Effects of high hydrostatic pressure on characteristics of pork slurries and inactivation of microorganisms associated with meat and meat products.

Pork slurries inoculated with various test microorganisms were prepared and subjected to high hydrostatic pressure at 1000 to 6000 atm for 10 min at 25 degrees C to examine for the pressure effects on characteristics of the slurries and the inactivation of the microorganisms associated with meat and meat products. Pressure treatment at higher than 3000 atm caused coagulation and discoloration of the pork slurries. Harder and more white coagulants were obtained by increasing the pressure. Pressure treatment at 3000 to 6000 atm killed all the microorganisms tested by more than 6-log colony-forming units (cfu)/g except Bacillus cereus spores. Gram-negative microorganisms were more labile to pressure than Gram-positive ones. Campylobacter jejuni, Pseudomonas aeruginosa, Salmonella typhimurium and Yersinia enterocolitica were inactivated at pressures higher than 3000 atm; Escherichia coli, Saccharomyces cerevisiae and Candida utilis at pressures higher than 4000 atm; Micrococcus luteus, Staphylococcus aureus and Streptococcus faecalis at 6000 atm. Only less than one-log cfu/g of B. cereus spores were inactivated at 6000 atm. Ultraviolet absorption spectra and acridine orange staining suggested that E. coli became permeable and leaked cytoplasmic RNA at lower pressure than S. aureus. From the present findings, the authors propose high hydrostatic pressure treatment as a promising means of preparing wholesome meat and meat products.