## LSU Historical Dissertations and Theses

1996

Dissertation

#### Degree Name

Doctor of Philosophy (PhD)

#### Department

School of Nutrition and Food Sciences

Robert M. Grodner

#### Abstract

The AmeriPure Process (AmeriPure Oyster Company, New Orleans, Louisiana), which is a mild heat treatment for a specific time period, proved effective in eliminating Vibrio vulnificus from the Gulf Coast oysters (Crassostrea virginica), thus reducing the risk of possible V. vulnificus infections. The treatment was effective in the reduction of V. vulnificus in both $1.5\times10\sp5$ MPN/g (high artificially contaminated level) and $2.4\times10\sp3$ MPN/g (low artificially contaminated level) to undetectable level (MPN $<$ 3/g). The mild heat treatment also reduced naturally occurring V. vulnificus $(8.9\pm3.7\times10\sp4$ MPN/g) present in shellstock oysters harvested in warmer months to undetectable levels. The D value for V. vulnificus present in shellstock oyster averaged 45.6 $\pm$ 3.3 seconds at the AmeriPure Process temperature. Mild heat treatment can also control aerobic plate count numbers during refrigerated storage (0-2$\sp\circ$C) and extend the shelf-life of raw oysters for at least 7 days over unprocessed samples. Mild heat treated oysters need to be refrigerated (${<}4\sp\circ$C) to ensure the safety and quality, as well as shelf-life. Oysters treated according to the AmeriPure Process when exposed to an average room temperature of 27$\sp\circ$C were found unacceptable after 24 hours due to the high number of aerobic plate count (10$\sp7$ CFU/g) and were considered not safe to eat. Although there was a slight lightening in color, sensory panels, composed of both traditional raw oyster consumers and infrequent consumers, found the treated product to be comparable in flavor, texture and smell to untreated oysters. According to the result of sensory evaluation, the good oyster flavor of treated samples increased and the off-flavor and off-odor of the treated oysters were significantly lower than the control samples after 7 days of storage on ice. Possible temperature variations, which could occur during the transportation and storage were studied in a temperature abuse study. The result showed that no Vibrio vulnificus was recovered and no significant microbiological quality change was observed after 10 hours of exposure to the room temperature of $22\pm2\sp\circ$C.

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