51A-16

H. HE¹, R. M. Adams², and M. T. Morrissey¹. (1) Food Science&Technology/OSU Seafood Lab, Oregon State University, OSU Seafood Lab, 2001 Marine Dr, Rm 253, 1772 Jerome St., Astoria, OR 97103, (2) OSU Seafood Lab, Oregon State University, OSU Seafood Lab, 2001 Marine Dr. Rm 253, Astoria, OR 97103

The Use of High Hydrostatic Pressure to Shuck Oysters and Extend Shelf-life Haian He, Roger M. Adams, Michael T. Morrissey

JUSTIFICATION: Consumers demand for oysters that retain original nutrients, flavor and appearance presents a tangible obstacle towards insuring microbial safety. Previous research has demonstrated that hydrostatic pressure (HHP) is a 'heatless process', which has an effect on microorganisms survival and enzymatic activity in foods. In addition, preliminary work with HHP and whole oysters has indicated that this treatment could be used for mechanically shucking oysters.

OBJECTIVE: The objective of this study is to determine how shelf-life and microbial survival is affected when oysters are shucked by HHP.

METHOD: Whole oysters were processed under a series of pressures from 30,000 to 45,000 psi at different times (0, 1, and 2 min) and then stored at <4oC. During the shelf-life study, the quality of oysters was determined by measuring pH, moisture content, microbial counts including aerobic, anaerobic and coliforms. Sensory testing was also performed by a trained panel.

RESULTS: Results indicated that HHP did not significantly affect pH (range was between 5.8-6.3). Moisture content of the control decreased about 3% while HHP treated samples increased approximately 2%. Pressure treatment did not significantly inhibit lipase activity during the shelf-life study. It was observed that HHP significantly had an effect on reducing initial microbial load by approximate 2 or 3 logs. Sensory test showed HHP treated oysters received higher quality scores than that of control during a storage trial of 22 days.

SIGNIFICANCE: Results from this study demonstrated quality improvement in HHP shucked oysters. In addition, the use of HHP to shuck oysters will greatly benefit producers who have continual problems with labor shortages for this type of work.