Changes in Soybean Lipids During Tempeh Fermentation

Changes in the lipids of soybeans brought about by Rhizopus orysae during the production of tempeh were studied. The mold possesses strong lipase activity and caused the hydrolysis of over one‐third of the neutral fat of the soybean during the three‐day fermentation. The fatty acid composition of soybean tempeh was compared with that of cooked soybeans by vapor‐phase chromatography of the methylesters. The neutral fat was composed of palmitic, stearic, oleic, linoleic, and linolenic acids, with linoleic acid predominating. These acids were liberated during fermentation in roughly the same proportions found in soybeans after heating 90 min at 100°C. During the most active mold growth, proportionately higher levels of palmitic acid were found, and the level of linoleic acid was somewhat lower. Except for the depletion of some 40% of the linolenic acid in the later stages of the fermentation, there apparently was no preferential utilization of any fatty acid.