A new study from food scientists at Cornell University suggests that a new filtration process for extending the shelf life of milk can potentially result in a pasteurization-resistant microbacterium entering fluid milk if equipment isn't properly sanitized.

According to the study, microfiltration — which is a processing technology for extending the shelf-life of milk wherein semipermeable membranes are used to keep out undesirable microbes — can introduce a tiny microbe called microbacterium to milk in the event that the processing equipment is not sanitized early in the process. The team’s findings reportedly point to the significance of sanitizing milk-processing equipment ahead of pasteurization.

"Fluid milk processors often rely on the pasteurization process to apply the final kill-step for organisms," the researchers explained, "but we're showing that to achieve a longer shelf-life with this newer technology, processors should thoroughly clean the intake equipment for raw milk long before they pasteurize. In other words, they should do everything they can to remove these microbes prior to processing."

Microfiltration is gaining in popularity — promising to extend conventional fluid milk products’ refrigerated shelf life of 14 to 21 days to 60 days and consequently reducing food waste — over methods like high-temperature pasteurization, which can result in undesirable flavors.

Using less energy and maintaining the flavor of milk with membrane pores measuring 0.8 microns to 1.2 microns, microfiltration is a reportedly gentler alternative for removing bacteria than high heat treatment.

Yet, the researchers determined in their examination of whole milk and skim milk processed using both microfiltration and high heat pasteurization methods that there were differences in bacterial concentrations for the microfiltered milk stored at different temperatures, but no difference in milk with different fat levels.

Further, the team identified a microbacterium as the source of the bacterial population in microfiltered milk.

An article detailing the researchers’ findings, "Microbacterium Represents an Emerging Microorganism of Concern in Microfiltered Extended Shelf-Life Milk Products" appears in the Journal of Dairy Science.