WO2001021011A1

WO2001021011A1 - Starch product

Info

Publication number: WO2001021011A1
Application number: PCT/NL2000/000653
Authority: WO
Inventors: Jacob Bergsma; Jan Aten; Ido Pieter Bleeker
Original assignee: Coöperatieve Verkoop- En Productievereniging Van Aardappelmeel En Derivaten Avebe B.A.
Priority date: 1999-09-17
Filing date: 2000-09-14
Publication date: 2001-03-29
Also published as: AU7561600A

Abstract

The invention relates to a process for preparing a starch product, wherein native starch or crosslinked starch in substantially ungelatinized state is treated with a debranching enzyme. The invention further relates to a starch product obtainable by said process and the use thereof in foodstuffs and pharmaceutical compositions.

Description

Title: Starch product

The invention relates to a process for preparing a starch product and to the starch product obtainable by said process. The invention further relates to the application of the novel starch product in foodstuffs and pharmaceutical compositions. In the food and pharmaceutical industries, hydrocolloids are in general used to thicken water-based foodstuffs. Gelatin is a popular hydrocolloid, which, contrary to other hydrocolloids which are mainly of a polysaccharide nature, is a protein. Gelatin is derived from animal slaughter offal, such as skins and bones, by hydrolysis of insoluble collagen into soluble gelatin. Collagen is the major structural component of white tissue fibers and present in all tissues and organs of animals where it constitutes almost 30% of total protein content.

Gelatin is used in a great number of food applications, where it is desired because it has a number of characteristics that are superior over other hydrocolloids used in the food industry. It is used for example as a thickening or gelling agent in jellied products such as confectionery and aspic type of foods; as a stabilizer and thickener in ice cream and icings, as emulsifier and thickener in dressings, desserts and sauces, as thickener in syrups and soups, as binder or thickener in general and as filling agent. For example, gelatin is used in gum and jelly products, such as wine gums, as gelling agent to give the end product an elastic, gummy structure. In particular, gelatin is superior over other thickening (gelling and binding) agents for the clarity and elasticity it renders to the food product. Moreover, the combination of both thickening (viscosity increasing) and gelling properties in one additive is very rare and not readily found among the polysaccharide based hydrocolloids.

The use of gelatin (or hydrolyzed collagen) in the food industry, however, has recently been criticized because of its animal origin. Traditionally, gelatin containing foodstuff has been avoided by vegetarian consumers and by consumers having a religious background that teaches to avoid gelatin. These traditional gelatin avoiding consumers were in general satisfied with buying products that contained less superior binding agents to accommodate their vegetarian and/or religious preferences. More recently, however, the general consumer, albeit not bound by vegetarian or religious preferences, is also shifting to a preference for foodstuff wherein gelatin is replaced by a different agent. This is understood as to have mainly been initiated by the recent occurrence of prion diseases such as seen with mad cow disease, and by concern that these prion diseases may infect humans when proteinaceous food of animal origin is eaten. The prion diseases bovine spongiform encephalopathy (BSE) and scrapie of cattle and sheep, respectively, are fatal neurodegenerative diseases caused by prion proteins and are characterized by a long incubation period. In humans Creutzfeldt-Jakob disease (CJD), Gerstmann-Straussler-Scheinker syndrome (GSS) and fatal familial insomnia belong to this category of transmissible spongiform encephalopathies (TSEs).

Although scrapie, the prototype of the family of TSE's, in sheep and goats has been known for over 200 years and has been diagnosed world-wide, it is only since 1986 that BSE has been described in cattle in the UK. By January 1998, there had been 170,259 confirmed cases of BSE in Great Britain and there may exist a great number of cases of not yet overt cases of BSE. BSE apparently emerged because scrapie contaminated sheep offal, via meat and bone meal had been included in cattle feed, and newly infected cattle material was then recycled and eaten by susceptible cattle.

Brain homogenates from cows with BSE produce a characteristic pattern of brain lesions in mice. This is identical to the pattern elicited by brain tissue from individuals who recently have died from new-variant Creutzfeldt-Jakob disease. Up to now, this variant has caused the death of 35 young Britons and one Frenchman.

There is also concern that the BSE strain that seems to be transmissible to humans may have infected sheep, where it could produce a disease hardly distinguishable from scrapie. Sheep BSE may be a threat to human health, although scrapie by itself seems not to transmit to humans. Indeed, BSE agent has been transmitted experimentally to sheep by the oral route and thus could have the potential to infect sheep under field conditions. Thus far, the only known cause of prion disease is an abnormal form of the normal prion protein called aberrant prion protein. Said aberrant prion protein is mainly characterized by its resistance to proteolytic hydrolysis, it is typically quite resistant against treatment with high or low pH, and generally only looses its infectivity after prolonged treatment under high temperature. Although most governments in Western society have taken strict measurements to alleviate public concerns related to mad cow disease, for example by strictly banning the use of animal products derived from animals with prion disease in the food industry, public concerns related to using the protein derived gelatin still exist, and seem to be growing. Consequently, among the general public lives a growing desire to consume non-gelatin derived foodstuff, that, however, has similar or comparable superior characteristics as the traditionally gelatin comprising foodstuffs have.

It is an object of the present invention to provide a non-protein hydrocolloid that has suitable characteristics to serve as gelatin replacement in foodstuff of varied nature or that can be used to prepare new types of foodstuff.

Surprisingly, it has now been found that a starch product which is debranched in a specific manner has the desired properties. Thus, the invention relates to a process for preparing a starch product, wherein native starch or crosslinked starch in substantially ungelatinized state is treated with a debranching enzyme. The invention further relates to a starch product obtainable by said process.

The present starch product has very advantageous properties that make it highly suitable for use as a rheology regulating agent. In particular, in water based systems it may provide both a thickening, viscosity increasing effect, and a gelling effect, which combination is highly unusual for polysaccharides used in such applications. Furthermore, the product has a very good elasticity and its clarity can be conveniently adjusted to the envisaged application by choosing a suitable natural source for the starch used for preparing the present starch product. In addition, it has been found that the starch product can be very conveniently processed. For instance, it allows for fast and easy separation/isolation by filtration.

Further it is noted, that due to the low viscosity of ungelatinized starch, enzymatic modification can be performed in concentrated starch systems such as suspensions up to 45 % (g starch dry solids/volume) or under semi-dry conditions, above 45 % (g starch dry solids/volume). The resulting starch product can easily be separated from salts and enzymes by washing without the use of more costly and laborious methods like ion-exchange chromatography. Furthermore, the starch product can be recovered from the water phase by relatively simple methods like filtration or sedimentation, thus avoiding the use of more costly methods like e.g. spray-drying. Moreover, enzymatically prepared starch products according to the invention retain their granular structure, thus preserving the properties of granular starches with respect to gelatmization in applications. In accordance with the invention, it is preferred that a native starch or a crosslinked starch is used. Suitable starches are for example chosen from maize, wheat, barley, rice, tnticale, millet, tapioca, arrow root, banana, potato, sweet potato, high amylose type starches, such as from amylomaize, wrinkled peas, mung beans, starches with a high amylopectm content, such as waxy maize, waxy barley, waxy wheat, waxy rice, amylopectm potato, amylopectm cassave, amylopectm sweet potato or amylopectm banana. Preferably, the starch is derived from corn, potato, wheat, rice, barley, cassava, arrowroot, sago or oat.

As used m the context of the present invention, the term 'native starch' is intended to refer to starch that is isolated from its natural source product, but which in principle has undergone substantially no physical or chemical modification. In fact, this term is commonly used in the art to refer to such starch products.

Crosslinked starch in general is a modified starch in which cross- links between starch macromolecules have been formed by means of bifunctional or polyfunctional chemical reagents. This results in the formation of large complexes of starch molecules of high molecular weight. Cross-links can be formed between amylose molecules, between amylopectin molecules, or between amylose and amylopectin molecules. Crosslinking starch in itself is a method known in the art for which several reagents are known. Examples of such reagents are epichlorohydrin, sodium trimetaphosphate, phosphorous oxychloride, adipic anhydride and reagents with two or more halogen, halohydrin or epoxide groups. The manner in which the crosslinking reaction can be carried out is, among others, described in "Modified Starches: Properties and Uses", O.B. Wurzburg, CRC

Press Inc., 1987. For food applications, it is preferred that crosslinked starch is prepared by reacting 1.2 to 12 grams of sodium trimetaphosphate or up to 2.5 grams of phosphorous oxychloride per kilogram of starch.

An important aspect of the present invention is that the native starch or crosslinked starch is treated with a debranching enzyme in substantially ungelatinized state. Starch, particularly native starch, consists of discrete granules which swell up when contacted with water. This swelling is reversible. If the wet, swollen starch is dried, the original granules are recovered. If a suspension of starch granules in water is heated, the granules take up significantly more water. At a certain point, the swelling becomes irreversible and the granules are disrupted. This point is different for different starch types. Beyond this point, the viscosity increases sharply and the starch is gelatinized. Instead of raising the temperature, gelatinization may also be effected in different manners, such as increasing the pH, addition of a salt or addition of an organic solvent. It is noted that the use of a debranched starch product in, for instance, foodstuffs is known per se. However, in the prior art the debranching is typically carried out using a pre gelatinized starch.

The US patent 5,849,090, for instance, discloses a method of producing a granular resistant starch comprising debranching the starch. However, before debranching, the granular native starch is heated to gelatinize.

In the European patent application 0 806 434, a high solids enzyme conversion process for preparing a liquified enzyme-converted starch is described. In a first step, a single phase powdered mixture without a visible free water phase is prepared. When the powdered mixture starch contains a granular starch, as the powdered mixture is heated, the heat and moisture initiate the swelling of the starch granules and the starch is completely or partially gelatinized and simultaneously converted. US patent 3,922,196 deals with enzymatic hydrolysis of granular starch. Enzymes that are employed for the solubilization of starch are α- amylase, glucoamylase, maltogenic amylase or β-amylase. Although the use of isoamylase is also mentioned, this enzyme is only applied to a hydrolysate of starch. In Cereal Chem. 69(4), 1992, 405-409, Jane et al. have described a process for debranching amylopectin. However, the starting material is a fractionated, solubilized starch product.

Kimura et al., Carbohydrate Research 287 (1996) 255-261, have made a comparison between a reaction of an isoamylase of Pseudomonas amyloderamosa with native and gelatinized starch granules. The reactions are all carried out at 37°C. The percentage reaction of all starches under these conditions is below 12%, for potato starch it is as low as 3.7%. The percentage reaction in this regard is defined as the ratio between the sum of the reducing capabilities of the dissolved and rest granule fractions and the reducing capability of the dissolved starch, after the reaction. In accordance with the present invention it is preferred that the temperature during the debranching reaction is much higher. The percentage reaction that is achieved is between 20 and 40%.

The European patent application 0 616 778 relates to a method for opacifying a reduced-fat food, employing a partially or fully debranched starch. The starch is prepared by enzymatic hydrolysis of the alpha-l,6-D-glucosidic bonds of pregelatinized starch, employing an endo-alpha-l,6-D- glucanohydrolase, such as pullalanse or isoamylase.

Similarly, the European patent application 0 480 433 disclose foods containing soluble high amylose starch. The starch is prepared by enzymatically debranching a spray-dried, uniformly gelatinized starch. In US patent 5,468,286, the use of enzymatically debranched starches as tablet excipients is disclosed. Before carrying out the debranching reaction, the starch is pregelatinized to permit efficient and uniform debranching.

The factor of debranching starch in substantially ungelatinized state in accordance with the invention leads to several important advantages. The reaction can be carried our in a very simple and convenient fashion, for instance in a slurry with very high concentrations of solids (up to 45%) or under semi-dry conditions. In addition, any by-products of the reaction can be conveniently removed by washing and/or filtration. Furthermore, the drying of the product is very easy. The product is in granular form and is not soluble in cold water. It is very good dispersable in water, substantially without formation of agglomerates or coagulation. Dispersions of the present product are very mixable with other components in cold water, in fact they are better mixable than dispersions of pregelatinized, cold water swellable starches.

In a preferred embodiment, the present process is carried out at a temperature below the gelatinization temperature of the starch used. For starch derived from potatoes, this temperature lies around 60°C. An optimum in process conditions has been found at temperatures between 8°C, preferably 6°C, below the gelatinization temperature and the gelatinization temperature itself.

The enzyme with which the starch is treated according to the invention is a debranching enzyme. This means that it is capable of enzymatically debranching starch. Mostly, the enzymatic treatment will lead to formation of short chain amylose. Debranching enzymes are roughly divisible into two categories: pullulanases and isoamylases. The first category is, by the International Union of Biochemistry (1984), officially referred to as E.C. 3.2.1.41 α-dextrin endo-l,6-glucosidase. By definition, enzymes of this category are capable of hydrolyzing 1,6-α-D-glucosidic bonds in pullulan, glycogen and in the α- and β-limits dextrins of amylopectin and glycogen. The second category falls with the class of E.C. 3.2.1.68. Enzymes of this category are capable of hydrolyzing 1,6-α-D-glucosidic bonds in glycogen, amylopectin and their respective β-limit dextrins. In general, isoamylases are well suited for debranching longer chains in the starch. Nevertheless, pullulanases have also been found to show this activity. Examples of suitable pullulanases are the commercially available products known by their trade names Optimax L300 (Genencor) and Promozyme 200L (Novo Nordisk). Optimax L300 has been found to lead to particularly good results. In general, these enzymes may be added in concentrations of 0.1 to 5% (volume/weight of dry starch solids), preferably of 0.5 to 3% (volume/weight of dry starch solids).

The pH during the enzymatic treatment is preferably chosen between 4 and 6, as the enzymes perform optimally within this range. It is further preferred that the process is carried out in a slurry or under semi-dry conditions.

The degree of the conversion can be determined by measurement of the reducing groups that are formed as a result of debranching. This can be done e.g. by measurement of the reducing power as dextrose equivalent (DE) according to commonly used methods like Luff-Schoorl. Completely debranched potato starch has a DE value of around 5.0. Products according to the invention preferably have DE-values between 0.1 and 2.0, more preferably between 0.2 and 2.0.

Once the enzymatic reaction has reached its desired extent of completion, the starch product may conveniently be recovered by e.g. filtration. As the starch processed in ungelatinized condition, the starch granules will have remained intact after the reaction. Accordingly, they allow for easy filtration. Finally, the product may be dried in any suitable manner. If desired, the product may be chemically or physically modified in any known manner. In a preferred embodiment of the invention, the native starch or crosslinked starch is pre-treated with a maltogenic α-amylase before it is treated with a debranching enzyme as disclosed above. Although it has exo activity, this enzyme is officially referred to as E.C. 3.2.1.1. α-amylase or 1,4-α- D-glucan glucanohydrolase. A suitable example of a maltogenic α-amylase is can be derived from Bacillus stear other mophilus, which is produced with the aid of a genetically modified strain of Bacillus subtilis. This enzyme is commercially available from Novo Nordisk under the trade name of Maltogenase. It has been found that this pre-treatment leads to a starch product with even better gelling properties.

This pre-treatment is preferably performed in a slurry or under semi-dry conditions at pH values between 4 and 6,preferably between 5 and 6 and a temperature between 8°C, preferably 6°C, below the gelatinization temperature of the starch.

The invention further relates to the use of a starch product according to the invention in the preparation of a foodstuff or pharmaceutical composition, preferably partly or fully replacing gelatin in said foodstuff or pharmaceutical composition. By using a product according to the invention, it is possible to replace gelatin for more than 50%, up to 80% or even 100%, depending on the requirements of the customer. It is thus now possible to reduce gelatin content and select and use minimal quantities of those gelatin batches that are absolutely prion protein free, or to fully replace animal derived thickeners, such as hydrolyzed collagen, or gelatin, that may be derived from slaughter offal comprising aberrant prion protein. In a preferred embodiment, said foodstuff is chosen from the group of baked goods, desserts, meat products, processed cheese, snacks, soups, sauces, gravies fruit fillings and confectionery, for example sugar confectionery such as hard or soft sugar confectionery, lozenges or dragees, or confectionery for diabetics wherein the sugar is replaced by artificial sweeteners. Such foodstuffs comprising the present starch product may be characterized by their elasticity and/or clarity. The invention furthermore provides a method for preparing a thickened (thickening herein also called gelling, stabilizing or binding) foodstuff comprising mixing a starch product according to the invention with a water-based liquid. Such a water-based liquid can for example be water, milk or another dairy product, a stock or bouillon, a sugar solution, a beverage or another water-based liquid food component known in the art. Of course, said method allows for the additional use of other ingredients, of which many are known in the art. Traditionally, gelatin was a first choice in thickening such liquids, however, due to consumer preference, a method to prepare non-gelatin foodstuffs is desired.

It is further envisaged that the product obtainable by the present method may be formulated with water or plasticizer in order to manufacture shells for soft capsules, which may for instance be used as pharmaceutical dosage forms.

The invention will now be elucidated by the following, non- restrictive examples.

Example 1. Debranching of potato starch granules.

Food-grade potato starch, containing 18 % moisture was suspended in a 2 L stirred double-walled reactor, which was equipped with a thermostated waterbath. The starch was suspended to a 35 % (weight dry substance / volume) concentration in demineralized water. The pH was adjusted to 4.4, with diluted HC1. The suspension was stirred at 35 r.p.m. until the content was at a temperature of 58°C. The reaction was initiated by the addition of 2 % (volume / g of starch dry substance) Optimax L300. After 17 hours of reaction the DE of the reaction mixture was 1.2. The enzyme activity was reduced by increase of the pH to 7.0 by adding diluted KOH. The mixture was filtered over filtration paper in a Bύchner funnel and the product was washed with 10 L of demineralized water and subsequently dried at ambient temperature.

Example 2. Debranching of crosslinked tapioca starch.

Tapioca starch was crosslinked with 0.1 g of phosphorous oxychloride per kg. starch dry substance. The washed product was suspended at 35 % (weight dry substance/ volume) in a 2 L stirred double-walled reactor, which was equipped with a thermostated waterbath. The pH was adjusted to 4.4 with diluted HC1. The suspension was stirred at 35 r.p.m. until the content was at a temperature of 60 °C. The reaction was initiated by the addition of 0.5 % (volume / g of starch dry solids) Optimax L300. After 24 hours of reaction the DE of the reaction mixture was 1.4. The enzyme activity was reduced by increasing the pH to 7.0 by adding diluted KOH. The mixture was filtered over filtration paper in a Buchner funnel and the product was washed with 10 L of demineralized water and subsequently dried at ambient temperature. Example 3. Filtration properties of debranched starch.

Food-grade potato starch, containing 18 % moisture, was suspended in a 2 L stirred double-walled reactor, which was equipped with a thermostated waterbath. The starch was suspended to a concentration of 35 % (weight of dry subsstance / volume) in demineralized water The pH was adjusted to 4.4 with diluted HC1. The suspension was stirred at 35 r.p.m. until the desired temperature was reached (see table 1). The reaction was initiated by the addition 1 % (volume / g of starch dry substance) Optimax L300. After reaction for 19 hours at the temperature indicated in Table 1, 500 ml portions of the reaction mixtures were filtered over filtration paper in a Bύchner funnel with a diameter of 17 cm. The filtration rate was determined by weighing the amount of fluid in the filtrate after filtration for one minute. The filtration rate is expressed as grams of filtrate per minute (Table 1.) Table 1. Filtration rate as function of reaction temperature.

Example 4. Rheology of starches debranched according to the invention.

Potato starches were debranched as described under Example 1, at the temperatures given in Figure 1. Figure 1 shows the force at fracture, modulus and strain at fracture of different samples treated with Optimax L300 at different temperatures. Gels were prepared after gelatinisation of suspensions of the starch samples (8% dry weight) in a rapid visco-analyser. Gels 15 mm long with a diameter of 13 mm were analysed in a SMS texture analyser. The gels were compressed with a constant velocity of 0.2 mm/s by means of a spindle of 50 mm diameter until fracture occured. The force necessary for rupturing the gels is given as Force [g]. The modulus is the derivative of strain to stress extrapolated to zero strain: dσ

whereas the (Hencky) strain at fracture is defined as

σ: stress ε: strain h: height E: modulus

Example 5. Application of starches treated according to the invention in pie- filling.

The starch described in example 2 was hydroxypropylated with 1,2- propyleneoxid to a substitution level of 0.050. The starch was formulated with other ingredients in bilberry pie filling as described below. Bilberry juice (30 % by weight) and water (45.4 % by weight) were mixed in a cooking pan. To this liquid was added a dry mix composed of: sugar (19 % by weight), the starch product (5.4 % by weight) and salt (0.2 % by weight). The mix was suspended with a whisk and the mixture was heated until boiling whilst stirring with a whisk. The mixture was kept boiling for 1 minute, after which the mixture was cooled to 4°C. After one day the mixture was gelled. After 7 days of storage at 4°C the mixture showed no synseresis.

Claims

1. A process for preparing a starch product, wherein starch in substantially ungelatinized state is treated with a debranching enzyme.

2. A process according to claim 1, wherein the starch is treated with the debranching enzyme at a temperature below the gelatinization temperature.

3. A process according to claim 1 or 2, wherein the debranching enzyme is a pullulanase, or isoamylase.

4. A process according to any of the preceding claims, wherein the starch is derived from corn, potato, wheat, rice, barley, cassava, arrowroot, sago or oat.

5. A process according to any of the preceding claims, wherein the starch is treated with the debranching enzyme at a pH of 4-6.

6. A process according to any of the preceding claims, wherein the starch is treated with the debranching enzyme in a slurry or under semi-dry conditions.

7. A process according to any of the preceding claims, wherein the native starch or crosslinked starch is pre-treated with a maltogenic α-amylase.

8. A starch product obtainable by a process according to any of the preceding claims.

9. Use of a starch product according to claim 8 in a food or pharmaceutical product.

10. Use according to claim 9, wherein the starch product at least partly replaces gelatine in said food or pharmaceutical product.

11. Use of a starch product according to claim 8 as a rheology regulating agent.

12. Foodstuff or pharmaceutical composition comprising a starch product according to claim 8.