Feasibility of hydrodynamic cavitation, in line with HTST pasteurization, for inactivating sporeformers and spores in skim milk.

Document Type


Publication Date



American Dairy Science Association


Journal of Dairy Science




Suppl. 2






hydrodynamic cavitation, sporeformer, spore


Sporeformers and their endospores are of concern for the dairy industry due to their thermal resistance. A previous study conducted in our laboratory revealed the effectiveness of a 6- to 8-pass cavitation effect (CE), in combination with batch pasteurization, in reducing vegetative cells and endospores of some common dairy sporeformers. In continuation, the current study evaluates the feasibility of reduced pass hydrodynamic cavitation, combined with HTST pasteurization for the reduction of sporeformers. The equipment set up was assembled in Davis Dairy plant to conduct a continuous cavitation and HTST pasteurization process. The spiking studies were conducted by inoculating sterilized skim milk with either vegetative cells (at 4.76 ± 0.03 log/mL) or spores (2.65 ± 0.09 log/mL) of a thermoduric strain of Bacillus coagulans (ATCC 12245). The flow of the spiked skim milk samples varied from 50 to 200 L/h, with a cavitation frequency of 60 Hz, using an APV cavitator. A small plate heat exchanger and a holding tube set up to achieve 73°C ± 1.0°C for 15 s effected the pasteurization. The spiked milk samples were processed through the above set-up for a single pass CE, followed by pasteurization to establish a baseline. The study was expanded up to 4-pass CE, combined with pasteurization, to observe their feasibility in enhancing spore inactivation. All trials were conducted thrice, with samples drawn in triplicates, and data were analyzed statistically using one-way ANOVA Tukey’s test. The initial load of 4.76 ± 0.03 log of vegetative cells was reduced to 0.91 ± 0.04 log by a single pass CE at a flow rate of 200L/h, followed by pasteurization, as compared with 1.19 logs by pasteurization alone. In the case of spores, a 4-pass CE at 100L/h flow rate was found necessary to reduce the mean spore counts from 2.65 ± 0.09 log to 2.06 ± 0.02 log. The single pass CE combined with HTST pasteurization appeared to be feasible for reducing thermoduric sporeformers; for spore reduction, multiple CEs were necessary. Further evaluation studies are in progress.