Amino Acid Studies on the Effect of Fermentation Time and Heat-Processing of Tempeh

SUMMARY In general, amino acids as analyzed by column chromatography declined slightly in tempeh fermented up to 72 br, and these declines were partially attributable to amino acid deficiencies in the fermentative mold. Tryptophan declined in the dehulled lactic-acid-soaked soybeans, increased in 24-hr-fermented tempeh, and decreased slightly as the fermentation continued to 72 hr. Free amino acids and ammonia increased during fermentation. Glucosamine was isolated from the mold and subsequently identified. An increase in glucosamine in tempeh during fermentation reflected large amounts in the mold. Deep-fat frying of tempeh caused some amino acids to decrease after 5 min, while most declined after 7 min. Lysine and cystine were most susceptible to heat destruction. Steaming of tempeh for 2 hr or less had no effect on the amino acids. Changes in amino acid indexes during fermentation and heat-processing were related and, in some instances, significantly correlated with animal data.