Amylopectin chemical composition

A second very widely distributed polysaccharide is starch, which is stored in the seeds, roots, and fibers of plants as a food reserve — a potential source of glucose. The chemical composition of starch varies with the source, but in any one starch there are two structurally different polysaccharides. Both consist entirely of glucose units, but one is a linear structure (amylose) and the other is a branched structure (amylopectin). 

White et al.8,30,31 have, in several papers, studied the chemical composition of oat starch amylose and amylopectin (Table 15.2). Gel permeation chromatography (GPC) of the total starch gave rise to two peaks, but some of the material had an unusual iodine affinity and was, therefore, described as an intermediate fraction.8... 

Figure 4A.11 Chemical composition of amylose and amylopectin. (a) Structure of amylose (b) Structure of amylopectin. ((a) and (b), Adapted from BeMillerJN, Whistler RL. Carbohydrates. Food Chemistry. 3rd ed. New York Marcel Deker 1996. pp. 157-223)...

Starches differ in their chemical composition and, except in rare instances, are mixtures of two structurally different polysaccharides, amylose and amylopectin. The proportions of these present in natural starches depend upon the source, although in most starches amylopectin is the main component, amounting to about 70-80 per cent of the total. An important qualitative test for starch is its reaction with iodine amylose produces a deep blue colour and amylopectin solutions produce a blue-violet or purple colour. 

Chemical Composition. Along with additives such as plasticizers and moisture content, the chemical structure of the macromolecules used as agropolymers also affects their mechanical properties. For starch, the amylopectin... 

Starch is a semi-crystalline biopolymer used for a number of applications. It is a branched homopolymer of glucose, with a-(1 4] linear links and ce-(l 6] branched links (Sweedman et al., 2013]. It serves as a carbohydrate reserve in roots, tubers, seeds, fruits, plants, and cereals (Zavareze and Dias, 2011]. Depending on the original source of starch, the starch granule has been found to vary in size, shape, structure, and chemical composition. Amylose and amylopectin macromolecules are the prime constituents of starch. Figure 1.12 shows the schematic and chemical composition of amylose and amylopectin (Sweedman et al., 2013]. 

Figure 1.12 Schematic of structural and chemical composition of amylose and amylopectin. Reprinted with permission from Sweedman et al. (2013]. Copyright 2013 Elsevier.

The blue reaction is very useful in determining the amylose-amylopectin composition of starch,69,196,277 and in controlling of the effect of mechano-chemical and enzymic treatment and fractionation of starch79,71,204,278-289... 

FIGURE 28.2 Chemical structures and compositions of (a) amylose and (b) amylopectin. 

The starch component of the Fantesk starch-oil composite can vary in its chemi-cal/structural properties (amylose, amylopectin, waxy) as well as in the type of crop source (corn, potato, rice, etc). Likewise, the oil component of the Fantesk starch-oil composite can have a variety of chemical/structural properties, compositions, and end uses. Over the years, Fantesk starch-oil composites of various combinations of starch and oil have been prepared and investigated for a variety of food and nonfood applications, including cosmetics, pharmaceuticals, polymers, coatings, and lubricants [4, 30-33]. 

FIGURE 3.1 Chemical structure and composition of linear amylose and branched amylopectin.85... 

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