Methods for annealing pea starch

Abstract

This invention relates to a method for preparing legume starch with a high slow digestible fraction (SDS) content, characterized by the following steps: 1) preparing a starch milk with a dry matter content of 30% to 40%, preferably 32% by weight; 2) heating the starch milk thus prepared to a temperature 10°C to 15°C below its gelatinization temperature; 3) maintaining the obtained starch milk at the temperature for 45 minutes to 7 hours, preferably 1 hour to 6 hours, while stirring; and 4) collecting, filtering, and drying the starch milk thus treated.

Description

[0001] This invention relates to a hydrothermal method for increasing the content of the slow-digestible fraction of pea starch.

[0002] It also involves the pea starch obtained from it. Background Technology

[0003] From a physiological perspective, most of the carbohydrates ingested during the eating process in humans or animals are in the form of starch. This is a unique energy storage molecule found in plants and is also the main component of starchy foods (pasta, flour, potatoes).

[0004] During digestion, starch molecules dissociate into linear dextran chains, which in turn dissociate into simple glucose that can be absorbed by the digestive system.

[0005] Starch is digested in the mouth during chewing by an enzyme in saliva called salivary amylase.

[0006] The initial breakdown of starch is inhibited by gastric acid through the action of pancreatic amylase and intestinal amylase, but it resumes in the duodenum (the first part of the small intestine).

[0007] The continuous action of all these amylases leads to the formation of the disaccharide maltose, which itself will be converted into two monosaccharides, glucose.

[0008] Starch synthesized through biochemical processes is not only a source of carbohydrates but also one of the most widely distributed organic materials in the plant kingdom, forming the nutritional reserves needed by organisms.

[0009] Therefore, it exists naturally in the reserve organs and tissues of higher plants, specifically referring to cereal seeds (wheat, corn, etc.), legume seeds (peas, broad beans, etc.), potato or cassava tubers, roots, bulbs, stems and fruits.

[0010] Starch is a mixture of two homopolymers, amylose and amylopectin, composed of D-glucose units linked together by α(1-4) and α(1-6) bonds that cause branching in the molecular structure.

[0011] These two homopolymers have different degrees of branching and polymerization.

[0012] Amylose is slightly branched into short chains and has a molecular weight between 10,000 and 1,000,000 Daltons. This molecule consists of 600 to 1,000 glucose molecules.

[0013] Amylopectin is a long-branched molecule, with each branch consisting of 24 to 30 glucose units linked by α(1-6) bonds. Its molecular weight ranges from 1,000,000 to 100,000,000 Daltons, and its degree of branching is approximately 5%. The total chain can comprise 10,000 to 100,000 glucose units.

[0014] The ratio between amylose and amylopectin depends on the plant source of the starch.

[0015] Starch is stored in reserve organs and tissues in granular form (i.e., semi-crystalline granules).

[0016] This semi-crystalline form is mainly due to the amylopectin macromolecules.

[0017] In its natural state, starch granules have a crystallinity between 15% and 45%, which depends mainly on the plant source and the extraction method used.

[0018] When granular starch is placed under polarized light, it displays a typical black cross pattern under a microscope, known as the "Maltese Cross" pattern.

[0019] This positive birefringence phenomenon is attributed to the semi-crystalline structure of these particles: the average orientation of the polymer chains is radial.

[0020] For a detailed description of granular starch, please refer to Chapter 2 of S. Perez’s book “Initiation to macromolecular chemistry and physico-chemistry”, 1st edition, 2000, Vol. 13, pp. 41-86, French Polymer Research and Application Group.

[0021] Depending on the plant source, the moisture content of dry starch varies from 12% to 20% by weight. This moisture content obviously depends on the residual moisture of the medium (for starch with aw=1, a maximum of 0.5 grams of water can be locked in per gram of starch).

[0022] In excess water, heating a starch suspension to near its gelatinization temperature causes the particles to expand irreversibly, dispersing them and then dissolving.

[0023] These characteristics are what give starch its interesting technical properties.

[0024] Starch granules will rapidly expand and lose their semi-crystalline structure (birefringence loss) within a given temperature range known as the "gelatinization range".

[0025] Within a temperature range of approximately 5°C to 10°C, all particles will expand to their maximum extent. The resulting paste consists of swollen particles constituting the dispersed phase and molecules (primarily amylose) that thicken the continuous aqueous phase.

[0026] The rheological properties of a paste depend on the relative proportions of the two phases and the expansion volume of the particles. The range of gelatinization depends on the plant source of the starch.

[0027] The starch paste reaches its maximum viscosity when it contains a large number of highly expanded particles. Upon continued heating, the particles burst, and the material disperses throughout the medium; dissolution only occurs at temperatures above 100°C.

[0028] Amylose-lipid complexes exhibit delayed swelling because this binding prevents the interaction of amylose with water molecules, and temperatures above 90°C are required for the granules to fully swell (as seen in corn starch-lipid complexes).

[0029] The disappearance of particles and the dissolution of macromolecules lead to a decrease in viscosity.

[0030] Due to the incompatibility between amylose and amylopectin, lowering the temperature of starch paste (by cooling) causes macromolecules to become insoluble and separate into phases, which then leads to the crystallization of these macromolecules.

[0031] This phenomenon is known as condensation.

[0032] When starch paste contains amylose, this molecule will be the first to precipitate.

[0033] The precipitation will involve the formation of double helices, which combine to form “crystals” (Type B), which will form a three-dimensional grid through the bonding regions.

[0034] The grid forms extremely rapidly, within hours. During this process, double helices, bonded by hydrogen bridges, replace water molecules bound to the helices, causing significant dehydration and shrinkage.

[0035] The structural complexity and physicochemical properties of starch mean that this type of carbohydrate will be assimilated and digested in different ways in humans and animals.

[0036] This is why starch can be classified into three categories based on its digestibility: fast digestion, slow digestion, or difficult digestion.

[0037] Starch, which exists in natural granular / semi-crystalline form, can be converted into "rapidly digestible starch" (RDS) when exposed to heat, pressure and / or humidity during food processing.

[0038] Compared to RDS, slow-digestible starch (SDS) takes longer to be broken down by digestive enzymes because it still has a crystalline structure and is not easily digested by enzymes.

[0039] The digestion of this SDS portion results in a moderate and regular release of glucose into the bloodstream. Next, we'll discuss starches with a low glycemic index (low GI).

[0040] Foods high in SDS result in lower postprandial glycemic response and lower insulin response compared to foods containing only small amounts of SDS.

[0041] Conversely, RDS are nutrient-rich carbohydrates because they release glucose into the bloodstream more quickly.

[0042] As for so-called resistant starch (RS), it is assimilated by intestinal enzymes into indigestible fiber (such as corn bran, oat fiber, and gums).

[0043] In the existing technology, total starch is considered to be the sum of its three components RDS, SDS and RS.

[0044] Therefore, different types of starch are digested at different rates in the human digestive system.

[0045] Therefore, SDS is considered to be digested more slowly than RDS. RS is the starch fraction that resists enzyme digestion in the small intestine. It will ferment in the large intestine and can therefore be considered dietary fiber.

[0046] Therefore, SDS and RS portions are sources of available glucose.

[0047] SDS is naturally found in certain uncooked grains (such as wheat, rice, barley, rye, and corn) and legumes (such as peas, broad beans, and lentils).

[0048] SDS content is mainly affected by starch gelatinization during subsequent food processing.

[0049] In fact, during this process, exposure to temperature, pressure, and humidity causes SDS to partially convert into RDS, making starch easier for enzymes to digest.

[0050] This conversion can be minimized by controlling cooking conditions to limit starch gelatinization.

[0051] Therefore, the original SDS content in a composition or food will depend on its preparation method.

[0052] Therefore, it can be seen that foods containing high levels of SDS include certain pasta, rice, barley, and certain biscuits, while breakfast puffed cereals or bread typically contain very low levels.

[0053] The SDS content of food is usually determined by in vitro methods, which were developed by HNENGLYST et al. (published in the European Journal of Clinical Nutrition, Vol. 46, pp. 33-50, 1992).

[0054] The ENGLYST method of 1992 will be referred to in the following description.

[0055] This method was developed to mimic the enzymatic digestion that occurs in the small intestine.

[0056] In the presence of digestive enzymes, the product or starch sample is added to a test tube, and the release of glucose is measured during the 120-minute reaction.

[0057] Therefore, this method can distinguish:

[0058] -RDS section, by measuring fast-release glucose (abbreviated as "RAG"), in this case, measuring the glucose released between 0 and 20 minutes;

[0059] -SDS section, by measuring slow-release glucose (abbreviated as "SAG"), in this case, measuring glucose released between 20 and 120 minutes;

[0060] The -RS portion corresponds to glucose that has not been released after 120 minutes and is calculated using the ENGLYST method by the following formula: TS – (RDS + SDS), where TS = total starch (total starch is considered equal to 100% when analyzing starch itself).

[0061] Foods rich in glucose, containing more than 50% by weight of available carbohydrates derived from starch, with at least 40% by weight of SDS, are generally considered to be SDS-rich foods.

[0062] Therefore, compared to SDS-poor foods, they are recommended for use to limit glycemic index and insulin production.

[0063] Of all the starches commonly used in these food applications, legume starches, more specifically pea starch, are a good choice.

[0064] In fact, pea seeds are known for their high starch content (between 55% and 70% by dry weight) and low glycemic index (Ratnayake et al., 2002, "Pea starch, composition, structure and properties – A review", Starch / Journal, Volume 54, pp. 217-234.

[0065] Therefore, ENGLYST believes that natural pea starch with an SDS content typically between 27% and 38% by weight is of great significance for nutritional applications.

[0066] However, in order to prepare foods with high SDS content, it is necessary to provide starch with a high content of slow-digesting carbohydrates.

[0067] In the prior art, it is known to alter the crystal structure of starch granules through annealing heat treatment.

[0068] More specifically, annealing is a term used in polymer science to describe optimizing crystallization by cooking at temperatures below the polymer's melting point, thereby inducing the growth of crystalline regions, refining the crystals, and making the structure more stable.

[0069] When applied to starch, annealing is defined as a hydrothermal process that involves heating starch granules in an excess of water to a temperature above the glass transition temperature but below the initial gelatinization temperature.

[0070] During the annealing process, the starch granules are designed to undergo limited but reversible expansion without damaging the structure of the granules and molecules or dissolving the starch polymer molecules.

[0071] Annealing is generally considered to be associated with the recombination of starch chains and amylopectin double helixes, which leads to enhanced interactions between starch chains and the formation of a specific double helix sequence.

[0072] Annealing can significantly alter the physicochemical properties of starch granules, but has little effect on the crystal structure and molecular order of starch granules.

[0073] Physicochemical changes typically include decreased swelling power and solubility (amylose leaching). As gelatinization temperature increases and enthalpy change increases, the thermal transition range narrows, gel stability increases, and sensitivity to enzymatic digestion increases.

[0074] Certain molecular events, such as increased particle stability, particle structure reorganization, or decreased free energy, have been used to explain these physicochemical changes that occur during annealing.

[0075] Extensive research has been conducted on starch annealing using starches from various plant sources, such as corn, potatoes, wheat, rice, sago, sorghum, barley, and peas.

[0076] Pea starch has been highly regarded because it contains a higher content of amylose than many other natural starches and contains a mixture of type A and type B polymorphic structures.

[0077] In their 2013 article (published in the journal Food Bioprocess Technology, Vol. 6, pp. 3564-3575), Wang et al. pointed out that annealing slightly alters the particle and crystal structure of pea starch granules, but significantly changes their function.

[0078] Under the conditions used in their study (annealing temperature much below the gelatinization temperature -4°C for 24 to 72 hours), annealing caused irreversible slight swelling of pea starch granules and leached out some amylose molecules, although the overall crystallinity did not change significantly.

[0079] The authors concluded that annealing primarily affects the amorphous regions of starch granules, while having almost no effect on the crystalline regions.

[0080] However, they pointed out the polycrystalline transition from type A to type B, which is attributed to the double-helix space in type A microcrystals being filled with more water molecules caused by hydrothermal treatment.

[0081] Eliminating some amylose molecules between amylopectin clusters leads to a decrease in the overall stability of starch granules, resulting in significant changes in the functional properties of annealed starch.

[0082] Regarding the changes in the digestibility of annealed pea starch, the authors demonstrated using the ENGLYST method (1992) that the percentage of enzymatic hydrolysis of pea starch gradually increased over time during the 4-hour incubation period.

[0083] Therefore, they pointed out that their annealing treatment improved the in vitro digestibility of pea starch granules.

[0084] They concluded that annealing resulted in a higher RDS content by reducing the RS content to SDS and then to RDS.

[0085] This observation has also been accepted by other authors, and therefore the main purpose of the conventional annealing method used in the prior art is to make the starch of legumes, especially peas, more digestible (see the article by CHUNG et al., published in Carbohydrate Polymers, 2009, Vol. 75, pp. 436-447).

[0086] However, contrary to this technological bias, the applicant company chose to optimize this annealing technology, not to increase the RDS portion, but to increase the SDS content of legume starch, especially pea starch, which was achieved by seeking and discovering annealing operation methods that were particularly suitable for this purpose.

[0087] Detailed description

[0088] Therefore, the present invention relates to a method for preparing legume starch with a high slow-digestible fraction (SDS) content, preferably pea starch, i.e., a hydrothermal treatment method, characterized in that the method includes the following steps:

[0089] 1) Prepare a starch milk with a dry matter content of 30% to 40% by weight, preferably 32% by weight.

[0090] 2) Heat the starch milk thus prepared to a temperature 10°C to 15°C below its gelatinization temperature.

[0091] 3) Maintain the obtained starch milk at this temperature for 45 minutes to 7 hours, preferably 1 hour to 6 hours, while stirring.

[0092] 4) Collect, filter and dry the starch milk that has been treated in this way.

[0093] In this invention, "high content of slow-digesting fraction" means that the weight content of SDS is increased by 10% to 20% relative to the weight content of SDS in the raw starch, preferably by 12% to 17%.

[0094] In this invention, "legumes" refers to any plant belonging to the Cactaceae, Mimosaceae, or Fabaceae families, especially any plant belonging to the Fabaceae family, such as peas, kidney beans, broad beans, small broad beans, lentils, alfalfa, clover, or lupins.

[0095] The article by R. HOOVER et al., entitled “Composition, structure, functionality and chemical modification of legume starches: a review”, published in Can. J. Physiol. Pharmacol., 1991, Vol. 69, pp. 79-92, describes the composition, structure, functionality and chemical modification of legume starches in detail in their tables on various legumes.

[0096] Preferably, the legumes are selected from peas, kidney beans, broad beans, and fava beans.

[0097] Advantageously referring to peas, the word "peas" is considered to have the broadest meaning here, and specifically includes:

[0098] - All wild varieties of "smooth pea", and

[0099] - All mutant varieties of "round pea" and "wrinkled pea", regardless of the conventional use of the variety (human food, animal feed and / or other uses).

[0100] These mutant varieties mainly include those known as "r mutant", "rb mutant", "rug 3 mutant", "rug 4 mutant", "rug 5 mutant" and "lam mutant", as described by CL HEYDLEY et al. in their article "Development of Novel Pea Starch", Proceedings of the Symposium of the Industrial Biochemistry and Biotechnology Group of the Biochemical Society, 1996, pp. 77-87.

[0101] According to another advantageous modification, legumes (e.g., various pea or broad bean varieties) are plants whose seeds contain at least 25% starch by weight, preferably at least 40% (dry matter / dry matter).

[0102] "Legumatic starch" refers to any composition extracted in any way from legumes, particularly from plants of the Fabaceae family, having a starch content of more than 40%, preferably more than 50%, and even more preferably more than 75%, these percentages being expressed as a percentage of the dry weight of the composition to the dry weight of the composition.

[0103] Advantageously, the starch content is higher than 90% (dry matter / dry matter). Specifically, it can be higher than 95% (by weight), including higher than 98% (by weight).

[0104] "Natural" starch refers to starch that has not undergone any chemical or enzymatic modification. Preferably, the starch according to the present invention is natural starch.

[0105] According to one specific embodiment of the present invention, the method does not include the step of enzymatic treatment of starch.

[0106] To determine the basic content of its SDS fraction, pea starch according to the present invention or not, was analyzed under in vitro digestion conditions proposed by HNEnglyst et al., in “Classification and measurement of nutritionally important starch fractions”, published in Eur. J. Clin. Nutr., Vol. 46 (Supplement 2), pp. 33-50 (1992).

[0107] This method includes measuring the rapidly digestible (RDS), slowly digestible (SDS), and indigestible (resistant) (RS) starch fractions in a food.

[0108] These measurements were taken after enzymatic digestion with pancreatic enzymes, amylase, and invertase.

[0109] The glucose released was measured by colorimetry using the glucose oxidase kit Glucose GOD FS (catalog number 1 2500 99 10 923) sold by DiaSys Distribution France Sarl, following the kit instructions.

[0110] The details of the method used for digestion measurements according to the ENGLYST method are as follows.

[0111] Reagents used:

[0112] - Anhydrous sodium acetate (Catalog No.: 71184, from SIGMA)

[0113] - Benzoic acid (Catalog No.: 242381, from SIGMA)

[0114] -CaCl2 (Catalyst No.: 1.02378.0500, from Merck)

[0115] -0.1M acetic acid (Catalog No.: 33209, from SIGMA)

[0116] - Porcine pancreatic enzyme 8×USP (Catalog No.: P 7545, from SIGMA)

[0117] -Amylase EC 3.2.1.3 (from SIGMA, activity ≥260 U / ml / ≈300 AGU / ml, Cat. No. A7095)

[0118] - Invertase EC 3.2.1.26 (from SIMA, activity ≥300 units / mg solids, Cat. No. I-4504)

[0119] -Guar gum (Product No.: G4129, from SIGMA)

[0120] -66° Ethanol

[0121] Operating method :

[0122] Preparation of saturated benzoic acid solution

[0123] Weigh 4g of benzoic acid and dissolve it in 1L of reverse osmosis water, then mix. This solution can be stored at room temperature for one month.

[0124] Prepare a 1 M / L CaCl2 solution.

[0125] Weigh 1.1098 g of CaCl2 and dissolve it in 10 ml of reverse osmosis water, then mix. This solution can be stored at room temperature for one month.

[0126] Prepare a 0.1M acetate buffer solution with pH 5.2.

[0127] Weigh out 8.203g of anhydrous sodium acetate and dissolve it in 250ml of saturated benzoic acid solution.

[0128] Add 500ml of reverse osmosis water and mix.

[0129] - Adjust the pH to 5.2 + / - 0.5 using 0.1M acetic acid.

[0130] Add reverse osmosis water to the volumetric flask and bring the volume to 1000ml.

[0131] Add 4 ml of 1 M CaCl2 solution to 1 L of the prepared buffer solution.

[0132] - Mix and check the pH value.

[0133] This solution can be stored at 4°C for 1 month.

[0134] Acetate buffer solution for preparing guar gum

[0135] Weigh 750 mg of guar gum and dissolve it in 300 ml of acetate buffer.

[0136] -Continuous stirring

[0137] Preparation of the sample to be analyzed and the enzyme to be used

[0138] Sample preparation

[0139] Accurately weigh 0.8g of the dry starch to be tested.

[0140] Add 20 ml of 0.1 M pH 5.2 acetate buffer solution + guar gum.

[0141] Place the bottle in a 37°C water bath and stir for 15 minutes.

[0142] Take 0.1 ml of the solution obtained at T = 0 min, and then add 0.9 ml of 66° ethanol (i.e., dilute 10 times).

[0143] The glucose content (unit: %) was determined by colorimetry at T = 0 min.

[0144] Blanks and standards (weighing 0.5 g of anhydrous glucose) were prepared under the same conditions as the prepared samples.

[0145] Preparation of enzyme cocktails

[0146] The enzyme cocktail is intended for testing 12 samples. It should be prepared on the same day according to the following protocol.

[0147] Preparation of porcine pancreatic enzyme 8×USP

[0148] Four types of pancreatic enzyme solutions were prepared to obtain 54 ml of supernatant.

[0149] to this end:

[0150] Weigh out 2.5g of porcine pancreatin 8×USP.

[0151] Add 20ml of reverse osmosis water, then mix for 10 minutes.

[0152] Centrifuge the solution at 1500G for 10 minutes.

[0153] - Collect 13.5 ml of supernatant.

[0154] Preparation of amylase

[0155] Dilute 3.7 ml of amylase EC 3.2.1.3 solution with 4.3 ml of reverse osmosis water, then mix for 10 minutes.

[0156] Take 6 ml of fresh solution, add 54 ml of trypsin supernatant, and then mix.

[0157] Preparation of invertase

[0158] Weigh out 50mg of invertase EC 3.2.1.26.

[0159] Add 6ml of reverse osmosis water, then mix for 10 minutes.

[0160] Take 4 ml of the solution, add 54 ml of pancreatic enzyme supernatant, and then mix.

[0161] Digestion plan

[0162] Add 5 ml of enzyme cocktail to the sample preparation.

[0163] -Incubate in water at 37°C with stirring for 120 minutes.

[0164] Take 0.1 ml of the solutions obtained at T = 20 min and T = 120 min, then add 0.9 ml of 66° ethanol (i.e., dilute 10 times).

[0165] Mix and then centrifuge the sample at 1500G for 3 minutes.

[0166] - Glucose content (in %) was determined by colorimetry at T=20 min and T=120 min.

[0167] Determination of free glucose (Fg) and total glucose (Fg) content

[0168] The free glucose (Fg) content corresponds to the measurement taken at 0 min.

[0169] The total glucose (Tg) content was measured as follows:

[0170] - Take 0.25 ml of the solution obtained at T = 120 min using an Eppendorf test tube.

[0171] Add 0.25ml of 4N hydrochloric acid and mix.

[0172] Place the test tube in a 100°C water bath for 45 minutes until dry, then cool to room temperature.

[0173] Neutralize the hydrolysate with 0.25 ml of 4N sodium hydroxide.

[0174] Add 0.25ml of reverse osmosis water and mix.

[0175] - Dilute with reverse osmosis water 10 times (0.1 ml dissolved in 0.9 ml). That is, the final dilution is 40 times.

[0176] Determination of RDS, SDS, and RS content

[0177] The released glucose was measured at the following times:

[0178] -T = 0 min (initial glucose content),

[0179] -T = 20min (the amount of glucose released after 20 minutes)

[0180] -T = 120 min (the amount of glucose released after 120 minutes).

[0181] According to the ENGLYST method:

[0182]

[0183] in

[0184] -At = Absorbance (sample) - Absorbance (blank)

[0185] -Vt = Total volume (sample, unit: ml)

[0186] -C = Standard concentration (glucose, unit: ml)

[0187] -D = Dilution factor

[0188] -As = Absorbance (Standard value - Absorbance (blank))

[0189] -Wt = Dry weight (sample, unit: mg)

[0190] The RDS, SDS, and RS measurements are as follows:

[0191] -RDS=(G20–FG)×0.9

[0192] -SDS=(G120–G20)×0.9

[0193] -RS=((TG–FG)×0.9)–(RDS+SDS)

[0194] According to this method, the RDS weight content of natural pea starch is typically between 13% and 16%, the SDS weight content is between 27% and 38%, and the RS weight content is between 45% and 56%. These values ​​have a standard deviation of + / - 2% due to the inherent variability of the Englyst enzyme assay.

[0195] In order to increase the SDS content, the annealing method according to the present invention developed by the applicant company is based on precise hydrothermal treatment.

[0196] Therefore, the present invention relates to a method for preparing legume starch with a high slow-digestible fraction (SDS) content, preferably pea starch, i.e., a hydrothermal treatment method, characterized in that the method includes the following steps:

[0197] 1) Prepare a starch milk with a dry matter content of 30% to 40% by weight, preferably 32% by weight.

[0198] 2) Heat the starch milk thus prepared to a temperature 10°C to 15°C below its gelatinization temperature.

[0199] 3) Maintain the obtained starch milk at this temperature for 45 minutes to 7 hours, preferably 1 hour to 6 hours, while stirring.

[0200] 4) Collect, filter and dry the starch milk that has been treated in this way.

[0201] The first step of the method according to the invention is to prepare a legume starch milk with a dry matter content of 30% to 40%, preferably 32%, in this case, a pea starch milk.

[0202] The second step of the method according to the invention involves heating the legume starch milk to a temperature 10°C to 15°C below its gelatinization temperature, in this case pea starch, to a temperature between 48°C and 53°C, preferably about 50°C.

[0203] The applicant company recommends using a heat exchanger with a temperature not exceeding 55°C. According to one embodiment of the invention, the method does not include a gelatinization step; that is, the starch milk is never at a temperature higher than or equal to the lower limit of the "gelatinization range" temperature.

[0204] The third step of the method according to the invention is to maintain the starch milk at the temperature for 45 minutes to 7 hours, preferably 1 hour to 6 hours, or even more preferably 1 hour, while stirring.

[0205] Adjust the stirring of the reaction medium to keep the starch suspended in the reaction medium. This can be achieved by mechanical stirring using an anchor, paddle, or turbine stirrer.

[0206] Therefore, the applicant company has found that, contrary to what is recommended in the prior art, for starches with high dry matter content (described as having a dry matter weight ratio of 60%), it is not necessary to use a temperature 10°C to 15°C below their gelatinization temperature for 24 to 72 hours for gelatinization. Instead, it is preferable to treat starches with relatively low dry matter content (approximately 30% by weight) for a shorter time (not exceeding 6 hours).

[0207] This treatment can increase the SDS content of the starch after processing.

[0208] The fourth and final steps of the method according to the invention include recovering, filtering, and drying the starch milk thus treated, as illustrated below.

[0209] The residual moisture content of the obtained dry starch is 10% to 15% by weight, approximately 13% by weight.

[0210] The SDS values ​​of these products obtained by measuring digestibility using the Englyst method are 10% to 20% (by weight), preferably 12% to 17% (by weight), higher than those of the raw starch.

[0211] As will be illustrated below, the SDS value of pea starch is 40% (by weight) or higher, preferably 40% to 50% (by weight).

[0212] These starches with high SDS content will be advantageous for use in food (especially for athletes) or medical (professional nutrition) applications.

[0213] The invention will be better understood through the following partial embodiments, which are by way of example only and not limitation, and some of the advantageous features according to the invention.

[0214] Example 1: Determining the most effective annealing conditions for pea starch

[0215] In the laboratory, a pea starch emulsion solution with a dry matter weight of 32% was prepared by adding natural pea starch, marketed by the applicant company under the trade name N735, to softened water at room temperature and stirring slowly.

[0216] The temperature of the emulsion was increased to a range of 50°C to 95°C (50°C, 60°C, 65°C, 68°C, 70°C, 80°C) to investigate the effect of heat treatment on the obtained SDS content.

[0217] Maintain the reaction mixture at this final temperature for 1 hour while stirring.

[0218] At the end of this stage, the starch milk is recovered, filtered through a sintered glass filter, and then dried. Therefore, its residual moisture content is approximately 13% (by weight).

[0219] [ Figure 1 ] Figure 1 The digestibility curves of Englyst (1992) measured at the stated temperature are shown.

[0220] It was observed that annealing at temperatures ≥60℃ resulted in an increase in RDS content, accompanied by the initiation of starch gelatinization.

[0221] Treatment at 50°C increased the SDS weight content of natural pea starch from 33% to 44% of hydrothermally treated starch, thus clearly reflecting a significant weight increase of 11%.

[0222] Water plays an important role, and it has been shown that the absence of water does not change the digestibility of pea starch.

[0223] DSC analysis was also performed on the annealing reaction products under these different conditions.

[0224] [Table 1]

[0225]

[0226]

[0227] No changes were observed when there was no water (50℃ control incubator).

[0228] Annealing showed that treatment at 50°C for 1 hour was most effective, with the set temperature increasing by about 5°C after only 1 hour of treatment, the peak temperature increasing slightly by +2°C, and the maximum temperature remaining almost unchanged.

[0229] Therefore, hydrothermal treatment has a rapid effect on the treated emulsion phase pea starch.

[0230] Example 2: Optimizing the increase of SDS content by controlling the RDS content to 35% (by weight). .

[0231] The annealing method described above shall be retained. Figure 1 Compared to the temperatures shown, the temperatures are refined, thus refining the range to ~50°C to 60°C.

[0232] [ Figure 2 ] Figure 2 Englyst digestibility curves obtained at different temperatures are shown.

[0233] This experiment showed that by changing the annealing temperature, the SDS fraction could be significantly increased while controlling the RDS fraction weight to be less than 35%.

[0234] Therefore, it was observed that 50°C is the ideal compromise temperature for controlling the method to achieve the target.

[0235] [ Figure 3 ] Figure 3 Englyst digestibility curves obtained for different dry masses are shown.

[0236] It was observed that increasing the dry matter mass to a fairly large value reduced the ability to produce more SDS fractions.

[0237] As mentioned above, the annealing temperature is set to 50°C.

[0238] Table 2 below shows the weight percentages of RDS, SDS, RS, and TS calculated using the ENGLYST method.

[0239] [Table 2]

[0240]

[0241]

[0242] It was observed that the digestibility of pea starch changed even 20 minutes after annealing.

[0243] The optimal balance is achieved between 1 and 6 hours of annealing.

[0244] By implementing this method, as shown below with two batches of natural pea starch, we were able to significantly increase the SDS fraction content (by 10% to 15% by weight) while controlling the increase in the RDS fraction (by <35% by weight).

[0245] [ Figure 4 ] Figure 4 This significant increase in the SDS portion is shown while controlling for the increase in the RDS portion.

Claims

1. A method for preparing pea starch, characterized in that... The method includes the following steps: 1) Prepare a starch milk with a dry matter content of 30% to 40% by weight. 2) Heat the starch milk thus prepared to a temperature 10°C to 15°C below its gelatinization temperature. 3) Maintain the obtained starch milk at the stated temperature for 2 hours while stirring. 4) Collect, filter, and dry the starch milk after this treatment. The method does not include the step of enzymatic treatment of starch. The content of slow-digestible starch (SDS) is increased by 10% to 20% relative to the SDS weight content of the raw starch.

2. The method according to claim 1, wherein step 1) comprises preparing a starch milk with a dry matter weight content of 32%.

3. The method according to claim 1, characterized in that, The content of slow-digestible starch (SDS) is increased by 12% to 17% relative to the SDS weight content of the raw starch.

4. The method according to claim 1 or 2, characterized in that, The starch milk is heated to a temperature between 48°C and 53°C.

5. The method according to claim 4, wherein the starch milk is heated to a temperature of 50°C.

6. The method according to claim 4, characterized in that, The pea starch milk is kept at the specified temperature for 2 hours.

7. A pea starch prepared according to any one of the preceding claims, characterized in that, The SDS content is higher than 40% by weight.

8. The starch according to claim 7, wherein the SDS content is between 40% and 50% by weight.

9. The application of starch according to claim 7 in the preparation of food and medical products.

10. The application according to claim 9 is used for preparing athlete food products or professional nutritional medical products.

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