18D-23 |
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R. A. MACKENZIE, A. P. Neilson, and F. M. Steele. Dept. of Nutrition, Dietetics & Food Science, Brigham Young Univ., S-221 ESC, Provo, UT 84602 Ceviche is a traditional fish dish served in Latin America. In place of cooking, ceviche relies on citrus juice acids to denature muscle tissue and inactivate microbes. The safety of ceviche is a concern due to the potential for microbial contamination of fresh fish and variations in preparation methods. There is conflicting data in the literature concerning the effectiveness of citrus juices in reducing microbial load. The purpose of this study was to examine the effects of various citrus juice treatments on bacterial survival in ceviche as well as to determine the buffering capacity of fish tissue. Fresh tilapia (Oreochromis spp.) fillets were purchased from a local vendor, cubed, and prepared according to a traditional Ecuadorian ceviche recipe using salt, onions, and citrus juice. The amount of citrus juice added varied from 0 to 1.5 mL per gram of tissue in 0.25 mL/gram increments. The prepared mixtures were refrigerated for 2.5 h. The pH of the marinades and the internal pH of the tissue were measured before and after refrigeration. Upon removal from refrigeration, representative samples from each treatment were diluted and homogenized. The homogenates were then plated in duplicate on Petrifilm® to obtain total and coliform plate counts. Log reductions ranged from 0 to 3.3 for total counts and from 0 to 3.4 for coliform counts, and reductions increased with increasing juice treatment. Coliform extinction was found for all juice treatments above 0.25 mL/gram. During the refrigeration period, the changes in tissue pH and solution pH ranged from -0.24 to 0.13 and from -0.14 to 0.46 pH units, respectively. Buffering of solution pH was minimal. Log reductions of total plate count increased with increasing juice treatment, and coliforms exhibited sensitivity to citrus juice. It appears that the volume of juice added to ceviche preparations influences the level of microbial inactivation.
Session 18D, Food Microbiology: General
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |