Starch constitution

The starch constitutes about 80% of the grain dry mass. In bread making the most important properties of starch are its water-holding capacity, gelatinization, and susceptibility to hydrolysis. 

Starches are altered in several ways. Derivatized starches have greater water solubility and changed rheological characteristics. Crosslinked starches increase viscosity and promote granule stability in solution. Depolymeiized starches create solutions with lower viscosity. Combinations of crosslinkages, depolymerizations, and derivatizations are common. Dextiins, a special class of modified starches, constitute a variety of industrially important starches. Modified and derivatized starches are used in numerous industries as adhesives, thickeners, stabilizers, and emulsifiers. 

The chemical composition of potatoes is very variable and is greatly influenced by variety, environment, and farming practices. Starch constitutes 65-80% of the dry weight of the tuber. 

Hybrid materials, containing biodegradable, but nonrenewable, petroleum-based polymers combined with renewable biopolymers (mainly starch), constitute an environmental compromise, but hybrids provide improved physical properties relative to the biopolymers alone they are biodegradable and, in many cases, they are compostable. Hybrids satisfy many of the growing environmental concerns of the major industrialized regions of North America, Europe, and Asia. 

Starch [9005-25-8] the main reserve food of plants, constitutes two-thirds of the carbohydrate caloric intake of most humans but only 47% of... 

The molecular uniformity of constituting components of a nb/lcb glucan fraction of potato starch was investigated with Sepharose CL 2B (Fig. 16.16) as well as with Sephacryl S-1000 (Fig. 16.17). Therefore, each of the subsequently eluted 3-ml fractions was analyzed on their potential to form inclusion complexes with iodine, a sensitive test for the presence of nb/lcb glucans. Results are shown in Fig. 16.17 in terms of branching index, the ratio of extinction of pure iodine solution and of nb/lcb glucan/iodine complex the higher the index, the more pronounced the nb/lcb characteristics. 

By means of gel electrophoresis on cross-linked, hydrolyzed starch,99 with simultaneous checking for proteins, lipids, and pectinesterase activity, it was found, however, that the product isolated after the separation on CM-Sephadex C-50 constitutes but one of five multiple forms of tomato pectinesterase, and is the one present in preponderant proportion98 (see Fig. 4). The accompanying lipid and sugar components were separated from this pectinesterase form in the course of the purification procedure. After analysis of the hydro-lyzate of the final product for fatty acids, as well as for carbohydrate components, it was possible to exclude the possibility of a lipoprotein,30 as well as glycoprotein,100 character of this form of tomato pectinesterase. 

Endosperm constitutes the main part of the corn kernel and consists of 85 to 90% starch, 8 to 10% protein, and a small amount of oil and other compounds. Corn endosperm can be divided into two distinct parts floury and horny endosperm. In floury endosperm, starch particles are round and are dispersed loosely in the protein matrix. In the horny endosperm, the protein matrix is stronger and starch particles are held more firmly. Starch granules are encased in the continuous protein matrix. The tighter setting in horny endosperm gives starch particles a polygonal shape. On average, the amount of horny endosperm in the corn kernel is twice that of the floury endosperm. However, this ratio is a function of the corn kernel protein content (Wolf et al., 1952). 

Of other recent experiments in the chemistry of the sugars the preparation of the anhydro-sugar laevoglueosan C6H1005 by the rapid distillation of starch or cellulose in a vacuum may be mentioned (Pictet). This interesting compound possibly has the constitution I. 

The starch industry has adopted standard conditions for liquefaction. These conditions constitute a short-term jet-cooking treatment of a 35-40% dry solids (DS) starch slurry at 105 C for 5 minutes, known as gelatinization or primary liquefaction, followed by a 90-minute hold at 95 C, known as dextrinization or secondary liquefaction ( ). 

The paper industry constitutes the largest single industrial market for starch in the world. If the world production of paper is about 235 MM tons, starch production for paper may be estimated at about 3 MM tons. This recognizes that large volume items such as newsprint and tissue are essentially non-starch users. 

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