Fate of Escherichia coli O157:H7 and Salmonella on fresh and frozen cut pineapples.

Abstract

Pineapples have been associated with outbreaks of Escherichia coli and Salmonella. Little is known about the behavior of E. coli O157:H7 and Salmonella on cut pineapple. The objectives of this study were to evaluate the fate of E. coli O157:H7 and Salmonella on fresh and frozen cut pineapples and the influence of acid adaptation on Salmonella survival on fresh cut pineapple at ambient storage (23 degrees C). Cut pineapples were spot inoculated with a four-strain cocktail of E. coli O157:H7 or a five-strain cocktail of Salmonella. Inoculated samples were air dried, placed in containers, and stored at 4, 12, 23, and -20 degrees C. Samples were stomached and then enumerated on nonselective and selective media at days 0, 1, 3, 5, 7, 10, 14, 21, and 28 (4 and 12 degrees C); 0, 1, 3, 5, and 7 (23 degrees C); and 0, 7, 14, 21, 28, 60, 90, 120, 150, and 180 (-20 degrees C). E. coli O157:H7 and Salmonella inoculated onto pineapple did not grow but survived for the shelf life at each temperature, with improved survival at lower temperatures. E. coli O157:H7 and Salmonella can survive on frozen cut pineapples for at least 180 days. Acid adaptation of Salmonella did not allow growth and did not increase survival. Fresh and frozen cut pineapples are potential vectors for E. coli O157:H7 and Salmonella transmission and preventive procedures should be implemented during production and postharvest processing.