Objectives

To evaluate the effect of SCF CO2 on cultures of the most critical contaminants commonly isolated from oysters (Vibrio vulnificus, Vibrio parahaemolyticus) and determine the proper conditions (temperature, pressure and time) to achieve the optimum bacterial inactivation in whole oysters after exposure to SCF CO2.

Methodology

Culture of Vibrio vulnificus and Vibrio parahaemolyticus will be treated with SFC CO2 at different temperatures, pressures, and exposure times. The quantification of Vibrio vulnificus will be completed on TSBS agar and specific media: CC agar for V. vulnificus and TCBS for V. parahaemolyticus. Optimization of the SFC CO2 conditions for whole oysters will be achieved by design and analysis experiments at different temperatures, pressures, and exposure times using orthogonal design. Microbial analysis of whole oysters will be conducted following the Bacteriological Analytical Manual (FDA, May 2004) and The Laboratory Procedure for the Examination of Seawater and Shellfish (American Public Health Association, 1985).

Rationale:
Seafood products carrying pathogenic organisms are dangerous when consumed raw and in large quantity. Of these products, oysters are of greatest concern and have been shown to be responsible for the largest number of outbreaks in infectious diseases related to the consumption of seafood products by a significant margin.  The development of milder techniques for pasteurization or inactivation will not only help extending the shelf life of these products but will also significantly reduce the transmission of seafood borne infectious diseases.  The use of dense phase carbon dioxide (DPCD) has generated interest in this regard, and has been applied to a few popular beverages and food products. The unique physical properties of SCF CO2 allow quick penetration of tissues producing an antibacterial and enzyme deactivating effect. Our preliminary data revealed the ability of SCF CO2 to significantly reduce the population of bacteria in whole oysters.