Identification of sporeforming bacteria in the milk chain and its potential sources in farm environment

The dairy industry is recently facing a quality problem due to the presence of sporeformer bacteria in different products. These bacteria are members mainly of the Bacillus taxonomic group and due to their abilities to survive pasteurization, can not be controlled by this process technology. Consequently, this bacteria population affects the quality of some products during storage (e.g. fluid milk) and limit their potential markets (e.g. milk powder). Since no technology/interventions are currently available to eliminate this bacteria type once they enter the milk chain, the identification of their entry points and sources is essential information to design potential interventions to control them at early stages. In order to address this issue, this research focused on identifying those "problematic" sporeforming bacteria across the milk chain (from sources at farm level, raw milk, fluid milk and condensed milk) using DNA-based methods (rpoB or 16S). Moreover, associations affecting their entrance into the milk chain were also studied, including weather and potential farm practices. The identification of problematic sporeformers suggests that Paenibacillus spp. are responsible for spoilage of fluid milk due to their ability to grow and survive the processing conditions encountered during pasteurization and condensation. Other Bacillus species found in condensed milk include: B. claussi, B. subtilis, Lysinibacillus sp., B. safensis, B. licheniformis, B. sonorensis and Brevibacillus spp. These last three species are capable of growing at thermophilic temperatures (55 °C) being potential problematic for the milk powder industry. Therefore, contamination of other dairy products could occur when condensed milk is used as ingredient. When evaluating the raw milk at the farm level, no seasonal effect was associated with the prevalence of sporeformers bacteria; however, farms seems to have an effect. Among the sources of problematic strains at the farm, it was found that milking equipment and cow teats are associated with a wide variety of psychrotrophic and thermophilic problematic strains, suggesting that any interventions at farm level should be targeting these areas. By better understanding the potential sources, scientists and farmers could design and implement suitable interventions to decrease sporeformer counts in raw milk improving the quality of dairy products.