Whole oysters were processed under a series of pressures from 30,000 to 45,000 psi at different holding times (0, 1, and 2 min) and then stored at <4°C, for 27 d. During the shelf-life study, the quality of oysters was determined by measuring pH, moisture content, and microbial counts including aerobic, anaerobic bacteria and coliform. Descriptive testing was also performed by a trained panel. The pH of high pressure process (HPP) samples decreased slightly from 6.3 to 5.7 during storage while the control dropped to pH 4.4. Moisture content of the control decreased slightly while HPP samples increased slightly. Pressure treatment did not significantly inhibit lipase activity during the shelf-life study. HPP reduced initial microbial load by approximately 2-3 logs and counts remained at a reduced level through the storage study. Descriptive tests showed that HPP treated oysters received higher quality scores than the control during the storage trial. Whole oysters were shucked under pressure of 35,000 psi, 2 min. After shucking, oyster meats were water packed in plastic containers and repressureized. Tests were performed at 45,000 psi, 30 s and 50,000 psi (0 holding time, 10 s). All samples were stored at <40C for 25 d. During the shelf-life study, oyster quality was determined by measuring pH, moisture content, protease, and microbial counts including aerobic, anaerobic bacteria and coliform. The pH of HPP samples decreased slightly from 6.5 to 5.7 during storage while the control I, hand-shucked oysters, dropped to pH 4.3. Pressure treatment seemed to increase protease activity during the shelf-life study. HPP reduced initial microbial load by approximately 2-3 logs and inhibited microbial growth during storage. / Graduation date: 2001