title: Proteomic study of proteolysis during ripening of Cheddar cheese made from milk over a lactation cycle.
abstract: Milk for cheese production in Ireland is predominantly produced by pasture-fed spring-calving herds. Consequently, there are marked seasonal changes in milk composition, which arise from the interactive lactational, dietary and environmental factors. In this study, Cheddar cheese was manufactured on a laboratory scale from milk taken from a spring calving herd, over a 9-month lactation cycle between early April and early December. Plasmin activity of 6-months-old Cheddar cheese samples generally decreased over ripening time. One-dimensional urea-polyacrylamide gel electrophoresis (PAGE) of cheese samples taken after 6 months of ripening showed an extensive hydrolysis of caseins, with the fastest hydrolysis of α(s1)-caseins in cheeses made in August. A proteomic comparison between cheeses produced from milk taken in April, August and December showed a reduction in levels of β-casein and appearance of additional products, corresponding to low molecular weight hydrolysis products of the caseins. This study has demonstrated that a seasonal milk supply causes compositional differences in Cheddar cheese, and that proteomic tools are helpful in understanding the impact of those differences.
authors.affiliation: School of Food and Nutritional Sciences, University College Cork, Cork, Ireland.
authors.forename: Katharina
authors.initials: K
authors.lastname: Hinz
authors.forename: Paula M
authors.initials: PM
authors.lastname: O'Connor
authors.forename: Bernadette
authors.initials: B
authors.lastname: O'Brien
authors.forename: Thom
authors.initials: T
authors.lastname: Huppertz
authors.forename: R Paul
authors.initials: RP
authors.lastname: Ross
authors.forename: Alan L
authors.initials: AL
authors.lastname: Kelly
mesh_terms: D000818:Animals; D002364:Caseins / Q000032:analysis / Q000378:metabolism; D002417:Cattle; D002611:Cheese / Q000032:analysis*; D004591:Electrophoresis, Polyacrylamide Gel; D005260:Female; D005341:Fibrinolysin / Q000378:metabolism; D005511:Food Handling / Q000379:methods; D007774:Lactation; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000032:analysis / Q000378:metabolism*; D059748:Proteolysis; D040901:Proteomics; D012621:Seasons
chemical_list: D002364:Caseins; D008894:Milk Proteins; D005341:Fibrinolysin