Rapid Cooling of Eastern Oysters (Crassostrea virginica) Using an On-Board Icing Unit to Slow the Growth of Vibrio vulnificus and Vibrio parahaemolyticus

Abstract

Oyster harvesting is a major industry along the Eastern and Gulf coasts of the United States. Eastern oysters (Crassostrea virginica) spawn when the waters start to warm between May and October in the Gulf of Mexico. The warmer temperature creates a problem with an increase of bacteria. The two major bacteria affecting the oyster industry are Vibrio vulnificus and Vibrio parahaemolyticus. These bacteria are the leading causes of seafood-borne illnesses in the United States. This increase of V. vulnificus and V. parahaemolyticus has led to stricter time/temperature requirements for harvesting oysters. The regulations are not plausible for smaller vessels too small to hold a refrigeration unit. Chilling the oysters to lower Vibrio levels using an on-board icing unit was proposed for further investigation. The oysters were tested for V. vulnificus and V. parahaemolyticus at each stage along with tested for gaping after 7 and 14 days in refrigerated storage. This experiment was conducted in May, July, and September 2015. The results will help advance the use of triploid oysters as viable options for the oyster industry during the spawning of diploid oysters. The total Vibrio parahaemolyticus and Vibrio vulnificus results were log10 transformed to compare the treated and controlled data for all three months. The data was run through a mixed procedure in SAS 9.4. The V. parahaemolyticus showed a significant difference in the sampling months (p<.001) but not a difference in the treatments (p=0.4715). The differences in the Vibrio vulnificus sampling months were significant (p<0.001) but not the treatments (p=0.2617). Pathogenic V. parahaemolyticus was not flourishing in this area. A difference could not be found in the months or treatment because of the low amounts of bacteria. The gaping data was significantly different between the iced and controlled oyster sacks (p<.001) along with the sampling months (p=.0014). Further work is needed to improve this design and process.