Effects of storage temperature on microbiota shifts in raw milk biofilm developed on stainless steel

This study aimed to investigate the microbiota in raw milk and the influence of storage temperature on the microbiota shift after biofilm formation. Raw milk stored at 4 °C and biofilms developed in raw milk incubated at 4 °C or 25 °C for 7 days were subjected to microbiota analysis as well as quantitative analyses of aerobic or anaerobic bacteria. The levels of aerobic bacteria increased during biofilm formation, while no significant changes were observed within anaerobic bacteria. In addition, there was a difference between aerobic and anaerobic bacterial counts in raw milk and biofilm stored for 7 days. The pattern of microbial composition differed by temperature. In addition, the genus Pseudomonas (53–71%) occupied a high proportion in raw milk, and the raw milk biofilm developed at 4 °C, while the genus Lactobacillus (75–83%) was predominant in biofilms developed at 25 °C. Intriguingly, bacterial richness was higher in raw milk on day 0 and biofilm developed at 4 °C than raw milk after 7 days of storage at 4 °C. These findings suggest that temperature critically affects the bacterial composition of both raw milk and its associated biofilm. •Raw milk and biofilm developed at 4 °C or 25 °C were subjected to microbiota analysis.•Pseudomonas was predominant in raw milk and raw milk biofilm stored at 4 °C.•Raw milk biofilm developed at 25 °C had the highest abundance of Lactobacillus.•Recognizable cluster patterns were observed between raw milk biofilm at 4 and 25 °C.•Microbial composition of raw milk biofilm was significantly affected by temperature.