Abstract

High pressure (HP) treatment at ambient temperature (25°C) was applied to freshly-prepared rennet-coagulated cheese of bovine (pasteurized) milk and the microbiological quality was examined for up to Day 31 using a Central Composite Design (CCD) of experiment. Bacterial counts were significantly (p < 0.05) reduced at the highest applied pressure. Estimated shelf life was 17 days for control samples but approached 31 days at HP treatments of 150 MPa at 1 and 15 min. Treatments above 150 MPa with treatment time up to 29 min caused highly significant reductions in bacterial counts (p < 0.01 to p < 0.001). Gram-positive cocci and rods as well as Gram-negative rods were found during spoilage of the fresh cheese.

Key words: Response surface methodology (RSM), microbial quality, cheese, spoilage, shelf-life.