Psychrotrophic bacterial populations in Chinese raw dairy milk

Four-hundred and eighty isolates isolated from raw milk samples collected from different farms in China were subjected to random amplified polymorphic DNA analysis and 16S rRNA sequencing for clustering and identification, respectively. All isolates comprised 24 genera and 74 species in total. Pseudomonas was the most prevalent genus, representing 58.8% of all isolates, followed by Acinetobacter (13.3%), Flavobacterium (6.0%) and Sphingobacterium (4.2%). Among the 25 species belonging to Pseudomonas, Pseudomonas fluorescens (15.8%) proved to be the most dominant species, followed by Pseudomonas fragi (7.1%) and Pseudomonas psychrophila (5.4%). Out of these isolates, 12.3% have not been reported in previous studies, highlighting that many psychrotrophic bacteria are rather underexplored in raw milk. In the future, a detailed investigation will be required to characterize these bacterial isolates based on their potential to deteriorate the quality of dairy products.