Ripening characteristics of Cheddar cheese made from bovine milks containing kappa-casein AA or BB genetic variants

The ripening characteristics of Cheddar cheeses made from K-casein AA/beta- lactoglobulin AB and kappa-casein BB/beta-lactoglobulin AB genetic variant milks were investigated over a 274 d period. kappa-Casein variant had no si gnificant effect (p > 0.05) on primary and secondary proteolysis, as monito red by nitrogen solubility at pH 4.6 or in 5% phos-photungstic acid, and to tal levels of free amino acids. Moreover, the profile of proteolysis produc ts was not influenced by kappa-casein variant, as indicated by the generall y similar peptide molecular weight distribution profiles in cheeses from th e kappa-casein AA or BE milks throughout the 274 d ripening period. Some am ino acids, however, (ie. methionine, leucine, phenylalanine, histidine and lysine) were significantly (p < 0.05) higher in kappa-casein BE cheese comp ared to kappa-casein AA cheese at 274 d ripening. kappa-casein variant had no significant effect on the rheological (fracture stress and firmness) cha racteristics or the grading scores awarded for flavour/aroma and body/textu re.