Inactivation of Salmonella enterica and Enterococcus faecium NRRL B2354 on cumin seeds using gaseous ethylene oxide

Long Chen; Xinyao Wei; Byron D Chaves; David Jones; Monica A Ponder; Jeyamkondan Subbiah

doi:10.1016/j.fm.2020.103656

Inactivation of Salmonella enterica and Enterococcus faecium NRRL B2354 on cumin seeds using gaseous ethylene oxide

Food Microbiol. 2021 Apr:94:103656. doi: 10.1016/j.fm.2020.103656. Epub 2020 Oct 6.

Authors

Long Chen¹, Xinyao Wei², Byron D Chaves², David Jones¹, Monica A Ponder³, Jeyamkondan Subbiah⁴

Affiliations

¹ Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68583, USA.
² Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA.
³ Department of Food Science and Technology, Virginia Tech, Blacksburg, VA, 24060, USA.
⁴ Department of Biological Systems Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68583, USA; Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA; Department of Food Science, University of Arkansas, Fayetteville, AR, 72704, USA. Electronic address: jsubbiah@uark.edu.

PMID: 33279081
DOI: 10.1016/j.fm.2020.103656

Abstract

The objectives of this study were to investigate the effects of processing parameters (relative humidity (RH), temperature, and exposure time) on the ethylene oxide (EtO) microbial inactivation of Salmonella spp. and to evaluate Enterococcus faecium NRRL B2354 as a suitable surrogate for Salmonella inactivation on cumin seeds. Five grams of cumin seeds inoculated with either Salmonella or E. faecium were treated with EtO at different temperatures (46, 53, and 60 °C) and RH (30, 40, and 50%) levels for different exposure time to investigate the effects of process parameters on the microbial inactivation. The Weibull model fit the survival data of both bacteria with a shape parameter p < 1, which showed a tailing effect with concave shape indicating that the sensitive cells were inactivated first, and the sturdy ones survived at low RH treatment conditions. In general, the log reductions of both bacteria on cumin seeds increased with the increasing RH and temperature for EtO treatment. RH is a critical factor for successful EtO inactivation treatment. RH must be higher than 40% to implement a successful and efficient EtO decontamination of cumin seeds. E. faecium consistently showed lower log reductions than those of Salmonella under all EtO treatment conditions investigated in this study, demonstrating that E. faecium is a suitable surrogate for Salmonella. Twenty minutes of EtO treatment at 50% RH achieved ~5 log reductions of both bacteria at all three temperatures. A response surface model was developed to predict the log reductions of both bacteria under different treatment conditions and the contour plots representing log reductions were created. Inactivation is positively correlated to temperature and RH. Therefore, a higher temperature is required to achieve the desired log reduction at lower RH and vice versa. The developed response surface model is a valuable tool for the spice industry in identifying the possible combinations of EtO process parameters (temperature, RH, and exposure time) required to achieve a desired microbial reduction of Salmonella for ensuring microbial food safety of spices.

Keywords: Cumin seeds; Ethylene oxide; Response surface model; Salmonella; Spices; Surrogate.

Publication types

Evaluation Study

MeSH terms

Colony Count, Microbial
Cuminum / microbiology*
Enterococcus faecium / drug effects*
Enterococcus faecium / growth & development
Ethylene Oxide / chemistry*
Ethylene Oxide / pharmacology*
Food Preservation / instrumentation
Food Preservation / methods*
Food Preservatives / chemistry
Food Preservatives / pharmacology
Food Safety
Gases / pharmacology
Microbial Viability / drug effects
Salmonella enterica / drug effects*
Salmonella enterica / growth & development
Seeds / microbiology
Spices / microbiology
Temperature

Substances

Food Preservatives
Gases
Ethylene Oxide