Hydrodynamic cavitation coupled with thermal treatment for reducing counts of B. coagulans in skim milk concentrate

摘要

We report the development of hydrodynamic cavitation coupled with thermal treatment for reducing counts of B. coagulans (ATCC 12245) in skim milk concentrate (SMC, 35 +/- 1% total solids). The process was evaluated in terms of analysis of cavitation parameters, characterization of the increase in the fluid temperature, and microbial inactivation. Inoculated SMC (4.67 +/- 0.18 log) was treated by cavitation (rotor speed of 3600 RPM and fluid flow rate of 100 L h(-1)), thermal treatment (75-85 degrees C for 14-106 s), or a combined cavitation-thermal treatment, using the aforementioned conditions. A 3.5 log CFU mL(-1) reduction was obtained by the combined cavitation-thermal treatment, while thermal treatment alone yielded a 2.77 log CFU mL(-1) reduction. Contrary, individual cavitation did not produce a significant reduction. The values of decimal reduction time at 75 degrees C (D-75) were lower when cavitation was followed by thermal treatment (375 +/- 62 s) than the values obtained for thermal treatment (470 +/- 66 s). The outcomes of this study present opportunities for reducing the counts of B. coagulans in skim milk concentrate by the combined effect of hydrodynamic cavitation and thermal treatment.