Starch physical treatment

Cold- Water Swelling Starches. Special physical treatment produces starch granules that will sweU in water without heating. Molecular dispersions can be formed by appHcation of shear to the swoUen granules. 

Starch annealing involves heating starches with sufficient hydration below their Tq to facilitate molecular mobility (Tester et ah, 2001). Annealing is defined as "a physical treatment that involves incubation of starch granules in excess (>60% w/w) or at intermediate (40-55% w/w) water content during a certain period of time at a temperature above the glass... 

Depolymerizing modification of starch usually involves the use of enzymes, acid- (and less frequently base-) catalyzed hydrolysis, and thermolysis alone and thermolysis combined with acid-catalyzed hydrolysis (see a recent survey in this Series2). Despite several studies, the physical treatment of starch has not yet resulted in major practical applications. The aim of this Chapter is to review physical methods as tools for the treatment of starch which deliver amounts of energy suitable for depolymerizing starch to target products. It should be noted that the duration of such processes does not need to exceed that for conventional, namely enzymic, chemical, and thermal modifications. Moreover, a potential advantage of nonconventional physical treatments is the fact that they generate no waste products. 

The finished starch slurry from the final hydroclone stage may be further processed in alternative ways (a) dried directly and sold as unmodified com starch (b) modified by chemical or physical treatment in a way that preserves the granule structure, then rewashed to remove residual reactants, and dried (c) gelatinized and dried (d) chemically or physically modified and then dried (e) hydrolyzed either completely to D-glucose or partially hydrolyzed to give mixtures of soluble oligosaccharides and D-glucose (see Chapter 21), which can be fermented to yield ethanol and other products. 

A variety of physical treatments are used to alter food starches, including heat with or without moisture, radiation and mechanical processing. These treatments provide improved processability or improved texture and stability.79 Moreover, physical modification (e.g. pregelatinization) may be used, as well as chemical modification for maximum overall performance. The following sections review the types of physical modification used or described for use in foods. A discussion of control of flow will be followed by a review of pregelatinization and physical modifications intended to otherwise alter starch performance. 

A. behaves like starch or amylose in reactions such as ->hydrolysis, derivatization or physical treatment (modified starches). Application of debranching - enzymes (pullulanase and iso-amylase) opens the possibility of total splitting of the a-1,6-linkages, thus enhancing hydrolysis as well as producing short-chain amyloses fit>m a. on a commercial scale. 

Ridomil, with which the treatment with starch solution was not carried out, is said to yield brown chromatogram zones on a pale yellow background [14]. Hence, it may be assumed that this detection is based not on the iodine azide reaction but on the physical adsorption and enrichment of iodine in the lipophilic chromatogram zones (cf. Iodine Reagents ). 

The characteristics of a starch can be modified by chemical, physical, and/or enzyme treatment to enhance or repress its intrinsic properties, or to impart new ones. This capability for modification has been a necessary factor in developing new uses for starch and in maintaining old markets. 

Modified starch Substance obtained by one or more chemical treatments of edible starches, which may have undergone a physical or enzymatic treatment, and may be acid or alkali thinned or bleached... 

Physical Heat/moisture/ Heat-moisture treatment - Heating starch at a temperature... 

OPT is a new method of physical modification, in which potato starch is suspended in solution saturated with a salt such as sodium sulfate and heated (autoclaved) at temperatures above 100° C for different times. This treatment has been reported to have the same effects on the starch properties as HMT but the starch modified using OPT exhibits better homogeneity (Pukkahuta et al., 2007). 

Following preliminary hypochlorite treatments, a coherent process path was identified and implemented. Corn starch was oxidized with 6.4% (w/w) hypochlorite for two hours and given a combined base-heat gelatinization process (Method A). This base material exhibited excellent physical characteristics (i.e., stable emulsion with 20% db lemon oil incorporation into an aqueous dispersion, low lemon oil vapor phase flux (low headspace content), lack of inherent flavor and aroma) and when finally tested for spray dried lemon oil (20% db) retention efficiency in a lab-scale mini-dryer, the viability of this polymer was ascertained. Nearly 70% of the added lemon oil was retained following the drying of this DE 1.45 starch, a measure of functionality matched only by gum arabic (34). 

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