Enterococci and pseudomonads as quality indicators in industrial production and storage of mozzarella cheese from raw cow milk

High-moisture raw milk mozzarella cheese (RMMC) is highly susceptible to microbial contamination. Enterobacteriaceae are often used as indicators of microbial quality. Complementary indicator organisms could provide additional surveillance information for RMMC plant hygiene, quality and safety during production and storage. The suitability of Pseudomonas spp. and Enterococcus spp. as indicator organisms in addition to Enterobacteriaceae for RMMC quality in production and storage was assessed. Curd stretching (85 °C) reduced enterococci from 3.8 to 4.9 to <2.0-2.7 log10 cfu g−1, followed by growth to 7.2 log10 cfu g−1 after 27 days storage at 8 °C. Enterobacteriaceae and Pseudomonas spp. were reduced below the detection limit (2.0 log10 cfu g−1). Pseudomonas spp. were only detected in one out of four batches in storage tests. Therefore, post-process contamination by Pseudomonas spp. and survival of enterococci support their recommendation as additional indicator bacteria for plant hygiene, product quality, spoilage and possibly safety of RMMC.