Abstract: [Objective] This study aimed at improving the accuracy of the discontinuous pH measurement in the determination of acidification activity by modeling fitting based on the modified Gompertz model.[Method] The model operated based on four key parameters：the lag phase time（λ）,maximal rate of pH decrease with time（μ）,initial pH（pH0）,and final pH（pH∞）. Based on the results of discontinuous pH measurement,the four parameters were identified by using nonlinear least square method,and then the acidification activity was determined by bisection method. The optimization was verified based on results of continuous pH measurement.[Result] The determination coefficient（R²）was 0.9988,root-mean-square error（RMSE）was 0.03,which showed that the model gave good fits of the data. The model decreased the relative error of discontinuous pH measurement from 10.62% to 2.21%.[Conclusion] The model can improved the accuracy of discontinuous pH measurement,however,the modified Gompertz model had limitations in providing other fermentation kinetic parameters due to the complicated biochemistry reation in actual fermentation process.

Key words: lactic acid bacteria, acidification activity, Gompertz model, discontinuous pH measurement