Control of growth and survival of Listeria monocytogenes on smoked salmon by combined potassium lactate and sodium diacetate and freezing stress during refrigeration and frozen storage

In this study, we evaluated the antimicrobial effects of different levels of a potassium lactate (PL) plus sodium diacetate (SDA) mixture against the growth and survival of Listeria monocytogenes Scott A inoculated onto smoked salmon stored at 4, 10, and -20degreesC. The effect of freezing stress on the growth kinetics of L. monocytogenes Scott A on smoked salmon at 4 and 10degreesC was also investigated. The use of PL+SDA at all tested levels (1.5, 3.3, and 5% of a 60% commercial solution of PURASAL P Opti.Form 4) completely inhibited the growth of L. monocytogenes Scott A On smoked salmon stored at 4degreesC during 32 days of storage. It also delayed the growth of L. monocytogenes Scott A on smoked salmon stored at 10degreesC for up to I I days, but a listeriostatic effect was observed only with 5% PURASAL P Opti.Form 4 at 10degreesC after 11 days. Addition of PL+SDA at all tested levels decreased the surviving populations of L. monocytogenes Scott A on smoked salmon during 10 months of frozen storage at -20degreesC. Freezing stress significantly (P < 0.001) extended the lag time and delayed the growth of L. monocytogenes Scott A at both 4 and 10degreesC. However, the effect of freezing stress was more significant at 4degreesC than at 10degreesC, indicating the importance of temperature control of smoked salmon during the retail storage period.