Application of high hydrostatic pressure on the microbial and physicochemical characteristics of pork

This study investigated the effects of high hydrostatic processing on the microbial safety and physicochemical properties of raw pork. Raw pork samples were treated at pressures of 0.1, 100, 300, and 500 MPa for 5-15 min and stored under refrigerated conditions for up to 2 weeks. Microbial populations, including Bacillus cereus, Escherichia coli, Salmonella Typhimurium, Listeria monocytogenes, and Staphylococcus aureus, were analyzed alongside physicochemical properties such as proximate composition, pH, water-holding capacity (WHC), shear force, thiobarbituric acid reactive substance, and volatile basic nitrogen. Microbial count decreased significantly with increasing pressure and holding time. The 500 MPa for 15 min treatment exhibited the strongest antimicrobial effect, reducing S. Typhimurium and L. monocytogenes to below detectable levels during storage. B. cereus, E. coli, and S. aureus showed substantial reductions, although partial survival was observed in pressure-tolerant microorganisms during storage. Increasing pressure and treatment time led to increases in water-holding capacity, shear force, and pH, while moisture and protein contents increased and fat and ash contents decreased. These physicochemical changes were attributed to pressure-induced denaturation and reorganization of myofibrillar proteins, resulting in a compact protein network. TBARS values increased due to high-pressure-induced membrane damage and the release of ions and free radicals, whereas VBN values were suppressed by microbial inactivation and pressure-induced enzyme modification. Increasing pressure intensity and holding time enhanced both microbial inactivation and physicochemical changes, indicating that high hydrostatic processing exerts combined physical and chemical effects on microorganisms, muscle fibers, myoglobin, and enzymes in raw pork.