Shelf-life boundaries of Listeria monocytogenes in cold smoked salmon during refrigerated storage and temperature abuse

Abstract

Cold smoked salmon (CSS) is a high-value ready-to-eat product, but it generally has a short shelf-life even under refrigeration and can support the growth of Listeria monocytogenes. Therefore, the objective of this study was to examine the growth and survival of L. monocytogenes in CSS during refrigerated storage and temperature abuse.The growth and survival data of L. monocytogenes (116 records, 465 data points) were retrieved from ComBase (https://www.combase.cc). All records contained storage time and temperature, but other information (aw, pH, and salt) was not fully documented. Each data point, normalized with the initial population to calculate relative growth (RG, log CFU/g), was used to classify the probability of growth. Eighty percent (80%) of the data were randomly sampled for examining the effect of storage time and temperature on growth of L. monocytogenes, while the remaining 20% were set aside for model validation.Logistic regression was used to develop a model for classifying L. monocytogenes growth according to 7 different control thresholds (CT), ranging from 0 to 3 log CFU/g in RG. A probability threshold was set to judge if the bacterial growth has exceeded a CT. The validation showed > 89% of true negative rate for not exceeding the control thresholds. A dynamic method was then developed and demonstrated to predict the growth probabilities under fluctuating temperature conditions. The result of this study suggested that storage time and temperature could be used to predict the growth of L. monocytogenes in CSS and to control listeriosis using a risk-based strategy. It can be used by the retailers and consumers to determine if a packaged product is safe to consume based on its time and temperature history.