Microfiltration reduces the microbes in raw milk using membrane pores measuring 0.8–1.2 microns. The solution requires less energy than pasteurization and does not compromise the flavor of the milk. Through the removal of bacteria, microfiltration can extend the refrigerated shelf life of fluid milk products from 14–21 days to up to 60 days. The process is already being used in Europe and is soon going to be adopted in the U.S.

While HTST is the standard final killstep in milk production, the Cornell study underlines the heightened importance of thoroughly cleaning intake equipment for raw milk long before the pasteurization process. If equipment is not cleaned adequately and early, microfiltration can pass very small, pasteurization-resistant microbacterium into fluid milk.

For the study, the researchers observed whole milk and skim milk samples that were processed using microfiltration and pasteurization, and were refrigerated at 3 °C, 6.5 °C, and 10 °C for 63 days. The amount of bacteria present in the milk samples increased with refrigeration temperature, but did not vary by fat content. The most significant finding was that of the microbacterium, which were able to permeate microfilter membranes, survive HTST pasteurization, and then grow at refrigeration temperatures.