Combined Effect of Temperature and Relative Humidity on the Survival of Salmonella Isolates on Stainless Steel Coupons

• Published in: International journal of environmental research and public health 2022-01, Vol.19 (2), p.909
• Main Authors: Bashir, Amreen, Lambert, Peter A, Stedman, Yvonne, Hilton, Anthony C
• Format: Article
• Language: English
• Subjects: Colony Count, Microbial; Epidemics; Experiments; Factories; Food contamination & poisoning; Food Microbiology; Food products; Heat; Humidity; Inactivation; Manufacturing; Microorganisms; Plant shutdowns; Relative humidity; Salmonella; Stainless Steel; Storage conditions; Survival; Temperature; Temperature effects
• ISSN: 1660-4601; 1661-7827; 1660-4601
• DOI: 10.3390/ijerph19020909

The survival on stainless steel of ten isolates from food factory, clinical and veterinary sources was investigated. Stainless steel coupons inoculated with were dried and stored at a range of temperatures and relative humidity (RH) levels representing factory conditions. Viability was determined from 1 to 22 days. Survival curves obtained for most isolates and storage conditions displayed exponential inactivation described by a log-linear model. Survival was affected by environmental temperatures and RH with decimal reduction times (DRTs) ranging from 22 days. Furthermore, temperatures and RH independently influenced survival on stainless steel; increasing temperatures between 10 °C and 37 °C and increasing RH levels from 30-70% both decreased the DRT values. Survival curves displaying a shoulder followed by exponential death were obtained for three isolates at 10 °C/70% RH. Inactivation kinetics for these were described by modified Weibull models, suggesting that cumulative injury occurs before cellular inactivation. This study highlights the need to control temperature and RH to limit microbial persistence in the food manufacturing environment, particularly during the factory shut-down period for cleaning when higher temperature/humidity levels could be introduced.