title: Proteolysis during ripening of Manchego cheese made from raw or pasteurized ewes' milk. Seasonal variation.
abstract: Changes in nitrogen compounds during ripening of 40 batches of Manchego cheese made from raw milk (24 batches) or pasteurized milk (16 batches) at five different dairies throughout the year were investigated. After ripening for six months, degradation of p-kappa- and beta-caseins was more intense in raw milk cheese and degradation of alpha(s2)-casein in pasteurized milk cheese. Milk pasteurization had no significant effect on breakdown of alpha(s1)-casein. Hydrophobic peptide content did not differ between raw and pasteurized milk cheese, whereas hydrophilic peptide content was higher in raw milk cheese. There were no significant differences between seasons for residual caseins, but hydrophobic peptides were at a higher level in cheese made in autumn and winter and hydrophilic peptides in cheese made in winter and spring. Raw milk cheese had a higher content of total free amino acids and of most individual free amino acids than pasteurized milk cheese. The relative percentages of the individual free amino acids were significantly different for raw milk and pasteurized milk cheeses. The relative percentages of Lys and lie increased, while those of Val, Leu and Phe decreased during ripening. There were also seasonal variations within the relative percentages of free amino acids. In raw milk cheeses, Asp and Cys were relatively more abundant in those made in autumn, Glu and Arg in cheeses made in winter, and Lys and Ile in cheeses made in spring and summer. Biogenic amines were detected only in raw milk cheese, with the highest levels of histamine, tryptamine and tyramine in cheeses made in spring, winter and spring, respectively.
authors.affiliation: Departamento de Tecnología de Alimentos, Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Carretera de La Coruña Km 7, Madrid, E-28040 Spain.
authors.forename: Pilar
authors.initials: P
authors.lastname: Gaya
authors.forename: Carmen
authors.initials: C
authors.lastname: Sánchez
authors.forename: Manuel
authors.initials: M
authors.lastname: Nuñez
authors.forename: Estrella
authors.initials: E
authors.lastname: Fernández-García
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001679:Biogenic Amines / Q000032:analysis; D002364:Caseins / Q000378:metabolism; D002611:Cheese / Q000032:analysis* / Q000382:microbiology; D015169:Colony Count, Microbial; D016002:Discriminant Analysis; D005260:Female; D005511:Food Handling; D008892:Milk / Q000201:enzymology*; D008894:Milk Proteins / Q000032:analysis / Q000378:metabolism; D010447:Peptide Hydrolases / Q000378:metabolism*; D010455:Peptides / Q000032:analysis / Q000378:metabolism; D012621:Seasons; D012756:Sheep
chemical_list: D000596:Amino Acids; D001679:Biogenic Amines; D002364:Caseins; D008894:Milk Proteins; D010455:Peptides; D010447:Peptide Hydrolases