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Title:
NON-CHEMICALLY MODIFIED STARCH WITH ENHANCED FUNCTIONAL PROPERTIES
Document Type and Number:
WIPO Patent Application WO/2022/162031
Kind Code:
A1
Abstract:
The invention pertains to a process for manufacturing inhibited starch, involving subjecting a prehydrolysed, chemically unmodified, granular starch in an amount of 5 - 40 wt% in an aqueous composition to conditions promoting inhibition at pH > 1.7 for at least one hour at a temperature below 60 °C, wherein the starch has been prehydrolysed to having a weight-average molecular weight (MW) which is 2 - 50 % of the weight-average MW, as determined with GPC-MALLS, of the corresponding starch composition when subjected to hydrolysis at pH 5 for 18 hours. The invention also pertains to an inhibited starch having (i) a final viscosity (FV) which is at least 10% higher compared to the FV of the chemically unmodified, granular starch that has not been subjected to prehydrolysation and inhibition; and/or (ii) viscostability expressed as a breakdown viscosity (BV) of less than 25%, together with a FV which is at least 10%, wherein the starch has an improved whiteness value (L* value) of at least 92.2 on a scale of 0-100 as defined e.g. by the CIE, Commission Internationale de I'Eclairage, wherein (100) represents absolute whiteness.

Inventors:
ESSERS, Maurice Karel Hubertina (NL)
VAN DEN BROEK, Lambertus Antonius Maria (NL)
Application Number:
PCT/EP2022/051815
Publication Date:
August 04, 2022
Filing Date:
January 26, 2022
Export Citation:
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Assignee:
STICHTING WAGENINGEN RESEARCH (NL)
International Classes:
A23L29/212; C08B30/12; C08B31/00; C09J103/02
Attorney, Agent or Firm:
NEDERLANDSCH OCTROOIBUREAU (NL)
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Claims:
Claims

1. A process for manufacturing inhibited starch, involving subjecting a prehydrolysed, chemically unmodified, granular starch in an amount of 5 - 40 wt% in an aqueous composition to conditions promoting inhibition at pH > 1.7 for at least one hour at a temperature at least 1 °C below the gelatinization temperature, preferably below 60 °C, wherein the starch has been prehydrolysed to having a weight-average molecular weight (MW) which is 2 - 50 % of the weight-average MW, as determined with GPC-MALLS, of the corresponding starch composition when subjected to hydrolysis at pH 5 for 18 hours, wherein the process results in an inhibited starch having (i) a final viscosity (FV) which is at least 10%, preferably 25% higher compared to the FV of the chemically unmodified, granular starch that has not been subjected to prehydrolysation and inhibition; and/or (ii) viscostability expressed as a breakdown viscosity (BV) of less than 10%, together with a FV which is at least 10%, preferably 25% higher compared to the peak viscosity (PV).

2. The process according to claim 1 , wherein the inhibited starch has an improved whiteness value (L* value) of at least 92.2, preferably at least 92.5, more preferably 93 - 98, more preferably 93 - 97 on a scale of 0-100 as defined e.g. by the CIE, Commission Internationale de I’Eclairage, wherein 100 represents absolute whiteness.

3. The process according to any one of the preceding claims, wherein the chemically unmodified, granular starch which is subjected to conditions promoting inhibition is present in an amount of 10 - 35 wt%, based on total weight of the aqueous composition.

4. The process according to any one of the preceding claims, wherein the starch has been prehydrolysed using acid hydrolysis at a pH between 1 .5 and 6.5, at a temperature below 60 °C.

5. The process according to any one of the preceding claims, wherein the starch is inhibited at a temperature which is higher than the temperature applied during prehydrolysis.

6. The process according to any one of the preceding claims, wherein the the starch has been prehydrolysed using starch-hydrolyzing enzymes, at a temperature below 60 °C.

7. The process according to any one of the preceding claims, wherein the the starch has been prehydrolysed using alkaline treatment at pH of at least 9, at a temperature below 60 °C.

8. The process according to any one of the preceding claims, wherein the inhibited starch is subjected to further processing steps such neutralisation and drying, wherein the inhibited starch is preferably neutralized by increasing the pH between 6.5 - 9.5, and/or wherein the inhibited starch is preferably dried at a temperature between 50 °C and 180 °C.

9. The process according to any one of the preceding claims, wherein the prehydrolysed starch subjected to inhibition has a weight-average molecular weight MW, as determined using GPC-MALLS, of at least 1 ,000,000 Da (1 ,000 kDa), more preferably at least 5,000,000 Da (5,000 kDa), even more preferably at least 10,000.000 Da (10,000 kDa), most preferably 10,000.000 - 100,000,000 Da (10,000 - 100,000 kDa).

10. The process according to any one of the preceding claims, wherein the prehydrolysed starch is subjected to inhibition at a pH between 1 .7 and 6.5, preferably pH 2 - 6.5.

11. An inhibited starch having (i) a final viscosity (FV) which is at least 10%, preferably 25% higher compared to the FV of the chemically unmodified, granular starch that has not been subjected to prehydrolysation and inhibition; and/or (ii) viscostability expressed as a breakdown viscosity (BV) of less than 25%, more preferably less than 10%, together with a FV which is at least 10%, preferably 25% higher compared to the peak viscosity (PV), wherein the starch has (a) an improved whiteness value (L* value) of at least 92.2, preferably at least 92.5, more preferably 93 - 98, more preferably 93 - 97 on a scale of 0-100 as defined e.g. by the CIE, Commission Internationale de I’Eclairage, wherein 100 represents absolute whiteness, and/or (b) a reduction in whiteness value L* of less than 2, more preferably less than 1 .5 compared to the whiteness value of the corresponding chemically unmodified, granular starch that has not been subjected to prehydrolysation and inhibition.

12. Use of the inhibited starch according to claim 11 or obtained by the process according to any one of claims 1 - 10, for use in food products, or for adding cohesiveness, e.g. in (Stein Hall) corrugating glues.

13. Use of the inhibited starch according to claim 11 or obtained by the process according to any one of claims 1 - 10, wherein said inhibited starch has a BV which is zero or negative, for gelatin replacement (in food applications).

Description:
NON-CHEMICALLY MODIFIED STARCH WITH ENHANCED FUNCTIONAL PROPERTIES

Field

The invention relates to non-chemically modified inhibited starch, with enhanced functional properties, and manufacturing methods for producing the same.

Background

Starch is extensively used in the food industry, not only for its energy content (carbohydrates), but also as a thickening or stabilizing agent. It provides the human body of energy as it is completely converted into sugar by the human digestive system, and it also contributes to the functionality in food products, e.g. the desirable viscosity and textural properties of the product. Natural, non-modified starches known as "native starches" are sometimes used as such, but have several drawbacks in terms of maintaining a short, heavy bodied texture for industrially processed food products due to the extra energy input from shear and the high heat input needed in the process to maintain enough of microbial sanitation after the full heating cycle of such products.

Starch is one of the few biopolymers that is allowed to be modified by means of chemical, physical and enzymatic processes in order to improve its functional characteristics in food applications. Food law distinguishes between native and modified starches and even between different types of modification. Native starch is considered a food ingredient, and is therefore not labelled, whereas chemically modified starches are considered food additives and therefore require labelling as modified starch, or the use of an E-number (such as E-1412, E-1414, E-1422, E-1442). Whatever the scientific background of this classification, E-number additives have a negative connotation in the consumer market. Chemical modifications of starch are less desired in food applications, even though some modifications are regarded as safe.

Many of these modifications find their origin in the fact that starches are sensitive to acid, which results in a rapid breakdown in viscosity. Acid conversion of starch refers to hydrolysis of the starch chain that subsequently leads to increase of the solubility on expense of viscosity properties and molar mass reduction as mentioned in Ulbrich et al. “Functional properties of acid-thinned potato starch: Impact of modification, molecular starch characteristics, and solution preparation" Starch 2019; 71 , 1900176. Acid hydrolysis takes place under very low pH levels (pH <1) by use of either slurry processes (starch content between 15-25% (w/v) in water) and at temperatures below the starting gel point, or under dry conditions (moisture content below 5% (w/w)) and temperatures above 100 °C. Several factors such as starch source (initial inherent starch properties), temperature, molar acid concentration (pH), acid type, and the duration of the hydrolysis (time) can affect the degree of hydrolysis and the related molecular weight, and the techno functional properties of the modified starch. The prime purpose of an acid conversion of starch (hydrolysis) is to reduce the molecular weight of the starch and the corresponding viscosity characteristics.

Hydrolysis can also take place under semi-dry conditions. Prior to the addition of the acid the starch is dehydrated to a moisture level below 5% (w/w). For this process acid concentrations of 0.1 to 0.2% (w/w) are used in general. Also in this case, the degree of hydrolysis is affected by the reaction temperature, amount of acid, type of acid, reaction time and final moisture level. The reaction temperatures can vary between 100 and 140 °C.

Besides hydrolysis, repolymerisation and transglycosylation can occur as well. This proceeds at higher temperatures (above 130 °C) and after prolonged reaction times. This process is called pyrodextrination. Via this mechanism, new glycosidic bonds are formed that are less prone to human digestion. Due to the prime hydrolysis reaction, the molecular weight is reduced from tens of million Dalton to less than 100,000 Da. These hydrolysed starches have less to no contribution to viscosity build-up properties but contribute to increase of the resistant starch level. These type of starches can only be used in specific food applications as bulk ingredient.

Perhaps the most widely known form of starch modification is crosslinking, in many ways the opposite of hydrolysis. Crosslinking of starch is a popular method to create new properties in starch for use in food applications. Such properties include better viscosity behaviour defined as a higher final viscosity and viscostability, as described in Shah et al. “Crosslinking of starch and its effect on viscosity behaviour” Rev. Chem. Eng. 2016; 32(2):265-270. Crosslinking will prevent starch granules from swelling under cooking conditions. While there are many chemical crosslinking agents available and permitted by food authorities, clean label requirements rule out chemical ways of crosslinking for instance using phosphorous oxychloride, adipate and epichlorohydrin. The degree of crosslinking determines the extent of viscostability and viscosity build up.

Physical modifications such as drum drying, spray cooking and alkaline roasting are considered as “native” starch and do not require any labelling, i.e. these starches are referred to as clean label. Some of these techniques may result in thermally inhibited starches. Inhibited starches are starches which have improved acid, alkali and shear stability, and reduced gelatinization. This is useful when food has to withstand heat treatment, as in canning or in acid foods. While starches are prone to acid hydrolysis, inhibition of starch results in viscosity build-up able to withstand heat treatments. The degree of swelling, peak viscosities, viscostability etc. is strongly dependent of these processes and the conditions applied therein.

Some of these processes require much energy and more stringent conditions such as high temperatures. One way of inducing viscostability in starch is alkaline roasting which proceeds via dehydration of an alkaline starch that is further treated at an elevated temperature above 150 °C for several hours. However, it appears that the control of the water household is essential in this respect as small changes in the process conditions can lead to insufficient functionality of the starch. Special equipment is needed to handle these energy-demanding conditions. Also, these elevated reaction temperatures and alkalinity causes undesirable discoloration (i.e. browning) and formation of side components that have to be washed out.

Hence, there is a need for providing inhibited starches with improved viscostability, enhanced gelling properties and reduced browning, as a clean label alternative to chemically modified (crosslinked) starches. There is also a need for more economical and simplified ways of manufacturing such inhibited starches without the formation of side components, at mild conditions (e.g. less energy-demanding) in a more environmental friendly manner. Summary of the invention

The inventors found a process for producing inhibited starch using acid conditions which enables the starch to restructure in order to obtain enhanced functional properties while avoiding huge reduction in molecular weight (i.e. hydrolysis) or formation of negative side components. The inventors found that it is key that the starch is only mildly hydrolysed in a first step. Without wishing to be tied down to any theory, it is believed that the mild degree of hydrolysis is required to form reducing end groups in the granular starch, these reducing end groups formed at pH levels above 1.7 and lower temperatures allow the starch to restructure, possibly repolymerize, thus contributing to significant viscosity changes that are not in response to a strong hydrolysis treatment. This is surprising given that repolymerisation was hitherto only associated with increased temperatures above 110 °C, and to dry conditions. With the possible formation of sufficient amounts of reducing groups in a prehydrolysis step it is thus possible to subsequently remodel starch while creating new functionalities (in terms of viscostability and end viscosity) instead of inducing losses known from typical hydrolysis conditions. In addition, the process does not require any chemical crosslinking agents to modify starch and the inhibition of starch is therefore considered as a clean label modification. The inventors found that there is an optimum in the amount of reducing groups created in the mild hydrolysis step: too many means that the starch has been hydrolysed too far, and - if any - subsequent restructuring would not show any advantageous impact on the viscosity profile anymore; if too little amount of reducing end groups are formed, restructuring of starch would not occur, and no advantageous viscosity profile would be obtained.

The invention thus pertains to a process for manufacturing inhibited starch, involving subjecting a prehydrolysed, chemically unmodified, granular starch in an amount of 5 - 40 wt% in aqueous composition (‘slurry’) to conditions for promoting inhibition or repolymerization at pH > 1.7 for at least one hour at a temperature at least 1 °C below the gelatinization temperature, preferably at least 5 °C below the gelatinization temperature and/or preferably below 60°C, preferably below glass point, wherein the starch has been prehydrolysed prior to inhibition to achieve a molecular weight (i.e. weightaverage MW) reduction to a MW which is 2 - 50 % of the weight-average MW, as determined with GPC- MALLS, of the corresponding starch (slurry) composition when subjected to hydrolysis at pH 5 for 18 hours, wherein with inhibition an inhibited starch is obtained having (i) a final viscosity (FV) which is at least 10%, preferably 25% higher compared to the FV of the chemically unmodified, granular starch that has not been subjected to prehydrolysation and inhibition; and/or (ii) viscostability expressed as a breakdown viscosity (BV) of less than 10%, together with a FV which is at least 10%, preferably 25% higher compared to the peak viscosity (PV). It is more preferred that the inhibited starch obtained complies with a combination of both (i) and (ii). In any case, the inhibited starch thus obtained preferably has an improved whiteness value (L* value) of at least 92.2, preferably at least 92.5, more preferably at least 93 on a scale of 0-100 as defined e.g. by the CIE, Commission Internationale de I’Eclairage, wherein 100 represents absolute whiteness. By working the second step at pH above 1 .7, the process of repolymerization will prevail over hydrolysis, since the rate of hydrolysis is much slower at these mild pH conditions.

During manufacturing, the granular structure of the starch is maintained through inhibition. Advantageously, it results in a clean label non-chemically modified starch with reduced colourization, and exhibiting improved viscostability and gelling behaviour. In other words, there is obtained an inhibited starch with improved whiteness, viscosity build-up, viscostability and final viscosity. There are also advantages to the process itself, in terms of reduced reaction time and associated reduced energy consumption. Hence, not only does the process lead to better product quality, the fact that less colourization of the starch occurs also means that less (extensive) processing, preferably less (extensive) recovery steps are required. Consequently, with the present process there are no or reduced (extensive) washing steps needed. With the term ‘inhibited starch’ it is meant that the resulting starch granule is capable of maintaining its granular integrity when exposed to high temperatures, high shear forces, or high temperatures, together or without shearing actions, as well as an acidic environment. The higher the degree of crosslinking, the more robust the starch will be protected against those parameters

The process for producing inhibited starch is distinct from conventional thermal inhibition processes in the art, working at much lower (‘mild’) temperatures, where the starch is hydrolysed to a small extent and reducing end groups are formed as mentioned above. The starch which is subjected to inhibition is characterized by a molecular weight (i.e. weight-average MW) reduction to a MW which is 2 - 50 %, preferably 20-50% of the weight-average MW, as determined with GPC-MALLS, of the corresponding starch (slurry) when subjected to hydrolysis at pH 5 for 18 hours. In other words, prehydrolysis should yield a starch exhibiting a molecular weight which is 2 - 50 %, preferably 20-50% compared to that of the reference starch which is hydrolysed at pH 5 for 18 hours as determined using GPC-MALLS, i.e. using the formula:

100% x (MW of prehydrolysed starch I MW of starch hydrolysed at pH 5 for 18 hours).

In practice it is challenging to determine the molecular weight of non-hydrolysed starch in a straightforward and quantitative manner whichever technique is used. However, in order to assess and quantify the limited extent of hydrolysis, which is essential to prepare the starch for the inhibition step, the molecular weight MW as determined by GPC-MALLS is compared to a reference where the starch has been subjected to mild hydrolysis at pH 5 for 18 hours. It is shown in Table 1 in the experimental part hereafter that hydrolysis at these conditions results in a consistent and stable MW reduction (here shown for potato starch) which can thus serve as a reference.

The desired extent of hydrolysis can be achieved by any conventional hydrolysis (either acid- or enzyme-catalysed hydrolysis), and even alkaline treatment would result in the required reduced molecular weight albeit at extended time scales. As evidenced in the experimental parts, the induced viscosity changes cannot be linked to a change in crystallinity. Without wishing to be tied down to any theory, the improved viscosity properties are believed to be due to repolymerization that involves formation of acetals from the reducing end groups and the neighbouring alcohol groups, and which repolymerization appears to be favoured over hydrolysis, which would be expected using conventional processes. The latter may well be linked to the significant number of reducing end groups made available after prehydrolysis. It may also be that a re-arrangement or crystallinity is induced at very low level, hardly or not measurable with XRD but sufficient enough to induce viscosity changes. The invention also pertains to an inhibited starch having a white colour (preferably a whiteness value (L* value) of at least 92.2, preferably at least 92.5, more preferably at least 93 on a scale of 0-100 as defined e.g. by the CIE, Commission Internationale de I’Eclairage, having (i) a final viscosity (FV) which is at least 10%, preferably 25% higher compared to the FV of the chemically unmodified, granular starch that has not been subjected to prehydrolysation and inhibition; and/or (ii) viscostability expressed as a breakdown viscosity (BV) of less than 10%, together with a FV which is at least 10%, preferably 25% higher compared to the peak viscosity (PV). It is more preferred that the inhibited starch complies with a combination of both (i) and (ii). The desired combination of functional properties of the inhibited starch depends on the actual application in food industry, particularly for gelatin and/or fat replacement, and for industrial application, and glues for corrugating

List of figures

Figure 1 shows the effect of only pH as a parameter on the viscosity of granular potato starch in a slurry of 30% (w/w) starch at a temperature of 50°C for 18 hours. Figure 2 shows the effect of the cascade reaction wherein prehydrolysis at pH 2 at a temperature of 50°C for 2 hours is followed by inhibition at pH 4 and pH 6 for 13 hours, and in Figure 3 there is plotted the viscosity profiles of native and inhibited potato starch suspended in acidic slurries treated by mild hydrolysis at pH 1 .5 for two hours, after which the pH was raised and the subseguent inhibition was performed using pH as a parameter (pH 2.2, 3.2, 3.8 or 5) for 13 hours, at a temperature of 50°C. Figure 4 shows the effects of prehydrolysis achieved by alkaline treatment, followed by inhibition at pH 5. These results are obtained with a waxy potato starch. Figure 5 shows the crystallinity profiles of native potato starch, hydrolysed potato starch at pH 11.2 for 2 hours, and inhibited potato starch at pH 1.5 for 2 hours and subseguent inhibition at pH 4. Figures 6 - 9 show RVA profiles for various cascade heat treatments to obtain inhibited potato starch.

Detailed description of the invention

The starch to be used in the process of the invention can be any common type of starch, including maize, potato, tapioca, rice, wheat, etc, and includes modified starches such as waxy potato starch, e.g. Eliane, provided that the starch is not chemically modified. Starches modified by chemical crosslinking such as phosphate crosslinking are excluded from the invention. The starch may contain at least e.g. 70% (w/w) of amylopectin. The starch or starch contained in the starch containing product may be any common type of starch, specifically any common type of granular starch, or combinations of starches, specifically combinations of granular starches. Said starch may be native starch and/or derivatives thereof. Potato starch preferably is understood to mean non-sweet potato starch. In a further embodiment so-called waxy starches, specifically granular waxy starches, are employed. These starches consist for more than 93 wt.% of amylopectin. Preferred waxy starches, specifically granular waxy starches, are waxy maize starch, waxy wheat starch, waxy barley starch, waxy sorghum starch, waxy rice starch, waxy potato starch, and/or waxy tapioca starch. Preferably the starch is maize or corn starch, rice starch, wheat starch, tapioca starch and/or potato starch, more preferably the starch is potato starch, rice starch and/or tapioca starch, even more preferably the starch is potato starch, most preferably the starch is waxy potato starch. The waxy potato starch can be modified starch, albeit not chemically modified starch.

The starch is a (non-pregelatinized) granular starch. Native starch granules typically show birefringence or a typical Maltese cross when viewed in polarized light. This property is brought about because the starch molecules are radially oriented within the granule. When starch is heated in water, birefringence or Maltese cross pattern in polarized light may be lost, which may be associated with disruption of the granular structure of the starch, forming non-granular starch. This is called starch gelatinization. Non-pregelatinized granular starch in the context of the invention preferably is understood to mean that the starch has lost less than 30%, preferably less than 20%, more preferably less than 10%, even more preferably less than 5%, even more preferably less than 1 %, most preferably substantially 0% of its birefringence and/or granular structure, specifically that the starch substantially preserves a granular structure and/or birefringence or Maltese crosses when illuminated using polarized light, preferably after processing the starch, more preferably after heating the starch, more preferably after heating the starch in the presence of water, specifically more than 5 wt%, more specifically more than 2 wt%, most specifically more than 1 wt% water, most preferably after hydrothermal treatment and/or thermal (inhibition) treatment of the starch. Preferably, no solvent, specifically no solvent other than water, preferably no alcohol or alcoholic medium is used in said processing, said heating, said hydrothermal treatment and/or said thermal (inhibition) treatment of the starch. The extent to which starch granules exhibit a granular structure and/or birefringence or Maltese crosses can be conventionally determined by the skilled person using techniques commonly known in the art such as illumination with polarized light and viewing under a (light) microscope.

The cascade process of the invention works particularly well with tubular starches including potato starch.

The molecular weight of the starch subjected to prehydrolysis ranges from 10 million to 500 million Daltons (Da), preferably 10 million to 300 million. Due to the complexity of the molecule, various methods for determining the molecular weight of starch are available, all with their pros and cons. Customary in the field, the molecular weight of starch can be measured by way of gel permeation chromatography coupled online to a multi-angle laser light scattering (GPC-MALLS). The starch can be characterized by a variety of definitions for molecular weight including the number average molecular weight (M n ), the weight average molecular weight (MW), the size average molecular weight (M z ), or the viscosity molecular weight (M v ). In the context of the invention, unless expressly mentioned otherwise the molecular weight of starch is understood to mean the weight average molecular weight (MW) in Dalton (Da). Further, in the context of the invention, GPC-MALLS is used to determine the molecular distribution and parameters related therewith.

Weight average MW of starch is preferably determined using GPC-MALLS (eluent 50 mM LiBr in DMSO/water (9:1 (v/v)) wherein 25 mg starch is prewetted with 50 pL 96% (v/v) ethanol and subsequently dissolved in 5 mL eluent by stirring for 1 hour at 600 rpm at 100 °C, and prior to GPC- MALLS analysis, filtered over a 5 pm PTFE filter; flow rate: 0.5 mL/min; injection volume: 0.100 mL; columns: PLgel Guard 5 p, MIXED-A 20 p and MIXED-D 3 p (Agilent); column temperature: 75 °C; Detection: - MALLS (Wyatt Dawn HELEOS II), 25 °C, dn/dc = 0.074 mL/g

Rl (Wyatt Optilab T-rEX), 25 °C, detector volume delay 0.195 mL;

LS software: Wyatt ASTRA for windows version 7.3.1.9 (ZIMM method with a first order fit for calculations of standards and samples with radius < 90 nm; BERRY method with a second order fit for calculations of samples with radius > 90 nm).

The native or non-chemically modified granular starch is suspended in water with a starch content between 5% - 40% (w/w) in water, preferably a starch content between 10% - 35% (w/w) in water, more preferably a starch content between 15% - 25% (w/w) (based on total weight of the aqueous composition). This composition is addressed as ‘(starch) slurry’ in the remainder of the specification. The slurry containing the native granular starch is mildly hydrolysed. Starch is made up of glucose monomers that are joined by a(1-4) or a(1-6) glycosidic bonds that can break by a mild hydrolysis treatment which thereby induces reducing end-groups in starch. These reducing end groups are essential for the next step in the process in which the prehydrolysed starch (slurry) is subjected to a pH higher than 1.7. Mild hydrolysis can be achieved using acid hydrolysis, alkaline or enzymatic hydrolysis, or combinations thereof, provided that elevated temperatures are avoided. If mild hydrolysis involves acid hydrolysis, acid may be added to the slurry. While the ingredients for acid and enzymatic hydrolysis are conventional acids and enzymes which belong to the skilled person’s knowledge, it is key for the invention that the hydrolysis conditions are carefully chosen to control the rate and extent of hydrolysis to avoid too extensive starch degradation. In case of overshooting the extent of hydrolysis, it was found that there is no possibility of restructuring of the hydrolysed starch and no inhibition takes place.

Mild hydrolysis of the starch slurry using acid conversion can be performed with any acid. Preferably it is an acid which is accepted for food purposes. The acid hydrolysis preferably involves a pH between 1.5 and 6.5, preferably 2 - 6, more preferably between 2.5 - 5. Examples include hydrochloric acid, phosphoric acid, sulphuric acid, acetic acid, lactic acid, citric acid etc. A relatively strong acid such as hydrochloric acid, sulphuric acid or phosphoric acid is preferred. Acid hydrolysis is a known concept in the field, and the skilled person can rely on existing knowledge about the appropriate conditions for instance from Ulbrich et al. “Impact of modification temperature on the properties of acid- thinned potato starch" Starch 2016; 68(9-10) 885-899 and Ulbrich et al. “Functional properties of acid- thinned potato starch: Impact of modification, molecular starch characteristics, and solution preparation" Starch 2019; 71 , 1900176. Compared to conventional acid hydrolysis, the constraint is that in the context of the invention hydrolysis is only carried out until a reasonable amount of molecular weight reduction is achieved. In order to realize a limited degree of hydrolysis, it is essential that the pH is at least above 1 .5. From carrying out initial mild hydrolysis experiments at low pH, the inventors gained advantageous insights: A more acidic solution (lower pH) strongly increases the extent and rate of hydrolysis, and thereby disappointingly reducing the viscosity behaviour of the starch (compared to native starch). Figure 1 shows the effect of pH on the viscosity of granular potato starch in a slurry of 30 % (w/w) starch at a temperature of 50°C for 18 hours. The results in terms of MW reduction are given in Table 1. It shows that the MW reduction is stable at pH 3 - 5 at 18 hours hydrolysis. At pH 0.5 and 1 a huge reduction of the molecular weight is reached which consequently leads to a vast reduction in the viscosity characteristics, while at pH 2 viscosity builds up and remains during the holding phase. It is particularly preferred that the pH is between 2 and 6, as a huge decrease of the molecular weight is avoided while still maintaining most of the original viscosity characteristics; there is obtained a granular starch exhibiting viscosity build-up which remains present also after the holding phase. In addition to viscosity build-up, the inhibited granular potato starch also exhibits improved viscostability.

With these insights about prehydrolysis this experiment was repeated at pH 2 but with shortened time scales, and this prehydrolysis was combined with a so-called inhibition step at conditions which are also typical of hydrolysis, the results of which are shown in Figure 2. In Figure 3 there was a pretreatment at pH 1.5 followed by inhibition at pH between 2.2 and 5. Viscosity was increased and viscostability improved.

A similar experiment with a slurry of granular potato starch is shown in Figure 4, albeit that the prehydrolysis was achieved not by acid hydrolysis but by using alkaline treatment (pH > 9). Alkaline hydrolysis of granular starch is a known technigue to break the intermolecular hydrogen bonds of granular starch under mild alkaline conditions. Alkali causes oxidative degradation resulting in a decrease of molecular weight, and the rate of hydrolysis is dependent on the amount and type of alkaline solution used as well as on temperature and pH. Typical alkaline solutions are sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide and sodium bicarbonate. A skilled person is able to determine these parameters in order to hydrolyse the starch as desired. Reference is made to Yu et al. “Effects of treatment temperature on properties of starch-based adhesives” BioResources 2015;10(2), 3520-3530. For sake of convenience, such an alkaline pretreatment will be encompassed within the term ‘prehydrolysis’. Strikingly, with such a combination of hydrolysis and inhibition, both final viscosity (FV) increase and viscostability emerged, and an inhibited granular starch with strong cohesiveness and reduced breakdown viscosity (BV) was obtained. It shows that the inhibited granular starch has a FV that can be improved (by preferably at least 10%, more preferably at least 25%) compared to its untreated native starch counterpart, and a stabilized hold viscosity (HV) resulting in a reduced BV compared to the untreated starch counterpart indicating viscostability.

From the above it follows that these improvements are determined by the extent and rate of the mild hydrolysis treatment, using the molecular weight of the hydrolysed starch for a parameter reflecting the extent and rate of the hydrolysis. While the presented experiments are carried out using mild acid hydrolysis or alkaline pretreatment, the inventors envisaged that the same improved viscosity properties can be achieved using different, traditional hydrolysis methods provided the molecular weight is controlled during the hydrolysis treatment as above. Such alternative methods may involve enzymatic hydrolysis. Typical starch-hydrolysing enzymes are a-amylase, p-amylase, amylomaltase and other starch branching enzymes (SBEs). The traditional method for hydrolysing starch using enzymes is known in the art and described in many reviews for example in Park et al. “Properties and applications of starch modifying enzymes for use in the baking industry” Food Sci. Biotechnol. 2018; 27(2): 299-312. Similar to using acid hydrolysis, the starch-modifying enzymes allow the granular starch to have more reducing end groups which are believed to be essential for the subsequent acid treatment and inducing higher final viscosity and viscostability. It is preferred to use starch-modifying enzymes at a temperature which is at least 3 °C below the gelatinization temperature of the native starch, preferably below 60 °C. A skilled person is able to determine the amount of enzyme based on the activity in order to mildly hydrolyse the native granular starch.

While the hydrolysing agents used for prehydrolysis according to the invention are those which are traditional to the art, the inventors found that the conditions (pH, time, temperature) in which these hydrolysing agents are typically applied in the art induce hydrolysis in a too fast extent. With ‘mild’ hydrolysis in the context of the invention it is understood that the starch that is obtained at the end of the starch slurry pre-treatment still has a relatively high molecular weight, compared to a starch slurry which would be subjected to acid hydrolysis for pH 5 for 18 hours. It is noted that 25% of the fraction of native (potato) starch can be measured using GPC-MALLS, which renders the native, non-hydrolysed starch a difficult reference for assessing the required extent of hydrolysis. Instead, the molecular weight of a mildly hydrolysed starch serves as a suitable reference. The starch which is subjected to inhibition is characterized by a molecular weight (i.e. weight-average MW) reduction to a MW which is 2 - 50 %, preferably 5 - 40%, more preferably 10 - 35%, even more preferably 15 - 30%, preferably 20-50% of the weight-average MW, as determined with GPC-MALLS, of the corresponding starch when subjected to hydrolysis at pH 5 for 18 hours. More specifically, the starch yielded at the end of the prehydrolysis treatment should have a weight-average molecular weight (MW), as determined using GPC-MALLS, of at least 1 ,000,000 Da (1 ,000 kDa), more preferably at least 5,000,000 Da (5,000 kDa), even more preferably at least 10,000.000 Da (10,000 kDa), most preferably 10,000.000 - 100,000,000 Da (10,000 - 100,000 kDa). This applies particularly to potato starch.

In one embodiment, the MW at the end of prehydrolysis is at least 50,000 kDa.

There is a minimum amount of hydrolysis required, a minimum amount of reducing end groups must be formed, reflected by the upper limit of the % MW compared to the MW of the slurry starch subjected to pH 5 for 18 hours. The selection of the appropriate pH, temperature and time conditions to achieve these hydrolysis numbers are within the skilled person’s skills, using for instance the above- mentioned molecular weight analysis methods. With the prehydrolysis the dextrose equivalent (DE) of the starch is increased to a detectable value. Dextrose Equivalent (DE) is a measure of the amount of reducing sugars present in the starch, expressed as a percentage on a dry basis relative to dextrose. The dextrose equivalent gives an indication of the average degree of polymerisation (DP) for starch sugars. As a rule of thumb, DE x DP = 120. The standard method of determining the dextrose equivalent is the Lane-Eynon titration, based on the reduction of copper(ll) sulphate in an alkaline tartrate solution, an application of Fehling's test. The DE can be calculated as 100*(180 1 Molecular mass(starch)). With no or limited hydrolysis, the dextrose equivalent of starch is about 0%.

During prehydrolysis, temperature is controlled below 60 °C, preferably below the starting gel point of the starch, i.e. the temperature at which the starch starts to gel or the crossover point of loss modulus and storage modulus. This gel point can be determined by commonly known methods and means, e.g. using an amyloviscograph. The temperature is preferably between 10 and 1 °C lower than the gel point of the starch (in native form) using the same conditions (pH, water content, pressure etc.). The gel point assessment may for instance be carried out using a viscograph, where the settings presented for the so-called ‘acid Brabender’ and ‘neutral Brabender’. The settings as presented in the experimental section preceding example 1 of WO2014/042537 are herein incorporated by reference, and could be used as a guide. A temperature between 25 and 55 °C is most preferred.

The mild hydrolysis time depends on temperature and pH, and the type of hydrolysis (acid, enzymes or alkali). Preferably the time covering the mild hydrolysis is between 0.5 and 10 hours, most preferably between 1 and 5 hours, more preferably up to 3 hours. The desired temperature during mild treatment also depends on the other parameters as pH and time. For example, a shorter time frame of a maximum of 2 hours is accompanied by increased temperatures, in order to obtain sufficient mildly hydrolysed starch. The skilled person may select the combination of time and temperature which is deemed appropriate for instance from an economical viewpoint.

After prehydrolysis, the prehydrolysed starch slurry is subjected to conditions which promote restructuring over hydrolysis, to produce an inhibited starch. The inhibition step involves a pH between 1.7 and 6.5, preferably 2 - 6.5, more preferably 3 - 6. In the context of the invention, the terms ‘restructuring’ and ‘repolymerization’ of the starch are used interchangeably. It is preferred that the molecular weight reduction achieved with prehydrolysis is not or not significantly decreased any further. Hence, in a preferred embodiment, the MW as determined using GPC-MALLS of the inhibited starch is at least 80%, preferably at least 90%, even more preferably at least 100% of the MW of the prehydrolysed starch prior to subjecting it to inhibition conditions. This is evidenced in the experimental parts hereafter, showing that the MW showed a slight increase reflecting that restructuring prevails over hydrolysis under these conditions.

After inhibition, the process of the invention can comprise further processing steps such as neutralisation and drying of the inhibited starch. Neutralization of inhibited starch involves increasing the pH, which may be any pH value between 6.5 - 9.5. The inhibited starch may be dried at a temperature between 50°C and 180°C.

The product resulting from the process is denoted as an inhibited starch, which is a well-recognized feature in the field. It is a starch that is inhibited from returning to its native state, and which has improved acid, alkali and shear stability, and reduced gelatinization. The inhibited starch is characterized by viscosity build-up able to withstand heat treatments, and the starch exhibits improved peak viscosities, viscostability and/or final viscosity when compared to the native counterpart. The product can be used as a thickener or emulsifier in food applications. The inhibition conditions are in accordance with those known to the skilled person in the art, i.e. a combination of pH, temperature and time is selected as to allow for the formation of crosslinks.

As an effect of the hydrolysis in the pre-treatment, the inhibited starch thus obtained exhibits improved viscosity behavior, either in terms of viscosity build-up, viscostability and/or increased final viscosity, while there is maintained acceptable whiteness values (i.e. reduced or no colour formation). The inhibited starch is preferably viscostable, in particular in combination with a high viscosity during the holding period and a high final viscosity, compared to the nonhydrolyzed and uninhibited (native) starch counterpart. Viscostability is indicative of the required degree of inhibition (crosslinking). In the art, viscostability is derived from the viscosity of the starch - as measured using a standard Rapid Visco Analyser (RVA super 4, Newport Scientific). Viscostability can preferably be measuring using RVA with a temperature profile of 25 °C for 1 min; heating at constant rate to 95 °C in 5 min; hold at 95 °C for 10 min (hold phase); cooling at constant rate to 25 °C in 10 min; hold at 25 °C for 5 min) - reaches a peak viscosity at 95 °C, and does not decrease substantially after the peak when the starch is held at 95 °C (hold phase). In general, heating starch (up to e.g. 95 °C) results in a viscosity increase until a maximum value is attained (peak viscosity, PV), after which a drop (breakdown viscosity, BV) or hold viscosity (HV) is reached; upon cooling, the viscosity may rise (setback viscosity: SV, also known as the difference between the final (or end) viscosity and HV), until a final value (final viscosity, FV = HV+SV) is achieved. The minimum viscosity during the hold period is called the Trough Viscosity (TV). In other words, ultimate viscostability is achieved when [BV/PV] * 100 = [(PV-TV) I PV] * 100 = zero. To measure viscostability, the breakdown viscosity is defined as ((Peak viscosity (PV)) minus viscosity after 5 minutes (i.e. hold viscosity (HV))/ PV) * 100, so that a substantially reduced breakdown means that the starch is viscostable. Peak viscosity is linked to the ease of cooking of the starch: a high peak viscosity means that the starch is easy to cook. In order to appreciate the various viscosity parameters that are considered of added value to characterize starch (modifications), reference is made to Sandhu and Singh “Relationships between selected properties of starches from different corn lines" I nt. J. Food Properties 2005; 8:3, 481-491 , and particularly figure 1 therein, distinguishing between peak viscosity, breakdown viscosity, trough viscosity, setback, and final viscosity. Its contents is herewith incorporated by reference. In the experimental parts also different RVA profiles have been used, all yielding the same viscosity properties as seplained here above.

The inhibited starch has (i) a final viscosity (FV) which is at least 10%, preferably 25% higher compared to the FV of the chemically unmodified, granular starch (in corresponding amounts) that has not been subjected to prehydrolysation and inhibition; and/or (ii) viscostability expressed as a breakdown viscosity (BV) of less than 25%, more preferably less than 10%, together with a FV which is at least 10%, preferably 25% higher compared to the peak viscosity (PV). In other words, the inhibited starch produced according to the invention exhibits an increased viscosity and is preferably viscostable, i.e. has a breakdown viscosity which is less than 25%, even more preferably less than 10%. In a most preferred embodiment, the inhibited starch complies with both (i) and (ii).

The inhibited starch preferably has a breakdown viscosity (BV) of less than 30%, preferably less than 10%, more preferably less than 5%, together with a final viscosity (FV) which is equal or higher than the peak viscosity (PV), and preferably at least 10% higher, more preferably at least 25% higher than the PV. In some embodiments, the BV is less than zero or equals 0, i.e. there is no breakdown but instead a viscosity build-up is observed during the hold and subsequent cooling phase. Such an inhibited starch is particularly useful for gelatin replacement (in food applications).

In a preferred embodiment, the inhibited starch exhibits a setback viscosity (SV) as defined above, which is at least 25%, more preferably at least 50%, even more preferably at least at least 100% higher than the hold viscosity (HV). The inhibited starch produced according to the invention has the important advantage of not being chemically modified i.e. a starch registered by law as a clean label food additive. ‘Clean label’ foods are produced by non-chemical processing treatments, foods that do not involve artificial additives and chemical substances. This leads to an ingredient list that is clear, simple, comprehensible and attractive to the consumer. Clean label starch has a wider acceptability, both in terms of legal and consumer acceptance. Hitherto, the prior art has not been successful in producing a non-chemically modified starch having the combination of viscostability and final viscosity, of chemically crosslinked starch (for example modified by sodium trimetaphosphate (STMP) or phosphoryl chloride). Chemically crosslinked starch has the ability to be viscostable, during the holding phase after pasting the starch, at higher viscosity levels, comparable to the level of the peak viscosity of the native starch. The process of the invention allows these characteristics to match, but conveniently without the need for chemical crosslinkers, and with reduced process times. The improved viscostability makes the inhibited starch particularly suited in food applications such as sweet and sour sauces; enhanced cohesiveness is useful for use in (Stein Hall) corrugating glues.

The inhibited starch according to the invention has an improved whiteness value L, as a consequence of the less stringent temperature conditions of the inhibition process of the invention. The products of the invention have (a) an excellent whiteness (L* value) of at least 92.2, preferably at least 92.5, more preferably 93 - 98, more preferably 93 - 97 on a scale of 0-100 as defined e.g. by the CIE, Commission Internationale de I’Eclairage, wherein 100 represents absolute whiteness, and/ or (b) a reduction in whiteness value L* of less than 2, more preferably less than 1 .5 compared to the whiteness value of the corresponding chemically unmodified, granular starch that has not been subjected to prehydrolysation and inhibition. It is most preferred that the inhibited starch complies with at least (a), particularly in case of tubular (preferably potato) starch. Whiteness can be determined by conventional equipment measuring UV emissions at a wavelength in the range of 420-720 nm. As examples a Reflectance Colorimeter of HunterLab (Labscan II 0/45) or whiteness meters available from Kett can be suitably used. The excellent whiteness allows the products of the invention to be used without further purification. Alcohol (e.g. ethanol) removal, optional washing and drying are sufficient for arriving at a product which is ready for use. Also, the inhibited starch of the invention can readily be applied in food products while retaining their normal colour. With no colourization of the food product caused by the starch, according to the invention, customer appreciation of the products appearance is maintained.

A particular advantage of the viscostable starch, specifically the viscostable inhibited waxy potato starch, according to the invention is that it exhibits viscostability under shear conditions that may be applied to food products as well as under pH circumstances that are typically present in food products, that is to say, at acid and neutral pH. This widens the range of food applications where the viscostable starch, specifically the viscostable waxy potato starch, may be used, including e.g. acidic food products such as soups or sauces. Shelf-life, stability, quality, appearance and customer appreciation are improved. Hence, the invention also relates to the use of the inhibited starch according to the invention in food applications, in glues, and in sweet and sour sauces. The starch according to the invention is also an excellent gelatin replacer, particularly where the starch has a negative breakdown viscosity. Examples

Example 1

Materials & methods:

Native potato starch

Eliane waxy potato starch (AVEBE)

Rapid Visco Analyser (RVA super 4, Newport Scientific)

Bruker D2 diffractometer

Konica Minolta Chroma Meter CR-410 with a D65 illumination condition (CIE standard)

MW determination

The molecular weight was determined using GPC-MALLS-RI: 25 mg starch was prewetted with 50 pL 96% (v/v) ethanol and dissolved in 5 mL eluent by stirring for 1 hour at 600 rpm in a capped pyrex glass tube in a heating block at 100 °C. Prior to GPC-MALLS analysis, the sample was filtered over a 5 pm PTFE syringe filter.

Eluent: 50 mM LiBr in DMSO/water (9:1 (v/v));

Flow rate: 0.5 mL/min;

Injection volume: 0.100 mL

Columns: PLgel Guard 5 p,MIXED-A 20 p and MIXED-D 3 p (Agilent);

Column temperature: 75 °C;

Detection:

- MALLS (Wyatt Dawn HELEOS II), 25 °C, dn/dc = 0.074 mL/g

Rl (Wyatt Optilab T-rEX), 25 °C, detector volume delay 0.195 mL

LS software: Wyatt ASTRA for windows version 7.3.1 .9

(ZIMM method with a first order fit was used for calculations of standards and samples with radius < 90 nm)

(BERRY method with a second order fit was used for calculations of samples with radius > 90 nm)

1.1 Preparation of potato starch slurry samples and effect of pH on starch viscosity

A 0.5 M hydrochloric acid (HCI) solution was prepared. This solution was used to adjust the pH of demineralized water. Different pH solutions were prepared with the pH ranging from 0.5 to 4. A potato starch slurry (30% w/w) was prepared by suspending 27g (on dry matter) of starch in the acidified pH solutions to a total mass of 90 g, and added to a closed glass vessel. The starch suspensions (with a pH ranging from 0.5 - 4) were stirred for 18 hours in a water bath at 50°C. The reaction was terminated by neutralisation with an 0.02 M NaOH solution with a final pH between 6-8. The starch was filtered by using a Buchner funnel, washed with 100 mL demineralized water and further dried in an oven at a temperature of 50°C.

Neutral RVA pasting profiles were determined by subjecting a 5% (w/w) starch suspension (dry mass base) in demineralized water (neutral) or in the buffer solution at pH 3.0 (error margin of 0.1 units) (acid) to a temperature profile using a Rapid Visco Analyser (RVA super 4, Newport Scientific). For neutral RVA, the stirring speed was 160 rpm and the temperature profile: 25 °C for 1 min; heating to 85 °C in 5 min; hold at 85 °C for 10 min; cooling to 25 °C in 10 min; hold at 25 °C for 5 min.

Figure 1 shows the effect of pH on the viscosity of potato starch in a slurry of 30 % (w/w) starch at a temperature of 50°C for 18 hours: An initial pH of 0.5 reduced end viscosity of potato starch, while subjecting potato starch to an acidic slurry with a pH above 2.0 viscosity build-up remained present. In addition, viscostability emerged when the potato starch was subjected to an acidic slurry of pH 2.

1 .2 Effect of pH on molecular weight

The same conditions as described in section 1 .1 is applied here. The molecular weight of potato starch was measured by use of a Gel permeation chromatography coupled online to a multi-angle laser light scattering (GPC-MALLS). Table 1 shows the weight average molecular weight (MW) in kiloDalton of potato starch suspended in acidic slurries ranging from pH 0.5 - 5. The molecular weight was affected by acidic pH and a more acidic solution resulted presumably in increased hydrolysis and consequently reduced molecular weights. At a pH 1 and higher, i.e. milder hydrolysis conditions, the molecular weight was less affected and remained at higher weights above 1 million Dalton.

Table 1 . Molecular weight (MW), of potato starch suspended in acidic slurries ranging from pH 0.5 - 5

Molecular weight (MW) was also studied after subjecting the potato to different treatments: When the potato starch was subjected to a 2 hour hydrolysis at a temperature of 50 °C at pH 1 .5, MW was reduced to 72,559 kDa. When the hydrolysis of the potato starch was continued at pH 1 .5 for a total of 18 hours, MW was measured at 27,289 kDa (Table 1). If after the initial two hours of hydrolysis at pH 1.5, the potato starch was subjected to conditions which favour repolymerization over hydrolysis (pH 4; 16 hours), the MW was 81 ,961 kDa. If the potato starch was subjected to pH 4 for 18 hours, MW was 322,664 kDa, similar to the reference (pH 5 18 hours) . 1.3.1 Inhibition of starch - two-step acid treatment at pH 2 and subsequently pH 4 or 6

A mild hydrolysis step was performed by suspending granular potato starch in a HCI solution (slurry 30% (w/w)) with a pH of 2 and stirring for approximately 2 hours in a water bath at 50 °C. With an 0.02 M NaOH solution the pH was raised to a pH 4 or 6. The second step of the process, where inhibition of the starch is induced, was executed by continuing the reaction for 13 hours at a temperature of 50 °C at these elevated pH values. The reaction was finished by neutralisation with an 0.02 M NaOH solution with a final pH between 6-8. The potato starch was filtered by using a Buchner funnel, washed with 100 mL demineralized water and further dried in an oven at a temperature of 50°C.

Viscosity was measured as described under section 1.1. Figure 2 shows the viscosity profiles of native and inhibited granular potato starch. Again, overall viscosity build-up was present in the inhibited starch obtained by the process according to the invention compared to native potato starch. In addition, Figure 2 shows that there was a substantial s increase of at least 180% of the final viscosity of the inhibited potato compared to native potato starch, suggesting strong cohesiveness of the granular potato starch.

Another observation was that viscostability in the inhibited potato starch subjected to a pH 2 and subsequently to a pH 4 can be already seen which emerged after peak viscosity.

1.3.2 Inhibition of starch - two-step acid treatment at pH 1.5 and subsequent higher pH’s.

A mild hydrolysis was performed by suspending granular potato starch in a HCI solution (slurry 30% (w/w)) with a pH of 1 .5 and stirring for approximately 2 hours in a water bath at 50°C. With an 0.02 M NaOH solution the pH was raised to a pH 2.2, 3.2, 3.8 or pH 5. The inhibition step of the process was executed by continuing the reaction for 13 hours at a temperature of 50 °C at these elevated pH values. The reaction was finished by neutralisation with an 0.02 M NaOH solution with a final pH between 6-8. The potato starch was filtered by using a Buchner funnel, washed with 100 mL demineralized water and further dried in an oven at a temperature of 50 °C.

Viscosity was measured as described under section 1.1. Figure 3 shows the viscosity profiles of native and inhibited granular potato starch. Viscostability was present in all starch suspensions subjected to the two-acid treatment. In more detail, breakdown viscosity is calculated by [BV/PV] * 100 = [(PV-TV) I PV] * 100. Inhibited granular starch subjected to a pH 1 .5 and subsequently to either a pH 2.2, 3.2, 3.8 or 5 had all a breakdown viscosity of less than 5%, in other words viscostability has reached nearly zero %.

From the experiments performed under section 1.3.1 and 1.3.2 can be concluded that viscostability is even more pronounced when using a combination of a pH of 1 .5 and subsequently a higher pH. The experiments reveal that with a two-acid treatment, higher end viscosity and/or viscostability can be reached in which an optimum is presumably present between pH 1 .5 and 2.

1 .3.3 Inhibition of starch - alkaline treated pre-modified starch with acid treatment at higher pH’s.

Another aspect of the invention is that the mild hydrolysis step can be performed using other convential techniques in the art. Eliane waxy potato starch is a native clean label starch which has been mildly crosslinked (hydroxypropylated) and further treated with alkaline. The hydroxypropylated and mildly crosslinked starch was suspended in an acidic solution to obtain an acidic slurry (30% (w/w)) with a pH 5. The inhibition step of the process was executed by continuing the reaction for 13 hours at a temperature of 50 °C at pH 5. The reaction was finished by neutralisation with an 0.02 M NaOH solution with a final pH between 6-8. The potato starch was filtered by using a Buchner funnel, washed with 100 mL demineralized water and further dried in an oven at a temperature of 50 °C.

From Figure 4 can be derived that modified waxy potato starch reveals a viscosity stability of ~0% after acid treatment at a pH of 5. In addition, final viscosity of the starch was increased by 125% compared to pre-modified alkaline treated starch without acid treatment. It should be noted that it is unclear in what manner the alkaline pre-treatment affected the inhibition process at pH, as the starch was also chemically crosslinked. Thus, the result shown in Figure 4 can be due to the alkaline treatment (mild hydrolysis), the chemical modifications or a combination of both.

1 .4 Effect of pH on crystallinity

To examine whether the crystallinity may affected the viscosity profiles as seen in section 1.3, a comparison was made between native potato starch, potato starch subjected to pH 1 .5 for 2 hours and potato starch subjected to pH 1 .5 for 2 hours and subsequently to pH 4 for 15 hours.

To measure the crystallinity, Wide Angle X-ray Scattering (WAXS) powder diffractograms were recorded on a Bruker D2 diffractometer in the reflection geometry in the angular range 5-35°(20), with a step size of O.O2°(20) and an acquisition time of 2.0 s per step. The Co Ka1 radiation ( = 1 .7902 A; X- ray tube is air cooled) from the anode, was generated at 30 kV and 10 mA and was monochromatized using a Ni filter. The diffractometer was equipped with a 1 mm divergence slit and a 0.5 mm knife edge above the sample stage (enabling measurement at low angel, i.e. from 4° 20 upwards). The LINEXEYETM Silico-strip detector had a 4° - 5° active area. Behind the opening were a Soller slit and a Ni filter.

Figure 5 shows the crystallinity of native potato starch, potato starch subjected to pH 1.5 for 2 hours and potato starch subjected to pH 1 .5 for 2 hours and subsequently to pH 4 for 15 hours. As can be seen, hydrolysis, using acid conversion affected the crystallinity of potato starch. Nevertheless this effect on crystallinity emerged already in the first 2 hours and the subsequential reaction at a higher pH level had no further impact on the crystallinity. Hence, the viscosity profiles as seen under point 1 .3 were not induced by changes in the crystallinity of potato starch.

1 .5 Colour analysis and effect of starch inhibition according to the invention on whiteness

Colour analysis of the starch products was performed using a Konica Minolta Chroma Meter CR-410 with a D65 illumination condition (CIE standard). The measurement area was 50 mm and the illumination area was 53 mm (suitable for the starch material). The observer condition was a 2° measuring angle (CIE standard). Before use the measurement was calibrated using a colour standard tile. The results of the measurements are recalculated and presented in L values. The L-value is a correlate of lightness scaled between 0 (black) and 100 (white) as defined e.g. by the CIE, Commission Internationale de I’Eclairage. Inhibited potato starch that had been subjected to an acid treatment by the process according to the invention (described in section 1 .2) and reached viscostability, had an L value of 94 identical to the L value of native potato starch.

There were small differences visible in the a and b values of the inhibited potato starch obtained from the process according to the invention compared to the native potato starch (Table 2). These differences may be due to coarseness of the commercially available starches as the starch particles were grinded for sale.

This shows that in the process according to the invention, at higher pH values and less stringent conditions, higher degrees of whiteness (higher L values) may be achieved in combination with viscostability.

Table 2. Whiteness values (L* value) of native potato starch and inhibited potato starch according to the invention.

RVA

In examples 2-5, a different RVA profile has been used:

A 5% suspension of starch product having a total weight 28.0 g was prepared by weighing off the appropriate amount of starch product, corrected for moisture content, into an aluminium RVA cup and then adding demineralised water until the total weight was 28.0g. The aluminium cup was then placed in the RVA instrument and measured using the following instrument settings:

Example 2

Demineralised water was acidified to the desired pH (2) with 0.5M HCI. A 30% native potato starch suspension was then prepared by introducing 6 moles (972g) of the starch into 2916g of the acidified demineralised water contained in a double-walled reactor vessel attached to a water bath; the suspension had a pH of around 2.4 after the suspension has been prepared. The temperature of the suspension was then raised to 50°C over a period of 3 hours. After a further 2 hours, the reaction was split into 2 portions. The pH of one portion was increased to pH3 (denoted as Sample pH3, 13 hours in the corresponding figure), and for the other portion to pH5 (denoted as Sample pH5, 13 hours in the corresponding figure). Both portions were then allowed to continue stirring for 13 hours at 50°C, following which the water batch was switched off and the suspension allowed to cool to around 20°C. Both suspensions were then neutralised to pH7 followed by filtration over a Buchner funnel. The filter cakes were washed with an amount of water that was 5 times greater than the amount of starch. The filtered products were then placed on plates to dry in an oven at 50°C, after which they were milled in a grinder and stored in sealed bags.

The RVA profiles are plotted in Figure 6. It shows that the end viscosity has increased in comparison to the final viscosity of native potato starch. This is an advantage for applications that require a strong cohesiveness of the starch, e.g. glues.

Example 3

A 42% starch suspension was prepared in a double-walled glass reactor vessel connected to a water bath by suspending 5 moles (810g) of native potato starch in the appropriate amount of demineralised water. The suspension temperature was increased to about 55°C after which the pH was adjusted to 1 .9 by the addition of H2SO4 (concentrated H2SO4 mixed to approximately 1 :5 with demineralised water). After 2 hours the suspension pH was adjusted to 5 by addition of 4.4% NaOH solution and the reaction allowed to proceed. One sample was taken after 20 hours stirring at pH5 I 55°C, as follows: approximately 300 mL of the suspension was collected in a plastic cup and poured directly into about 1 L of demineralised water, after which it was filtered over a Buchner funnel and washed with 3 x 1 L demineralised water. The filtered product was dried in an oven at 40°C for at least 24 hours after which it was milled by grinding and placed in a sealed plastic bag. After 23 hours, the suspension was filtered directly over Buchner funnel and washed with 3 x 2L demineralised water. The filtered product was dried in an oven at 40°C for at least 24 hours after which it was milled by grinding and placed in a sealed plastic bag. The corresponding RVA profiles were measured after drying.

The results are plotted in Figure 7. It shows that the breakdown has been reduced significantly (<10%). The final viscosity is higher than the peak viscosity.

Example 4

A 42% starch suspension was prepared in a double-walled glass reactor vessel connected to a water bath by suspending 5 moles (810g) of native potato starch in the appropriate amount of demineralised water. The suspension temperature was increased to about 55°C after which the pH was adjusted to 1 .9 by the addition of H2SO4 (concentrated H2SO4 mixed to approximately 1 :5 with demineralised water). After 2 hours the suspension pH was adjusted to 9 by addition of 4.4% NaOH solution and the reaction allowed to proceed. One sample was taken after 20 hours stirring at pH9 I 55°C, as follows: approximately 300 mL of the suspension was collected in a plastic cup and poured directly into about 1 L of demineralised water, after which it was filtered over a Buchner funnel and washed with 3 x 1 L demineralised water. The filtered product was dried in an oven at 40°C for at least 24 hours after which it was milled by grinding and placed in a sealed plastic bag. After 23 hours, the suspension was filtered directly over Buchner funnel and washed with 3 x 2L demineralised water. The filtered product was dried in an oven at 40°C for at least 24 hours after which it was milled by grinding and placed in a sealed plastic bag.

The results are plotted in Figure 8. A further reduction in the breakdown has been achieved (<5%)

Example 5

A 42% starch suspension was prepared in a double-walled glass reactor vessel connected to a water bath by suspending 5 moles (810g) of native potato starch in the appropriate amount of demineralised water. The suspension temperature was increased to about 57°C after which the pH was adjusted to 1 .9 by the addition of H2SO4 (concentrated H2SO4 mixed to approximately 1 :5 with demineralised water). After 2 hours, the suspension pH was adjusted to 5 with 4.4% NaOH solution. One sample was then taken (Denoted as Sample 2 hours in the corresponding figure), as follows: approximately 300 mL of the suspension was collected in a plastic cup and poured directly into about 1 L of demineralised water, after which it was filtered over a Buchner funnel and washed with 3 x 1 L demineralised water - the corresponding RVA profile was then measured directly, before drying. The temperature of the remaining suspension was lowered to about 55°C, and the reaction allowed to proceed. After 20 hours at pH5 and 55°C, the suspension was filtered directly over a Buchner funnel and washed with 3 x 2L demineralised water. The filtered product was dried in an oven at 40°C for at least 24 hours after which it was milled by grinding and placed in a sealed plastic bag.

The results are plotted in Figure 9. A negative breakdown has been reached, rendering the inhibited starch particularly useful as a gelatin replacement.

Example 6

A 30% starch suspension was prepared in a double-walled glass reactor vessel connected to a water bath by suspending 4 moles (648g) of native potato starch in the appropriate amount of demineralised water. The suspension temperature was increased to about 55°C after which the pH was adjusted to 3.85 by the addition of 0.5M HCI.. After 2 hours, the suspension pH was adjusted to 7 with 4.4% NaOH solution. One sample was then taken (Denoted as Sample 2 hours in the corresponding figure), as follows: approximately 300 mL of the suspension was collected in a plastic cup and poured directly into about 1 L of demineralised water, after which it was filtered over a Buchner funnel and washed with 3 x 1 L demineralised water - the corresponding RVA profile was then measured directly, before drying. The reaction was allowed to proceed for 17 hours at pH7 and 55°C, after which the suspension was filtered directly over a Buchner funnel and washed with 3 x 2L demineralised water. The filtered product was dried in an oven at 40°C for at least 24 hours after which it was milled by grinding and placed in a sealed plastic bag. The results are plotted in Figure 10. A negative breakdown has been reached, rendering the inhibited starch particularly useful as a gelatin replacement.