Controlling Listeria monocytogenes in fresh cheeses with high voltage atmospheric cold plasma (HVACP) treatment--Phase II

Obj 1. Evaluate direct HVACP treatment at 80 kV and 100 kV for 0, 1, 2 and 3 minutes Obj 2. Evaluate the effect of high voltage atmospheric cold plasma (HVACP) treatments on Listeria monocytogenes on queso fresco cheese with 28 days of storage. Obj 3. Examine the effect of HVACP treatments on quality of queso fresco cheese. Obj 4. Examine the effect of HVACP treatments on toxicity of queso fresco cheese. Abstract: The previously funded DMI project (Phase 1) demonstrated the ability of HVACP technology to significantly reduce Listeria innocua in QFC along with yeast and mold without significant changes to the product quality. The limitations of this previous study were small sample sizes of 25 grams, use of non-pathogenic Listeria innocua, and lack of toxicity testing. Phase II aims to develop and evaluate the ability of a high voltage atmospheric cold plasma (HVACP) decontamination system to reduce LM and extend shelf-life of Queso Fresco in a larger 100 g sample size. Also, initial toxicity testing of treated product will be performed. Because of the success in the first funded project (Phase 1), a Phase II research project has been developed to study the capability of HVACP treatment to inactivate multiple LM isolates from 100 gram samples of Queso Fresco Cheese over 28 days of shelf-life. Additionally, a toxicology assay and quality analysis (lipid oxidation and color) will also be performed on HVACP treated Queso Fresco cheese during 28 days of refrigerated storage. The toxicology proposed in this study is a preliminary examination. As a field of study, toxicology is a complex science similar to nutrition, where any single result has to be viewed in light of the experimental conditions no single result can be considered definitive in either a positive or a negative effect. Further, individual cells will show a range of different toxicities based on their growing conditions and their lineage. For this study, we have selected two different cell types for exposure to extracted materials from plasma treated cheese: epithelial cells (Caco-2) and Monkey kidney cells (COS-1). Assuming successful completion of this second study, we would look to develop a Phase III project scaling the technology for a suitable container or industrial process line, further reduce the required treatment time and build a prototype that could be easily adapted to the current fresh cheese manufacture, and perform sensory evaluation of treated cheeses.