Growth Characteristics of \u3ci\u3eLactobacillus wasatchensis\u3c/i\u3e and Its Detection and Enumeration Using Quantitative Polymerase Chain Reaction

There are numerous challenges encountered during the manufacturing and storage of cheese by both the large-scale and artesian producers. One such challenge has been the formation of late gassy defect, which occurs when gas is produced by certain lactic acid bacteria found in the cheese block during storage and aging over a three month time period. Negative consequences of late gas production are slits and cracks in the cheese block and puffy cheese packaging, which cause significant financial losses for manufacturers along with poor consumer acceptance. Lactobacillus wasatchensis is one such lactic acid bacterium shown to produce gas during cheese storage. This bacterium has now been found in cheese samples exhibiting late gas defect in the Midwest and Western states. The goal of this study was to further characterize and understand the growth attributes of Lb. wasatchensis, and thereby gain some understanding on how it enters the cheese vats and if there are possible ways to limit or inhibit its subsequent growth. An additional goal was to determine if we could effectively extract Lb. wasatchensis DNA from cheese samples and visualize using the qPCR molecular technique. If possible, this detection method would allow a faster and more sensitive approach to determining if Lb. wasatchensis is present in cheese blocks, which would help manufacturers know how long they should age their cheeses. It was discovered that Lb. wasatchensis does not survive processing through an industrial heat exchanger and therefore must be entering the cheese vats by other means such as: cross-contamination, biofilm formation or aerosolizing. We also showed growth of Lb. wasatchensis is limited at an increased salt-in-moisture ratio in cheese. Additionally, we found that Lb. wasatchensis DNA can be extracted from cheese and visualized using qPCR, although further experimentation is needed to optimize this method