Natural starch

The qua si-crystalline stmcture of natural starch granules causes them to be insoluble in water at normal room temperature and gives them relative resistance to carbohydrases other than a-amylase and glucoamylase unless the granules become swollen. Three-dimensional arrangements of crystalline and amorphous zones in starch granules have been suggested (2). 

In contrast to monophosphates, starch phosphate diesters contain cross-links between two or more starch chains. This covalent linkage in the granule produces a starch product which swells less but is more resistant to heat, agitation, and acid than natural starch. 

Among other polysaccharides studied were those elaborated by Neisseria per-flava (starch-type polysaccharide), Polytomella coeca (a starch richer in amy-lopectin than most natural starches), Pseudomonas morsprunorum (Wormald) (levan), Acetobacter acetigenum (cellulose), Aerobacter aerogenes (NCTC 8172) (Klebsiella Type 164), Bacillus megaterium. Bacterium pruni, and Bacterium prunicola (polyfructoses of the levan type). 

Not all modified starches are suitable for removal by aqueous dissolution alone. Such modifications of natural starches are carried out to reduce solution viscosity, to improve adhesion and ostensibly to enhance aqueous solubility. Commercial brands vary [169], however, from readily soluble types to those of limited solubility. Indeed, some may be as difficult to dissolve as potato starch if they have been overdried. It is thus very important to be sure of the properties of any modified starch present. If there are any doubts about aqueous dissolution, desizing should be carried out by enzymatic or oxidative treatment. Even if the size polymer is sufficiently soluble, it is important to ensure that the washing-off range is adequate. Whilst the above comments relate to modified starches, other size polymers such as poly(vinyl acetate/alcohol) and acrylic acid copolymers vary from brand to brand with regard to ease of dissolution. 

In nature, starch is based on crystalline beads of about 15-100 microns in diameter. Crystalline starch beads in plastics can be used as fillers or can be transformed into thermoplastic starch, which can either be processed alone or in combination with specific synthetic polymers. To make starch thermoplastic, its crystalline structure has to be destroyed by pressure, heat, mechanical work or use of plasticisers. Three main families of starch polymer can be used pure starch, modified starch and fermented starch polymers. 

The second point concerns water that is usually held by natural starch, that is, a state that can be considered as the natural starch-water inclusion complex. In this case also, the concentration of such water depends on the same factors as those just mentioned. Corresponding data are given in Table XIV. 

Starch complexes with aromas and flavoring agents are usually synthetic in origin. In nature, starch sometimes includes some aroma- and flavor-genic components that generate flavor and aroma on processing (see, for instance, ref. 678). Such agents include mainly aldehydes, ketones, and carboxylic esters however, hydrocarbons, alcohols, carboxylic acids, and haloalkanes have also been used. 

Hand building finishes that lose their effect after one or two launderings are considered non-durable. The two major product types of non-durable hand builders are starch derivatives and polyvinyl alcohol. Natural starch is produced commercially from potatoes, com, wheat, rice and tapioca. Its two main components are polymers of a-glucose, amylopectin and amylose, shown in Fig. 4.1. The thickening effect of starch is mainly due to the long and branched amylopectin chains. 

With some natural starches or with glycogen it is possible that the action of the /5-amylase is stopped before all end chains are removed because the substrate molecule has so complicated a network of chains that the enzyme, which presumably has a large molecule, can not penetrate into the inner parts of the substrate molecule. This point has been stressed in the case of glycogen by Meyer and Jeanloz. These authors degraded the substrate by a short treatment with hydrochloric acid to the extent that all end chains were accessible for the enzyme and a true saccharification limit was reached. Experiments with different starches and... 

The parent CDs in Japan are classified as natural starches that have received approval by the Ministries of Health for use in foods. Relative to pharmaceutical applications, monographs for a- and p-CD have been included in the Japanese Pharmaceutical Excipients compendium (JPE). Even though nine pharmaceutical products with CD formulations have been marketed in Japan, the use of CDs has not been extensive enough in approved formulations to receive precedent status. ... 

Polysaccharides commonly found in nature (starch, cellulose, mannan, xylan, laminaran, gum, etc.) are playing an important role not only in the food industry but also for use as materials. However, recent research tends to focus on applying these polysaccharides as substances with diverse biochemical functions or medicines. This section will outline the biochemical functions of polysaccharides and synthetic carbohydrate-bound polymers and the perspectives of their medicinal/medical use. 

Hydroxypropyl starch is a derivative of natural starch it is described in the JPE 2004 as a hydroxypropyl ether of corn starch. 

Hydroxypropyl starch is produced industrially from natural starch, using propylene oxide as the modifying reagent in the presence of alkali, adding hydroxypropyl (CH(OH)CH2CH3) groups at the OH positions by an ether linkage. 

Starch adhesive Aqueous adhesive based on natural starch. 

Common natural starch contains less of amylose than the amylopectin one, and 3-25% of the former is wrapped within a framework of the latter. Composition of starches from different plants with respect to the above two classes are shown in Table 5.23b. 

Starch is the main energy reserve in plants glycogen is the main energy reserve in animals. Starch is a homopolysaccharide and has two forms amylopectin and a-amylose. In nature, starch is approximately 10 to 30... 

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