Influence of milk source and ripening time on free amino acid profile of Picante cheese

The evolution of concentration of free amino acids in Picante cheese throughout ripening was studied for several volumetric ratios of ewe's and goat's milks. The concentrations of all free amino acids, except asparagine, gamma-aminobutyric acid, and cysteine, generally increased as ripening time elapsed. Analyses of variance have indicated that ripening time and, to a lesser extent milk composition have significant effects on the overall concentration of free amino acids. The major free amino acids present in the various cheeses along the ripening period were valine, leucine, and phenylalanine; these three amino acids accounted for 50, 49, 57, 46 and 42% of total free amino acids at 0 days and 42, 42, 43, 39 and 36% of total free amino acids at 180 days for cheeses manufactured with 0, 25, 50, 75 and 100% goat's milk, respectively. Significant differences could be detected in terms of amino acid profile when the relative proportions of ewe's and goat's milks were altered (eg valine changed from 251. 79 +/-0.99 to 352.20 +/-16.49 mg/100g of dry matter; leucine from 181.48 +/- 1. 77 to 226.00 +/- 11.60 mg/100 g of dry matter and phenylalanine from 120.39+/-1.44 to 155.36+/-8.39mg/100g of dry matter in 140-day ripened cheeses when plain ewe's milk was replaced by plain goat's milk). The correlation coefficients between the concentrations of valine, isoleucine, leucine and phenylalanine, on the one hand, and ripening time, on the other; were greater than 0.93. (C) 1998 Elsevier Science Ltd. All rights reserved.