Survival of Listeria innocua and Listeria monocytogenes in muscle of cod (Gadus morhua L.) during salt-curing and growth during chilled storage of rehydrated product

Thermal inactivation and growth potential of Listeria innocua in rehydrated salt-cured cod prepared for ready-to-eat products

“…The strain L. monocytogenes NCTC 11994 has previously been used in thermal inactivation studies of minced beef (Bolton et al, 2000) and L. monocytogenes isolate No. 4006 has shown the ability to survive during the salt-curing process (Lorentzen et al, 2010). A volume of 0.5 mL of each bacteria culture at stationary phase was transferred to 6 mL glass tubes with diameter of 12 mm (VWR International, Leicestershire, UK) and heated at 60°C up to 180 s in a water bath (HAAKE 8, Germany).…”

“…From the loin part of the cod fillets, cubic samples of approximately 20 g each were cut. The cubes were either used directly, as fresh, or after rehydration of salt-cured muscle cubes as previously described (Lorentzen et al, 2010). The samples were screened for Listeria spp.…”

“…have only been studied to a very limited degree (Lorentzen et al, 2010). However, survival of L. monocytogenes after a pre-treatment at a low level of salt followed by an increase to 25% NaCl (Duche & Labadie, 2003) or to 20% NaCl (Adrião et al, 2008) have been reported.…”

“…Among the assortment of RTE products available today, some are prepared from salt-cured fish, such as cod (Lorentzen, Olsen, Bjørkevoll, Mikkelsen, & Skjerdal, 2010). Minced products of fresh or rehydrated salt-cured cod increase in popularity and they are used as cold cut, snacks, or as main ingredient in heated dishes.…”

“…Until recently, products of salt-cured fish have been considered microbiologically safe because of the salt-barrier. However, it has now been shown that L. monocytogenes is able to survive during salt-curing and grow in the rehydrated salt-cured product during storage (Lorentzen et al, 2010). Regarding products of minced fish, the possibility of undercooking of RTE products is present because of difficulties in controlling the core temperature.…”