Microbiological and physicochemical properties of smoked ricotta cheese during refrigeration and temperature abuse storage

In the last years changes occurred in the production process of ricotta mustia, a traditional smoked, salted and sometimes ripened ricotta cheese, produced in Sardinia. Fresher, slightly smoked and with reduced salt content products, were introduced into the market to meet changes in consumer's preferences for milder products. The present study of durability was conducted on an innovative fresh and smoked industrial product, also characterized by the small size and the packaging in modified atmosphere. A durability test to assess the evolution of microbiological and physicochemical profile of the product stored at refrigeration (4 degrees C) and mild abuse (7 degrees C) temperatures was carried out. A total of 126 ricotta samples smoked for either 1, 2, or 3 h were analyzed at intervals during shelf-life for the determination of aerobic mesophilic counts, Enterobacteriaceae, yeast, moulds, L. monocytogenes, Pseudomonas spp. and B. cereus. Intrinsic properties, physic-chemical and headspace gas composition were also analyzed. Average and standard deviation were respectively 6,06 +/- 0,22 for pH, 0,982 +/- 0,05 for aW, 74,67%+/- 1,81% for moisture, 10,25%+/- 1,35% for fat, 10,92%+/- 0,46% for protein and 1,70%+/- 0,42% for salt content. Total bacterial count ranged between 3.88 +/- 0.48 log cfu/g at T-0 and 3.25 +/- 1.02 at T-45. L. monocytogenes, Pseudomonas spp. and E. coli were always below the detection limit. Enterobacteriaceae prevalence (percentage) was 3.17% (2.62 +/- 0.42 lg10 cfu/g) and was limited to samples stored longer than 30 days while B. cereus was recovered in 5.55% (2.36 +/- 0.35 lg10 cfu/g) of the samples and was never observed in samples after 45 days of refrigerated storage. The durability study is preliminary to challenge test to assess the shelf-life of this product in compliance with the requirements of Regulation (EC) 2073/2005.