SURVIVAL OF THREE SALMONELLA SEROTYPES ON BEEF TRIMMINGS DURING SIMULATED COMMERCIAL FREEZING AND FROZEN STORAGE

Abstract

This study investigated the survival of three Salmonella serotypes (S. Brandenberg, S. Dublin and S. Typhimurium) on beef trimmings during simulated commercial freezing, frozen storage for 9 months and subsequent abusive slow thawing and refreezing conditions. This was achieved by plating samples monthly and after thawing and refreezing on nonselective Tryptic Soy Agar (TSA) and selective Xylose Lysine Desoxycholate Agar (XLD) and incubating both at 37C for 24 h to determine Salmonella counts, aerobic counts and the presence, if any, of sublethal injury of this pathogen. Two freezing temperatures (−18C or −35C) to simulate slow or rapid freezing respectively, and two inoculation levels (103 cfu g−1 or 105 cfu g−1) were used. Aerobic counts and counts of all the Salmonella serotypes did not change significantly (p > 0.05) during frozen storage or for any of the other treatments applied in this study. This finding was attributed to the insulating nature of the subcutaneous fat layer in this manufacturing cut. These results are important with respect to food safety associated with ground beef processing.

Combined high pressure–sub-zero temperature processing of smoked salmon mince: phase transition phenomena and inactivation of Listeria innocua

“…No significant inactivation nor sub-lethal injury of Listeria innocua was observed. The absence of microbial inactivation during conventional freezing has been reported for various micro-organisms (Bolton et al, 2002;Dykes & Moorhead, 2001;Moorhead & Dykes, 2002;Novak & Juneja, 2003).…”

Microbial inactivation by pressure-shift freezing: effects on smoked salmon mince inoculated with Pseudomonas fluorescens, Micrococcus luteus and Listeria innocua

“…No significant reduction of bacterial counts was observed. Dykes and Moorhead (2001) investigated the survival of three Salmonella serotypes (S. brandenberg, S. dublin, S. typhimurium) introduced on beef trimmings (10% fat) during freezing at À18 C or À35 C. The evolution of aerobic plate counts of noninoculated beef trimmings was also studied. Aerobic counts and counts of all the Salmonella serotypes did not change significantly for either of the two freezing temperatures during the 9-month storage period.…”

“…Freezing and frozen storage of foods do not induce a marked inactivation of most detrimental microorganisms (Dykes & Moorhead, 2001;Uyttendaele, Vankeirsbilck, & Debevere, 2001;Moorhead & Dykes, 2002;Novak & Juneja, 2003). The effects of pressure processing on the inactivation of microorganisms present or introduced in foods are also well documented, but mainly for pressure treatments above 0 C (see Tewari, Jayas, & Holley, 1999).…”

Use of quantitative microbial risk assessment when investigating foodborne illness outbreaks: The example of a monophasic Salmonella Typhimurium 4,5,12:i:− outbreak implicating beef burgers

“…confidence intervals of means did not overlap, whatever the enumeration method was used. Even though the impact of thawing out for Salmonella in meat seems to be limited (Dykes and Moorhead, 2001;Lianou and Koutsoumanis, 2009), results from burgers I to V were not used for modelling initial contamination in thawed beef burgers.…”