Processing soybeans into foods: Selected aspects of nutrition and flavor

Abstract

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.

Comparison of the Food Value of Immature, Mature, and Germinated Soybeans

“…Maximum growth occurs in rats fed soy diets in which only 79% of the TI activity was eliminated by live steam treatment, and pancreatic hypertrophy did not occur with only 54% destruction of TI (49). Biochemical threshold level effects in long-term rat feeding studies confirm these findings (50).…”

Effect of radiation and soaking on trypsin inhibitor and protein content of chickpea (Cicer arientinum L.)

“…Radiation of seeds prior to soaking results in even greater destruction of TI without affecting the protein content. It has been reported that 70-80 % of TIA in soybean needed to be destroyed in order to achieve maximum gain in weight and PER with rats [23]. In this connection, it is important to note that there are significant varietal differences [24], which may influence the effectiveness of autoclave inactivation of TIA, the treatment which is believed to destroy almost 80 % of the TIA in most legumes.…”

Protein Structural Changes During Preparation and Storage of Surimi

“…Isolated soy proteins have found widespread application in forrnulated food products, and are also used directly as nutritional supplements (Rackis et al, 1975).…”