Hygienic conditions and microbial contamination in six ewe's-milk-processing plants in Sardinia, Italy

Abstract

In Sardinia, ewe's milk is almost exclusively used for cheese manufacture, and it is usually processed in small dairies which do not have sufficient technical and scientific knowledge for large-scale controlled production. This study was carried out to identify the sources of contamination and the kinds of contaminating microorganisms present in six ewe's milk processing plants in Sardinia. Samples were collected during production hours three times over a period of 6 months. Raw milk, heat-treated milk, curd. 30-day-old cheese, lactic culture, rennet, and water used in processing lines were analyzed and the microbial contamination of air and surfaces was evaluated. Total mesophilic aerobic counts, coliforms, Escherichia coli, gram-negative psychrotrophs. Staphylococcus aureus, Salmonella spp., Listeria spp., yeasts, and molds were determined. Our survey confirmed that the production of food of high microbiological quality is strictly dependent on the microbiological quality of the raw material, optimization of the parameters for the heat treatment, water of potable quality, well-defined cleaning and disinfection procedures, and properly hygienic processing conditions. In fact, only plants characterized by raw milk and rennet of acceptable quality, generally clean work surfaces, and low microbial counts in the air of working areas made finished products of high microbiological quality. Standardization of technological parameters and achievement of properly hygienic processing conditions will help minimize the risk of developing food-safety problems, in compliance with public health regulatory requirements. These actions would help guarantee an adequate quality of Sardinian ewe's milk cheeses and might also lead to access to the international market.