P1-155 Effects of Vinegar Powder and Storage Temperature on Morganella morganii Growth and Histamine Production in Tuna Salad

Monday, August 1, 2016
America's Center - St. Louis
Susan McCarthy, U.S. Food and Drug Administration, Gulf Coast Seafood Laboratory, Dauphin Island, AL
Kristin Bjornsdottir-Butler, U.S. Food and Drug Administration, Gulf Coast Seafood Laboratory, Dauphin Island, AL
Ronald Benner, U.S. Food and Drug Administration, Gulf Coast Seafood Laboratory, Dauphin Island, AL
Jasdeep Saini, WTI, Inc., Jefferson, GA
Introduction: Scombrotoxin (histamine) fish poisoning is associated with consumption of scombroid fish species such as tuna.  Commercial tuna salad can present a food safety hazard when contaminated with histamine-producing bacteria (HPB) (e.g., Morganella morganii; Mm) from food handlers, processing equipment, or added ingredients, and combined with temperature abuse during processing/storage.

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.