Evaluation of Enterococcus faecium NRRL B-2354 as a surrogate for Salmonella enterica in milk powders at different storage times and temperatures

Abstract

While the increase in thermal resistance of microorganisms at reduced water activity is demonstrated for low-moisture food products, the effect of storage time on the thermal resistance of microorganisms in lowmoisture foods is not well established. As low-moisture foods are stored for long periods and are used as ingredients, cross-contamination can occur at any time period before the lethality step. Therefore, this study was designed to investigate the effect of storage time (30, 60, and 90 d) on the thermal resistance of Salmonella and Enterococcus faecium NRRL B-2354 in milk powders at a low water activity of 0.10 (conservative level). In this study, 2 milk powders, whole milk powder (WMP) and nonfat dry milk (NFDM), were inoculated with a 5-serotype Salmonella cocktail or E. faecium and equilibrated to a water activity of 0.10. The thermal resistance of Salmonella and E. faecium in WMP and NFDM were determined at different storage times (30, 60, and 90 d) at 85°C. The storage time had no effect on the thermal inactivation kinetics of Salmonella within 90 d of storage at 85°C. In the second part of this study, isothermal treatments were also conducted at higher temperatures (90 and 95°C) to evaluate the suitability of E. faecium as a surrogate for Salmonella in milk powders. The D-values of Salmonella in WMP with 30 d of storage at 85, 90, and 95°C were 7.98, 3.35, and 1.68 min. The corresponding values for E. faecium were 16.96, 7.90, and 4.16 min. Higher D-values of E. faecium indicates that it is a conservative surrogate. Similar results were found for NFDM. In general, Dvalues of both microorganisms are slightly higher in NFDM than WMP. Two primary models (log-linear and Weibull) were compared for their goodness-of-fit. The Weibull model was found to be more appropriate than the log-linear model. This study provides valuable information for establishing process validation for the pasteurization of milk powders.

Persistence of Salmonella enterica and Enterococcus faecium NRRL B-2354 on Baby Spinach Subjected to Temperature Abuse after Exposure to Sub-Lethal Stresses

“…E. faecium NRRL B-2354 has recently been used as an effective surrogate when investigating the survival of S. enterica in low-moisture foods [ 52 , 53 ]. As far as we are aware of, there is still a paucity of evidence regarding the use of E. faecium NRRL B-2354 as a surrogate for S. enterica on leafy greens during storage.…”

Impact of food residue on recovery of Listeria monocytogenes and Salmonella Typhimurium from stainless steel surface

“…For all three LMF types, the preparation of the inoculated food residues is the same and adapted from Wei et al (2021). One hundred grams of food was weighed and poured into a stomacher bag with no filter.…”

“…Moreover, the FDA has administered six major recalls of bulk wheat and tree nut flours within the last decade (FDA, 2019a(FDA, , 2019b(FDA, , 2020b(FDA, , 2020c(FDA, , 2021(FDA, , 2023. Due to this evolving threat, there has been a significant amount of research conducted on the persistence and thermal resistance of Salmonella in LMF products and processing environments (Beuchat et al, 2011;Finn et al, 2013;Gruzdev et al, 2011;Koseki et al, 2015;Michael et al, 2022;Sekhon et al, 2021;Wei et al, 2021). This persistence in LMF and dry food processing environments was best demonstrated in the recurrent outbreak of Salmonella enterica serotype Agona in 1998 and 2008 in dry, unsweetened cereal manufactured by the same company at the same processing facility (Russo et al, 2013).…”

Evaluation of Various Lactic Acid Bacteria and Generic E. coli as Potential Nonpathogenic Surrogates for In-Plant Validation of Biltong Dried Beef Processing

“…A variety of organisms have been used as surrogates in place of pathogens to mimic pathogenic responses in commercial food processes, predominantly E. faecium, Pediococcus spp., and Biotype 1 E. coli. Enterococcus faecium ATCC 8459 (NRRL B-2354), used as a surrogate for Salmonella Enteritidis PT 30 in the thermal processing of wheat flour [11], as a S. enterica surrogate for storage time and temperature of milk powders [12], in thermal extrusion of low-moisture foods [13], and in plant-level validation of thermal processes for peanuts and pecans [14]. Investigators also found that Pediococcus strains had similar heat tolerances to Salmonella spp.…”