51H-2

S. F. Lee, S. C. Yu, Y. C. LIU, F. L. Lee, and C. C. Liao. Culture Collection and Research Center, Food Industry Research and Development Institute, P. O. Box 246, Hsinchu, 30099, Taiwan

Stinky tofu, also known as stinky soybean curd, is a traditional fermented food made from tofu. When the brine medium comprising several vegetables, tofu and shrimp becomes stinky after fermentation, tofu squares are dipped in it for a few hours before deep-fried or steamed. This gives special odors to and produces a sponge-like structure inside the tofu through the action of microorganisms. Traditionally the stinky brine is produced from natural fermentation which takes more than six months. Moreover, it is easy to be contaminated with pathogens and maggots during the open-type fermentation. This study was designed to study the optimal conditions for production of stinky brine and to identify the fermenting strains. In this study, A2 microbial group was used to ferment for stinky brine. Production of ammonia was used as an indicator of the progress of fermentation. Changes of ammonia concentration in stinky brine were determined at different conditions. Fermentation isolates from stinky brines were identified by four rapid identification systems- Biolog system, API kit, VITEK system, and Microbial Identification System(MIDI), and conventional physiological and biochemical tests (Micro-IS system). Increase the inoculum of A2 microbial group would accelerate the fermentation at the beginning. The amount of ammonia was the highest when A2 microbial group was incubated at 35°C for one month. It was the best that the stinky brine was made by submerged fermentation and the caps of the fermentation bottles were loosely capped. Microorganisms for stinky brine fermentation can be preserved by freezing and freeze-drying methods. Identification results showed that Bacillus sphaericus and lactic acid bacteria (such as Enterococcus sp. and Lactobacillus sp.) were dominant in A2 microbial group. This study determined the best condition for fermenting the brine medium to improve traditional process and identified the fermenting isolates.