CARATTERIZZAZIONE IGIENICO-SANITARIA E QUALITATIVA DI CAGLI TRADIZIONALI SICILIANI

ABSTRACT Artisanal lamb rennet paste is used for the production of some Sicilian PDO, Slow Food and PAT cheeses. This enzyme complex is considered not only as processing adjuvant, but also as ingredient able to influence the microbial flora of cheese. The artisanal lamb rennet preparation is generally empiric and depends on the farmers tradition. The aims of this study were: i) characterize the artisanal rennet used by Sicilian farms; ii) observe the effect of different processing techniques on the microbiological and enzymatic features of rennet; iii) study by challenge test, the effect of NaCl on the Clostridium perfringens; iv) evaluate the effect of this microorganism on cheesemaking. Twenty-two samples analyzed showed an acid pH (around pH 4,0) and a low aw (< 0,760). Lipolytic activity, determined with titrimetric method, is rather high in most of the rennets, and the milk-clotting activity evaluated using a Formagraph apparatus, resulted variable. Microbial flora was characterized by absence of pathogenic bacteria. Coliformi, Enterobasteriaceae and Escherichia coli were present only few samples. Lactic bacteria and Clostridium sulphite-reducing were, instead, the most characterizing. Five production were examined to observe the effect of different techniques on the features of rennet. In all the samples the value of Enterobacteriaceae, total Coliforms and Escherichia coli were always < 2 Log CFU/g until T30 (Aw < 0.770; pH <4.6), reaching charge < 1 Log CFU/g at the end of process Tf (Aw < 0.760; pH <4.5). The detection of Salmonella spp. and Listeria monocytogenes was always negative. Yeast and molds were found at T0, T30 and T60 only in the sample maintained at room temperature. The presence of Clostridium were independent by salting conditions. The charge of lactic acid bacteria decrease during the process (from T0 to T60) until to result absents at T180, except for the samples, in which were added cheese before blending. According to previous studies, the lipolitic and proteolytic activity depend on type of feeding of young lambs. These results showed the good hygienic quality of artisanal rennet. The challenge test for Cl. perfringens highlighted as the survival of this microorganism was independent of the amount of added NaCl and thermal shock, thanks to its ability to generate spores