N. P. Mangia - Department of Environmental Agricultural Sciences and Agro-Food Biotechnologies, University of Sassari, ۰۷۱۰۰ Sassari, Italy.
M. A. Murgia - Department of Environmental Agricultural Sciences and Agro-Food Biotechnologies, University of Sassari, ۰۷۱۰۰ Sassari, Italy.
G. Garau - Department of Environmental Agricultural Sciences and Agro-Food Biotechnologies, University of Sassari, ۰۷۱۰۰ Sassari, Italy.
P. Deiana - Department of Environmental Agricultural Sciences and Agro-Food Biotechnologies, University of Sassari, ۰۷۱۰۰ Sassari, Italy.

The effect of a selected autochthonous starter culture made up by Streptococcus thermophilus, Lactobacillus delbrueckii subsp. lactis and Lactobacillus helveticus on the microbiological and physicochemical properties of Pecorino Romano cheese during ripening was investigated. The suitability of the experimental starter culture was tested at industrial scales in cheese-making trials of Pecorino Romano. Pecorino Romano cheese manufactured by use of scotta-fermento served as control. The lactic microflora increased significantly in experimental cheeses as compared to the control and this was also accompanied by a substantial decrease of spoilage microorganisms in experimental cheeses. Free amino acids (FAAs) were more abundant in experimental cheeses, arginine+g-aminobutyric acid and leucine in particular. These differences could be likely due to a different enzymatic activity of the selected starter culture as compared to the scotta-fermento used in the control trials. Oleic (C۱۸:۱), palmitic (C۱۶:۰), butyric (C۴), stearic (C۱۸:۰) and myristic (C۱۴:۰) acids were the most abundant Free Fatty Acids (FFAs) detected in both brand of cheeses at the end of ripening. Overall, the level of FFAs in experimental and control cheeses did not show significant differences, even if the average values in experimental cheeses were always slightly higher than those recorded for the control. Moreover, the average content of FFAs of Pecorino Romano was found the lowest when compared with the other Sardinian PDO cheeses; most likely the high content of sodium chloride and the low aW of Pecorino Romano influenced all the lipase activities, even those present in the rennet paste. Despite this, the employment of the selected starter culture revealed useful to improve the physico-chemical features of Pecorino Romano while preserving its tipicity.

Autochthonous starter culture, Free amino acids, Free fatty acids, Pecorino Romano cheese, Thermophilic microflora