title: Influence of residual milk-clotting enzyme on alpha(s1) casein hydrolysis during ripening of Reggianito Argentino cheese.
abstract: Milk-clotting enzyme is considered largely denatured after the cooking step in hard cheeses. Nevertheless, typical hydrolysis products derived from rennet action on alpha(s1)-casein have been detected during the ripening of hard cheeses. The aim of the present work was to investigate the influence of residual milk-clotting enzyme on alpha(s1)-casein hydrolysis in Reggianito cheeses. For that purpose, we studied the influence of cooking temperature (45, 52, and 60 degrees C) on milk-clotting enzyme residual activity and alpha(s1)-casein hydrolysis during ripening. Milk-clotting enzyme residual activity in cheeses was assessed using a chromatographic method, and the hydrolysis of alpha(s1)-casein was determined by electrophoresis and high performance liquid chromatography. Milk-clotting enzyme activity was very low or undetectable in 60 degrees C- and 52 degrees C-cooked cheeses at the beginning of the ripening, but it increased afterwards, particularly in 52 degrees C-cooked cheeses. Cheese curds that were cooked at 45 degrees C had higher initial milk clotting activity, but also in this case, there was a later increase. Hydrolysis of alpha(s1)-casein was detected early in cheeses made at 45 degrees C, and later in those made at higher temperatures. The peptide alpha(s1)-I was not detected in 60 degrees C-cooked cheeses. The results suggest that residual milk-clotting enzyme can contribute to proteolysis during ripening of hard cheeses, because it probably renatures partially after the cooking step. Consequently, the production of peptides derived from alpha(s1)-casein in hard cheeses may be at least, partially due to this proteolytic agent.
authors.affiliation: Programa de Lactología Industrial, Facultad de Ingeniería Química, Universidad Nacional del Litoral, Santiago del Estero 2829 S3000AOM Santa Fe, Argentina. ehynes@fiqus.unl.edu.ar
authors.forename: E R
authors.initials: ER
authors.lastname: Hynes
authors.forename: L
authors.initials: L
authors.lastname: Aparo
authors.forename: M C
authors.initials: MC
authors.lastname: Candioti
mesh_terms: D016282:Aspartic Acid Endopeptidases / Q000378:metabolism*; D002364:Caseins / Q000378:metabolism*; D002611:Cheese / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D005524:Food Technology; D006358:Hot Temperature; D006868:Hydrolysis; D010446:Peptide Fragments / Q000378:metabolism; D013997:Time Factors
chemical_list: D002364:Caseins; D010446:Peptide Fragments; D016282:Aspartic Acid Endopeptidases; C022517:rennin-like enzyme (Aspergillus ochraceus)