a1 School of Food and Nutritional Sciences, University College Cork, Cork, Ireland
a2 Teagasc Food Research Centre, Moorepark, Fermoy, Ireland
a3 Animal and Grassland Research and Innovation Centre, Teagasc, Moorepark, Fermoy, Ireland
a4 NIZO food research, Ede, The Netherlands
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 αs1-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.
(Received May 27 2011)
(Accepted December 15 2011)
(Online publication February 27 2012)