Method for producing a thermally modified starch blend

Abstract

The present invention relates to a method for preparing a blend of at least two thermally modified starches, wherein the starches are granular starches from different plant sources, and the method comprises the steps consisting of: (i) preparing a starch milk containing at least two starches from different plant sources, having a total solids content between 30% by weight and 40% by weight, preferably between 35% by weight and 37% by weight; (ii) adding an alkaline reagent in order to obtain a final conductivity of the powder resuspended to 20% solids content between 0.5 mS / cm and 5 mS / cm; (iii) ensuring a contact time between 0.5 hour and 5 hours; (iv) filtering and drying the starch milk to a moisture content between 10.5% and 15% in order to obtain a starch powder having a conductivity between 0.5 mS / cm and 2.5 mS / cm and a pH between 9 and 10.5; (v) heating the dried starch powder so that its temperature is above 130°C, preferably between 130°C and 220°C, for a residence time between 10 minutes and 6 hours.

Description

[0001] The present invention relates to a method for producing a blend of at least two thermally modified starches, wherein the starches are granular starches of different plant origins, and the method comprises blending the starches of different plant origins before carrying out the actual heat treatment.

[0002] More specifically, the present invention relates to a method for producing a blend of thermally modified potato starch and waxy maize starch.

[0003] Such blends of at least two thermally modified starches make it possible to enhance their viscosity characteristics while retaining the tempering characteristics exhibited by thermally modified starches prepared from starches of a single plant origin.

[0004] Such thermally modified starches are then used as thickeners and tempering agents in many food applications, mainly in soups and sauces and in dairy products. Technical Field

[0005] As a biochemically synthesized carbohydrate source, starch is one of the most widely distributed organic materials in the plant kingdom, where it constitutes the nutritional reserve of living organisms.

[0006] Starch has been used in the food industry not only as a nutritional component but also, due to their technical properties, as thickeners, binders, stabilizers or gelling agents.

[0007] For example, native starch is used in products that require cooking. In particular, maize starch forms the basis of "pie flour".

[0008] Because it is rich in amylose, it retrogrades and thus strongly forms gels. This makes it possible to obtain firm pies after cooking and cooling.

[0009] It is also suitable for custards.

[0010] However, these cannot be used in pastries intended for freezing because, upon thawing, the syneresis phenomenon (which is reflected in the expulsion of water) destroys the texture of the custard.

[0011] Thus, in its natural state, starch has limited applicability due to syneresis, but also due to:

[0012] - its low tolerance to shear stress and heat treatment,

[0013] - its high retrogradation,

[0014] - its limited processability, and

[0015] - its low solubility in common organic solvents.

[0016] Therefore, in order to meet today's demanding technical requirements, the properties of starch must be optimized by various methods known as "modification".

[0017] Therefore, these main modifications aim to adapt starch to the technical constraints generated by cooking as well as by freezing / thawing, by sterilization or pasteurization, and to make it compatible with modern foods (microwave, instant, "high temperature", etc.).

[0018] Therefore, starch modification aims to correct one or more of the above-mentioned defects, thereby improving its versatility and meeting the needs of consumers.

[0019] The techniques used for modifying starch are generally divided into four categories: physical techniques, chemical techniques, enzymatic techniques, and genetic techniques, with the ultimate goal of producing various derivatives with optimized physicochemical properties.

[0020] Chemical modification and physical modification are the most commonly applied.

[0021] Chemical treatment involves introducing functional groups into starch, which significantly changes its physicochemical properties. In fact, this modification of granular native starch greatly alters their behavior in terms of gelatinization, adhesion, and retrogradation.

[0022] Generally, these modifications are carried out by chemical derivatization, such as esterification, etherification, crosslinking, or grafting.

[0023] However, even though some modifications are considered safe, chemical modification is less sought after by consumers in food applications (also for environmental reasons).

[0024] Therefore, various physical modifications have been proposed, such as:

[0025] - Heat-moisture treatment (HMT), which involves treating starch at a controlled moisture content (22 - 27%) and high temperature for 16 hours to change the structure and physicochemical properties of starch;

[0026] - Annealing, which involves treating starch in excess water at a temperature below the gelatinization temperature in order to approach the glass transition temperature;

[0027] - High-pressure treatment (HPP), by which the amorphous regions of starch granules are hydrated, resulting in deformation of the crystalline part of the granules and promoting the accessibility of the crystalline regions to water;

[0028] - Glow discharge plasma treatment, which generates high-energy electrons and other highly reactive species at ambient temperature. When applied to starch, these reactive species excite chemical groups in starch and cause significant crosslinking of macromolecules;

[0029] - Osmotic pressure treatment (OPT), which is carried out in the presence of a solution with a high salt content. The starch is suspended in sodium sulfate to produce a homogeneous suspension.

[0030] After treatment, the starch changes from type B to type A, thus obtaining a significantly increased gelatinization temperature;

[0031] - "Thermal inhibition" treatment. Generally, thermal inhibition means dehydrating the starch until it reaches an anhydrous or substantially anhydrous state (i.e., <1% moisture content), and then heat-treating it at a temperature above 100 °C for a sufficient period of time to "inhibit" the starch, in this case endowing it with the properties of cross-linked starch. In addition, before the forced dehydration step, the starch must be placed under at least neutral to preferably alkaline pH conditions.

[0032] An alternative method of carrying out the "thermal inhibition" treatment in the solvent phase has been proposed, and it involves heating un-pregelatinized granular starch in an alcohol-based medium in the presence of an alkali and a salt at a temperature of 120 °C to 200 °C for 5 minutes to 2 hours.

[0033] In any case, the thermal inhibition method thus results in obtaining a starch paste with increased resistance to viscosity breakdown and a non-sticky texture.

[0034] The technical field to which the present invention pertains is the thermal inhibition treatment of starch in the absence of a water-containing alcohol solvent.

[0035] In this specific technical field, reference may be made more specifically to patent US 6,221,420, which describes thermally inhibited starch obtained by dehydration followed by heat treatment.

[0036] The main steps are:

[0037] - Dehydrating the starch at a temperature between 100 °C and 125 °C until the water content is less than 1%, and then

[0038] - Heat-treating the dry starch thus obtained in a reactive fluidized bed at approximately 140 °C for a duration of approximately 20 hours.

[0039] Preferably, before the starch dehydration step, an alkalization step of the starch is recommended so that the pH value of the starch suspension can reach a value between 7 and 10, preferably between 8 and 10.

[0040] At this stage, before the appropriate dehydration step before the inhibition step, the water content of the starch (as shown by way of example) is between 8% and 10%.

[0041] Patent application US 2001 / 0017133 describes a similar method, in which, before the start of the inhibition process (at a temperature above 100 °C, preferably between 120 °C and 180 °C, more preferably between 140 °C and 160 °C), the starch is also dehydrated at a temperature below 125 °C for a duration of up to 20 hours, preferably between 3:30 hours and 4:30 hours.

[0042] Before the dehydration step, a conventional alkalization step produces a starch suspension having a pH value between 7.5 and 11.2, preferably between 8 and 9.5, and a water content between 2% and 15%.

[0043] A variant is proposed in patent application WO 2014 / 042537, which involves heating the alkaline starch to a temperature between 140 °C and 190 °C while ensuring that the inhibition method is initiated and carried out in the presence of a sufficient amount of water (i.e., more than 1% water).

[0044] In other words, the method recommends thermal inhibition of the pre-alkalized starch without a dehydration step.

[0045] Therefore, the starch product or starch is brought to a pH between 9.1 and 11.2, preferably to a value of approximately 10, and the moisture content is adjusted to between 2% and 22%, preferably between 5% and 10%.

[0046] Subsequently, the powder or the starch is directly thermally inhibited at a temperature between 140 °C and 190 °C, preferably between 140 °C and 180 °C, for a duration of 30 minutes.

[0047] The applicant's company has developed its own method for preparing thermally modified starch, which is described in its application WO 2019 / 122749 and includes:

[0048] (i) Preparing a starch milk having a solids content between 30% by weight and 40% by weight, preferably between 35% by weight and 37% by weight,

[0049] (ii) Adding an alkaline reagent to obtain a final conductivity between 0.7 mS / cm and 2.5 mS / cm,

[0050] (iii) Ensuring a contact time between 0.5 hours and 5 hours,

[0051] (iv) Filtering and drying the starch milk,

[0052] (v) Heat the dried starch so that its temperature is higher than 180 °C for a residence time between 12 minutes and 35 minutes.

[0053] The advantages of this technique are undeniable. It can not only significantly reduce the reaction time, but also process starches from all plant sources. However, even if the tempering ability of these products is satisfactory, it can be noted that the viscosity characteristics of the thermally modified starches produced by this technique can be further improved.

[0054] In the prior art, different alternatives have been proposed to improve the thermal inhibition rate of starches in order to improve their technical properties.

[0055] Thus, in patent EP 1,102,792, doping of starch in the presence of oligosaccharides having 1 to 20 sugar units was proposed.

[0056] Under certain implementation conditions, the blend of starch and oligosaccharide then exhibits better stability to refrigeration.

[0057] However, for certain food applications, a large number of purification steps must be added to remove the oligosaccharides from the starch after heat treatment.

[0058] In patent EP 2,251,358, a powder blend of starch and water-soluble hemicellulose in specific proportions is preferably used.

[0059] The heat treatment includes performing hydrothermal treatment at a temperature of 100 °C to 200 °C.

[0060] It is also recommended to incorporate sodium carbonate (or a similar alkaline compound) and hemicellulose into cassava flour, glutinous rice, or waxy maize starch.

[0061] However, a method for modifying starches is particularly sought such that the swelling and / or disintegration (e.g., rupture) of starch granules is effectively inhibited without any chemical treatment.

[0062] According to this patent, the aim is not to improve the technical properties of the starch thus thermally modified per se, but to prevent the starch used for making pastry cream from gelatinizing.

[0063] Therefore, there is still a need to provide new methods for preparing thermally modified starches that endow the thermally modified starches with improved viscosity characteristics while maintaining their excellent tolerance, or even enabling them to further develop tolerance to freeze / thaw cycles.

[0064] The applicant's company has found that this need can be met by proposing a heat treatment method for blends of at least two granular starches from different plant sources. Detailed Description

[0065] According to the present invention, a method for preparing a blend of at least two thermally modified starches, wherein the starches are granular starches of different plant origins, comprises the steps consisting of:

[0066] (i) preparing a starch milk containing at least two starches of different plant origins, having a total solids content between 30% by weight and 40% by weight, and preferably between 35% by weight and 37% by weight;

[0067] (ii) adding an alkaline reagent in order to obtain a final conductivity of the powder resuspended to 20% solids content between 0.5 mS / cm and 5 mS / cm;

[0068] (iii) ensuring a contact time between 0.5 hour and 5 hours;

[0069] (iv) filtering and drying the starch milk to a moisture content between 10.5% and 15% in order to obtain a starch powder having a conductivity between 0.5 mS / cm and 2.5 mS / cm and a pH between 9 and 10.5;

[0070] (v) heating the dried starch powder so that its temperature is higher than 130 °C, preferably between 130 °C and 220 °C, for a residence time between 10 minutes and 6 hours.

[0071] By choosing to blend starches of different plant origins before alkaline impregnation and actual heat treatment, the Applicant's company goes against the teachings of the prior art.

[0072] It is indeed known to produce starch blends to optimize their functional properties, but this is done by blending thermally modified starch varieties with native starches, as described in international patent application WO 2020 / 018061.

[0073] Furthermore, the thermal modification of blends of starches of different plant origins makes it possible to ensure the same degree of modification of the two (or more) components of the blend.

[0074] This international patent application actually protects a starch-based composition comprising:

[0075] - potato starch subjected to heat-moisture treatment (HMT), the amount of which varies between 60% and 70% by weight of the total starch composition, and

[0076] - native cassava starch, the amount of which is between 30% and 40% by weight of the starch composition.

[0077] Alternatively, if the blend is heat-treated, it is particularly recommended for blends of starch and binder. As described, for example, in patent application EP 3,345,932, starch of a given plant origin is selected and mixed with starch of the same origin but which has been enzymatically or chemically treated.

[0078] As far as the Applicant's company is aware, there has been no prior disclosure of a heat-treatment method for a prior blend of at least two starches of different plant origins.

[0079] The starch used in the method of the present invention can be of any origin, such as corn, waxy corn, high amylose corn, wheat, waxy wheat, peas, broad beans, potatoes, waxy potatoes, cassava, waxy cassava, rice, konjac, etc.

[0080] Preferably, potato starch is selected to be blended with corn starch, more specifically, with waxy corn starch (which has a high amylopectin content).

[0081] According to a specific embodiment, the method according to the present invention can involve the preparation of a blend of two thermally modified starches, wherein the starches are granular starches of different plant origins and are present in equal amounts in the blend, thus forming a 50 / 50 blend by weight.

[0082] The method according to the present invention requires the preparation of at least two starch slurries of different plant origins, which have a total solids content between 30% by weight and 40% by weight, preferably between 35% by weight and 37% by weight. As will be shown by way of example below, the solids content is set at 36.5% by weight.

[0083] The next step then involves controlling the alkaline impregnation of the blended starch.

[0084] The alkaline reagent is preferably selected from sodium hydroxide, sodium carbonate, sodium pyrophosphate, ammonium orthophosphate, disodium orthophosphate, trisodium phosphate, calcium carbonate, calcium hydroxide, potassium carbonate and potassium hydroxide, used alone or in combination, and even more preferably sodium carbonate.

[0085] The alkaline impregnation is carried out with sodium carbonate, for example by adding the alkaline reagent in powder form, to obtain a final conductivity between 0.5 mS / cm and 5 mS / cm for the powder resuspended to a 20% solids content.

[0086] Then a contact time between 0.5 hours and 5 hours, preferably between 0.5 hours and 1 hour, is ensured.

[0087] Then the actual heat-treatment is carried out. As will be described below, this embodiment is carried out in a ventilated oven at 170 °C, but these conditions can be fully translated into an implementation in a continuous turbo dryer or a reactive fluidized bed apparatus.

[0088] In these industrial installations, the conductivity and pH set points of the blended starch powder before heat treatment are as follows:

[0089] - Conductivity: between 0.5 mS / cm and 2.5 mS / cm,

[0090] - pH: between 9.5 and 10.5.

[0091] In a first embodiment of the method according to the invention, the next heat treatment step itself can be carried out in a heat treatment device that combines heat exchange by conduction and by convection, which is a device of the turbo dryer type, such as at least one continuous turbo dryer of the VOMM type. Thus, depending on the size of the VOMM, this allows for a very short reaction time of about a few minutes, i.e., less than 5 minutes for each heat treatment stage.

[0092] The temperature set point is then set to a value greater than 190 °C, preferably between 200 °C and 210 °C, for a residence time between 10 minutes and 60 minutes, and even more preferably between 15 minutes and 35 minutes.

[0093] ΔT is between 17 °C and 27 °C, where ΔT is defined as the temperature difference between the set point temperature and the temperature of the product at the reactor outlet.

[0094] In a second embodiment of the method according to the invention, the actual heat treatment can be carried out in a device of the "reactive fluidized bed" type.

[0095] As is known to those skilled in the art, this device consists of a reactor, which allows for the suspension of solids separated by a gas (in this case an air / nitrogen blend). The velocity of the gas is adjusted according to the feedstock.

[0096] The heat treatment temperature (temperature of the product) is between 130 °C and 200 °C, and the reaction time varies between 30 minutes and 6 hours, preferably between 2 hours and 4 hours.

[0097] The heat-modified starches according to the invention will advantageously be used as thickeners or texturizers in food applications, particularly in soups, sauces, and dairy products, based on their respective properties.

[0098] One of the main limitations of heat-modified starches made from a single plant source is that the viscosity produced is slightly lower than that of commercially available chemically modified starches, so that in the case of a 100% natural and "with the smallest possible chemical conversion" ("clean label") solution, an excess is required in the case of replacement.

[0099] Therefore, these blends are described as a simple and effective solution for the industry for manufacturing, for example, sauces.

[0100] More specifically, these blends seem to meet the technical requirements of pasteurization, average shear, and acidic pH.

[0101] The present invention will be better understood with the aid of the following examples, which are intended to be illustrative and non - limiting.

[0102] Examples

[0103] Materials and Methods

[0104] Measurement of Electrical Conductivity

[0105] The method implemented herein is adapted from the European Pharmacopoeia - current official version - Conductivity (§2.2.38).

[0106] Equipment :

[0107] A KNICK 703 electronic conductometer, also equipped with its measuring chamber, and verified according to the procedure described in its instruction manual.

[0108] Procedure :

[0109] Prepare a solution containing 20 g of the sample in powder form and 80 g of distilled water with a resistivity greater than 500,000 ohms.cm.

[0110] Use the conductometer to measure at 20 °C, referring to the procedure shown in the user manual of the instrument.

[0111] These values are expressed in millisiemens per centimeter (mS / cm).

[0112] Measuring the viscosity of starch suspensions using a Rapid Visco Analyzer ( RVA )

[0113] This measurement is carried out under predetermined concentration conditions and according to a suitable temperature / time analysis curve.

[0114] Prepare two buffer solutions:

[0115] Buffer solution A

[0116] Add the following substances to a 1 - liter beaker containing 500 mL of deionized water:

[0117] - 91.0 g of citric acid monohydrate (purity > 99.5 %), and homogenize,

[0118] -33.0 g of sodium chloride (purity > 99.5%) and homogenize until completely dissolved,

[0119] -300.0 g of 1N caustic soda.

[0120] Decant the contents into a 1 L volumetric flask and add deionized water to 1 L.

[0121] Buffer solution B

[0122] Mix 100 g of buffer A with 334.0 g of deionized water.

[0123] Prepare the product to be analyzed as follows:

[0124] Directly introduce 1.37 g of the dry product to be analyzed, obtained in this way, into the container of the viscometer, and introduce buffer solution B until a mass equal to 28.00 ± 0.01 g is obtained. Homogenize using the stirring blade of a Rapid Visco Analyzer (RVA - NewPort Scientific).

[0125] Then perform the time / temperature and speed analysis curves in the RVA as follows:

[0126] Table 1

[0127]

[0128] End of test: 00:20:05 (hh:mm:ss)

[0129] Initial temperature: 50 °C ± 0.5 °C

[0130] Data acquisition interval: 2 seconds

[0131] Sensitivity: low

[0132] The measurement results are given in RVU (the unit used to represent the viscosity obtained on the RVA), and it is known that 1 RVU unit = 12 centipoise (cP).

[0133] As a reminder, 1 cP = 1 mPa.s.

[0134] Therefore, the results will be shown in mPa.s.

[0135] The viscosity measurement results will be obtained "at the peak" (i.e., the maximum viscosity value between 4 minutes and 6 minutes) and "during the decline" (i.e., the difference between the viscosity value at the peak and the viscosity value measured at 17 minutes).

[0136] Example 1: Obtaining a thermally modified starch blend in a ventilated oven

[0137] These first tests were carried out in an oven on a laboratory scale in order to select the optimal ratio of potato starch and waxy maize starch in the blend before conducting industrial tests.

[0138] Preparation of the starch blend and impregnation with sodium carbonate.

[0139] The native starches (waxy maize starch and potato starch) are products sold by the applicant's company under these same names.

[0140] The waxy maize starch and the powdered potato starch were introduced in the proportions shown in Table 2 below.

[0141] The powder blend was then suspended in deionized water in order to obtain a total solids content of 36.5% by weight.

[0142] The pH and conductivity of the suspension were then measured.

[0143] Sodium carbonate was added to the milk under the following alternative conditions:

[0144] - If sodium carbonate was added in powder form: an amount sufficient to obtain a final conductivity between 0.5 mS / cm and 1 mS / cm measured for the powder resuspended to 20% solids. A contact time of 2 hours was allowed.

[0145] - If sodium carbonate was added in solution at a 30% by weight concentration: an amount sufficient to obtain a conductivity between 2 mS / cm and 4 mS / cm for the milk. Given that the sodium carbonate was already 30% dissolved in solution, a contact time of 30 minutes was sufficient.

[0146] It was filtered and dried to a starch equilibrium moisture between 10% and 14%.

[0147] Table 2

[0148] Tests Weight percentage of waxy maize starch Weight percentage of potato starch E-1* 100 0 E-2 94 6 E-3 90 10 E-4 70 30 E-5 50 50 E-6* 0 100

[0149] (*) : Tests E-1 and E-6 are starch controls from a single plant source.

[0150] Heat treatment in an oven

[0151] Equipment used:

[0152] - MEMMERT ventilated oven.

[0153] - Aluminium cups for METTLER LJ16 (humidity measurement scale).

[0154] - Ruler.

[0155] Procedure:

[0156] - Weigh the starch matrix to be tested, ~40 g / aluminum cup.

[0157] - Place the cup in a MEMMERT oven pre-set to 170 °C.

[0158] - Start the timer after inserting the cup into the oven.

[0159] - Then remove the cup from the oven at each point of the reaction kinetics.

[0160] Neutralization and washing of the resulting product

[0161] After reacting at 170 °C, resuspend the test substance of 36% solids in deionized water.

[0162] Adjust the pH to between 5.5 and 6 with HCl.

[0163] Filter it and wash it by percolation to obtain a conductivity of <500 mS / cm for the final product resuspended to 20% solids.

[0164] Dry the obtained "cake" overnight at ambient temperature under a fume hood.

[0165] Coarsely grind it on a basic IKA A11 grinder and then sieve it through a 315 μm sieve.

[0166] Example 2: Characterization of the thermally modified starch blend

[0167] Perform RVA viscosity measurements at 92 °C and show them in Table 3 below.

[0168] Table 3

[0169]

[0170]

[0171] Compared to native starch, the thermally modified starch according to the present invention has improved stability during use: less viscosity increase and retrogradation are observed when using these starches. In this regard, it is actually observed that the more the RVA decline trend tends towards 0 or becomes negative, the more the product will be functionalized, the more tolerant it will be and the less retrogradation it will exhibit.

[0172] Construct comparisons with commercially available modified chemical starch ( CH2020) and waxy heat-inhibiting starch ( 2600, 2300 and PLUS). The results are shown in Table 4.

[0173] Table 4

[0174]

[0175] The products shown in the table are produced from a single plant source, in this case waxy corn starch.

[0176] Heat-inhibited starches such as 2600, 2300, and PLUS, and heat-modified starches E-1 and E-6 have in common the fact that they all have a lower peak viscosity than CH2020 which is a chemically modified starch.

[0177] By producing a blend of potato starch and waxy corn starch, the peak viscosity is higher than that of the modified starches obtained from a single plant source.

[0178] The 50 / 50 blend provides the best compromise between its peak viscosity (representing the viscosity formed by the product) and its breakdown viscosity (representing its tolerance level).

[0179] The 50 / 50 blend makes it possible to benefit from the advantages of both raw materials in terms of texture, tolerance, and viscosity generation.

[0180] Example 3: Preparation of thermally modified starch blend A in a VOMM continuous turbo dryer.

[0181] 1) The alkalization of the starch blend is carried out according to the following steps:

[0182] - Prepare a suspension of 50 / 50 wt% waxy corn starch and potato starch having 36.5% solids;

[0183] - Add sodium carbonate in powder form so as to obtain a final conductivity between 0.5 mS / cm and 1 mS / cm for the powder resuspended to 20% solids;

[0184] - Ensure a contact time of 2 hours;

[0185] - Filter and dry to a starch equilibrium moisture content between 10% and 14%.

[0186] Instead of adding sodium carbonate in powder form, it is perfectly possible to:

[0187] - Prepare an aqueous solution of sodium carbonate at a concentration of 30 wt% and heat it to 40 °C - 50 °C to facilitate carbonate dissolution;

[0188] - Add the 30 wt% sodium carbonate solution so as to obtain a conductivity between 2 mS / cm and 4 mS / cm for the milk;

[0189] - Ensure a contact time of 30 minutes.

[0190] This allows for a reduction in contact time as the carbonate is already 30% well dissolved in the solution.

[0191] 2) Heat treatment

[0192] The product obtained in this way is heat-treated in a continuous turbo dryer of the VOMM type in series, the set-point temperature of which is set to 210 °C and which is configured to subject the product to a residence time of 30 minutes and to have a temperature difference (referred to as ΔT) between the set-point and the product temperature at the reactor outlet of approximately 21 °C.

[0193] Process parameters

[0194] Table 5

[0195]

[0196] RVA viscosity measurements are carried out and shown in the table below.

[0197] Results

[0198] Table 6

[0199] Experiments Decrease in RVA (MPa.s) Peak RVA (MPa.s) 50 / 50 waxy starch / potato starch matrix 990 1169 A-1 -158 577

[0200] The 50 / 50 blend here also provides the best compromise between its peak viscosity (representing the viscosity formed by the product) and its breakdown viscosity (representing its tolerance level).

[0201] Example 4: Preparation of thermally modified starch blend B in a VOMM continuous turbo dryer 。

[0202] 1) Alkalinization of the starch blend is carried out according to the following steps :

[0203] - Prepare a suspension of 50 / 50 wt% waxy corn starch and potato starch having 36.5% solids;

[0204] - Add sodium carbonate in powder form so as to obtain a final conductivity between 0.5 mS / cm and 1 mS / cm for the powder resuspended to 20% solids;

[0205] - Ensure a contact time of 2 hours;

[0206] - Filter and dry to a starch equilibrium moisture content between 10% and 14%.

[0207] Instead of adding sodium carbonate in powder form, it is perfectly possible to:

[0208] - Prepare a sodium carbonate solution at a concentration of 30% by weight and heat it to 40°C - 50°C to promote the dissolution of the carbonate;

[0209] - Add the sodium carbonate solution at a concentration of 30% by weight in order to obtain a conductivity between 2 mS / cm and 4 mS / cm for the milk;

[0210] - Ensure a contact time of 30 minutes.

[0211] This makes it possible to reduce the contact time because the carbonate is already well dissolved in the solution at 30%.

[0212] 2) Heat treatment

[0213] The product obtained in this way is heat-treated in a continuous turbo dryer of the VOMM type in series, the setpoint temperature of which is set at 210°C and which is configured to subject the product to a residence time of 35 minutes to 40 minutes and to make the temperature difference (called ΔT) between the setpoint and the product temperature at the reactor outlet a value of approximately 24°C to 25°C.

[0214] Process parameters

[0215] Table 7

[0216]

[0217] RVA viscosity measurements are carried out and shown in the table below.

[0218] Results

[0219] Table 8

[0220] Experiments Decrease in RVA (MPa.s) Peak RVA (MPa.s) 50 / 50 waxy starch / potato starch matrix 990 1169 B-1 -386 648 B-2 -497 469

[0221] The 50 / 50 blend here also provides the best compromise between its peak viscosity (representing the viscosity formed by the product) and its breakdown viscosity (representing its tolerance level).

[0222] Example 5: Preparation of thermally modified starch blend C in a VOMM continuous turbo dryer 。

[0223] 1) Alkalinization of the starch blend is carried out according to the following steps :

[0224] - Prepare a suspension of 50 / 50% by weight of waxy maize starch and potato starch, which has 36.5% solids;

[0225] - Add sodium carbonate in powder form to obtain a final conductivity between 0.5 mS / cm and 1 mS / cm for the powder resuspended to 20% solids;

[0226] - Ensure a contact time of 2 hours;

[0227] - Filter and dry to a starch equilibrium moisture content between 10% and 14%.

[0228] Instead of adding sodium carbonate in powder form, it is entirely possible that:

[0229] - Prepare a 30 wt% concentration sodium carbonate solution and heat it to 40 °C - 50 °C to facilitate carbonate dissolution;

[0230] - Add the 30 wt% concentration sodium carbonate solution to obtain a conductivity between 2 mS / cm and 4 mS / cm for the emulsion;

[0231] - Ensure a contact time of 30 minutes.

[0232] This allows for a reduction in contact time as the carbonate is already 30% well dissolved in the solution

[0233] 2) Heat treatment

[0234] The product obtained in this way is heat-treated in a VOMM type continuous turbo dryer in series, the set point temperature of which is set to 210 °C and which is configured to subject the product to a residence time of 45 minutes to 50 minutes and to have a temperature difference (referred to as ΔT) between the set point and the product temperature at the reactor outlet of approximately 22 °C to 25 °C.

[0235] Process parameters

[0236] Table 9

[0237]

[0238] RVA viscosity measurements are carried out and shown in the table below.

[0239] Results

[0240] Table 10

[0241] Experiments Decrease in RVA (MPa.s) Peak RVA (MPa.s) 50 / 50 waxy starch / potato starch matrix 990 1169 C-1 -504 345 C-2 -457 181

[0242] The thermally modified starch blend C represents the product that is most tolerant to shear, to the acidity of the medium, and to heat treatment.

[0243] The heat-modified starch blend B has slightly lower tolerance than the heat-modified starch blend C, and the heat-modified starch blend A has slightly lower tolerance to some extent than the heat-modified starch blend B.

[0244] If the reaction times between the method in the oven and the method in the VOMM type turbo dryer are compared, a reaction time of about 35 minutes in the series-connected VOMM type turbo dryer gives a product with a functionality close to that of product E-5 obtained after a 1.5-hour reaction time.

[0245] Similarly, a reaction time between 40 minutes and 45 minutes is required in the series-connected VOMM type turbo dryer to obtain a product with a functionality close to that of product E-5 obtained after a 2-hour reaction time.

[0246] The choice of using these starch blends will be based on the intended application and thus on the shear, acidity, and temperature conditions of implementation.

Claims

1. A method for preparing a blend of at least two thermally modified starches, wherein the starches are granular starches from different plant sources, the method comprising the steps consisting of: (i) preparing a starch milk containing at least two starches from different plant sources, having a total solids content between 30% and 40% by weight, (ii) adding an alkaline reagent to obtain a final conductivity of the powder resuspended to 20% solids content between 0.5 mS / cm and 5 mS / cm, (iii) ensuring a contact time between 0.5 hour and 5 hours, (iv) filtering and drying the starch milk to a moisture content between 10.5% and 15% to obtain a starch powder having a conductivity between 0.5 mS / cm and 2.5 mS / cm and a pH between 9 and 10.5, (v) heating the dried starch powder to a temperature above 130 °C for a residence time between 10 minutes and 6 hours.

2. The method according to claim 1, wherein The plant sources of the starches are selected from corn, wheat, peas, broad beans, potatoes, cassava, rice, and konjac.

3. The method according to claim 2, wherein The corn is waxy corn or high amylose corn.

4. The method according to claim 2, wherein The wheat is waxy wheat.

5. The method according to claim 2, wherein The potato is waxy potato.

6. The method according to claim 2, wherein The cassava is waxy cassava.

7. The method according to claim 2, wherein The plant sources of the starches are selected from potato starch and waxy corn starch.

8. The method according to claim 1, characterized in that In step (i), the starch milk has a total solids content between 35% and 37% by weight.

9. The method according to claim 1, wherein In step (v), the dried starch powder is heated to a temperature between 130 °C and 220 °C for a residence time between 10 minutes and 6 hours.

10. The method according to claim 1, wherein The alkaline reagent is selected from sodium hydroxide, sodium carbonate, tetrasodium pyrophosphate, ammonium orthophosphate, disodium orthophosphate, trisodium phosphate, calcium carbonate, calcium hydroxide, potassium carbonate, and potassium hydroxide, used alone or in combination.

11. The method according to claim 1, characterized in that The alkaline reagent is sodium carbonate.

12. The method according to claim 10, wherein In step (v), heating the dried starch powder is carried out in a continuous turbo dryer type device, the set point temperature of the continuous turbo dryer type device is set to be greater than 190 °C, for a residence time between 10 minutes and 60 minutes, and ΔT is between 17 °C and 27 °C, where ΔT is defined as the temperature difference between the set point temperature and the product temperature at the reactor outlet.

13. The method according to claim 10, characterized in that In step (v), heating the dried starch powder is carried out in a continuous turbo dryer type device, the set point temperature of the continuous turbo dryer type device is set to be between 200 °C and 210 °C, for a residence time between 15 minutes and 35 minutes, and ΔT is between 17 °C and 27 °C, where ΔT is defined as the temperature difference between the set point temperature and the product temperature at the reactor outlet.

14. The method according to claim 10, wherein In step (v), heating the dried starch powder is carried out in a reaction fluidized bed type device, the set point temperature of the reaction fluidized bed type device is set to be greater than 130 °C, for a residence time between 30 minutes and 6 hours.

15. The method according to claim 10, wherein In step (v), the heating of the dried starch powder is carried out in a reaction fluidized bed type apparatus, and the set point temperature of the reaction fluidized bed type apparatus is set to be between 130 °C and 200 °C for a residence time between 2 hours and 4 hours.

16. Use of the heat-modified starch produced by the method according to any one of the preceding claims as a thickening agent or texturizer in food applications, in particular in soups and sauces and in dairy products.

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