Journal article
Enterococcus faecium as a Salmonella surrogate in the thermal processing of wheat flour: Influence of water activity at high temperatures
Food microbiology, Vol.74, pp.92-99
09/2018
Handle:
https://hdl.handle.net/2376/104648
PMID: 29706342
Abstract
This study investigated the influence of temperature-dependent water activity (aw) on thermal resistances of Enterococcus faecium NRRL B-2354 (E. faecium) and Salmonella Enteritidis PT 30 (S. Enteritidis) in wheat flour. The aw for wheat flour samples at 20, 40, and 60 °C was determined by a vapor sorption analyzer and at 75, 80 and 85 °C using custom-built thermal cells with high temperature humidity sensors. Full-factorial isothermal inactivation studies of both strains in sealed aluminum-test-cells included three temperatures (75, 80, and 85 °C) and three aw,25°C levels (0.30, 0.45 and 0.60 within ±0.02 range, prior to the thermal treatments).
Isotherm results of wheat flour demonstrate a significant increase (P < 0.05) of aw as temperature rises (e.g. aw,25°C = 0.45 ± 0.02 became aw,80°C = 0.71 ± 0.02 in a closed system). Inactivation kinetics of both microorganisms fitted a log-linear model, the yielded D-values varied from 2.7 ± 0.2 min (D85°C of S. Enteritidis at aw,25°C 0.60 ± 0.02) to 65.8 ± 2.5 min (D75°C of E. faecium at aw,25°C 0.30 ± 0.02). The zT of E. faecium and S. Enteritidis decreased from 16.4 and 16.9 °C, respectively, to 10.2 °C with increased moisture content (dry basis) from 10 to 14%.
Under all tested conditions, E. faecium exhibited equal or higher (1.0–3.1 times) D- and zT-values than those of Salmonella. Overall, E. faecium should be a conservative surrogate for Salmonella in thermal processing of wheat flour for control of Salmonella over a moisture content of 10–14% and treatment temperatures between 75 and 85 °C.
•Water sorption isotherms of wheat flour at 20, 40, 60, and 80 °C are provided.•At fixed moisture content, water activity of wheat flour increased as temperature rose from 25 to 80 °C.•Reduced water activity increased D-and zT-values of Salmonella and E. faecium in wheat flour.•E. faecium appears to be a valid surrogate for thermal inactivation of Salmonella in wheat flour.
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Details
- Title
- Enterococcus faecium as a Salmonella surrogate in the thermal processing of wheat flour: Influence of water activity at high temperatures
- Creators
- Shuxiang Liu - Department of Biological Systems Engineering, Washington State University, Pullman, WA, USARossana V Rojas - Escuela de Ingeniería y Ciencias, Tecnologico de Monterrey, Monterrey, Nuevo León, MexicoPeter Gray - Department of Biological Systems Engineering, Washington State University, Pullman, WA, USAMei-Jun Zhu - School of Food Science, Washington State University, Pullman, WA, USAJuming Tang - Department of Biological Systems Engineering, Washington State University, Pullman, WA, USA
- Publication Details
- Food microbiology, Vol.74, pp.92-99
- Academic Unit
- Biological Systems Engineering, Department of; Food Science, School of
- Publisher
- Elsevier Ltd
- Identifiers
- 99900547065501842
- Language
- English
- Resource Type
- Journal article