METHOD FOR ANNEALING PEA STARCH

Abstract

The present invention relates to a method for preparing a legume starch with a high content of slowly digestible fraction (SDS), a hydrothermal treatment method characterized in that it comprises the following steps:

1) Preparing a starch milk with a dry matter content of between 30 and 40% by weight, preferably 32% by weight,
2) Heating the starch milk prepared in this way to a temperature 10 to 15° C. lower than its gelatinization temperature,
3) Stirring the starch milk obtained in this way at this temperature for between 45 minutes and 7 hours, preferably between 1 hour and 6 hours,
4) Recovering, filtering and drying the starch milk treated in this way.

Claims

1-7. (canceled)

8. A method for preparing a legume starch with a high content of slowly digestible fraction (SDS) comprising the following steps: 1.) Preparing a starch milk with a dry matter content of between 30 and 40% by weight, preferably 32% by weight, 2.) Heating the starch milk prepared in this way to a temperature 10 to 15° C. lower than its gelatinization temperature, 3.) Stirring the starch milk obtained in this way at this temperature for between 45 minutes and 7 hours, preferably between 1 hour and 6 hours, 4.) Recovering, filtering and drying the starch milk treated in this way.

9. The method according to claim 8, wherein the legume starch is selected from the group of pea, bean, broad bean, field bean, lentil, alfalfa, clover and lupine starches, and is particularly pea starch.

10. The method according to claim 8, wherein the high content of slowly digestible fraction (SDS) corresponds to an increase of 10 to 20% by weight, preferably 12 to 17% by weight with respect to the SDS content by weight of the initial starch.

11. The method according to claim 8, wherein for pea starch, the starch milk is heated to a temperature of between 48 and 53° C., preferably to a temperature of the order of 50° C.

12. The method according to claim 11, wherein the pea starch milk is maintained at this temperature for 1 hour to 6 hours, preferably 1 hour.

13. A pea starch with a high content of slowly digestible fraction prepared according to the method of claim 8, wherein the SDS content is greater than 40% by weight, preferably between 40 and 50% by weight.

14. Use of a starch according to claim 13 in food and medical fields of application, especially for food for sportspersons or specialist nutrition.

Description

DETAILED DESCRIPTION

[0087] Thus, the invention relates to a method for preparing a legume starch, preferably pea starch, with a high content of slowly digestible fraction (SDS), a hydrothermal treatment method characterized in that it comprises the following steps: [0088] 1) Preparing a starch milk with a dry matter content of between 30 and 40% by weight, preferably 32% by weight, [0089] 2) Heating the starch milk prepared in this way to a temperature 10 to 15° C. lower than its gelatinization temperature, [0090] 3) Stirring the starch milk obtained in this way at this temperature for between 45 minutes and 7 hours, preferably between 1 hour and 6 hours, [0091] 4) Recovering, filtering and drying the starch milk treated in this way.

[0092] In the meaning of the present invention, “high content of slowly digestible fraction” is understood to mean an SDS content increase of 10 to 20% by weight, preferably 12 to 17% by weight with respect to the SDS content by weight of the starch from which it is prepared.

[0093] For the purposes of the present invention, “legume” means any plant belonging to the families of the cesalpiniaceae, mimosaceae or papilionaceae, and particularly any plant belonging to the family of the papilionaceae, for example pea, bean, broad bean, field bean, lentil, alfalfa, clover or lupin.

[0094] 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, 69 pages 79-92) especially discloses various legumes in its tables.

[0095] Preferably, the legume is selected from the group comprising pea, bean, broad bean and field bean.

[0096] Advantageously, it is pea, the term “pea” being considered here in its broadest sense and including in particular: [0097] all the wild varieties of “smooth pea”, and [0098] all the mutant varieties of “smooth pea” and of “wrinkled pea”, regardless of the uses for which said varieties are generally intended (human food, animal feed and/or other uses).

[0099] Said mutant varieties are in particular those named “mutants r”, “mutants rb”, “mutants rug 3”, “mutants rug 4”, “mutants rug 5” and “mutants lam” as described in the article by C-L HEYDLEY et al. entitled “Developing novel pea starches”, Proceedings of the Symposium of the Industrial Biochemistry and Biotechnology Group of the Biochemical Society, 1996, pages 77-87.

[0100] According to another advantageous variant, legumes (for example varieties of pea or field bean) are plants giving grains containing at least 25%, preferably at least 40%, by weight of starch (dry/dry).

[0101] “Legume starch” is intended to mean any composition extracted, by any means, from a legume and in particular from a papilionaceae, the starch content of which is greater than 40%, preferably greater than 50% and even more preferentially greater than 75%, these percentages being expressed as dry weight relative to the dry weight of said composition.

[0102] Advantageously, this starch content is greater than 90% (dry/dry). It may in particular be greater than 95% by weight, including greater than 98% by weight.

[0103] “Native” starch means a starch which has not undergone any chemical or enzymatic modification. In a preferred manner, the starch according to the invention is a native starch.

[0104] According to one embodiment of the invention, the method does not comprise a step of enzymatic treatment of the starches.

[0105] In order to determine their base content of SDS fraction, pea starches, according to the invention or not, are analyzed according to the in vitro digestion process conditions of the method by H. N. Englyst et al in “Classification and measurement of nutritionally important starch fractions”, Eur. J. Clin. Nutr., 46 (Supp. 2), S33-S50 (1992).

[0106] The method consists of measuring the fractions of rapidly digestible starch (RDS), slowly digestible starch (SDS) and non-digestible (resistant) starch (RS) contained in a food.

[0107] These fractions are determined after enzymatic digestion with pancreatin, amyloglucosidase and invertase.

[0108] The released glucose is measured by colorimetry, using a Glucose GOD FS glucose oxidase kit, referenced 1 2500 99 10 923, marketed by the company DiaSys Distribution France Sari, following the protocol of said kit.

[0109] The details of the method implemented to measure digestion according to Englyst are as follows.

[0110] Reagents Used: [0111] Anhydrous sodium acetate (ref: 71184, by the company SIGMA) [0112] Benzoic acid (ref: 242381, by the company SIGMA) [0113] CaCl.sub.2 (ref: 1.02378.0500, by the company MERCK) [0114] Acetic acid 0.1M (ref: 33209, by the company SIGMA) [0115] Pig pancreatin 8×USP (ref: P 7545 by the company SIGMA) [0116] Amyloglucosidase EC 3.2.1.3 (by the company SIGMA, activity≥260 U/ml/≈300 AGU/ml, Cat. NO. A7095) [0117] Invertase EC 3.2.1.26 (by the company SIMA, activity≥300 units/mg solid, Cat. NO. I-4504) [0118] Guar (ref: G4129, by the company SIGMA) [0119] 66% ethanol

Procedure

[0120] Preparation of the Saturated Benzoic Acid Solution

[0121] Weigh 4 g of benzoic acid in 1 L of reverse osmosis water then mix. The solution can be stored at room temperature for 1 month.

[0122] Preparation of 1 M/L CaCl.sub.2 Solution.

[0123] Weigh 1.1098 g of CaCl.sub.2 in 10 ml of reverse osmosis water then mix. The solution can be stored at room temperature for 1 month.

[0124] Preparation of 0.1 M Acetate Buffer—pH 5.2. [0125] Weigh 8.203 g of anhydrous sodium acetate in 250 ml of saturated benzoic acid solution, [0126] Add 500 ml of reverse osmosis water then mix, [0127] Adjust the pH to 5.2+/−0.5 using 0.1 M acetic acid, [0128] Top up with the reverse osmosis water to 1000 ml in a graduated flask, [0129] Add 4 ml of the 1 M CaCl.sub.2 solution for 1 L of prepared buffer, [0130] Mix and check the pH.

[0131] The solution can be stored at 4° C. for 1 month.

[0132] Preparation of the Guar Gum Solution in the Acetate Buffer Solution [0133] Weigh exactly 750 mg of guar gum in 300 ml of acetate buffer [0134] Stir continuously

PREPARATION OF SAMPLES TO BE ANALYZED AND ENZYMES USED

[0135] Preparation of Samples [0136] Weigh exactly 0.8 g of dry starch to test, [0137] Add 20 ml of 0.1 M acetate buffer solution—pH 5.2+guar gum, [0138] Place the vials in a water bath for 15 minutes while stirring at 37° C., [0139] Take 0.1 ml of the solution obtained at T=0 minutes then add 0.9 ml of 66% ethanol (i.e. a 1:10 dilution), [0140] Glucose assay (as a %) by colorimetry at time T=0 min.

[0141] A blank and a standard (Weigh 0.5 g of anhydrous dextrose) are produced under the same conditions as the sample preparation.

[0142] Preparation of the Enzyme Cocktail

[0143] The enzyme cocktail is intended to test 12 samples. It must be prepared on the same day according to the following protocols.

[0144] Preparation of the Pig Pancreatin 8×USP

[0145] Prepare 4 solutions of pancreatin in order to obtain 54 ml of supernatant.

[0146] To do this: [0147] Weigh 2.5 g of pig pancreatin 8×USP, [0148] Add 20 ml of reverse osmosis water then mix for 10 minutes, [0149] Centrifuge the solution at 1500g for 10 minutes, [0150] Recover 13.5 ml of supernatant.

[0151] Preparation of the Amyloglucosidase [0152] Dilute 3.7 ml of amyloglucosidase solution EC 3.2.1.3 with 4.3 ml of reverse osmosis water then mix for 10 minutes, [0153] Take 6 ml of the new solution then add it to the 54 ml of pancreatic supernatant then mix,

[0154] Preparation of the Invertase [0155] Weigh 50 mg of invertase EC 3.2.1.26, [0156] Add 6 ml of reverse osmosis water then mix for 10 minutes, [0157] Take 4 ml of the solution then add it to the 54 ml of pancreatic supernatant then mix.

DIGESTION PROTOCOL

[0158] Add 5 ml of enzyme cocktail to the sample preparations [0159] Incubate for 120 minutes at 37° C. in a stirring heat-controlled bath, [0160] Take 0.1 ml of the solution obtained at T=20 min and at T=120 min then add it to 0.9 ml of 66% ethanol (i.e. a 1:10 dilution), [0161] Mix then centrifuge the samples at 1500g for 3 minutes, [0162] Glucose assay (as a %) by colorimetry at time T=20 min and T=120 min

[0163] Determining the free glucose level (Fg) and the total glucose level (Tg)

[0164] The free glucose level (FG) corresponds to the measurement performed at time 0 min.

[0165] The total glucose level (TG) is measured as follows: [0166] Take 0.25 ml of the solution obtained at T=120 min and place it in an “Eppendorf” type tube, [0167] Add 0.25 ml of 4N hydrochloric acid, mix, [0168] Place the tube in a dry water bath at 100° C. for 45 minutes, allow to cool to room temperature, [0169] Neutralize the hydrolyzed solution with 0.25 ml of 4N soda, [0170] Add 0.25 ml of reverse osmosis water, mix [0171] Make a 1:10 dilution in reverse osmosis water (0.1 ml in 0.9 ml). Namely a 1:40 final dilution.

DETERMINATION OF THE RDS, SDS AND RS LEVELS

[0172] Determining the free glucose at different times: [0173] T=0 min (initial glucose content), [0174] T=20 min (free glucose content after 20 minutes) and [0175] T=120 min (free glucose content after 120 minutes).

[0176] According to the Englyst method:

[00001]$\mathrm{Glucose}\left(\%\right)=\frac{\mathrm{At}\times \mathrm{Vt}\times C\times D}{\mathrm{As}\times \mathrm{Wt}}\times 100$

[0177] Where [0178] At=Absorbance (sample)−Absorbance (blank) [0179] Vt=Total volume (sample in ml) [0180] C=Standard concentration (glucose in mg/ml) [0181] D=Dilution factor [0182] As=Absorbance (standard)−Absorbance (blank) [0183] Wt=Dry weight (sample in mg)

[0184] Where [0185] At=Absorbance (sample)−Absorbance (blank) [0186] Vt=Total volume (sample in ml) [0187] C=Standard concentration (glucose in mg/ml) [0188] D=Dilution factor [0189] As=Absorbance (standard)−Absorbance (blank) [0190] Wt=Dry weight (sample in mg)

[0191] The RDS, SDS and RS fractions are determined as follows: [0192] RDS=(G20−FG)×0.9 [0193] SDS=(G120−G20)×0.9 [0194] RS=((TG−FG)×0.9)−(RDS+SDS)

[0195] According to this method, the native pea starch conventionally has an RDS content of between 13 and 16% by weight, an SDS content of between 27 and 38%, and an RS content of between 45 and 56% by weight. These values are given with a standard deviation of +/−2%, given the intrinsic variability during the Englyst enzymatic test.

[0196] To increase the SDS level, the annealing method according to the invention, developed by the Applicant company, uses a precise hydrothermal approach.

[0197] The invention thus relates to a method for preparing a legume starch, preferably pea starch, with a high content of slowly digestible fraction (SDS), a hydrothermal treatment method characterized in that it comprises the following steps: [0198] 1) Preparing a starch milk with a dry matter content of between 30 and 40% by weight, preferably 32% by weight, [0199] 2) Heating the starch milk prepared in this way to a temperature 10 to 15° C. lower than its gelatinization temperature, [0200] 3) Stirring the starch milk obtained in this way at this temperature for between 45 minutes and 7 hours, preferably between 1 hour and 6 hours, [0201] 4) Recovering, filtering and drying the starch milk treated in this way.

[0202] The first step of said method in accordance with the invention consists of preparing a legume starch milk, in this particular case of pea, having a dry matter content of between 30 and 40% by weight, preferably 32% by weight.

[0203] The second step of the method in accordance with the invention consists of heating the legume starch milk to a temperature 10 to 15° C. lower than its gelatinization temperature, in this particular case for pea starch, to a temperature of between 48 and 53° C., preferably to a temperature of the order of 50° C.

[0204] The Applicant company recommends using a heat exchanger, the temperature of which does not exceed 55° C. According to one embodiment of the invention, the method does not comprise a gelatinization step, i.e. the starch milk is never subjected to a temperature greater than or equal to the lowest temperature of the “gelatinization range”.

[0205] The third step of the method in accordance with the invention consists of maintaining the starch milk at said temperature, whilst stirring, for between 45 minutes and 7 hours, preferably for between 1 h and 6 hours, in an even more preferred manner 1 hour.

[0206] The stirring of the reaction medium is adjusted so as to keep the starch in suspension in the reaction medium. This may be obtained by mechanical-type stirring using an anchor, propeller or turbine-type moving body.

[0207] The Applicant company has thus found that, contrary to what is recommended in the aforementioned prior art, there is no need to resort to an annealing approach on a starch with high dry matter content (up to 60% by weight of DM is disclosed) at a temperature 10 to 15° C. lower than the gelatinization temperature of the starch for 24 to 72 hours, but rather to favor short times (no more than 6 hours) on a starch with relatively low dry matter content (of the order of 30% by weight).

[0208] It is via this approach that it will be possible to increase the SDS level of the treated starch.

[0209] The fourth and final step of the method in accordance with the invention thus consists of recovering, filtering and drying the starch milk treated in this way, as exemplified hereinafter.

[0210] The residual moisture content of the dry starch obtained is between 10 and 15% by weight, of the order of 13% by weight.

[0211] The Englyst digestibility measurement of these products gives SDS values increased by 10 to 20% by weight, preferably 12 to 17% by weight with respect to the initial starch.

[0212] As will be shown below, this SDS value for pea starch is above 40% by weight, preferably between 40 and 50% by weight.

[0213] These starches with high SDS content will then be advantageously used in fields of application relating to food (intended especially for sportspersons) or medicine (specialist nutrition).

[0214] The invention will be better understood on reading the following examples, which are intended to be illustrative, only mentioning certain embodiments and certain advantageous properties according to the invention, and are non-limiting.

EXAMPLE 1: DETERMINING THE MOST EFFECTIVE CONDITIONS FOR ANNEALING PEA STARCH

[0215] In the laboratory, pea starch milk in water at 32% by weight of dry matter is prepared by introducing a native pea starch marketed by the Applicant company under the trade name N735 in demineralized water at room temperature and under gentle stirring.

[0216] The temperature of this milk is increased to a value varying from 50° C. to 95° C. (50° C., 60° C., 65° C., 68° C., 70° C. and 80° C.) to study the impact of the heat treatment on the SDS content obtained.

[0217] The reaction mixture is stirred for 1 hour at this final temperature.

[0218] At the end of this period, the starch milk is recovered, filtered via a sintered glass filter, then dried. It then has a residual moisture content of the order of 13% by weight

[0219] FIG. 1 presents the Englyst digestibility profile (1992), determined at said temperatures.

[0220] It is observed that treatment with an annealing temperature at a value≥60° C. results in an increase in the RDS fraction content, concomitant with the start of the starch gelatinization process.

[0221] The treatment at 50° C. results in an increase in the SDS content from the value of 33% by weight for the native pea starch, to a value of 44% by weight for the hydrothermally treated starch, which therefore results in a remarkable increase of 11% by weight.

[0222] The amount of water plays an important role, and it is confirmed that the absence of water does not change the digestibility profile of the pea starch in any way.

[0223] DSC analyses were also performed on the annealing reaction products at these different temperatures.

TABLE-US-00001 TABLE 1 % moisture treatment by Onset PEAK Max. Sample type weight t° t° t° Enthalpy Pea Starch none 11.9 62.5 70 77.1 2.5 Native pea oven 12.4 62.5 70.1 77.3 2.5 starch (oven 50° C.) 50° C.-1 h Annealing 9.0 67.9 72 76.8 2.5 60° C.-1 h Annealing 9.8 75.2 78.1 81.4 1.8 65° C.-1 h Annealing 5.1 76.8 80.7 84.3 1 68° C.-1 h Annealing 4.3 NA NA NA NA 70° C.-1 h Annealing 4.7 48.5 59.8 80 1.1 95° C.-1 h Annealing 6.1 51.3 63.2 72.5 1.1

[0224] No change is observed in the absence of water (control oven at 50° C.).

[0225] The annealing treatment demonstrates that treatment at 50° C. for 1 hour is the most effective, with an onset temperature increase of approximately 5° C. after only 1 hour of treatment, a slight increase of the peak t° of +2° C., and practically no change in the max. t°.

[0226] The hydrothermal treatment is therefore quick to act on the treated pea starch in milk phase.

EXAMPLE 2: OPTIMIZING THE INCREASE IN SDS CONTENT BY CONTROLLING THE RDS FRACTION TO A VALUE OF LESS THAN 35% BY WEIGHT

[0227] The annealing method is maintained as described previously. The temperature is refined with respect to that presented in FIG. 1 so as to refine the range between ˜50 and 60° C.

[0228] FIG. 2 presents the Englyst digestibility profiles obtained at different temperatures.

[0229] In this experiment, we observe that it is possible to substantially increase the SDS fraction by controlling the RDS fraction<35% by weight by changing the annealing treatment temperature.

[0230] Thus, it can be observed that a temperature of 50° C. is a perfect compromise to master the method whilst making it possible to achieve the target.

[0231] FIG. 3 presents the Englyst digestibility profiles obtained with different dry matter contents.

[0232] It is observed that increasing the amount of dry matter to substantial values reduced the ability to produce a higher SDS fraction.

[0233] The annealing temperature is set at 50° C., as explained above.

[0234] Table 2 below gives the contents as a percentage by weight of RDS, SDS, RS and TS calculated according to the ENGLYST method.

TABLE-US-00002 TABLE 2 TS Kinetic point SC (%) RDS SDS RS (total) 20 min H.sub.2O 10.6% 89.4 17 41 41 99 40 min H.sub.2O 10.1% 89.9 16 41 35 93 1 h H.sub.2O 11.0% 89.0 20 42 38 100 2 h H.sub.2O 10.3% 89.7 19 46 32 96 3 h H.sub.2O 10.2% 89.8 23 39 39 101 4 h H.sub.2O 11.0% 89.0 18 41 47 106 6 h H.sub.2O 11.2% 88.8 19 40 44 104 24 h H.sub.2O 10.5% 89.5 20 43 37 100 48 h H.sub.2O 15.7% 84.3 18 39 40 97

[0235] It can be observed that even after 20 minutes of annealing treatment, the digestibility profile of the pea starch changes.

[0236] The best balance is found between 1 and 6 hours of annealing treatment.

[0237] By using this method, we are able, as shown below by means of 2 batches of native pea starch, to significantly increase the SDS fraction (+10 to 15% by weight) whilst controlling the increase in the RDS fraction (<35% by weight).

[0238] FIG. 4 presents this significant increase in the SDS fraction whilst controlling the increase in the RDS fraction.