Navigation

P1-63 Validation of Enterococcus faecium NRRL B2354 as a Surrogate for Salmonella in Thermal Treatment of Wheat Flour at Different Water Activities

Sunday, July 26, 2015
Exhibit Hall (Oregon Convention Center)
Shuxiang Liu , Washington State University , Pullman , WA
Qingping Zhong , Department of Biological Systems Engineering, Washington State University , Pullman , WA
Danielle Smith , Department of Biosystems and Agricultural Engineering, Michigan State University , East Lansing , MI
Rossana Villa-Rojas , Washington State University , Pullman , WA
Juming Tang , Washington State University , Pullman , WA
Mei-Jun Zhu , Washington State University , Pullman , WA
Bradley Marks , Michigan State University , East Lansing , MI
Introduction: Non-pathogenic surrogates are important tools for evaluating the efficacy of pathogen-reduction processes for low-moisture food products. Enterococcus faecium NRRL B2354 (EFB2354) has been identified as a surrogate for Salmonella in validating almond pasteurization processes; however, very limited information is available to support its use in other low-moisture products. 

Purpose: The objectives were: (1) To quantify thermal resistance of EFB2354 in wheat flour and compare it to the thermal resistance of Salmonella Enteritidis PT30 (SPT30) under the same conditions, and (2) To evaluate the stability of EFB2354 thermal resistance in wheat flour during storage (60 days) at 4°C. 

Methods: Wheat flour was inoculated with EFB2354 and SPT30, respectively, and equilibrated to different aw (0.25, 0.45 and 0.65 for EFB2354; 0.31, 0.43 and 0.60 for SPT30). The samples were sealed in small metallic cells, heated isothermally (70 - 85°C), cooled after treatment, plated, and enumerated to obtain thermal inactivation parameters (D- and z-values). For the storage test, thermal inactivation parameters were obtained every 14 days. 

Results: Results indicated log-linear kinetics for both organisms at all aw levels (R2=0.93 - 0.99). The D-values of EFB2354 were higher than those of SPT30 at all aw levels (e.g., at aw 0.44 ± 0.01 and 75, 80, and 85°C, D-values of EFB2354 were 22.02 ± 2.20, 7.29 ± 2.12 and 2.26 ± 0.04 min, respectively; the corresponding D-values of SPT30 were 9.97 ± 0.46, 5.51 ± 0.22 and 2.11 ± 0.09 min). The z-values of both varied from 10.1 to 21.8°C, depending on aw. The lowest were at aw 0.44 ± 0.01, with zEFB2354=10.12°C, zSPT30=14.83°C. No significant changes in population or thermal resistance were observed during 60 days at 4°C storage.

Significance: EFB2354 appears to be a valid surrogate for Salmonella in thermal treatment of wheat flour, and exhibits stable thermal resistance after 60 days storage at 4°C.

Back to: Poster Session 1 – Laboratory and Detection Methods, Low-water Activity; Retail and Food Service Safety; Seafood; Communication Outreach and Education; Produce; Food Toxicology; Non-microbial Food Safety; Food Defense; Microbial Food Spoilage
<< Previous Abstract | Next Abstract >>