.

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