Purpose: The objective of this study was to determine the effects of natural preservatives, added ingredients, and temperature on growth and histamine (Hst) production by Mm in tuna salad preparations.
Methods: Ten (Hst analysis) and twenty-five (MPN-PCR) g of plain tuna salad (TS) and tuna salad with sanitized celery and onion (C/O) were inoculated with a three-strain cocktail of Mm (2 log CFU/g) that were previously isolated from raw scombroid fish. DV, a natural buffered vinegar powder (WTI, Inc., Jefferson, GA), was added to treated preparations at a concentration of 2% by weight; untreated preparations were used as controls. Samples were stored at 4° and 10°C for 4 weeks and 25°C for 3 days. HPB (Mm) were enumerated by MPN-PCR; Hst was determined fluorometrically.
Results: Mm did not grow at 4°C. At 10°C, Mm numbers ranged from 4 log MPN/g (307 ppm Hst) in TS to 8.3 log MPN/g (1164 ppm Hst) in C/O after 4 weeks. At 25°C, Mm numbers were 8.9 log MPN/g in both TS (1855 ppm Hst) and C/O (1589 ppm Hst) after 3 days. DV inhibited growth of Mm in TS and C/O at 10° (1.8 log MPN/g after 4 weeks) and 25°C (2.3 log MPN/g after 3 days).
Significance: We established that storage of TS and C/O at 4°C and addition of DV to TS and C/O inhibit Mm growth and Hst production that can result from temperature abuse of prepared tuna salad.