PurposeTo control the growth and tyramine production ability of Enterococcus faecalis by establishing the simulated fermentation culture system and optimizing the fermentation conditions, providing a reference for the optimization of the production process of fermented meat products.
MethodE. faecalis was cultured in a simulated fermentation system. The effects of fermentation temperature, initial pH, NaCl content and oxygen content on the growth and tyramine production of E. faecalis were investigated. The optimum fermentation conditions for controlling tyramine production were obtained by response surface test.
ResultThe optimum temperature for E. faecalis growth was 25 ℃ and low temperature could effectively weaken the tyramine production ability of E. faecalis. The initial pH of the culture medium had little effect on the change of pH in the culture system. When the initial pH was about 5.0, the tyramine yield of the system was higher. Appropriate salt concentration could effectively inhibit the growth and reproduction of E. faecalis and the production of tyramine in the system. The effect of oxygen supply conditions on pH was not obvious, but the yield of tyramine in the system was low under oxygen enriched conditions. The optimum technological conditions for controlling tyramine production by E. faecalis were obtained by response surface optimization as follows: temperature 29.68 ℃, initial pH of 5.22 and 5.49% NaCl. The yield of tyramine measured by verification test had little difference from the theoretical value.
ConclusionIn this study, we can explore the growth of E. faecalis in food and the level of its influencing factors, and determine the key control condition of tyramine formation by establishing the culture model of E. faecalis. Therefore, it is feasible and practical significance to reduce the tyramine production in the culture system by controlling the temperature, initial pH, salt concentration and oxygen supply conditions of the fermentation system.
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