NUTRITIONAL AND CHEMICAL STUDIES OF THREE PROCESSED SOYBEAN FOODS

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Abstract
Three different processing methods were used to prepare foods based on whole soybean. Product A was prepared by soaking the beans overnight, blanching at 210° for 20 min, blending and drum drying at 40 psig steam. Product B was water‐packed canned soybeans, blanched at 210°F for 20 min and thermally processed in cans at 250° F for 60 min, then blended, frozen and freeze dried. Product C, a mixture of soy and banana (1:1 solid basis), was prepared by the same method as Product A. The amino acid composition of the three products determined by gas chromatography was compared. The thermally processed product (B) showed a considerable decrease in methionine compared to Product A (from 23.4 to 11.3 mg Met/g protein). Product A showed superior quality (PER = 2.43; NPU = 46.3), but as a result of methionine supplementation (0.5%) the PER of the thermally processed product (B) was increased from 1.61 to 2.94 and the NPU from 33.2 to 49.3. The effect of the different processing procedures on the quality of the end products, such as browning, nitrogen solubility index (NSI) and amino acid partition between the soluble and the nonsoluble fractions was compared. Product (A) was superior to the thermally processed product (B) considering browning (A420= 0.072 compared to 0.156), but was inferior considering NSI (14.92% compared to 23.89%). Amino acid analysis of the soluble fraction indicated a relatively high amount of soluble lysine (114.5 mg/g protein). Cost analysis of the three products shows their economic advantage compared to casein as a protein source.