The Effects of High Pressure Processing on Total Mesophilic Aerobic Bacteria Number and Color Properties of Frozen and Unfrozen Beef Mince

High hydrostatic pressure processing (HPP) is a cold pasteurization technology that can be applied after packaging to products damaged by heat treatment. In this study, the effects of different levels (300, 350 and 450 MPa) of pressure applied at different temperatures (-5, 0 and 10 oC) and durations (5, 10 and 15 min) on the total mesophilic aerobic bacteria count (TMAB) and color values of frozen and unfrozen beef mince were investigated. The most effective factor on the number of TMAB was pressure. Freezing resulted in increased inactivation. In the application performed at constant temperature (10 oC), the difference in inactivation between frozen and unfrozen samples was seen maximum at 300MPa pressure application. Inactivation increased with increasing pressure level and time. At different application temperatures, the most effective inactivation of 300 MPa HPP in frozen and unfrozen samples occurred at -5 oC in 15 minutes. The increase in L* value of frozen samples was less than that of non-frozen samples. This contributes to the preservation of freshness properties in meat. An increase in the L* value was observed with the increase in pressurization time. Increasing the pressure level caused a decrease in the a* value, and freezing caused an increase in the a* value. It was determined that the 300-450 MPa HPP range was not large enough to observe changes in b* values. ΔE values in frozen samples were determined to be higher than in non-frozen samples. If freezing and pressure are applied in combination, a microbiologically safer product with a color closer to fresh properties can be obtained.