Method for annealing pea starch

Abstract

The present invention relates to a method for preparing legume starch having a high content of slowly digestible fraction (SDS), which is a hydrothermal treatment method, said preparation method comprising the following steps: 1) preparing a starch milk with a dry matter content of 30-40% by weight, preferably 32% by weight; 2) heating the starch milk thus prepared to a temperature 10 to 15°C lower than its gelatinization temperature; 3) stirring the starch milk thus obtained at this temperature for 45 minutes to 7 hours, preferably 1 hour to 6 hours; 4) recovering, filtering and drying the starch milk thus treated.

Description

Technical Field

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[0001] The present invention relates to a hydrothermal method for increasing the content of the slowly digestible fraction of pea starch.

[0002] It also relates to pea starch thus obtained.

[0003] From a physiological point of view, most of the carbohydrates ingested in the diet in humans or animals are represented by starch, which is an energy storage molecule characteristic of plants and is the main constituent of starchy foods (pasta, wheat flour, potatoes).

[0004] During digestion, starch molecules dissociate into linear glucan chains that dissociate into single glucose molecules that can be absorbed by their own digestive systems.

[0005] The digestion of starch begins during chewing in the mouth by the enzyme in saliva: salivary amylase.

[0006] This initial breakdown of starch is stopped by the acidity of the stomach but resumes in the duodenum (the first part of the small intestine) by the action of pancreatic and intestinal amylases.

[0007] The continuous action of all these amylases produces the disaccharide, maltose, which is converted to two monosaccharides, glucose.

[0008] Starch, which is biochemically synthesized and a source of carbohydrates, is one of the most widely present organic substances in the plant kingdom and constitutes the storage of nutrients in organisms.

[0009] Starch is thus naturally present in the storage organs and tissues of higher plants, particularly in grains (wheat, corn, etc.), legume seeds (pea, bean, etc.), potato or cassava tubers, roots, bulbs, stems and fruits.

[0010] Starch is a mixture of two homopolymers, amylose and amylopectin, which are composed of D-glucose units linked to each other via α-(1-4) bonds and α-(1-6) bonds that give rise to branching in the molecular structure.

[0011] These two homopolymers differ in their degree of branching and their degree of polymerization.

[0012] Amylose is slightly branched with short branches and has a molecular weight of 10,000 to 1,000,000 daltons. The molecule is formed from 600 to 1,000 glucose molecules.

[0013] Amylopectin is a branched molecule with long branches of 24 to 30 glucose units each, mediated 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 entire chain can contain 10,000 to 100,000 glucose units.

[0014] The amylose-to-amylopectin ratio depends on the plant source of the starch.

[0015] Starch is stored in storage organs and tissues in a granular state, that is, in the form of semi-crystalline particles.

[0016] This semi-crystalline state is essentially due to amylopectin polymers.

[0017] In their natural state, starch particles have a degree of crystallinity ranging from 15 to 45% by weight, substantially depending on their plant origin and the methods used for their extraction.

[0018] Therefore, granular starch placed under polarized light exhibits a characteristic black cross known as the "Maltese cross" when examined under a microscope.

[0019] This phenomenon of positive birefringence is due to the semi-crystalline structure of the particles, and because the average orientation of the polymer chains is radial.

[0020] For a more detailed explanation of granular starch, refer to Chapter 2, "Structure et morphologie du grain d'amidon" ("Structure and morphology of the starch grain") by S. Peres, pp. 41-86, Volume 13, 2000, of the French Polymer Group's "Initiation a la chimie et a la physico-chimie macromoleculaires" ("Introduction to macromolecule chemistry and physical chemistry").

[0021] Dry starch has a water content ranging from 12 to 20% by weight, depending on the plant from which it is derived. This water content clearly depends on the residual moisture of the medium (when aw=1, starch can retain up to 0.5g of water per gram of starch).

[0022] When a starch suspension is heated with excess water to a temperature close to its gelatinization temperature, the particles irreversibly swell and disperse, and then dissolve.

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

[0024] Within a predetermined temperature range called the "gelatinization range," starch particles swell very rapidly and lose their semi-crystalline structure (loss of birefringence).

[0025] All particles swell as much as possible within a temperature range of approximately 5-10°C. A paste is obtained consisting of swollen particles constituting the dispersed phase and molecules (mainly amylose) that thicken the aqueous continuous phase.

[0026] The rheological properties of the paste depend on the relative proportions of these two phases and the swelling volume of the particles. The gelatinization range varies depending on the plant from which the starch is derived.

[0027] The maximum viscosity is obtained when the starch paste contains a large number of highly swollen particles. As heating continues, the particles rupture and the substance disperses in the medium, but it only dissolves at temperatures above 100 °C.

[0028] The amylose-lipid complex has a slower swelling due to the inhibition of the interaction between amylose and water molecules by their combination, and a temperature above 90 °C is required to obtain complete swelling of the particles (because amylomaize forms a complex with lipids).

[0029] The viscosity decreases due to the disappearance of the particles and the dissolution of the polymers.

[0030] Lowering the temperature of the starch paste (by cooling) causes phase separation due to the insolubilization of the polymers and the incompatibility between amylose and amylopectin, and the crystallization of these polymers is observed.

[0031] This phenomenon is known by the name of retrogradation.

[0032] When the paste contains amylose, amylose is the first molecule to undergo retrogradation.

[0033] It is composed of the formation of double helices and the combination of these double helices, forming a "crystal" (type B) that produces a three-dimensional network through the junction zone.

[0034] This network is formed very rapidly within a few hours. During the growth of this network, the association of the double helices via hydrogen bonds replaces the water molecules bound to the helices, resulting in significant syneresis.

[0035] The structural complexity of starch and its physicochemical properties mean that this class of carbohydrates is absorbed and digested in a variety of ways in humans and animals.

[0036] This is why starch can be classified into three categories based on its digestibility: easily digestible, slowly digestible, or poorly digestible.

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

[0038] Slow-digestible starch (SDS) takes longer to be broken down by digestive enzymes compared to RDS because it still retains a crystalline structure and is less likely to come into contact with digestive enzymes.

[0039] The digestion of this SDS fraction releases a moderate and constant amount of glucose into the bloodstream. These are known as low-glycemic index ("low GI") starches.

[0040] As a result, foods with a high SDS content produce a lower postprandial blood glucose response and a lower insulin response than foods with a low SDS content.

[0041] Conversely, RDS is a nutritious carbohydrate because it releases those glucose molecules into the bloodstream much faster.

[0042] Next, regarding so-called resistant starch (RS), these are equivalent to fibers that cannot be digested by intestinal enzymes (such as corn bran, oat fiber, and gum).

[0043] Prior art has shown that all starch is 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, it is presumed that SDS is digested more slowly than RDS. RS is a fraction of starch that is resistant to enzymatic digestion in the small intestine. This fraction ferments in the large intestine and can therefore be considered dietary fiber.

[0046] Therefore, the SDS and RDS fractions are available glucose sources.

[0047] In nature, SDS is found in the seeds of some uncooked grains such as wheat, rice, barley, rye, and corn, as well as in legumes such as peas, field beans, and lentils.

[0048] The SDS content is mainly influenced by the gelatinization of starch during subsequent food processing.

[0049] In fact, during this process, exposure to temperature, pressure, and moisture converts the SDS fraction to RDS, allowing the starch to come into contact with more of the enzymes for digestion.

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

[0051] Therefore, the initial content of SDS in a composition or food depends on the method by which it was prepared.

[0052] Therefore, unlike puffed breakfast cereals or bread, which usually contain little to no SDS, foods known to be high in SDS include certain types of pasta, parboiled rice, pearl barley, and certain types of cookies.

[0053] The SDS content of food products is traditionally determined using an in vitro method developed by HNENGLYST and his collaborators (European Journal of Clinical Nutrition, volume 46, pp. 33-50, published in 1992).

[0054] The remainder of this explanation will describe this 1992 method, which "followed the ENGLYST."

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

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

[0057] By this method, - Measuring rapidly available glucose (RAG), in this case, the RDS fraction by measuring the glucose released between 0 and 20 minutes, - Measuring gradually available glucose (SAG), in this case, the SDS fraction by measuring the glucose released between 20 and 120 minutes, - The RS fraction corresponding to glucose not released after 120 minutes can be distinguished, where the RS fraction is calculated according to the ENGLYST method by the following formula: TS - (RDS + SDS), where TS = total starch (if the analysis is performed on such starch, total starch is considered to be equal to 100%).

[0058] Foods rich in carbohydrates, containing more than 50% by weight of usable carbohydrates from starch, and in which at least 40% by weight is SDS, have traditionally been considered to have a high SDS.

[0059] Therefore, they are recommended for suppressing the glycemic index and insulin production compared to foods with lower SDS content.

[0060] Of all the starches conventionally used in these food applications, leguminous starches, more specifically pea starch, are the leading candidates.

[0061] In fact, pea seeds are known to have a high starch content (55-70% by weight of the dry material) and a low glycemic index (Ratnayaka et al., 2002, Pea starch, composition, structure and properties - A review, Starch / Starke, 54, 217-234).

[0062] Natural pea starch, which conventionally exhibits an SDS content of 27-38% by weight according to ENGLYST, is therefore of interest in nutritional use.

[0063] However, in order to prepare foods with a high SDS content, it is necessary to use starch with a higher proportion of slow-digestible carbohydrates.

[0064] Prior art has shown that the crystalline structure of starch particles can be altered by annealing-type heat treatment.

[0065] More specifically, annealing is a term used in polymer science to describe the optimization of crystallization by heating polymers to temperatures below their melting point in order to grow crystalline regions, complete crystals, and transform them into more stable crystalline structures.

[0066] When used with starch, annealing is defined as a hydrothermal process that involves heating starch particles in excess water to a temperature higher than the glass transition temperature but lower than the gelatinization onset temperature.

[0067] During the annealing process, the starch particles are assumed to swell to a limited but reversible degree without losing their granular and molecular structure, or the solubilization of the starch polymer molecules.

[0068] Annealing is generally thought to involve the reorganization of starch chains and amylopectin double helices, thereby increasing the interaction between starch chains and improving order within the double helix.

[0069] The annealing process does not significantly affect the crystalline and molecular alignment of starch particles, but it can drastically alter their physicochemical properties.

[0070] Physicochemical modifications generally include a decrease in swelling strength and solubility (amylose leaching), a narrowing of the range of thermal transitions with increased gelatinization and enthalpy change temperatures, increased stability of the adhesive mass, and increased sensitivity to enzymatic digestion.

[0071] To explain these physicochemical changes that occur during annealing, certain molecular phenomena have been proposed, such as improved particle stability, reorganization of particle structure, or a decrease in free energy.

[0072] Starch annealing has been the subject of detailed research using starches derived from various plants, including corn, potatoes, wheat, rice, sago, sorghum, barley, and peas.

[0073] Pea starch is highly valued because it has a higher amylose content than many other natural starches and contains a mixture of A and B polymorphic structures.

[0074] In their 2013 paper (published in a review in Food Bioprocess Technol, vol. 6, pp. 3564-3575), Wang et al. showed that annealing slightly alters the granular and crystalline structure of pea starch particles, but significantly alters their functionality.

[0075] Under the conditions used in their study (annealing temperature was considerably lower than gelatinization temperature -4°C for 24–72 hours), the overall degree of crystallinity did not change significantly, but annealing induced slight, irreversible swelling of pea starch particles, accompanied by the leaching of certain amylose molecules.

[0076] From this, the authors concluded that annealing primarily acts on the amorphous region of starch particles and has little effect on the crystalline region of starch particles.

[0077] However, they demonstrated a polymorphic transition from type A to type B, resulting from the filling of double helix spaces in type A microcrystallites by more water molecules induced by hydrothermal treatment.

[0078] Subsequently, the removal of certain amylose molecules between amylopectin clusters weakens the overall stability of the starch particles, and thus substantially alters the functional properties of the annealed starch.

[0079] Regarding the changes in the digestibility of annealed pea starch, the authors used the ENGLYST method (1992) to show that the percentage of enzymatic hydrolysis of pea starch gradually increased over time during a 4-hour incubation.

[0080] Therefore, they demonstrated that their annealing treatment increased the in vitro digestibility of pea starch particles.

[0081] They concluded that the annealing process reduces the RS content, converts it to SDS, and then to RDS, thereby increasing the RDS content.

[0082] Therefore, since the annealing methods commonly used in conventional techniques primarily aim to make leguminous plant starches, especially pea starch, more digestible, this observation has also been accepted by other authors (see CHUNG et al., Carbohydrate Polymers, 2009, vol. 75, pp. 436-447).

[0083] However, contrary to this technical preconception, the applicant's company chose to optimize this annealing technique not to increase the RDS fraction of leguminous plant starches, particularly pea starch, but to increase the SDS content, by exploring annealing process conditions that are particularly suitable for this purpose. [Modes for carrying out the invention]

[0084] Therefore, the present invention relates to a method for preparing leguminous plant starch, preferably pea starch, having a high content of slow-digestible fraction (SDS), and is a hydrothermal treatment method, wherein the preparation method consists of the following steps, namely: 1) A step of preparing starch milk having a dry matter content of 30-40% by weight, preferably 32% by weight, 2) A step of heating the starch milk prepared in this manner to a temperature 10 to 15°C lower than its gelatinization temperature, 3) The starch milk obtained in this way is stirred at this temperature for 45 minutes to 7 hours, preferably 1 hour to 6 hours. 4) The present invention relates to a method characterized by comprising the steps of recovering the starch milk processed in this manner, filtering it, and drying it.

[0085] In the context of this invention, "high content of slow-digestible fraction" is understood to mean an increase in SDS content of 10 to 20% by weight, preferably 12 to 17% by weight, relative to the SDS content by weight of the starch prepared.

[0086] For the purposes of this invention, "legume plants" means any plant belonging to the subfamily Caesalpinioideae, Mimosoideae, or Papilionaceae, and in particular any plant belonging to the subfamily Papilionaceae, such as peas, kidney beans, broad beans, field beans, lentils, alfalfa, clover, or lupin beans.

[0087] The paper by R. HOOVER et al., titled "Composition, structure, functionality and chemical modification of legume starches" (a review published in Canada, J. Physiol. Pharmacol. 1991, pp. 69, 79-92), particularly its table, discloses various leguminous plants.

[0088] Preferably, the legumes are selected from the group including peas, kidney beans, broad beans, and field beans.

[0089] For the sake of convenience, it is a pea, and the term "pea" is considered in its broadest sense herein, specifically, - All wild-type varieties of "smooth pea", and - This includes all variants of "smooth pea" and "wrinkled pea," regardless of the variety's generally intended use (human food, animal feed, and / or other uses).

[0090] Specifically, the mutant varieties in question are those named "mutants r," "mutants rb," "mutants rug3," "mutants rug4," "mutants rug5," and "mutants lam," as described in the paper titled "Developing novel pea starches" by C.L. HEYDLEY et al., Proceedings of the Symposium of the Industrial Biochemistry and Biotechnology Group of the Biochemical Society, 1996, pp. 77-87.

[0091] In another advantageous mutant, the leguminous plant (e.g., a variety of pea or field bean) is a plant that yields grains containing at least 25% by weight, preferably at least 40% by weight, of starch (dried / dried).

[0092] "Leguminous plant starch" is intended to mean any composition extracted from leguminous plants, particularly from the subfamily Fabaceae, by any means, wherein the starch content is greater than 40%, preferably greater than 50%, and more preferably greater than 75%, where these percentages are expressed as dry weight relative to the dry weight of the composition.

[0093] Advantageously, this starch content is over 90% (dry / dry). Specifically, it may be over 95% by weight and may contain over 98% by weight.

[0094] "Natural" starch means starch that has not been chemically or enzymatically modified. Preferably, the starch of the present invention is natural starch.

[0095] In one embodiment of the present invention, the method does not involve a step of enzymatically treating the starch.

[0096] To determine the content of the underlying SDS fraction, pea starch according to the present invention, or not, is analyzed according to the in vitro digestion process conditions of the method described by HNEnglyst et al., "Classification and measurement of nutritionally important starch fraction", Eur.J.Clin.Nutr., 46(Supp.2), S33~S50 (1992).

[0097] The method involves measuring the fractions of easily digestible starch (RDS), slow-digestible starch (SDS), and indigestible (resistant) starch (RS) contained in food.

[0098] These fractions are determined after enzymatic digestion using pancreatin, amyloglucosidase, and invertase.

[0099] The released glucose is measured by colorimetric analysis using the Glucose GOD FS glucose oxidase kit (reference 1 2500 99 10 923), commercially available from DiaSys Dispersion France Sarl, according to the kit's protocol.

[0100] Details of the method used to measure digestion by Englyst are as follows:

[0101] Reagents used: - Anhydrous sodium acetate (reference number: 71184, Sigma-Ace) - Benzoic acid (Reference number: 242381, Sigma-Ace) - CaCl2 (Reference number: 1.02378.0500, Merck) - 0.1M acetic acid (Reference number: 33209, Sigma-Ace) - Butapancreatine 8x USP (Reference number: P7545, Sigma-A) - Amyloglucosidase EC3.2.1.3 (Sigma-America, activity ≥260 U / ml / ≈300 AGU / ml, catalog number A7095) - Invertase EC3.2.1.26 (Sigma-America, activity ≥ 300 units / mg - solid, catalog number I-4504) - Guar (Reference number: G4129, Sigma Corporation) - 66% ethanol

[0102] procedure Preparation of saturated benzoic acid solution

[0103] Mix 4g of benzoic acid into 1L of reverse osmosis water. The solution can be stored at room temperature for one month.

[0104] Preparation of a 1 M / L CaCl2 solution.

[0105] Mix 1.1098 g of CaCl2 into 10 mL of reverse osmosis water. The solution can be stored at room temperature for one month.

[0106] Preparation of 0.1 M acetate buffer solution at pH 5.2. - Weigh 8.203 g of anhydrous sodium acetate into 250 mL of saturated benzoic acid solution, - Add 500 mL of reverse osmosis water and mix. - Adjust the pH to 5.2+ / -0.5 using 0.1M acetic acid. - Refill the volumetric flask with reverse osmosis water to make 1000 mL, - Add 4 mL of 1 M CaCl2 solution to 1 L of prepared buffer solution. - Mix and check the pH. The solution can be stored at 4°C for one month.

[0107] Preparation of guar gum solution in acetate buffer - Accurately measure 750 mg of guar gum into 300 mL of acetate buffer. - Stir continuously

[0108] Preparation of the sample to be analyzed and the enzymes to be used

[0109] Sample preparation Accurately weigh 0.8g of dry starch to be tested, Add 20 mL of 0.1 M acetate buffer at pH 5.2 + guar gum. While stirring, place the vial in a 37°C water bath for 15 minutes. Take 0.1 mL of the solution obtained at T=0 min, add 0.9 mL of 66% ethanol (i.e., a 1:10 dilution), A glucose assay (expressed as a percentage) is performed by colorimetric analysis at time T=0 minutes.

[0110] Prepare a blank and a standard (weighing 0.5 g of anhydrous dextrose) under the same conditions as the sample preparation.

[0111] Preparation of enzyme cocktails

[0112] The enzyme cocktail is intended to test 12 samples. It must be prepared on the same day according to the following protocol.

[0113] Preparation of porcine pancreatin 8x USP

[0114] To obtain 54 mL of supernatant, prepare four pancreatin solutions.

[0115] To do this, - Weigh out 2.5g of porcine pancreatine 8xUSP, - Add 20 mL of reverse osmosis water and mix for 10 minutes. - Centrifuge the solution with 1500g for 10 minutes. - Collect 13.5 mL of the supernatant.

[0116] Preparation of amyloglucosidase - Dilute 3.7 mL of amyloglucosidase solution EC3.2.1.3 with 4.3 mL of reverse osmosis water and mix for 10 minutes. - Take 6 mL of fresh solution and then add it to 54 mL of pancreatin supernatant and mix.

[0117] Preparation of invertase - Weigh out 50 mg of invertase EC3.2.1.26, - Add 6 mL of reverse osmosis water and mix for 10 minutes. - Take 4 mL of the solution, then add it to 54 mL of pancreatin supernatant and mix.

[0118] Digestive protocol - Add 5 mL of enzyme cocktail to the sample preparation. - Incubate in a heated, heat-controlled bath at 37°C for 120 minutes. - Take 0.1 mL of the solution obtained at T=20 min and T=120 min, and add it to 0.9 ml of 66% ethanol (i.e., a 1:10 dilution), - After mixing, centrifuge the sample at 1500g for 3 minutes. - Perform a glucose assay (as a percentage) by colorimetric analysis at time T=20 minutes and T=120 minutes.

[0119] Determination of free glucose levels (Fg) and total glucose levels (Tg)

[0120] The free glucose level (FG) corresponds to the measurement taken at time 0 minutes.

[0121] Total glucose levels (TG) are measured as follows: - Take 0.25 mL of the solution obtained at T=120 minutes and put it into an "Eppendorf" type tube. - Add 0.25 mL of 4N hydrochloric acid and mix. - Place the tube in a 100°C dry water bath for 45 minutes, then let it cool to room temperature. - Neutralize the hydrolyzed solution with 0.25 mL of 4N sodium bicarbonate solution. - Add 0.25 mL of reverse osmosis water and mix. - Prepare a 1:10 dilution using reverse osmosis water (0.1 mL in 0.9 mL). This is the final 1:40 dilution.

[0122] Determining RDS, SDS, and RS levels

[0123] Determine the free glucose at different time points. - T=0 min (initial glucose content), - T=20 minutes (free glucose content after 20 minutes) and - T = 120 minutes (free glucose content after 120 minutes).

[0124] According to the Englyst method,

number

[0125] During the ceremony, - At = Absorbance (Sample) - Absorbance (Blank) - Vt = Total volume (sample in mL) - C = Standard concentration (glucose in mg / ml) - D = dilution factor - As = Absorbance (Standard) - Absorbance (Blank) - Wt = dry weight (sample in mg)

[0126] The RDS, SDS, and RS fractions are determined as follows: - RDS=(G20-FG)×0.9 - SDS = (G120 - G20) × 0.9 - RS = ((TG - FG) × 0.9) - (RDS + SDS)

[0127] According to this method, natural pea starch typically contains 13–16% RDS, 27–38% SDS, and 45–56% RS. These values ​​are given with a standard deviation of + / - 2%, considering the intrinsic variability during the Englyst enzyme test.

[0128] To increase SDS levels, the annealing method of the present invention, developed by the applicant's company, uses a precise hydrothermal approach.

[0129] Therefore, the present invention relates to a method for preparing leguminous plant starch, preferably pea starch, having a high content of slow-digestible fraction (SDS), and is a hydrothermal treatment method, wherein the preparation method consists of the following steps, namely, 1) A step of preparing starch milk having a dry matter content of 30-40% by weight, preferably 32% by weight, 2) A step of heating the starch milk prepared in this manner to a temperature 10 to 15°C lower than its gelatinization temperature, 3) The starch milk obtained in this way is stirred at this temperature for 45 minutes to 7 hours, preferably 1 hour to 6 hours. 4) The present invention relates to a method characterized by comprising the steps of recovering the starch milk processed in this manner, filtering it, and drying it.

[0130] The first step of the method of the present invention is to prepare a leguminous plant starch milk, which in this specific case of peas has a dry matter content of 30-40% by weight, preferably 32% by weight.

[0131] The second step of the method of the present invention is to heat the leguminous plant starch milk to a temperature 10 to 15°C lower than its gelatinization temperature, which in this specific case of pea starch is 48 to 53°C, preferably about 50°C.

[0132] The applicant's company recommends the use of a heat exchanger whose temperature does not exceed 55°C. In one embodiment of the present invention, the method does not include a gelatinization step; that is, the starch milk is not exposed to temperatures above the lowest temperature of the “gelatinization range”.

[0133] The third step of the method of the present invention is to maintain the starch milk at the temperature for 45 minutes to 7 hours, preferably 1 hour to 6 hours, and more preferably 1 hour, while stirring the starch milk.

[0134] The stirring of the reaction medium is adjusted to maintain the suspension of starch within the reaction medium. This can be achieved by mechanical stirring using anchors, propellers, or turbine-type moving parts.

[0135] Therefore, contrary to what is recommended in the aforementioned prior art, the applicant's company found that it is not necessary to rely on an annealing approach with high dry matter content starch (up to 60% by weight DM is disclosed) at a temperature 10-15°C lower than the gelatinization temperature of starch for 24-72 hours, but rather that a shorter time (6 hours or less) with a relatively low dry matter content starch (approximately 30% by weight) is preferable.

[0136] This approach can increase the SDS level of the treated starch.

[0137] Therefore, the fourth and final step of the method of the present invention consists of recovering the starch milk thus processed, filtering it, and drying it, as illustrated below.

[0138] The residual moisture content of the obtained dried starch is 10% to 15% by weight, and is approximately 13% by weight.

[0139] Englyst's digestibility measurements of these products show an increase in SDS value of 10-20% by weight, preferably 12-17% by weight, compared to the original starch.

[0140] As shown below, the SDS value of pea starch is greater than 40% by weight, preferably 40-50% by weight.

[0141] As a result, these starches with high SDS content can be advantageously used in applications related to food (especially for athletes) or medicine (specialist nutrition).

[0142] The present invention will be better understood by reading the following examples, which are intended to be illustrative and do not describe or limit any particular embodiment or particular beneficial characteristic of the present invention.

[0143] Example 1: Determining the most effective conditions for annealing pea starch.

[0144] In the laboratory, natural pea starch, commercially available from the applicant's company under the trade name N735, is added to desalinated water at room temperature under gentle stirring to prepare pea starch milk in water containing 32% by weight of the dried product.

[0145] The temperature of this milk will be increased to various values ​​from 50°C to 95°C (50°C, 60°C, 65°C, 68°C, 70°C, and 80°C) to investigate the effect of heat treatment on the resulting SDS content.

[0146] Stir the reaction mixture at this final temperature for 1 hour.

[0147] At the end of this time, the starch milk is collected, filtered through a sintered glass filter, and dried. As a result, it has a residual moisture content of approximately 13% by weight. [Brief explanation of the drawing]

[0148] [Figure 1] Figure 1 shows the digestibility profile of Englyst determined at the given temperature (1992).

[0149] It has been observed that processing at annealing temperatures of ≥60°C results in an increase in RDS fraction content, which occurs simultaneously with the initiation of the starch gelatinization process.

[0150] Treatment at 50°C resulted in an increase in SDS content from 33% by weight in natural pea starch to 44% by weight in hot water-treated starch, thus resulting in a significant increase of 11% by weight.

[0151] The amount of water plays a crucial role, and it has been confirmed that the absence of water does not alter the digestibility profile of pea starch in any way.

[0152] DSC analysis was also performed on the annealing reaction products at these different temperatures.

[0153] [Table 1]

[0154] In the absence of water, no change is observed (control oven at 50°C).

[0155] The annealing process has shown that a 1-hour treatment at 50°C is the most effective, with an increase of approximately 5°C in the starting temperature, a slight increase of +2°C in the peak t°, and virtually no change in the maximum t° after only 1 hour of treatment.

[0156] Therefore, the hydrothermal treatment acts rapidly on the pea starch being treated in the milk phase.

[0157] Example 2: Optimization of increasing SDS content by controlling the RDS fraction to a value of less than 35% by weight.

[0158] The annealing method remains the same as described above. To further elaborate on the temperature range between ~50 and 60°C, we will refer to the method shown in Figure 1.

[0159] [Figure 2] Figure 2 shows the digestibility profiles of Englyst obtained at different temperatures.

[0160] In this experiment, we observed that by varying the annealing temperature to control the RDS fraction to less than 35% by weight, the SDS fraction could be substantially increased.

[0161] Therefore, a temperature of 50°C can be observed to be a perfect compromise for both achieving the goal and effectively utilizing the method.

[0162] [Figure 3] Figure 3 shows the digestibility profiles of Englyst obtained at different dry matter content levels.

[0163] It was observed that significantly increasing the amount of dry material reduced its ability to produce more SDS fractions.

[0164] As explained above, the annealing temperature should be set to 50°C.

[0165] Table 2 below shows the content as weight percentages of RDS, SDS, RS, and TS calculated according to the ENGLYST method.

[0166] [Table 2]

[0167] Even after a 20-minute annealing treatment, changes in the digestibility profile of pea starch can be observed.

[0168] The best balance can be seen 1 to 6 hours into the annealing process.

[0169] By using this method, we can significantly increase the SDS fraction (+10-15% by weight) while controlling the increase in the RDS fraction (<35% by weight) using two batches of natural pea starch, as shown below.

[0170] [Figure 4] Figure 4 shows this significant increase in the SDS fraction while controlling the increase in the RDS fraction.

Claims

1. 1. A method for preparing legume starch having a high content of slowly digestible fraction (SDS), said preparation method comprising the following steps: 1) preparing a starch milk with a dry matter content of 30-40% by weight, preferably 32% by weight; 2) heating the starch milk thus prepared to a temperature 10-15°C lower than its gelatinization temperature; 3) stirring the starch milk thus obtained at this temperature for 45 minutes to 7 hours, preferably 1 hour to 6 hours; 4) recovering, filtering and drying the starch milk thus treated.

2. 2. The method of claim 1, wherein the legume starch is selected from the group of pea, kidney bean, broad bean, field bean, lentil, alfalfa, clover, and lupin starches, in particular pea starch.

3. 3. The method according to claim 1 or 2, characterized in that the high content of slowly digestible fraction (SDS) corresponds to an increase of 10 to 20% by weight, preferably 12 to 17% by weight, relative to the SDS content by weight of the original starch.

4. 4. A method according to any one of claims 1 to 3, characterized in that in the case of pea starch, the starch milk is heated to a temperature of 48-53°C, preferably to a temperature of about 50°C.

5. 5. A method according to claim 4, characterized in that the pea starch milk is kept at this temperature for 1 hour to 6 hours, preferably for 1 hour.

6. Pea starch with a high content of slowly digestible fraction prepared according to the method according to any one of claims 1 to 5, characterized in that the content of SDS is more than 40% by weight, preferably between 40 and 50% by weight.

7. 7. Use of the starch according to claim 6 in the food and medical application fields, in particular for food products for sports or specialist nutrition.

Images