Abstract: [Objective] To study the effects of different culture media,culture temperatures and culture times on the levels of psychrotrophiles microorganisms in raw cow's milk,aiming to improve the accuracy and consistency of the detection of psychrophiles detection in raw cow's milk.[Method] This experiment adopted the 6.5 ℃ colony counting method（referred to as“PCMA method”）in the first method and the 21 ℃ colony counting method（referred to as“PCMA rapid method”）in the second method of“SN/T 2552.4-2010 Microbiological Testing methods for Milk and Dairy Products”and “ISO 6730：2005 Milk—Enumeration of colony forming units of psychrotrophic microorganisms—Colony-count technique at 6.5 ℃”（referred to as“PCA Method”）and“ISO 8552：2004 Milk—Estimation of psychrotrophic microorganisms— Colony-count technique at 21 ℃ （Rapid Method）”（referred to as“PCA Rapid Method”） was used to detect the levels of psychrophiles in a total of 66 raw cow's milk samples from 2 dairy products of 8 dairy farms in South China in 2017 under different culture conditions.[Result] The data consistency of the PCA method and the PCA rapid method was poor when detecting the same type of raw cow's milk. The PCMA method and the PCMA rapid method also showed the problem of poor data consistency when detecting raw cow's milk. Although the PCA method and the PCMA method were consistent in quantity when detecting the same type of raw material milk,the culture medium of the PCMA method was relatively turbid,and the colony morphology was small,which was prone to misjudgment.[Conclusion] Different culture media,culture temperatures and culture times have an impact on the detection results of psychrophilic bacteria in raw cow's milk. The PCMA rapid method can be used to make a preliminary judgment on the level of psychrophiles in raw cow's milk. However,for more accurate colony technology results,it is still recommended to use the PCA method as the final determination basis.

Key words: psychrophiles, detection, culture medium, culture temperature, culture time