Evaluating the efficacy of ozonated recycled dairy process water against spoilage microorganisms: focus on Pseudomonas spp. and Enterobacteriaceae.

Fresh stretched-curd cheeses, such as high moisture mozzarella and burrata cheeses, consume approximately 3 liters of water for kilogram of cheese produced. The development of an innovative approach based on membrane filtration, ozonation, and electrolysis technologies, integrated by fermentation processes, has led to the recycling of dairy process waters. The use of these water bodies reduces the consumption of clean (blue) water enhancing dairy water footprint. In this work we evaluated the ability of dairy water deriving from a combined filtration/ozonation process to support the survival of nine spoiler strains usually contaminating process water, governing liquid (the low concentrated salt solution used to store high-moisture stretched cheeses under cold storage), and fresh cheeses. These strains, belonging to Pseudomonas, Escherichia, Serratia, Hafnia and Klebsiella genera, were incubated for 72 hours in the filtered/ozonated water or in the governing liquid. Governing liquid, with or without the inclusion of 1% skim milk powder, supported the growth of spoilage microorganisms, while filtered/ozonated water inhibited the growth depending on the strain. Growth curve parameters, such as average and maximum growth rate, time to max rate, time to change and the half-run absorbance value, for each strain were calculated confirming the ability of filtered/ozonated water to control the growth of spoiler microorganisms. At the end of incubation, viable cell counts for all strains in filtered/ozonated water (+1% skim milk) resulted lower than those in governing liquid (+1% skim milk) showing an average value of 2.07 log cfu/ml and 4.45 log cfu/ml for Pseudomonas and Enterobacteriaceae, respectively. The improved control of spoilage microbial populations by filtered/ozonated water, compared to the control governing liquid, suggests that fresh cheeses cold-stored in these recycled waters could show improved microbial quality and consequently an extended shelf life.