Evaluation of internal temperature of oysters following standard thermal process recipes

Abstract

Background & Purpose: The seasonal demand for shellfish such as oysters is on the rise. Shellfish are nutritious foods that may be enjoyed in a variety of ways, from slurping raw oysters to cooking oysters by means of boiling, steaming, pan frying and baking. Most consumers of oysters are aware of potential food safety issues with shellfish. Raw or undercooked shellfish can carry bacteria, viruses and toxins, potentially resulting in foodborne illness. Past outbreaks associated with the consumption of raw and undercooked oysters, prompted the British Columbia Centre for Disease Control (BCCDC) to develop guidelines for those preparing, cooking and consuming shellfish. The recommended cooking temperature and time from the guideline was compared with the temperature and time of standard cooking methods from the Fanny Bay Oyster Market restaurant. The purpose of this project was to determine whether standard cooking methods from restaurants attain the guideline’s recommended 90oC for 90 seconds. Method: Four common cooking methods of Oysters were chosen based on recommendation from Chef Chris Andraza and BCCDC researcher Lorraine McIntyre. Oysters were pan fried, deep fried, baked and grilled. Internal temperatures of cooked oysters were then measured with a probe thermometer. Results for each method were analyzed and compared with the standard of 90oC using the one sample t-test from the statistical software package, NCSS11. Results: One sample t-tests showed statistically differences from the deep fried, baked and grilled methods when compared to the standard of 90oC (p = 0.000). The power for all three methods was 100%, therefore there is confidence that the findings reflect the truth. Experimental temperatures were consistently less than the standard. The pan fried method showed no statistically significant difference when compared to the standard of 90oC (p = 135). The power for pan fried method was 29.2%, therefore there is limited confidence that the findings reflect the truth. Therefore the deep fried, baked and grilled methods required additional cooking time to raise internal temperatures of the oysters. Whereas the pan fried method had achieved the standard but further experimentation is required to eliminate the chance of a type II error. Conclusion: It can be concluded that three out of the four cooking methods (deep fried, baked and grilled) can have significantly different mean temperatures. However, different thermal preparation methods prior to final thermal processing requires consideration to determine cooked oyster consumption safety. One out of the four cooking methods (pan fried) attained the standard temperature 90oC. Therefore, it is recommended for deep fried, baked and grilled cooking methods that the cooking time be extended to achieve an internal temperature of 90oC or higher.