Effect of initial 5 days fermentation under low salt condition on the quality of soy sauce

A two-stage moromi fermentation method was employed to the soy sauce making in order to shorten the overall fermentation time. At the first stage, the koji was mixed with 10% brine solution and incubated at 40 degrees C for 5 days. The second fermentation stage was conducted under three different treatments, including reduced temperature from 40 degrees C to 30 degrees C, outdoor without temperature control, and indoor ambience temperature up to 3 months with the brine content increased from 10% to 18%. The increases of total nitrogen (TN) and amino nitrogen (AN) contents were mainly occurred at the first stage while maintain constant during the second stage. Both TN and AN values satisfied the requirement of first-grade soy sauce of Taiwan. Unlike TN and AN, the reducing sugar and total acid contents still increased with fermentation time during the second stages. Since most of the changes of these biochemical properties occurred within 5 days' moromi fermentation, the use of high temperature and low salt fermentation condition in the first stage was very important to rapid fermentation process of soy sauce.