Evolution of the microbiological profile of vacuum-packed ricotta salata cheese during shelf-life

Abstract

<em>Ricotta salata</em> cheese is a salted variety of ricotta traditionally made in Sardinia (Italy) from the whey remaining after the production of <em>Pecorino Romano</em> protected designation of origin or other sheep milk cheeses. <em>Ricotta salata</em> cheese is very critical for the possible growth of pathogenic and spoilage microorganisms. Sporadic cases of listeriosis associated with <em>ricotta salata</em> cheese have been reported over recent years. The objective of the present study was to assess the evolution of spoilage and pathogen microorganism of vacuum-packed <em>ricotta salata</em> cheese during the entire product shelf-life. The durability study was conducted on 18 vacuum-packed <em>ricotta salata</em> cheese samples analysed at the beginning of the shelf-life and after 60 and 90 days of refrigerated storage. Pathogens as <em>Listeria monocytogenes</em> and <em>Bacillus cereus</em> were never detected. During shelf-life total bacterial counts ranged between 7.90±0.64 and 9.19±0.58 CFU g-1 on the rind and between 2.95±0.68 and 4.27±1.10 CFU g^-1 in the inner paste, while <em>Enterobacteriaceae</em> ranged between 4.22±0.66 and 5.30±0.73 CFU g^-1 on the rind and 3.13±1.80 and 2.80±0.88 CFU g^-1 in the inner paste. By considering the technology used, the intrinsic properties and the almost total absence of competing microflora, <em>ricotta salata</em> cheese can support the growth of spoilage and pathogen microorganisms originating from the processing environment. The high level of total bacterial counts and <em>Enterobacteriaceae</em> observed both on the rind and in the inner paste suggests contamination of the product from the processing environment. Therefore, a strict implementation of hygiene during processing is essential in order to reduce the load of environmental contaminants that may grow during refrigerated storage.