The Improvement Of The Flavor, Aroma And Safety Of Soy Sauce By Employing Tetragenococcus Halophilus In Fermentation

Soy sauce is a popular delicious condiment with unique aroma and nutritional. Ethyl carbamate( EC) is a group 2A carcinogen, which widly exists in fermented foods such as soy sauce. In the process of soy sauce production, EC was mainly formed through citrulline and ethanol reaction. For food processing it is required to use non-genetic modified microorganisms. Thus it is of great importance to develop novel strategies for control and reduce EC and its precursors to improve fermented foods safety. In this work, a soy sauce mormomi isolate Tetragenococcus halophilus R23 was employed to verify its potential applications in reducing EC precursors in soy sauce and improvement of soy sauce aroma. And pilot test was carried out in the factory. The main results are as follows.(1) T. halophilus R23, when added in a 8 L soy sauce fermentation tank, can degrade arginine into ornithine through the arginine deiminase pathway(ADI). It was found that, T. halophilus R23, when added at level of 106 CFU·m L-1 and 107 CFU·mL-1 during moromi fermentation, decreased citrulline by 85.6%, and EC reduced by 53.9%, 79.3%, respectively. Physicochemical properties of soy sauce added with R23 have no obvious change. The volatile compounds increased. Soy sauce inoculated with 106 CFU·m L-1 T. halophilus R23 has been detected to contrain 8 extra volatile compounds. Acids, aldehydes, ketones, esters, phenols and pyrazines were increased 20.6%,23%,5.2%,6.7%,6.5%, 4.8% repectively when R23 is added during soy sauce fermentation.(2) Employment of T. halophilus R23 for 60 L pilot and 90 m3 soy sauce fermentation trail were carried out simultaneously due to the long duration time of soy sauce fermenation. Results showed that addition of T halophilus R23 in 90 m3 soy sauce fermenter reduced both citrulline(10%) and EC(33%) levels. However, employment of T halophilus R23 for the 60 L soy sauce fermentation pilot didn’t change citrulline and EC levels. When T halophilus R23 used for 90 m3 soy sauce fermentation, the main physicochemical properties have no change, the numbers and quantity of volatile compounds have been improved. The sensory evalution results deomonstrated the specialized ester aroma contributed by T. halophilus R23.(3) Soy sauce fermentation process was greatly affected by production volume and environmental factors. For the 60 L and 90 m3 soy sauce fermentation trial, T halophilus R23 did not work as efficient as it was for 8 L fermentation system. The possible reason for that are: The duration at low temperature for 90 m3 jar soy sauce fermentation was 2 times of that done in the laboratory(8 L). growth of T. halophilus R23 was strongly inhibited at 16℃, citrulline and arginine utilization capability of T. halophilus R23 was also dramatically reduced at low temperature; Moreover, relatively high reducing sugar content in 60 L and 90 m3 soy sauce moromi repressed degradation of arginine through ADI pathway by T halophilus R23; For the 90 m3 soy sauce fermentation trail, citrulline in the moromi was 1.5 times higher than that of normal batches, which made it more difficult for T. halophilus to reduce EC precursor.