P1-34 Heat Resistance Stability of Enterococcus faecium NRRL B-2354 and Salmonella Enteritidis PT30 on Almonds during Extended Storage at 4 and 25°C

Monday, August 4, 2014
Exhibit Hall D (Indiana Convention Center)
Shirin Abd, The National Food Lab, Livermore, CA
Carrie Ferstl, The National Food Laboratory, Inc., Livermore, CA
Introduction: Almond Board of California published protocols for the preparation, storage, and heat resistance verification of Enterococcus faecium NRRL B-2354 on inoculated almonds prior to use as a surrogate for Salmonella Enteritidis PT30. The protocol specifies storage at a temperature of 4°C for up to 14 days followed by heat treatment at 280°F for 15 minutes in a Fisher Scientific Isotemp 851F oven (Forced Air) to verify heat resistance. This study investigates extension of the specified shelf life. 

Purpose: The purpose of this study was to evaluate the change in heat resistance of Enterococcus and Salmonella on inoculated almonds during 60 days of storage at 4 and 25°C.

Methods: Almonds were inoculated with Enterococcus or Salmonella, and stored at 4 or 25°C. Over 60 days of storage, inoculated almonds were sampled periodically and heat-treated using Forced Air (280°F/15 minutes) and Gravity Ovens (300°F/15 minutes). Log reductions following heat treatment for each storage condition and sampling time (n = 6) were compared using ANOVA.

Results: Log reductions of Enterococcus following both oven treatments over 60 days of storage were not significantly different (P > 0.05) when inoculated almonds were stored at 4°C, and ranged between 0.91 ± 0.55 and 1.84 ± 0.82 logs (n = 6), or 0.25 ± 0.12 and 0.83 ± 0.43 logs (n = 6) for Forced Air and Gravity Oven treatments, respectively. Conversely, differences between log reductions of Enterococcus on almonds were statistically significant (P < 0.05) for both oven treatments over 60 days of storage at 25°C. No significant differences were observed for Salmonella on almonds stored at either 4 or 25°C over a period of 60 days in either oven type. 

Significance: Results indicate that the current shelf life of almonds inoculated with Enterococcus can be extended to 60 days at 4°C without significant impact to the heat resistance of this organism.