Causes of alkalinization in tempe solid substrate fermentation

The aim was to determine whether ammonia production and/or lactic acid cons umption were sufficient to entirely account for alkalinization during the f ermentation of bacteria-free tempe prepared with acidified soybean cotyledo ns and Rhizopus oligosporus NRRL 2710 at 30 degrees C. The pH rose from an initial value of 4.6 to 6.6 in mature tempe after 46 h and 7.1 in aging tem pe after 72 h. By the end of the fermentation, approximately 80% of the ini tial lactic acid had been used, but its consumption accounted for less than 3% of the overall alkali production. Ammonia production accounted for appr oximately 40% of the measured alkalinization in mature tempe (46 h) and was almost entirely responsible for alkali production in aging tempe (46-72 h) . The extent of amino acid utilization was estimated to be approximate to 1 0 g/kg initial dry matter during the growth phase, sufficient to yield only approximate to 9% of the observed fungal biomass (54 g/kg initial dry matt er) in mature tempe at 46 h. (C) 1999 Elsevier Science Inc. All rights rese rved.