Amylose molecular compositions

The amylose-iodine interaction has a dipolar nature, as deduced from a distinct difference between the molecular coefficient of iodine in starch and in nonpolar solvents.123 The additional stabilization may result from the formation of resonating polyiodine chains at high dipolar interactions. The composition of the total energy of stabilization is shown5 in Table VI. 

In many foods, both starch and protein can be encountered so that understanding interactions between them would be useful. The selectivity in interaction between proteins and starches is best seen in results of dynamic rheological studies. The results depend upon the molecular structure of protein, the starch state of the granules and the amylose/amylopectin ratio, the composition of protein and starch, as well as the phase transition temperatures are important factors influencing protein-starch interaction. Because proteins and starches are thermodynamically different polymers, their presence together may lead to phase separation, inversion, or mutual interaction with significant consequences on texture (Morris, 1990). 

In retrograding solutions we expected a preferential precipitation of the DP loo amylose. However, the ratio of the components in each fraction was found to be similar to the 1 1 composition of the solution. The same results were obtained with a 1 3 or a 3 1 composition ratio in the starting solution. The results show clecurly that the high molecular weight product is involved in the association process from the very beginning. 

Insofar as the monosaccharides do occur as such in nature, it is more common to find the sugars occurring naturally in pairs (disaccharides) or in threes (trisaccharides) and, more likely, as the high-molecular-weight polysaccharides (Table 3.7). It is the polysaccharides which most probably contribute to the source material, especially the two well-known polysaccharides cellulose and starch. The fibrous tissue in the cell wall of plants and trees contains cellulose and starch also occurs throughout the plant kingdom in various forms but usually as a food reserve. The chemical composition of starch vanes with the source but in any one starch there are two structurally different polysaccharides. Both usually consist entirely of glucose units but one is a linear structure (amylose) whereas the other is a branched structure (amylopectin). 

Starch is generally composed of 10—30% amylose and 70—90% amylopectin the composition varies depending on the geological area where the starch is produced as well as the plant variety. Cellulose is most commonly contained in cell walls and is distinguished from other polysaccharides produced by plants by its very long molecular chain. 

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