Patent Description:
The global market demands a growing amount of starch products for various applications. Drivers for this market dynamic in the food segment is an increasing consumption of ready-to-eat meals and drinks as well as an upcoming trend for vegetarian food. To guarantee the starches' abilities to act as thickener or as gelling agent, chemical modifications have been established to maintain the stability during food processing, e.g. against low pH, heat treatment, shear forces and freeze-/thaw cycles. However, in addition to the solely thickening effect, starch products have to fulfil versatile functions in foods including volume expander, adsorbent properties for oils, spices and flavours, texturizer, structure and mouthfeel enhancer, carrier material, moisture regulator, film-forming agents, flowing aid in dry mixes, etc. However, a majority of starch products is not suitable for these applications because of the accompanying thickening effect especially when starch products were used in higher concentrations. Hence, there is a demand for low viscosity starch products in the food industry.

Oxidized starches used as food additive are produced by means of chemical modification. The use of sodium hypochlorite in a starch slurry results in low molecular weight starches labelled in the European Union under the E number <NUM>. Major disadvantages are high consummation of chemicals, emergence of wastewater and labelling issues for chemically modified starches.

White and yellow dextrins are obtained by dry roasting of acidified starch. On a chemical basis, the dextrinization is accompanied by hydrolysis, transglycosidation and repolymerization reaction, whereas the starch kernels remain intact (crystallinity of starch granules is reduced). Commercial available white dextrins are not <NUM>% cold water-soluble (CWS). Yellow dextrins show a higher CWS compared to white dextrins but may be also limited in food use by solubility issues and additionally by their coloring.

Maltodextrins are obtained through partial hydrolysis of starch from crops like wheat, potatoes and maize. In short, the cold water-soluble maltodextrins are typically produced by i) preparation of starch solution, ii) acid-/ or enzymatic conversion, iii) inactivation of enzymes and iv) spray-drying procedure. Maltodextrins are used for manifold reasons in foods, especially in dry food applications but also in the beverage industry. They comprise several functional properties like texturizing, gelling, emulsifying abilities, flowability enhancer, and filling and adhering ingredient in dry mixtures. Moreover, maltodextrins have been described to be suitable to partly replace fat and gelatine from food recipes.

Although the functional properties of maltodextrins are undisputed, there is a deficit in perception from a consumer's perspective. In addition, production of maltodextrins is cost-intensive and plant-specifically challenging because of the spray-drying process used in the conventional process. Maltodextrins can be classified by the dextrose equivalent (DE) value, expressing the content of reducing sugars. Starch conversion products exhibiting DE levels between <NUM> and <NUM> are claimed to be maltodextrins. DE levels between <NUM> and <NUM> describe glucose syrup, a DE of <NUM> equals to pure glucose and DE levels below <NUM> are claimed to be starch (Starch Europe). Processes for enzyme-related maltodextrin production have been widely described in literature and were subjects for patent applications (e.g. <CIT>).

A physical modification of starch is heat moisture treatment (HMT). This clean label treatment procedure has been developed in the late 1970th (e.g. <CIT>). The treatment increases the gelatinization temperature making the cock-up starch suitable to being applied as a thickener in boiling soups and sauces without formation of lumps. In addition, heat moisture treatment of starches aims in the generation of high viscous starch products, in order to maintain the thickening performance. Especially after temperature breakdown, HMT starches show an increase in viscosity leading to comparable characteristics as chemically modified cross-linked starches. Thus, HMT starches are often being applied in catering systems.

<CIT> discloses extrusion of starch in acidic medium.

A first aspect of the present invention concerns a process for the production of a low-viscosity starch product comprising the following first step and (subsequent) second step:.

A further aspect of the present invention concerns a low-viscosity starch product obtainable according to the process above or described further herein. The low-viscosity starch product of the invention has a content of reducing sugars of less than <NUM> wt. -% (measured according to Luff-Schoorl), and a cold water solubility of <NUM> wt. The low-viscosity starch product of the invention has an end viscosity of less than <NUM> BU, in particular less than <NUM> BU (measured according to standardized Brabender method).

Yet a further aspect of the present invention concerns the use of the low-viscosity starch product described herein, obtainable according to the process above or described further herein, in a nutritional, pharmaceutical of veterinary composition, in particular as a substitute for maltodextrin.

The inventors have found that the process of the invention as described herein surprisingly allows the production of a very low viscosity starch product without chemical modification in a convenient and economic way. The starch products according to the invention, obtainable by the process of the invention, have advantageous properties comparable to or even superior to maltodextrins, without requiring the more cost- or energy-consuming steps of maltodextrin preparation according to the prior art. The starch products according to the invention are even superior to prior art starch products in their functional properties like texturizing, gelling, emulsifying abilities, use as flowability enhancer, filling and adhering ingredients in dry mixtures, and partial replacements for fat and gelatine in food recipes. They have a pure white colour and excellent flowability properties. The starch products according to the invention do not require a classification as maltodextrins in Europe.

It has been found that the pre-treatment of a starch (see steps a1 and a2 above), in particular a native starch, as specified in the process described herein, advantageously enables preparation of an intermediate starch product which can conveniently be converted into a low starch product by conventional extrusion in an extruder as known in the art. The final product of the process according to the invention advantageously provides cold water solubility, very low end viscosity as defined herein, at least comparable to conventional maltodextrins, and a very low content of reducing sugars, below the conventional maltodextrins of the prior art. From a producer's prospective, it provides alternative products to maltodextrins and their production processes, saving production-related resources, waste streams and costs, and providing even superior properties.

The term "low viscosity starch product" as used herein describes a starch product which provides properties corresponding to and even superior to commercial maltodextrins without being prepared in accordance with the prior art preparation of maltodextrins, and not requiring in Europe labelling as maltodextrins. Low viscosity, sometimes called very low viscosity or ultra-low viscosity herein, shall preferably designate a starch or starch product having an end viscosity of less than <NUM> BU, in particular less than <NUM> BU, more particular less than <NUM> BU. The determination of Brabender viscosity is known to the skilled person. Any Brabender viscograph known in the art can be used for determining the Brabender viscosity as used herein. Preferably, the Brabender viscosity is measured according to a standardized Brabender method as described in Methods below. Moreover, the content of reducing sugars of the low-viscosity starch product of the invention is less than <NUM> wt. -%, in particular less than about <NUM> wt. -%, more particular at most <NUM> wt. It has surprisingly been found that the advantage of such a low content of reducing sugar may be obtained by the process of the invention as described herein, offering advantages regarding the usability and calorimetric properties while maintaining the (ultra-)low viscosity of conventional maltodextrins, and their cold water solubility. Thus, the low viscosity starch products of the present invention also provide a cold water solubility of <NUM> wt.

In the first step of the process of the invention, starch, in particular native (natural) starch, is used. The native starch is preferably not chemically modified. Waxy starches and high amylose starches, i.e. (chemically unmodified) starches with a very high amylopectin content or a very high amylose content are also considered within the term native starch as used herein. The starch may be obtained from any starch-producing plant, in particular potato starch, maize starch, corn starch, starch from tapioca, arrowroot, wheat, rice, sago, mung bean or the like. Potato starch is particularly preferred.

In the first step of the process of the invention, the (native) starch is subjected to a heat-moisture treatment, i.e. a combination of heat and a specific moisture content of the starch is used for this treatment step.

Heat moisture treatment (HMT) in the prior art is a physical methodology for starch processing aiming at achieving highly viscous sauce thickeners exhibiting elevated gelatinization temperature. However, the present invention relates to the use of an overexpressed heat moisture treatment leading to a significant reduction of starch viscosity. Although not desired for the production of regular HMT starch used as sauce thickener, surprisingly, overexpressed HMT starch (called "intermediate starch product" in the process of the invention) has been shown to be a very suitable feeding material for processing by means of extrusion in order to obtain a very advantageous final starch product as defined herein. To obtain overexpressed HMT starch, (native) starch is treated under "harsh" conditions regarding temperature and treatment time.

It has been found that a temperature of at least about <NUM> is required in order to obtain satisfactory results of the treatment, preparing the resulting starch product (called intermediate starch product herein) for the subsequent extrusion step. Preferably, the temperature should be at most about <NUM>, in particular about <NUM>. According to a particular preferred embodiment of the present invention, the temperature used in the first step, namely the heat-moisture treatment, is from about <NUM> to about <NUM>.

Further, it is required that the heat-moisture treatment, is performed for a time period of more than about <NUM> hours at a moisture content of the starch of about <NUM> to about <NUM> wt. -%, based on the total weight of the (native) starch. The HMT is preferably performed in a tightly closed vessel.

Surprisingly, the present inventors have found that, together with the temperature of the HMT as specified above, this minimum time of about <NUM> hours together with the particular moisture content as specified above is required in order to obtain a physical modification of the starch preparing it advantageously for the subsequent extrusion step when aiming at a very low viscosity starch product as specified herein.

Thus, it has been found that a moisture content of the (native) starch of below <NUM> wt. -% as well as a too high moisture content above <NUM> wt. -%, based on the total weight of the (native) starch does not impact the starch in a reliable and advantageous way, and does not prepare it sufficiently for subsequent extrusion, aiming at the low viscosity starch product as described herein, in particular having full cold water-solubility, very low or ultra-low viscosity, no viscosity peak when heating, and a content of reducing sugars of less than <NUM>%. Preferably, native starch is adjusted to a water (moisture) content of about <NUM> to about <NUM>% by weight, based on the total weight of the (native) starch, for the HMT.

Subsequent to the HMT as described above (but before the extrusion step), the moisture content of the starch is slightly lowered to a range from about <NUM> to about <NUM> wt. -%, based on the total weight of the heat-moisture treated starch. It has been found that such a slight reduction of moisture or drying of the starch after the HMT is advantageous for an efficient extrusion when aiming at the low viscosity starch product as described herein.

It has further been found that, as an alternative to the HMT as the first step of the process of the invention, also an acid-heat treatment, also called AHT, may be performed.

According to this alternative of the inventive process, the (native) starch is adjusted to a moisture content of about <NUM> to <NUM> wt. At this moisture content, about <NUM> to about <NUM> wt. -%, in particular about <NUM> to about <NUM> wt. -% of a diluted aqueous acid solution (based on the total weight of the starch used for the AHT) are added, wherein the acid concentration is <NUM> to <NUM> wt. -%, based on the total weight of the aqueous acid solution, in order to obtain an acid-treated starch. Any acid conventional in the art may be used. Hydrochloric acid (HCl) is preferred. The acidification is performed for about <NUM> minutes to about <NUM> hour. The exact time is not critical and is normally achieved within short time. The starch, having the moisture content as adjusted above, and the diluted aqueous acid solution are usually mixed in order to allow a homogenous mixture of the acid with the starch. The mixing is preferably carried out for (at least) several minutes. Room temperature or a temperature different from room temperature may be used for adding the diluted aqueous acid solution and/or mixing.

Subsequently, the acid-treated starch is dried to a moisture content of below about <NUM> wt. -%, in particular about <NUM> to <NUM> wt. -%, based on the total weight of the acid-treated starch, and then heated to a temperature within the range of about <NUM> to about <NUM>, preferably <NUM> to <NUM>, more preferably <NUM> to150°C, for a time period of about <NUM> to about <NUM> minutes. Preferably, treatment time is <NUM> to <NUM> minutes. More preferably, treatment time is <NUM> to <NUM> minutes. Preferably, the starch is stirred during heat treatment at the adjusted temperature level.

Diverging from the aforementioned conditions of the AHT will pose a risk that feeding the resulting material in the extruder causes considerable impairments of the extrusion process, e.g. blocking of barrels or other extrusion processing problems.

After the heating step (in the ATH), the resulting material will be preferably cooled to a certain temperature, ideally ambient temperature. Also, the moisture content is adjusted to about <NUM> to about <NUM> wt. -%, in particular about <NUM> to about <NUM> wt. -%, based on the total weight of the acid-heat treated starch. It has further been found advantageous to (partially) achieve this adjustment in the moisture content by allowing the (dry) acid-heat treated starch to cool in an open atmosphere, absorbing moisture from the surrounding atmosphere (for the subsequent extrusion step).

It has been found that, as an alternative to the specific HMT as described above, the AHT with the steps as specified above allows obtaining an immediate starch product which is particularly suitable for subsequent conventional extrusion in order to obtain a low viscosity starch product as described herein.

In general, the intermediate starch product has a content of reducing sugars of less than <NUM> wt. -%, in particular less than about <NUM> wt. -%, more particular less than about <NUM> wt. Determination of the content of reducing sugars is known to the person skilled in the art and can for example be measured as indicated in the Method section below. Furthermore, the intermediate starch product has a cold water solubility of less than <NUM> %, in particular less than <NUM> %, preferably in the range of <NUM> to <NUM> %, more preferably in the range of about <NUM> to <NUM>%. The cold water solubility can be measured as indicated in the section Methods below.

Preferably, the intermediate starch product obtained after the first step (a1 or a2) of the process of the invention has a viscosity of less than <NUM> cp according to RVA at <NUM>. The RVA viscosity as specified above can be determined as known in the art. Preferably, it is measured in a standardized RVA method as described in the Methods Section below.

All indications of percentage as used herein are wt. -% based on the total weight of the composition, unless indicated differently.

According to the process of the invention, the intermediate starch product obtained from the first step is subjected to a second step, wherein the intermediate starch product is subjected to an extrusion process in an extruder in order to obtain the low viscosity starch product as described herein. The specific process step of the first step according to the inventive process allow preparing an intermediate product which is particularly suitable for subsequent extrusion, using standard extrusion devices and parameters, in order to obtain the desired low-viscosity starch product of the invention.

Application of extrusion to native starch according to the prior art is limited to a certain degree of viscosity in the extruded starch product and has disadvantages regarding the impact on the properties of final extruded product and its functional utility. An overexertion of extrusion conditions which may lead to production issues, such as blocking of barrels, an off-white colouring or partly burned starch, or non-desirable fluctuations of bulk-weight density in the end product is avoided by the present invention.

The present invention, combining a specific pre-treatment (first step) as described herein and subsequent extrusion allows to surprisingly obtain a low viscosity (CWS) starch product having the advantageous properties as described herein.

Standard extruder devices and parameters are known to the skilled person and can be used in the present invention. According to a preferred embodiment of the invention, a twin-screw extruder device may be used.

According to a preferred embodiment, during the heat-moisture treatment, the starch has a moisture content of <NUM> to <NUM> wt. -%, in particular <NUM> to <NUM> wt. -%, based on the total weight of the native starch. It has been found that this moisture content allows a particularly advantageous HMT.

As indicated above, in the prior art, a HMT process was used in order to delay and increase the viscosity development of a starch. In contrast, it has surprisingly been found by the present inventors that a HMT process, if the specific parameters as set out herein are followed, may be used in order to prepare an intermediate starch product not having an increased or delayed viscosity, but being adapted for transforming into a low viscosity starch product as described herein (having properties not only similar to but even superior to maltodextrins) by a simple extrusion process.

According to a further preferred embodiment of the invention, the HMT is performed at a temperature of <NUM> to <NUM>.

Also, preferably, the moisture content is adjusted to <NUM>-<NUM> wt. -%, based on the total weight of the heat-moisture treated starch, following the HMT.

As explained above, it has been found advantageous to adjust/lower the moisture content of the heat-moisture treated starch to <NUM> to <NUM> wt. It has further been found advantageous to (partially) achieve this adjustment/reduction in the moisture content by allowing the moisture-heat treated starch to cool in an open atmosphere, removing moisture (for the subsequent extrusion step).

In a further preferred embodiment of the present invention, in the AHT, <NUM> to <NUM> wt. -% of a diluted aqueous acid solution, preferably HCl solution, are added to the (native) starch as described above.

According to a preferred embodiment of the present invention, during the extrusion in an extruder (second step of the process of the invention), the highest temperature in the extruder is about <NUM> to <NUM> if the intermediate starch product (used for extrusion) is obtained according to a HMT as described herein, and about <NUM> to <NUM> if the intermediate starch product is obtained according to the AHT as described herein.

The inventors have surprisingly found that the present process of the invention, combining a simple pre-treatment step (first step in the process according to the invention) with a convenient extrusion step allows simple and continuous production of a very advantageous low viscosity starch product.

According to a further aspect of the present invention, the low viscosity starch product of the invention as described herein may be advantageously used in a nutritional, pharmaceutical or veterinary composition. In particular, it may be used, partially or completely, as a replacement for maltodextrins in such compositions.

According to a preferred embodiment of the present invention, the nutritional composition may be a food or beverage composition, in particular a dry food or beverage composition.

A further preferred embodiment of the present invention pertains to the use of the low viscosity starch product of the invention (as described herein) as an emulsifying agent, a flowability-enhancing agent, a filling, binding or adhering agent. It has surprisingly been found that the low viscosity starch product of the present invention, as described herein, provides advantageous in relation to the above uses desirable for the skilled person in the art.

<FIG> shows the viscosity curves (Brabender viscosity determined as described above) of low viscosity starch products according to the invention (Examples <NUM> and <NUM>) in comparison to non-treated (native) extruded starch and a commercial maltodextrin.

The RVA viscosity values as indicated herein can be measured in a standardized RVA method: RVA (Rapid Visco Analyzer Super-<NUM>, NewPort Scientific) was used for viscosity measurement. <NUM> dry starch was added to <NUM> distilled water and subjected to RVA analysis. The slurry was heated to <NUM> followed by a cooling phase to <NUM> where the end viscosity was determined. "Dry starch" shall mean that the material was dried to constant weight at <NUM> in an oven (normally achieved after about <NUM>-<NUM>).

This can be measured in a standardized Brabender Method: The viscosity of cold water-soluble low viscosity starch products were measured according to a customized Brabender method (Brabender Viscograph Type E, measuring range 250cmg, temperature gradient <NUM> to <NUM>) by mixing <NUM> dry starch to <NUM> ethylene glycol and <NUM> distilled water. End viscosity was measured at a temperature of <NUM>. "Dry starch" shall mean that the material was dried to constant weight at <NUM> in an oven (normally achieved after about <NUM>-<NUM>).

Determination of cold water solubility of starch is known in the art. According to a preferred embodiment, it can be performed according to the method of Höppler, see e.g. <NPL>, <NPL>.

The cold water solubility of starch can alternatively be determined by measuring the refractive index of a starch solution. <NUM> of starch on dry weight basis are dispersed in <NUM> distilled water. The suspension is filtrated through a folded filter and the obtained solution is measured by means of a refractometer. The determined refractive index is directly correlated to the degree of cold water solubility. "On dry weight basis" shall mean that the material was dried to constant weight at <NUM> in an oven (normally achieved after about <NUM>-<NUM>).

The content of reducing sugars can be measured according to the method of Luff-Schoorl (see e.g. <NPL>and following).

The moisture or water contents in wt. -% as indicated herein are determined by drying the material to constant weight at <NUM> in an oven and comparing the weight of the sample before and after drying.

In the following, the invention will be further illustrated by the following examples.

A diluted aqueous solution of hydrochloric acid (<NUM> wt. -%) was sprayed on native potato starch and intensively mixed. After conditioning at ambient temperature for <NUM> minutes, the HCl-treated starch was dried to a water content less than <NUM>%. Immediately after that, the starch was transferred to a pan and roasted for <NUM> minutes at <NUM>. The resulting material was then rehydrated to <NUM> wt. -% moisture content (partially by allowing the heated starch after the roasting to absorb moisture from the environment) and exhibited a cold water-solubility (CWS) of <NUM>%, a molecular weight of less than <NUM>/mol, and a content of reducing sugars below <NUM>%. It had a viscosity of <NUM> cp according to RVA at <NUM>, measured as indicated above (Methods).

The pre-treated starch (intermediate starch product) was used as feeding material (variable feeding rate <NUM> to <NUM>/h) in a co-rotating Werner & Pfleiderer twin screw extruder (screw speed <NUM> rpm) equipped with two reverse elements, a volumetric feeding system, and temperature-controlled casing blocks. Standard parameters as indicated by the manufacturer were used for extrusion.

Native potato starch was moistened to a water content of <NUM>% and transferred to tightly closed vessels. After incubation for <NUM> hours at <NUM>, the HMT starch was cooled down to ambient temperature in open atmosphere so that moisture could evaporate, and adjusted to a moisture content of <NUM>%.

The pre-treated starch (intermediate starch product) was used as feeding material for a standard extrusion as set out in Example <NUM> above.

For comparison, native potato starch (not pre-treated by AHT or HMT) conventionally extruded under conditions as used in Examples <NUM> and <NUM>, and a commercially available maltodextrin were used.

Claim 1:
Process for the production of a low-viscosity starch product comprising the following first step and subsequent second step:
a) in the first step, native starch is subjected to
a1) an acid-heat treatment wherein
- the native starch is adjusted to a moisture content of <NUM> to <NUM> wt.-%,
- <NUM> to <NUM> wt.-% of a diluted aqueous acid solution are added, wherein the acid concentration is <NUM> to <NUM> wt.-%, based on the total weight of the aqueous acid solution, in order to obtain an acid treated starch,
- drying the acid-treated starch to a moisture content of below <NUM> wt.-%, based on the total weight of the acid-treated starch,
- heating to a temperature within the range of <NUM> to <NUM> for a time period of <NUM> to <NUM>,
- adjusting the moisture content to <NUM> to <NUM> wt.-%, based on the total weight of the acid-heat treated starch, or
a2) a heat-moisture treatment at a temperature of <NUM> to <NUM> for a time period of more than <NUM> hours at a moisture content of the native starch of <NUM> to <NUM> wt.-%, based on the total weight of the native starch, followed by adjusting the moisture content to <NUM> to <NUM> wt.-%, based on the total weight of the heat-moisture treated starch,
in order to obtain an intermediate starch product having a content of reducing sugars of less than <NUM> wt.-%, based on the total weight of the intermediate starch product, and a cold water solubility of less than <NUM>%, in particular less than <NUM> %,
b) in the second step, subsequent to the first step, the intermediate starch product is subjected to an extrusion process in an extruder, preferably a twin screw extruder, in order to obtain the low-viscosity starch product, wherein the low-viscosity starch product has an end viscosity measured according to the Brabender method of less than <NUM> BU, a content of reducing sugars of less than <NUM> wt.-%, and a cold water solubility of <NUM> wt.-%.