Growth of Listeria monocytogenes Inoculated on Packaged Fresh-Cut Turnips Stored at 4 and 10°C

Abstract

The ecology of Listeria monocytogenes has been previously investigated in various whole and minimally processed raw vegetables, but not in turnips. A 2018 national Canadian recall for packaged fresh-cut turnips contaminated with L. monocytogenes raised concerns about turnips being able to support the growth of this microorganism. Thus, this study examined the growth potential of L. monocytogenes in fresh-cut turnips stored at 4 and 10°C. The bacterial microbiota of each brand of purchased turnips was also partially determined to evaluate the diversity of bacteria present on the product. Turnips were mist inoculated at an initial level of 3.0 log CFU/g using a five-strain L. monocytogenes cocktail. Samples were then stored at either 4 or 10°C for 10 days, with enumeration occurring at 0, 5, and 10 days. L. monocytogenes did grow on turnips stored at 10°C, with increases ranging from 0.87 to 1.84 log CFU/g over the 10-day storage period (P < 0.05). In contrast, L. monocytogenes was able to survive but not grow on turnips stored at 4°C for 10 days. This study reinforces the importance of strict temperature control within processing, retail, and household consumer settings. Avoiding temperature abuse conditions and storing packaged fresh-cut turnips under refrigerator conditions (≤4°C) can serve as an important hurdle to prevent and/or limit the growth of L. monocytogenes on these products.