Effect of ewe's-milk pasteurization on the free amino acids in Idiazabal cheese

This study compared the use of raw and pasteurized milk in the manufacture of Idiazabal ewe's-milk cheese. Two indigenous starters, A and B were tested in an attempt to find a starter culture potentially capable of developing the typical characteristics of Idiazabal cheese traditionally made from raw milk while using pasteurized milk. The nitrogen fractions and free amino acids were analysed over the ripening period. Pasteurization caused a considerable decrease in amino acid release in the cheese during ripening as reflected by the levels of non-protein-nitrogen and total free amino acids with starter A, but not when starter B was used. Multivariate analysis confirmed increases in asparagine, serine, and taurine and decreases in aspartic acid and glycine with pasteurization, irrespective of the starter used. The changes recorded in the levels of certain amino acids may be directly or indirectly responsible for the atypical sensory characteristics of the cheeses. Pasteurization of the milk for the manufacture of Idiazabal cheese is not recommended with either of the two starters tested. (C) 1999 Elsevier Science Ltd. All rights reserved.