Effect of diet, cheese making techniques and ripening on D and L free amino acid content of milk and Pecorino cheese

Free L and D amino acid content in Pecorino cheese as affected by ripening, diet, and cheese making technique were studied. Free L and D amino acid contents were detected in Pecorino cheese manufactured using the milk obtained from 2 homogeneous groups of 240 Sardinian ewes fed 2 different diets: 1) pasture + commercial supplement (control); 2) pasture + commercial supplement along with a mixture of calcium salts of long-chain fatty acids (LCFA). In each group 2 different cheese making processes were used: a) from raw milk; b) from heat-treated milk with added native starter cultures. Milk and cheese samples at 7, 30, 60, and 180 d of ripening were taken for analyses. D-amino acids detected in milk were D-Glu, D-Asp, D-Lys, D-Ala and D-Tyr. Small differences between feeding treatments were detected in the cheese. Free amino acid content significantly increased during ripening. The use of starter cultures in heat-treated milk decreased the total content of free amino acids in cheese at the end of ripening. The amino acids most represented in ripened cheeses were L- and D-Glu (512,2 and 22,18 mg/100 g), L-Leu (270,8 mg/ 100 g), and L- and D-Lys (225,2 and 17,18 mg/100 g).