| Abstrakt: |
Since many new soy protein products are being developed which differ in enzyme activity, protein dispersibility, flavor, nutritive value, and functional properties, quality control is assuming increasing significance. The effects of dry and moist heat and hexane:ethanol azeotrope extraction upon various enzymatic activities, protein solubility, and nutritive value of defatted soy flakes differ considerably. Specifications and guidelines initially developed to establish the degree of moist heat treatment required to produce edible grade products need to be reevaluated for these processes. Flavor scores of hexane:ethanol azeotrope-extracted flakes and proteinates prepared from them are significantly higher than those prepared by current commercial practices. Because peroxidase is a much more stable enzyme than lipoxygenase, determination of peroxidase activity may be a more suitable method to define proper processing conditions which improve the flavor of soy products. A combination of hexane:ethanol extraction and steaming improves the flavor and nutritive value of defatted soy flakes. Azeotrope extraction alone does not inactivate trypsin inhibitors; nutritive value of the extracted flakes is low, and pancreatic hypertrophy occurs when they are fed to rats. Protein efficiency ratio of the processed flakes is 2.2 on a basis of a value = 2.5 for casein. Other factors to be considered to prepare soy protein isolates of good nutritional quality are: choline deficiency, variability in sulfur amino acid content, and formation of phytate complexes that affect bioavailability of essential minerals, particularly zinc. |
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