Identification and Control of Heat-Resistant Bacteria in Raw Milk

With the increasing demand for liquid milk, it is particularly important to ensure its quality and safety. The presence of heat-resistant microorganisms in liquid milk is a non-negligible cause of its quality defects. Therefore, this study employed high-throughput sequencing to explore the microbial diversity of raw milk. Heat-resistant microorganisms were isolated in pure culture and identified by 16S rDNA sequencing and their biological diversity and morphological characteristics were analyzed. Subsequently, the identified bacteria were inoculated into normal sterilized milk and skim milk to simulate the spoilage process of products contaminated by them, and their tolerance was examined to provide ideas to screen and control abnormal milk products. The results showed that the heat-resistant microorganisms in raw milk are mainly of the genus Bacillus, and three colony forms were found by Gram staining. Particle precipitation and delamination after inoculation of different types of Bacillus into sterilized milk; yellow color and bitter taste after inoculation into skim milk. All three Bacillus species had strong temperature tolerance but poor tolerance to peracetic acid. Milk enterprises can combine peracetic acid-based disinfectants with Clean-in-Place cleaning to effectively kill residual heat-resistant microorganisms on the production line.