The effect of lime juice on Vibrio parahaemolyticus and Salmonella enterica inactivation during the preparation of raw fish dish ceviche

Ceviche is a Peruvian raw fish dish. It is extremely popular in the South American countries and has recently gained prominence in USA. It can be made with many types of seafood but is most commonly in USA with tilapia. The most characteristic feature of ceviche is the use of lime juice for marinating the raw fish. No ingredient of the dish is cooked in the conventional sense of applying heat. There have been confirmed cases of cholera in Peru, New Jersey and Florida, associated with ceviche. Since lime juice is sole means of controlling risk in ceviche recipes across the world, it is important to study its anti-bacterial effects. Even though the literature is very rich in the use of organic acids as anti-bacterial agents, little data exists for their effect in seafood systems. The objective of the study was to study the anti-bacterial effects of lime juice marination in ceviche as it would be prepared in restaurants or homes. Target pathogens were Vibrio parahaemolyticus and Salmonella enetrica. Samples were incubated at room temperature (25°C) and refrigeration temperature (4°C) for time intervals up to 150 minutes. In experiments with Salmonella at room temperature, a mean log reduction of 0.8 was observed while at refrigeration temperature a mean log reduction of 2.1 was observed. Reduction in Vibrio parahaemolyticus could only be estimated based on starting levels and detection limits as the plate counts were always below the detection limit for all the times studied (10-150 minutes), both at room and refrigeration temperatures. In experiments at room temperature, log reductions varied from >4.5 to >5.2 while at refrigeration temperature, log reductions varied from >3.5 to >4.3. In experiments testing the inhibitory effect of lime juice, without the fish matrix, more than 5 log reductions in counts was observed on both bacteria. We conclude that preparing ceviche reduces Vibrio parahaemolyticus risk significantly but is less effective for control of Salmonella enetrica.M.S.Includes bibliographical referencesby Prateek Mathu