Effect of sugar content and acidity on growth of Zygosaccharomyces rouxii

The effect of sugar content and acidity on potential maximum growth rate (μmax) and lag phase duration (λ) of Zygosaccharomyces rouxii at 25℃ was investigated. The effect of sugar content and acidity on the time for spoilage (TFS) was also analyzed under isothermal (25℃) and non-isothermal conditions. The values of μmax and λ in all sugar content and acidity combinations were obtained through fitting the growth curves by using Baranyi and Roberts model. The results showed that the determination coefficients (R2) of all fitting curves were above 0.95, which indicated that a good fitting was obtained. The effect of sugar content and acidity on μmax and λ at 25℃ and the effect of sugar content and acidity on the TFS under isothermal (25℃) and non-isothermal conditions were analyzed by using response surface (RS) method, and quadratic regression models were obtained. The results showed that R2 of each model was 0.9921 (μmax), 0.9625 (λ), 0.9866 (TFS, isothermal) and 0.9958 (TFS, non-isothermal), which effectively revealed the influence of sugar content and acidity on the growth of Z. rouxii. The influence magnitude of each factor on the growth of Z. rouxii was analyzed by comparing their standard regression coefficients. The results showed that the main limiting factor that affected Z. rouxii growth was the acidity whereas sugar content had less impact. The growth of Z. rouxii was largely inhibited at pH value of 2.3 and it was fully inhibited at pH value of 2.0. The results provide a research basis for predicting and controlling the contamination of apple juice concentrate by Z. rouxii in future. ©, 2015, Chinese Society of Agricultural Machinery. All right reserved.