Modelling survival behaviour of Salmonella enterica ser. Enteritidis, Typhimurium and Tennessee on table eggs during storage at different temperatures

Effect of nisin, EDTA, and abuse temperature on the growth of Salmonella Typhimurium in liquid whole egg during refrigerated storage

Salmonella spp. can be present in pasteurized liquid egg products because of its heat resistance or post-processing contamination, thereby representing a food safety risk. The effect of 1000 IU nisin/ml plus 20 mM disodium ethylenediaminetetraacetic acid (EDTA), two refrigerated temperatures (7 °C and 10 °C), and two inoculation levels (103 and 105 cfu/ml) were studied in the growth of S. Typhimurium in pasteurized liquid whole egg (LWE). Two mathematical models were used to fit the microbial curves. Physicochemical characteristics of LWE, such as pH and color, were assessed for 31 days at the two storage temperatures, and no significant changes (p < 0.05) were observed for most of the samples. Results showed the significant impact of temperature on microbial growth. Samples kept at 7 °C showed the decay of microbial cells during storage; meanwhile, the effect at 10 °C was shown as fast growth. The combination of nisin plus EDTA and 7 °C accelerated the decay of microbial cells during the storage showing a synergistic effect. The Weibull model described the decline of cells during the shelf-life. Meanwhile, the logistic model fitted the growth of Salmonella in LWE at 10 °C. Adding these additives to LWE, combined with the correct temperature during pasteurization and adequate conditions during the cold chain, can minimize the food safety risk related to Salmonella.

Viability of Salmonella Typhimurium biofilms on major food-contact surfaces and eggshell treated during 35 days with and without water storage at room temperature

Salmonella is one of the main foodborne pathogens that affect humans and farm animals. The Salmonella genus comprises a group of food-transmitted pathogens that cause highly prevalent foodborne diseases throughout the world. The aim of this study was to appraise the viability of Salmonella Typhimurium biofilm under water treatment at room temperature on different surfaces, specifically stainless steel (SS), plastic (PLA), rubber (RB), and eggshell (ES). After 35 D, the reduction of biofilm on SS, PLA, RB, and ES was 3.35, 3.57, 3.22, and 2.55 log CFU/coupon without water treatment and 4.31, 4.49, 3.50, and 1.49 log CFU/coupon with water treatment, respectively. The d_R value (time required to reduce bacterial biofilm by 99% via Weibull modeling) of S. Typhimurium without and with water treatment was the lowest on PLA (176.86 and 112.17 h, respectively) and the highest on ES (485.37 and 2,436.52 h, respectively). The viability of the S. Typhimurium on ES and the 3 food-contact surfaces was monitored for 5 wk (35 D). The results of this study provide valuable information for the control of S. Typhimurium on different surfaces in the food industry, which could reduce the risk to consumers.