Abstract: [Objective]The raw milk fermentation experiment takes a long time to reach the fermentation end point,and the abnormality can be found only after the fermentation is completed. The bromocresol purple fermentation method can intuitively find the abnormality of the fermentation process in advance through the change of color during the fermentation process.[Method]Add 4~5 mL of mother strain and 1 mL of 0.1 g/L bromocresol violet indicator to the boiled and cooled raw milk,and incubate in a water bath at（45±1） ℃.[Result]After incubation for 2 hours,the color of the sample solution changes from blue to yellow with the fermentation, which is normal fermentation. [Conclusion]This method can observe the change of fermentation color after fermentation for 2 hours. Compared with the commonly used fermentation methods, the fermentation situation can be observed in advance and the abnormal situation can be analyzed and handled earlier, which can be used as an auxiliary in practical application.

Key words: sample fermentation, bromocresol violet solution, pH value