Characterization of the Casein Hydrolysis of Idiazábal Cheese Manufactured from Ovine Milk

Abstract

Idiazabal cheese is an uncooked pressed cheese made from raw ovine milk. Because of the seasonality of ovine milk production, this cheese is mainly manufactured between January and June. Variation in the composition of the milk during lactation may have a strong influence on the cheese characteristics. Therefore, the main objectives of the present study were to characterize Idiazabal cheese that has been manufactured in accordance with the regulations of the Idiazabal Cheese Appellation of Origin and to ascertain the level of product uniformity. We focused mainly on general descriptive parameters, the different N fractions (pH 4.6-soluble N and 15% trichloro-acetic acid-soluble N), and HPLC analysis of the free amino acids. The mean contents of pH 4.6-soluble N (11.52%) and 15% trichloroacetic acid-soluble N (14.40%), expressed as percentage of total N, were indicative of low levels of proteolysis in Idiazabal cheese. The five major free amino acids were glutamic acid, leucine, valine, lysine, and phenylalanine. Principal component analysis of the free amino acids showed that a high percentage of the variance in Idiazabal cheese (73%) could be explained by the two principal components: the free amino acids associated with the stage of amino acid release and the free amino acids associated with amino acid catabolism. The principal function obtained by applying stepwise discriminant analysis to the free amino acids explained most of the variability between cheese manufacturing establishments and was associated with the geographical location, altitude, or climatic conditions of those establishments.