Dry baked rice starch

Abstract

The present invention relates to a method for producing a thermally modified rice starch having heat resistance, acid resistance and shear resistance and having a stable viscosity, the method comprising the step of heating the rice starch to a temperature of between 150 DEG C and 200 DEG C, a residence time of between 0.5 hours and 6 hours. The invention also relates to a thickening or texturing agent in food applications, in particular in yoghurt, catsup, salad flavorings, sauces, comprising the thermally modified starch obtained according to the method of the invention.

Description

[0001] This invention relates to the production of dry-roasted rice starch, which has improved heat resistance, acid resistance and shear resistance, and has a stable viscosity after such heat treatment.

[0002] These heat-modified starches can then be used as texturers and thickeners in many food applications, especially as natural texturers, particularly for acidic foods and foods requiring shearing, such as yogurt, ketchup, salad dressings, sauces, etc. Technical Field

[0003] As a source of carbohydrates synthesized through biochemistry, starch is one of the most widely distributed organic materials in the plant kingdom, where it constitutes the nutrient reserves of organisms.

[0004] Starch has long been used in the food industry, not only as a nutrient but also as a thickener, binder, stabilizer, or gelling agent due to its functional properties.

[0005] For example, natural starches are known to be used in preparations that require cooking. Specifically, corn starch forms the basis of "pie flour".

[0006] When it is rich in amylose, it retrogrades and thus forms a strong gel. Therefore, a firm pie can be obtained after cooking and cooling. It is also suitable for milk cakes.

[0007] However, these cannot be used in pastries intended for freezing because the well-known dehydration shrinkage (manifested as the expulsion of water) occurs during thawing, thus ruining the texture of the cake.

[0008] Therefore, starch has limited applicability in its natural state, due to dehydration shrinkage, and also because:

[0009] - Its low tolerance to shear stress, heat treatment, and acidic pH.

[0010] - Its limited processability, and

[0011] - Its low solubility in common organic solvents.

[0012] Therefore, in order to meet today's demanding technical requirements, the properties of starch must be optimized through various methods known as "modification".

[0013] Therefore, these major modifications aim to adapt starch to the technical constraints imposed by cooking, freezing / thawing, sterilization or disinfection, and acidic pH, and to make it compatible with modern foods (microwave, fast food, "high temperature", etc.).

[0014] Therefore, starch modification aims to correct one or more of the above-mentioned defects, thereby improving its versatility and meeting consumer needs.

[0015] Technologies used for starch modification are generally classified into four categories: physical technologies, chemical technologies, enzyme technologies, and genetic technologies. The ultimate goal is to produce various derivatives with optimized physicochemical properties.

[0016] Chemical modification and physical modification are the most commonly used methods.

[0017] Chemical treatments involve introducing new functional groups onto starch molecules, which significantly alters their physicochemical properties. In fact, such modifications to granular natural starch drastically change their behavior in gelatinization, pasting, gelling, and retrogradation.

[0018] Typically, these modifications are achieved through chemical derivatization, such as esterification, etherification, crosslinking, or grafting.

[0019] However, even though some modifications are generally considered to be safe for human consumption (GRAS), chemical modifications are less sought after by consumers in food applications (also for environmental reasons).

[0020] Therefore, various physical modifications have been proposed, such as:

[0021] - Humid heat treatment (HMT) involves treating starch for 16 hours or longer at controlled moisture content (typically 22% to 27%) and high temperature to alter the structure and physicochemical properties of the starch.

[0022] - Annealing, which involves treating starch in excess water at a temperature below the gelatinization temperature in order to approach the glass transition temperature;

[0023] - High pressure processing (HPP), through which the amorphous regions of starch granules are hydrated, thereby causing the crystalline portions of the granules to deform and promoting the accessibility of the crystalline regions to water.

[0024] - Glow discharge plasma treatment generates high-energy electrons and other highly reactive substances at ambient temperature. When applied to starch, these reactive substances excite chemical groups in the starch and cause significant cross-linking of macromolecules;

[0025] - Osmotic pressure treatment (OPT) is carried out in the presence of a solution with a high salt content. Starch is suspended in a saturated salt solution (high osmotic pressure) and then exposed to high temperatures. This treatment significantly increases the gelatinization temperature of the starch. It also changes the crystalline structure of starches with type B crystallinity (such as potato starch) to type A crystallinity;

[0026] - "Dry heat" treatment (DHT) involves treating starch at high temperatures, typically between 100°C and 150°C, under conditions of reduced moisture (<10%).

[0027] - "Heat inhibition" treatment. Typically, heat inhibition refers to dehydrating starch until it reaches anhydrous or substantially anhydrous state (i.e., <1% moisture), and then heat-treating it at above 100°C for a sufficient period of time to "inhibit" the starch, thus providing the properties of cross-linked starch. Furthermore, the starch must be adjusted to at least neutral to preferably alkaline pH conditions before the forced dehydration step.

[0028] An alternative method for “thermal inhibition” treatment in a solvent phase has been proposed, which involves heating ungelatinized granular starch in an alcohol-based medium at a temperature of 120°C to 200°C for 5 minutes to 2 hours in the presence of alkali and salt.

[0029] In any case, the heat-inhibition method thus results in starch pastes with increased resistance to viscosity disintegration and non-sticky properties.

[0030] In this specific technical field, more specific reference can be made to U.S. Patent No. 6,221,420, which describes heat-inhibited starch obtained by dehydration followed by heat treatment.

[0031] The main steps are:

[0032] - Dehydrate the starch to anhydrous or nearly anhydrous state (<1% moisture), then

[0033] - The dried starch obtained therefrom is heat-treated at 100°C to 180°C for a maximum of 20 hours.

[0034] Prior to the starch dehydration step, it is recommended to perform an alkalization step to bring the starch pH value to a value between 7 and 10, preferably between 8 and 10.

[0035] At this stage, prior to the forced dehydration step before the inhibition step, the water content of the starch (as shown by way of example) is between 8% and 10%.

[0036] US 2001 / 0017133 describes a similar method in which starch is also thermally or non-thermally dehydrated to anhydrous or substantially anhydrous (i.e., <1% moisture), and then the process is inhibited at a temperature above 100°C, preferably between 120°C and 180°C.

[0037] Prior to the dehydration step, a conventional alkalization step produces a starch suspension with a neutral or greater pH, preferably between 7 and 9.5, and a water content between 2% and 15%.

[0038] A variation is proposed in patent application WO 2014 / 042537, which involves heating alkaline starch at a temperature between 140°C and 190°C while ensuring that the inhibition method is initiated and carried out in the presence of sufficient water (i.e., more than 1% water).

[0039] In other words, this method recommends thermal inhibition of pre-alkalized starch, rather than a forced dehydration step to an anhydrous state.

[0040] Therefore, the pH of the starch preparation or starch should be between 9.1 and 11.2, preferably about 10, and the water content should be adjusted to between 2% and 22%, preferably between 5% and 10%.

[0041] The powder or starch is then subjected to direct heat inhibition at a temperature between 140°C and 190°C, preferably between 140°C and 180°C, for at least 30 minutes and at most 3 hours.

[0042] Based on the foregoing, it should be noted that the heat inhibition method implemented to stabilize starch viscosity requires the following conditions:

[0043] - Long processing duration, i.e., up to 20 hours at temperatures above 100°C.

[0044] - Adjust the pH of the starch to neutral or alkaline, and / or

[0045] -Based on the methods proposed in the prior art, the water content of starch is controlled to be less than 1% or alternatively between 2% and 22% before heat inhibition treatment.

[0046] Therefore, a new method for inhibiting starch is needed, which would allow for further reduction in reaction or preparation time without requiring control of the water content of the starch to be "heat-inhibited" or adjustment of its pH. Summary of the Invention

[0047] Therefore, the present invention relates to a method for producing heat-modified starch, the method comprising the steps of: heating rice starch to a temperature between 150°C and 200°C, preferably 170°C, and holding it for a time between 0.5 hours and 6 hours, more preferably between 1 hour and 2 hours.

[0048] Rice starch can be natural standard (or ordinary) rice starch or natural glutinous (or sticky) rice starch.

[0049] Starch can be used in purified or fine powder form, as described in the following examples.

[0050] The method according to the present invention first requires the use of dried rice starch powder, whose natural moisture content is in equilibrium with the relative humidity of the air at room temperature.

[0051] Then, unlike conventional inhibition methods, alkali impregnation and / or precise control of water content are not required before heat treatment.

[0052] The next step then involves heating the starch powder at a temperature between 150°C and 200°C, preferably at 170°C, for a residence time between 0.5 hours and 6 hours, more preferably between 1 hour and 2 hours.

[0053] Those skilled in the art will recognize the method as commonly referred to as dry roasting.

[0054] To the applicant's knowledge, dry-roasting technology has never been used to "inhibit" starch, that is, to impart to it significant heat resistance, acid and shear resistance, as well as stable viscosity.

[0055] In fact, not only as described in JP 2012100650 and WO 93 / 09145, but also as described in scientific papers such as Srivastava et al., 1970, Starch-Stärke, 22 (2), pp. 49-54; and Ueno et al., 1976, Starch-Stärke, 28 (3), pp. 77-83, baking and drying starch is a common method for dextrinization (also known as caramelization), which is used to break down the molecular chains in starch granules to provide smaller structural units.

[0056] As will be shown in one of the following embodiments, the applicant found that all starches from various plant sources (except rice) experienced a decrease in peak viscosity after dry-roasting, which was more pronounced after dry-roasting at higher temperatures or for longer periods, confirming the phenomenon of thermal degradation or dextrinization.

[0057] Therefore, it is surprising and unexpected that the dry-roasting method is considered to be able to optimize the properties of rice starch processed in this way.

[0058] Furthermore, the applicant commendably discovered that the solution uses a specific starch extracted from common or glutinous varieties, regardless of its origin.

[0059] As shown below, compared with the natural counterpart, the thermally modified rice starch produced according to the method of the present invention exhibits an increased trough value to peak viscosity ratio during heating in demineralized water.

[0060] More specifically, the ratio of valley viscosity to peak viscosity is greater than 60%, more preferably greater than 70%, and even greater than 80%.

[0061] Similar to the paste-forming properties in demineralized water, dry-roasting also increases the ratio of trough value to peak viscosity of the thermally modified starch during heating in acidic solutions compared to the natural counterpart.

[0062] Dry roasting treatment inhibits the growth of both regular and glutinous rice starch, improving the starch granules' tolerance to acid hydrolysis during heating, similar to the phenomenon observed in chemically cross-linked starches.

[0063] More specifically, the ratio of valley viscosity to peak viscosity is greater than 50%, more preferably greater than 65%, and even greater than 80%.

[0064] In another implementation, the temperature increase can be carried out on a laboratory scale, such as using a hot air oven. It can also be carried out on a pilot and industrial scale, such as using a VOMM dryer, a fluidized bed dryer, or a cone dryer.

[0065] The present invention also relates to a heat-modified starch obtained according to the above method.

[0066] The heat-modified starch according to the invention will be advantageously used as a texturer and thickener in a variety of food applications based on its respective properties, particularly as a natural texturer, especially for acidic foods and foods requiring shearing, such as yogurt, ketchup, salad dressings, sauces, etc.

[0067] The invention will be better understood with the aid of the following embodiments, which are intended to be illustrative and non-limiting.

[0068] Attached Figure :

[0069] Figure 1 Pasteurization curve of dry-roasted common rice starch from source 1 in demineralized water.

[0070] Figure 2 Pasteurization curves of dry-roasted and chemically cross-linked glutinous rice starch from source 1 in demineralized water.

[0071] Figure 3 Pasteurization curve of dry-roasted glutinous rice starch from source 2 in demineralized water.

[0072] Figure 4 Pasteurization curve of dry-roasted common rice starch from source 1 in citric acid solution.

[0073] Figure 5 Pasteurization curves of dry-roasted and chemically cross-linked glutinous rice starch from source 1 in citric acid solution.

[0074] Figure 6 Pasteurization curve of dry-roasted glutinous rice starch from source 2 in citric acid solution.

[0075] Figure 7 Pasteurization curves of dry-roasted ordinary and glutinous rice flour in demineralized water.

[0076] Figure 8 Pasteurization curves of dry-roasted ordinary and glutinous rice flour in citric acid solution.

[0077] Figure 9 Pasteurization curve of dry-roasted pea starch in demineralized water.

[0078] Figure 10 Pasteurization curve of dry-roasted cassava starch in demineralized water.

[0079] Figure 11 Pasteurization curve of dry-roasted potato starch in demineralized water.

[0080] Figure 12 Pasteurization curve of dry-roasted glutinous corn starch in demineralized water.

[0081] Figure 13 Pasteurization curve of dry-roasted ordinary corn starch in demineralized water.

[0082] Figure 14 Pasteurization curve of dry-roasted pea starch in citric acid solution.

[0083] Figure 15 Pasteurization curve of dry-roasted cassava starch in citric acid solution.

[0084] Figure 16 Pasteurization curve of dry-roasted potato starch in citric acid solution.

[0085] Figure 17 Pasteurization curve of dry-roasted glutinous corn starch in citric acid solution.

[0086] Figure 18 Pasteurization curve of dry-roasted ordinary corn starch in citric acid solution.

[0087] Figure 19 Pasteurization curves of glutinous rice starch in citric acid solution after dry baking at 170℃ for 0 to 6 hours.

[0088] Figure 20 Pasteurization curves of ordinary rice starch in citric acid solution after dry-roasting at 170℃ for 0 to 6 hours.

[0089] Figure 21 The relationship between the sedimentation volume of glutinous rice and ordinary rice starch and the drying time at 170℃. Example

[0090] Example 1. Dry-roasted glutinous rice and ordinary rice starch .

[0091] Starch materials

[0092] - Common rice starch, from Anhui Shunxinshengyuan Biological Food Co., Ltd., China (Source 1).

[0093] - Glutinous rice starch, from Anhui Shunxinshengyuan Biological Food Co., Ltd., China (Source 1).

[0094] - Glutinous rice starch, from Wuhan Meiyuan Bioengineering Co., Ltd., China (Source 2).

[0095] -As a control, cross-linked glutinous rice starch was prepared as follows:

[0096] Starch slurry (36% w / w) was prepared using glutinous rice starch from Source 1 and decarbonated water. Sodium bisulfite (100 ppm, dry starch-“dsb”) and sodium chloride (2% w / w, dsb) were added to the starch slurry.

[0097] Adjust the pH of the slurry to 8 using a dilute sodium hydroxide solution, then add an additional 1% w / w (dsb) sodium hydroxide by slowly adding the dilute solution. Set the temperature to 35°C and maintain it throughout the reaction. Add sodium trimetaphosphate (0.6% w / w, dsb) to initiate the reaction.

[0098] The reaction was terminated after 2, 4, and 6 hours (corresponding to mild, moderate, and high chemical crosslinking, respectively) by neutralizing the pH to 6 with dilute hydrochloric acid solution. The resulting crosslinked starch was collected by vacuum filtration, washed with decarbonated water, and dried in a fluidized bed dryer (Retsch TG200, Germany).

[0099] process

[0100] Dry roasting

[0101] Without any pretreatment or pH adjustment, place 25g of natural glutinous or ordinary rice starch on an aluminum pan and heat at 170°C for 1 or 2 hours or at 190°C for 1 hour.

[0102] Analytical methods

[0103] Pasting properties in demineralized water

[0104] Paste formation analysis of demineralized water was performed using a rapid viscosity analyzer (RVA) from Perten Instruments, Australia, to understand the tolerance of starch paste to heat and shear.

[0105] In an aluminum can, starch was mixed with demineralized water to obtain an 8% w / w slurry. The slurry was isothermally heated at 50°C for 1 minute, then heated to 92°C at a rate of 10.5°C / min (for a total of 4 minutes), isothermally heated at 92°C for 5 minutes, cooled to 50°C at a rate of 10.5°C / min (for a total of 4 minutes), and finally isothermally heated at 50°C for 11 minutes.

[0106] To ensure better mixing, the stirring was started at 100 rpm, increased to 500 rpm and 960 rpm after 10 and 20 seconds respectively, and then reduced to 160 rpm after 30 seconds, where it was kept constant until the end of the test.

[0107] The RVA heating curves are summarized in Table 1.

[0108] Table 1. Analytical parameters for the paste-forming characteristics of demineralized water .

[0109]

[0110] The terminology for smearing curves is as follows:

[0111] - The paste-forming temperature is the temperature at which the viscosity begins to increase.

[0112] - Peak viscosity is the maximum viscosity during heating from 50°C to 92°C and during isothermal heating at 92°C.

[0113] - The valley value is the minimum viscosity during isothermal heating at 92°C and cooling from 92°C to 50°C.

[0114] - The final viscosity is the viscosity at the end of the measurement.

[0115] The disintegration value is the difference between the peak viscosity and the valley viscosity.

[0116] - The reversion value is the difference between the final viscosity and the valley value.

[0117] Figures 1 to 3 The pasteurization curves of dry-roasted rice starch and chemically cross-linked rice starch in demineralized water are shown.

[0118] Table 2 shows the paste-forming characteristics of dry-roasted rice starch and chemically cross-linked rice starch in demineralized water.

[0119] Table 2. Pasteurizing characteristics of dry-roasted rice starch and chemically cross-linked rice starch in demineralized water .

[0120]

[0121] 1 Ratio = Valley value / Peak viscosity

[0122] Generally, compared to their natural counterparts as starting starch materials, dry-roasting reduces the pasteurization temperature and disintegration of common rice starch and glutinous rice starch, while increasing their trough value to peak viscosity ratio during heating in demineralized water. Figures 1 to 3 (and Table 2).

[0123] The results showed that dry roasting inhibited the heat and shear resistance of both common rice starch and glutinous rice starch. Some of the dry-roasted common and glutinous starches from Source 1 exhibited higher peak viscosity, trough value, and / or overall pasteurization viscosity than their natural counterparts, similar to lightly chemically cross-linked starches (such as...). Figure 2 (and the 2-hour crosslinking in Table 2).

[0124] Mild cross-linking can fix the swollen starch granules, preventing them from breaking down during heating and shearing, thus producing a higher paste viscosity than natural starch.

[0125] However, when starch is dry-roasted at higher temperatures or for longer periods, the overall paste viscosity decreases due to higher levels of thermal inhibition, which delays particle swelling during heating, similar to highly chemically cross-linked starches (such as...). Figure 2 (and the 6-hour crosslinking in Table 2).

[0126] In fact, the two dry-roasted common rice starches from Source 1 lacked peak viscosity and trough value, and therefore no disintegration was observed, indicating high heat and shear resistance. The dry-roasted common and glutinous rice starches from Source 1 had a higher trough value to peak viscosity ratio than the dry-roasted glutinous rice starch from Source 2, indicating that the former was subject to more inhibition than the latter.

[0127] Pasting properties in citric acid solution

[0128] The starch paste was also analyzed in citric acid solution using RVA to understand its tolerance to low pH or acid.

[0129] In a tank, starch is mixed with a citric acid solution (pH ~3) to obtain an 8% w / w slurry.

[0130] The citric acid solution contains 2.1% w / w citric acid, 0.76% w / w NaCl and 0.277% w / w NaOH.

[0131] Each sample was isothermally heated at 50°C for 1 minute, then heated to 92°C at a rate of 10.5°C / min (4 minutes in total), isothermally heated at 92°C for 12 minutes, cooled to 50°C at a rate of 14°C / min (3 minutes in total), and finally isothermally heated at 50°C for 15 seconds.

[0132] To ensure better mixing, the stirring was started at 100 rpm, increased to 500 rpm and 960 rpm after 10 and 20 seconds respectively, and then reduced to 160 rpm after 30 seconds, where it was kept constant until the end of the test.

[0133] The RVA heating curves are summarized in Table 3.

[0134] Table 3. Analytical parameters for paste-forming properties in citric acid solution .

[0135]

[0136] Figures 4 to 6 The pasteurization curves of dry-roasted rice starch and chemically cross-linked rice starch in citric acid solution are shown.

[0137] Table 4 shows the paste-forming characteristics of dry-roasted rice starch and chemically cross-linked rice starch in citric acid solution.

[0138] Table 4. Paste-forming characteristics of dry-roasted rice starch and chemically cross-linked rice starch in citric acid solution .

[0139]

[0140] Similar to the pasteurization characteristics in demineralized water, dry-roasting treatment reduced the pasteurization temperature and disintegration value of common rice starch and glutinous rice starch compared to their natural counterparts, while increasing the ratio of valley value to peak viscosity during heating in citric acid solution. Figures 4 to 6 (and Table 4).

[0141] Acids can hydrolyze starch molecules at a rate that increases with temperature, leading to viscosity breakdown. Therefore, in acidic media, a low breakdown value and a high ratio of trough to peak viscosity indicate high viscosity stability of starch.

[0142] In addition, some dry-roasted starches exhibit higher peak viscosity, trough value, or overall paste viscosity than their natural counterparts.

[0143] When starch is dry-roasted at higher temperatures or for longer periods of time, its disintegration value is lower.

[0144] In fact, one type of dry-roasted common rice starch lacks peak viscosity and trough value, so no disintegration was observed, indicating high tolerance to acidic pH.

[0145] The results showed that the dry-roasting treatment inhibited the growth of both ordinary and glutinous rice starch, and improved the tolerance of starch granules to acid hydrolysis during heating, similar to the phenomenon observed in chemically cross-linked starch.

[0146] As the degree of chemical cross-linking increases, the disintegration value of glutinous rice starch decreases, while the ratio of its valley value to peak viscosity increases. Figure 5 (and Table 4).

[0147] Dry-roasted common and glutinous rice starch from source 1 exhibited higher acid resistance than dry-roasted glutinous rice starch from source 2, indicating that the former was subject to more inhibition than the latter.

[0148] Settlement test

[0149] Sedimentation tests were performed to confirm that the decrease in peak viscosity observed when the paste-forming properties were determined by RVA was indeed caused by thermal inhibition, rather than by thermal degradation.

[0150] Place 1.0 g dry weight of starch in a 250 mL wide-mouth glass bottle and mix it with 100 mL of a solution containing 10% w / w zinc chloride and 26% w / w ammonium chloride.

[0151] After sealing and thoroughly mixing, heat the wide-mouth jar in a boiling water bath for 10 minutes.

[0152] After cooling, thoroughly mix the contents of the wide-mouth bottle again and transfer them to a 100mL graduated cylinder.

[0153] After the slurry has been allowed to stand for 24 hours, the settling volume is recorded as a percentage of the total volume (Table 5).

[0154] Table 5. Sedimentation volumes of dry-roasted rice starch and chemically cross-linked rice starch .

[0155]

[0156] All natural glutinous rice starches showed only a turbid solution without any sedimentation, while natural common rice starches showed two layers, with white sediment at the bottom and a turbid solution at the top (Table 5).

[0157] The turbidity confirmed that the swollen starch granules were completely ruptured through heat treatment.

[0158] The white precipitate is due to amylose (in common rice starch) maintaining the integrity of the swollen starch granules without breaking them.

[0159] Dry-roasted common rice starch and glutinous rice starch from source 1 showed a clear separation between the white precipitate of swollen starch granules and the clear solution, indicating that although dry-roasted glutinous rice starch lacks amylose, the rupture of swollen granules is limited.

[0160] When starch is dry-dried at higher temperatures or for longer periods, the settling volume is smaller. This is similar to chemically cross-linked starch granules, where higher levels of cross-linking reduce the settling volume because it prevents the starch granules from swelling.

[0161] On the other hand, the dry-roasted glutinous rice starch from source 2 showed three layers: a small amount of white precipitate at the bottom, a large amount of turbid solution in the middle, and another small amount of clear solution at the top.

[0162] The results showed that dry-roasted glutinous rice starch from source 2 was more inhibited than natural starch, but less inhibited than dry-roasted common and glutinous rice starch from source 1, which was consistent with the effect of demineralized water ( Figures 1 to 3 (and Table 2) and citric acid solution ( Figures 4 to 6 The paste-forming characteristics are consistent with those in Table 4.

[0163] Gelatinization characteristics

[0164] The gelatinization characteristics of dry-roasted rice starch and chemically cross-linked rice starch were analyzed using a differential scanning calorimeter (DSC 8000, Perkin Elmer, USA).

[0165] Each starch sample was mixed with water to obtain an 18% w / w starch suspension. The suspension (15 mg) was then placed in an aluminum pan and hermetically sealed. The pan was equilibrated at 5°C and then heated from 5°C to 110°C at a rate of 10°C / min.

[0166] Based on the endothermic reaction in the DSC thermogram, the initial temperature (T) was obtained. o Peak temperature (T) p ), End temperature (T) c ) and gelatinization enthalpy (ΔH). Some samples also showed T o Previous acromion, and some samples showed T c The acromion that follows.

[0167] Table 6. Thermal properties of dry-roasted rice starch and chemically cross-linked rice starch .

[0168]

[0169] ND = Not detected

[0170] Generally speaking, the gelatinization temperature decreases with increasing dry-baking temperature or time (Table 6), which is consistent with the trend of gelatinization temperature observed using RVA. Figures 1 to 6 ).

[0171] ΔH also decreased with increasing dry-baking temperature or time, indicating that the dry-baking process may have disrupted the arrangement of the microcrystals, making them less perfect and / or less stable.

[0172] Furthermore, the gelatinization temperature range of dry-roasted starch is similar to or slightly narrower than that of its natural counterpart.

[0173] These results differ from those of annealing and heat treatment (HMT).

[0174] Annealing typically results in higher gelatinization temperatures, while HMT allows for a wider gelatinization temperature range.

[0175] Furthermore, the thermal properties of chemically cross-linked glutinous corn starch are similar to those of its natural counterpart (Table 6).

[0176] Example 2. Dry-roasted glutinous rice and ordinary rice flour .

[0177] Fine powder materials

[0178] - Ordinary rice flour, from Eaglobe Co., Ltd., China. A product from Thailand.

[0179] - Finely ground glutinous or sticky rice flour, sourced from Eatoglobe Ltd., China. A product from Thailand.

[0180] Dry roasting

[0181] Without any pretreatment or pH adjustment, place 25g of ordinary or glutinous rice flour on an aluminum pan and heat at 170°C for 1 or 2 hours or at 190°C for 1 hour.

[0182] Pasting properties in demineralized water

[0183] The method is the same as that in Example 1 above.

[0184] Figure 7 The paste-forming properties of dry-roasted ordinary and glutinous rice flour in demineralized water are shown.

[0185] Dry-roasted glutinous rice flour did not exhibit a significant peak viscosity, which is quite different from their natural counterparts. Furthermore, the overall paste viscosity of both regular and glutinous rice flour decreased rapidly after dry-roasting due to thermal degradation.

[0186] Pasting properties in citric acid solution

[0187] The method is the same as that in Example 1 above.

[0188] Figure 8 The paste-forming properties of dry-roasted ordinary and glutinous rice flour in lemon aqueous solution are shown.

[0189] Dry-roasted regular and glutinous rice flours have a lower overall paste viscosity than their natural counterparts.

[0190] However, during heating from 50°C to 92°C and during isothermal heating at 92°C, the paste viscosity of dry-roasted glutinous rice flour decreased at a slower rate than that of natural glutinous rice flour, and dry-roasted ordinary rice flour did not show a significant decrease in paste viscosity during the analysis.

[0191] The results showed that, despite significant thermal degradation, the acid resistance of both ordinary and glutinous rice starch was improved (thermal inhibition) by dry-roasting treatment. However, the thermal inhibition effect was not as pronounced as that observed in ordinary rice starch and glutinous rice starch from Example 1.

[0192] Settlement test

[0193] The method is the same as in Example 1 above. The results are summarized in Table 7.

[0194] Table 7. Sedimentation volumes of dry-roasted ordinary and glutinous rice flour .

[0195]

[0196] Unlike the natural glutinous rice and ordinary rice starch in Example 1, both the natural glutinous rice and ordinary rice flour showed some sedimentation with a clear solution at the top.

[0197] This may be attributed to the presence of proteins and cell walls, which prevent starch granules from fully swelling and breaking down during the heating process.

[0198] The sedimentation volume decreased after dry roasting, and it decreased further with increasing heating time, indicating stronger thermal inhibition (Table 7).

[0199] Example 3. Dry-roasted starches from various plant sources .

[0200] Starch materials

[0201] - Pea starch, from Roquette Frères, France.

[0202] - Tapioca starch, from Banpong Tapioca, Thailand.

[0203] - Potato starch, from Roquette Frères, France.

[0204] - Regular cornstarch, Roquette Frères, France.

[0205] -Glutinous corn starch, Roquette Frères, France.

[0206] Dry roasting

[0207] Without any pretreatment or pH adjustment, place 20g of natural pea, cassava, or potato starch on an aluminum pan and heat at 150°C, 170°C, or 190°C for 1 hour.

[0208] Without any pretreatment or pH adjustment, place natural glutinous or regular corn starch (25g) on ​​an aluminum pan and heat at 170°C for 1 or 2 hours or at 190°C for 1 hour.

[0209] Pasting properties in demineralized water

[0210] The method is the same as that in Example 1 above.

[0211] Figures 9 to 13 The pasteurization curves of dry-roasted starch from various plant sources in demineralized water are shown.

[0212] Generally speaking, all starches from various plant sources experience a decrease in peak viscosity after dry-roasting, which is more pronounced after dry-roasting at higher temperatures or for longer periods. Figures 9 to 13 This indicates a thermal degradation phenomenon.

[0213] However, potato starch dry-roasted at 150°C for 1 hour showed a slightly higher pasteurization viscosity than its natural counterpart during the holding period at 92°C and during cooling from 92°C to 50°C, indicating improved viscosity stability during heating and shearing.

[0214] Pasting properties in citric acid solution

[0215] The method is the same as that in Example 1 above.

[0216] Figures 14 to 18 Pasteurization curves of dry-roasted starches from various plant sources in lemon aqueous solution are shown.

[0217] Table 8 shows the paste-forming characteristics of these different dry-roasted starches in citric acid solution.

[0218] Table 8. Paste-forming properties of dry-roasted starches from various plant sources in citric acid solution. .

[0219]

[0220] 1 Ratio = Valley value / Peak viscosity

[0221] Apart from dry-roasted common corn starch, all dry-roasted starches from other plant sources typically exhibit lower disintegration values ​​and higher trough-to-peak viscosity ratios when heated in citric acid solution compared to their natural counterparts, indicating greater tolerance to acidic pH during heating due to thermal inhibition. Figures 14 to 18 (and Table 8).

[0222] As the drying temperature and time increased, both peak viscosity and disintegration value decreased. In fact, pea starch dried at 190°C for 1 hour lacked peak viscosity and trough value, so no disintegration was observed, indicating high tolerance to acidic pH.

[0223] On the other hand, for some starches, there is a parabolic trend in the ratio of trough viscosity to peak viscosity with drying temperature, where the ratio increases after drying to 170°C, but decreases at higher temperatures (190°C).

[0224] The latter may be due to the fact that thermal degradation is stronger than thermal inhibition.

[0225] The effects of dry-roasting on pea, cassava, potato, and glutinous corn starches were similar to those observed in Example 1 on ordinary and glutinous rice starches, except that heat inhibition was more pronounced on ordinary and glutinous rice starches, especially at high dry-roasting temperatures.

[0226] The thermal degradation of ordinary corn starch is more pronounced. After dry roasting, its overall pasteurization viscosity in citric acid solution decreases, while the shape of the pasteurization curve remains unchanged. Figure 18 (and Table 8).

[0227] Following dry roasting, the ratio of trough value to peak viscosity of ordinary corn starch also decreased, confirming that the decrease in disintegration value was not due to improved acid resistance, but rather to a decrease in paste viscosity caused by thermal degradation.

[0228] Example 4. Dry-roasted glutinous rice and ordinary rice starch .

[0229] Starch materials

[0230] Ordinary rice starch, sourced from Anhui Shunxinshengyuan Biological Food Co., Ltd., China.

[0231] Glutinous rice starch, sourced from Anhui Shunxinshengyuan Biological Food Co., Ltd., China.

[0232] Dry roasting

[0233] Without any pretreatment or pH adjustment, place 30g of natural glutinous or ordinary rice starch on an aluminum pan and heat at 170°C for 0 to 6 hours.

[0234] Pasting properties in citric acid solution

[0235] The method is the same as in Example 1 above, except that starch (2g dry weight) is mixed with citric acid solution (pH~3) in a tank to obtain a total of 28g slurry. In addition, the isothermal heating time at 50°C after cooling is longer (10 minutes, compared to 15 seconds in Example 1).

[0236] Table 9. Analytical parameters for paste-forming properties in citric acid solution

[0237]

[0238] Similar to the results of Example 1, dry-baking treatment lowered the pasteurization temperature of glutinous rice starch, but its effect was less affected by the duration of dry-baking treatment. Figure 19 ).

[0239] The peak viscosity of glutinous rice starch dried at 170℃ for 1 hour increased, but the peak viscosity of the sample dried for 2 hours decreased (Table 10).

[0240] As the dry-roasting time increases, the disintegration value decreases, while the ratio of valley value to peak viscosity increases.

[0241] After dry-baking at 170℃ for 3 hours, the peak viscosity and the corresponding disintegration value were not significant.

[0242] Conversely, for glutinous rice starch that was dry-roasted at 170°C for 4 and 6 hours, the viscosity continued to increase during heating in the RVA, indicating greater tolerance to acidic pH.

[0243] Table 10. Results of dried glutinous rice and regular rice starch in citric acid solution after drying at 170℃ for 0 to 6 hours. Paste-forming characteristics .

[0244]

[0245] 1 Ratio = Valley value / Peak viscosity

[0246] 2 No peak viscosity was observed during heating from 50°C to 92°C and during isothermal heating at 92°C.

[0247] After dry drying at 170℃, the peak viscosity and disintegration value of ordinary rice starch decreased, while the ratio of gluten value to peak viscosity increased. Figure 20 (See Table 10). Similar to dry-roasted glutinous rice starch, after 2 hours of dry roasting at 170°C, the peak viscosity and corresponding disintegration value of dry-roasted ordinary rice starch were not significant. The viscosity continued to increase during heating in the RVA, indicating stronger tolerance to acidic pH. However, with prolonged dry roasting time, the overall paste viscosity decreased, indicating some thermal degradation occurred during the dry roasting process.

[0248] Settlement test

[0249] The method is the same as that in Example 1 above.

[0250] Set the sedimentation volume of the sample that has been dry-roasted for 0 hours to 100%, and compare it with the sedimentation volume of other samples.

[0251] After dry-baking at 170℃, the sedimentation volume decreased, and it decreased further with the extension of the dry-baking duration. Figure 21The results confirmed the thermal inhibition of both glutinous and ordinary rice starch by dry-roasting, as the swelling capacity of starch granules decreases after heating. During dry-roasting at 170℃ for 1 to 6 hours, the sedimentation volume change of ordinary rice starch was greater than that of glutinous rice starch, indicating that glutinous rice starch experienced stronger thermal inhibition after shorter dry-roasting times.

Claims

1. A method for producing heat-modified rice starch with heat resistance, acid resistance, shear resistance, and stable viscosity, the method comprising the following steps: Rice starch is heated to a temperature between 150°C and 200°C, preferably 170°C, and the residence time is between 0.5 hours and 6 hours, more preferably between 1 hour and 2 hours.

2. The method according to claim 1, characterized in that, The rice starch mentioned is glutinous rice starch.

3. The method according to claim 1, characterized in that, The rice starch mentioned is ordinary rice starch.

4. The method according to any of the preceding claims, characterized in that, The thermally modified rice starches exhibit an increased trough value to peak viscosity ratio during heating in demineralized water compared to their natural counterparts.

5. The method according to claim 4, characterized in that, The ratio of the valley viscosity to the peak viscosity is greater than 60%, more preferably greater than 70%, and even greater than 80%.

6. The method according to any of the preceding claims, characterized in that, The thermally modified rice starches, compared to their natural counterparts, exhibit an increased trough-to-peak viscosity ratio during heating in citric acid solution.

7. The method according to claim 6, characterized in that, The ratio of the valley viscosity to the peak viscosity is greater than 50%, more preferably greater than 65%, and even greater than 80%.

8. A thickener or texturer for use in food applications, particularly in yogurt, ketchup, salad dressings, and sauces, said thickener or texturer comprising thermally modified starch prepared by the method of claim 1.

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