Process for preparing resistant starch

Details Process for preparing resistant starch Process for preparing resistant starch

2000-03-09

2003-09-23

Prats, Francisco (Department: 1651)

Chemistry: molecular biology and microbiology

Micro-organism, tissue cell culture or enzyme using process...

Preparing compound containing saccharide radical

C435S101000, C536S102000, C536S124000, C426S549000, C426S661000, C426S028000, C127S038000, C127S071000

Reexamination Certificate

active

06623943

ABSTRACT:

The present invention relates to a process for preparing resistant starch of type 3, the resistant starch obtainable from this process and its use.
The use of resistant starch (RS,) is gaining increasing importance in the food industry. The organism obtains energy only to a small extent from the breakdown of RS-containing products. This energy supply relates exclusively to the oxidative degradation of adsorbed short-chain fatty acids from the large intestine. These short-chain fatty acids are end products of the carbohydrate metabolism of the intestinal microflora. The intake of RS-containing foods provides substrates for the energy metabolism of the intestinal microflora and the large-intestine epithelial cells. The latter, to maintain their structure and function, depend on the luminal supply of short-chain fatty acids and, in particular, butyrate.
U.S. Pat. No. 3,729,380 discloses that the proportion of highly branched amylopectin can be reduced by enzymatic treatment with debranching enzymes and starch debranched in this manner has a stronger tendency to retrogradation than native starch.
In retrogradation (also termed crystallization), what are termed &agr;-amylase-resistant starch structures form, which are termed “resistant starch” (RS), i.e. they are not degraded by &agr;-amylases. A distinction is made between the following types of resistant starch:
RS
1
starch physically inaccessible to digestion, e.g. in undigested plant cells or starch granules
RS
2
indigestible starch granules, e.g. raw potatoes, green bananas etc.
RS
3
indigestible retrograded starch, e.g. as a result of thermal and/or enzymatic treatment, such as bread, cooked potatoes etc.
RS
4
indigestible chemically modified starch, e.g. due to crosslinking or esterification (acetylation etc.) etc.
RS, in foods or food compositions, because of their decreased ability to be metabolized are a reduced-energy component supplying body in the sense of a dietary fiber or what is termed a “fat replacer”.
In contrast to RS
4
, the RS types 1 to 3 can be made accessible to alpha-amylase degradation by dissolution in NaOH or dimethyl sulfoxide.
EP-A-0 564 893 describes a process for preparing an Re-containing product by gelatinizing a roughly 15% strength aqueous suspension of a starch which consists of at least 40% amylose, treating it with a debranching enzyme and then retrograding the resultant intermediate product. The product comprises at least 15% RS. If, in this process, a starch having an amylose content of 100% is used, the product comprises about 50% RS.
EP-A-0 688 872 describes a process for preparing a product comprising 25 to 50% RS from an approximately 20% strength aqueous suspension of a so-called “partially degraded”, gelatinized starch
1
, and a maltodextrin, which are enzymatically debranched and then retrograded. In the process, the starting material used is a starch having an amylose content of less than 40%.
“Partially degraded” starch in EP-A-0 688 872 means a starch which has been reduced in molecular weight by suitable physical or chemical treatment, the shortening in chain length effecting both the amylose and also the amylopectin. The degradation includes both hydrolysis processes (acid- or enzyme-catalyzed) and extrusion, oxidation or pyrolysis.
The debranching enzymes used in EP-A0 688 872 are pullulanases and isoamylases. After the enzymatic treatment, the retrogradation is performed in a temperature range from 0 to 30° C. and a time period of 1 to 3 days, by allowing the aqueous reaction product to stand. The process product is then dried by spray-drying. The pulverulent product has an RS content of up to 60% (w/w).
EP-A-0846704 describes a retrograded starch which consists of more than 55% readily-fermentable resistant starch, more than 50% of which is composed of chains having a DP between 10 and 35 and has a DSC melting temperature of below 115° C.,
EP-A-0846704 sets forth that the extent of retrogradation of the starch increases with the amylose content in the starch, whereas a high amylopectin content in the starch counteracts the formation of RS.
The object of the present invention is to provide an alternative preparation process for resistant starch (RS) or compositions comprising RS which offers the advantages of an economic process procedure or makes it possible to prepare RS-containing products in improved quality and quantity.
The process of the invention uses as starting material for this, in addition to conventionally available starches from potatoes, corn, wheat, peas, soy and/or sweet potatoes, preferably potatoes, corn and/or wheat, in particular also vegetable starches which have been modified by genetic engineering methods, preferably with respect to their side-chain distribution and in particular those from potatoes, corn and/or wheat, especially so-called waxy starches. Genetically modified starches of this type are disclosed, for example, by the patent applications or patents below: WO 90/12876-A1, WO 91/19806-A1, WO 92/11375-A1, WO 92/11376-A1, WO 92/11382-A1, WO 92/14827-A1, WO 94/09144-A1, WO 94/11520-A1, WO 95/04826-A1, WO 95/07355-A1, WO 95/26407-A1, WO 95/34660-A1, WO 95/35026-A1, WO 96/15248-A1, WO 96/19581-A1, WO 96/27674-A1, WO 96/34968-A1, WO 97/04112-A1, WO 97/04113-A1, WO 97/11188-A1, WO 97/16554-A1, WO 97/20040-A1, WO 97/22703-A1, WO 97/45545-A1, WO 98/11181-A1, WO 98/15621-A1, WO 98/37213-A1, WO 98/37214-A1 and also CA 2,061,443, DE 19820607.0, DE 19820608.9, DE 19836097.5, DE 19836098.3, DE 19836099.1, EP-A-0 521 621, EP-A-0 703 314, EP-A-0 737 777, EP-A-0 779 363 or U.S. Pat. No. 5,300,145. In a particular embodiment of the process of the invention, what are termed waxy starches are used to prepare RS.
The present invention, surprisingly, makes it possible to prepare resistant starch of type 3 (RS) or RS products (i e. compositions comprising RS) in relatively high quantity and/or quality which can advantageously be used in a varied manner to prepare foods, food compositions and food precursors and which also resist thermal stress. Particularly surprisingly, the present invention makes it possible to prepare RS or RS products having high thermally stability from what are termed waxy starches,
The present invention thus relates to a process for preparing resistant starch, in which
a) a suspension is prepared from starch and water in a concentration range of about 5-50%;
b) said suspension is gelatinized by heating and then cooled;
c) the pH of the resultant suspension from b) is set to about 3-7.5 and the solids content to about 5-50%;
d) the suspension is again heated to a maximum of 150° C. and finally
e) is cooled stepwise or gradually at a rate of 0.1-10 K/min, preferably 0.5-5 K/min, preferably under the action of shear forces.
If appropriate the starch used in the process of the invention can be debranched enzymatically using debranching enzymes (e.g. isoamylases, pullulanases or other debranching enzymes) and then the debranching enzyme or enzymes can be inactivated or removed, preferably after setting the pH as specified in step c) of the process according to the invention.
In a particularly preferred embodiment of the process according to the invention, the intermediate obtained after step b) is freed from buffer salts, in particular from acetate, i.e. is washed salt-free or acetate-free.
In a further embodiment of the process according to the invention, a further process step follows, in which the process product is subjected, under conditions of water excess, to a hydrothermal treatment (annealing) below the conversion temperature, preferably below about 65-70° C.
If desired, the intermediate obtained after step b) and/or the resultant RS product can be dried, e.g. by spray-drying, freeze drying or other drying processes known to those skilled in the art
In the context of the present invention the RS content is the content of alpha-amylase-resistant starch polysaccharides, as can be determined by the method of Englyst et al. (Classification and measurement of nutritionally important starch fractions, Europ. J. Clin. Nutr. (1992) 46 (Supp

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