Amino acid processes affecting nutritional

Processes Affecting Nutritional Value of Amino Acids. 

Other than a nutritional role linked to mineralization processes, humic compounds have been hypothesized to directly affect plant nutrition, since it has been suggested that roots may take up low-molecular-weight humic molecules (21). Interestingly, plants have been ob.served to express carriers for amino acids (22) and small peptides (23) at the root level. Certain components of the humic fraction have been found inside root cells and were, moreover, translocated to the shoots (24,25). Recent experiments performed on rice cells in suspension culture seem to suggest that they may use carbon skeletons from humic molecules to synthesize proteins and DNA (26). 

During the processing of foods, several chemical reactions affect the structure of some amino acids reactions with reducing sugars and polyphenols, interaction of the side chains of the amino acids, oxidation, etc. In some cases, these chemical modifications do not seem to change the nutritional availability of the amino acids involved, while in other cases, they do. In all cases, the presence of the newly formed molecules induces biochemical and physiological changes. 

This effect is similar to that caused by cooking an egg. The secondary bonds hold the protein in an egg together in a certain way. When the egg is heated, the protein is denatured, or the secondary bonds are broken. When these bonds are broken, the product loses its distinctive physical appearance. If the egg was cooked to extreme temperatures, the primary bonds holding the amino acids together would be destroyed, thus affecting their nutritional value. The extrusion process does not adversely affect the primary bond, but does create sufficient heat to denature or break down the secondary bonds. 

The arguments offered above call for caution and the careful, however scientifically sound, evaluation of the safety of food items for human consumption. Close toxicological and pharmacological surveillance of nutritional products with additives and/or the history of chemical or physical processing is of paramount importance. The importance of this surveillance is demonstrated most convincingly by observations made recently in the field of hyperalimentation. Here the patient, deprived of the ability of oral food intake, is dependent on the intravenous infusion of solutions of essential amino acids. For solution stabilization sodium bisulfite was added. This presumed preservative, however, reacts with tryptophan (20) with the formation of products which affect liver tissue adversely (21). 

Knowledge regarding the major constituents of food (e.g., carbohydrates, amino acids, proteins, lipids, dietary fiber, and nutritional and antinutritional components) is necessary so as to guage the extent of any structural change that occurs during processing and storage of foods, which may affect the quality and safety of the food product. 

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