An Investigation of the Shelf-life of PDO Vastedda della Valle del Belice Cheese Subjected to Different Packaging Systems Alternative to Vacuum

Abstract

The aim of this study was to evaluate the effect of different packaging systems alternatives to vacuum that is commonly applied for PDO Vastedda della Valle del Belice (VdB) cheese, a tipical pasta filata cheese, made with raw ewes’ milk. After production following the traditional cheesemaking protocol, VdB cheeses were packaged as follows: vacuum, paraffin wax and two different Modified Atmosphere Packaging (MAP) consisting of a gas mixture of 70% CO2-30% N2 (MAP1) and 100% N2 (MAP2). Cheeses were stored at 4°C and analyzed (25 g) at time 0 and after 15, 30, 60, 90, 120 and 180 days. All the samples were subjected to microbiological analyses for the evaluation of total mesophilic aerobic bacteria, Enterobacteriaceae, total coliform, Escherichia coli, enterococci, lactic acid bacteria, positive coagulase staphylococci, sulphite reducing anaerobes, Pseudomonas spp., Listeria monocytogenes and Salmonella spp.). Moreover, the physicochemical parameters such as pH, water activity, dry matter, fat, protein, salt, total solids, total and soluble nitrogen and ash content were also determined. Chemical, physical and microbiological data were analyzed by a two factors ANOVA model (GLM procedure of SAS) which included the effect of packaging and time of storage. The results did not show significant differences among chemical and physical parameters of the cheeses subjected to the different packaging during storage. No pathogens and spoilage microbial species/group were detected in any of the samples examined. Lactic acid bacteria reached the highest levels for all samples. Total microbial counts detected for paraffin packaged cheeses were higher than those of the other cheeses, regardless the storage time. This observation was probably due to the higher percentage of oxygen allowed by paraffin respect to the other packaging strategies. For this reason, paraffin was excluded as a possible tool for long term storage of VdB cheese. It was also observed an increase of the total microbial load in all packaging systems after 60 days of storage. Sensory analyses are still ongoing.