Journal Article


Alan L Kelly
Jorge C Oliveira
Anthony Crudden



caseins hot temperature milk proteins metabolism lactoglobulins protein denaturation micelles kinetics female milk cattle chemistry animals mathematics fibrinolysin

Kinetics of changes in plasmin activity and proteolysis on heating milk. (2003)

Abstract Heat-induced inactivation of bovine plasmin, denaturation of beta-lactoglobulin (beta-lg), the interactions between both species and casein micelles and the subsequent net effect on proteolysis of beta-casein was studied in a model system consisting of phosphocasein and beta-lg in synthetic milk ultrafiltrate. The inactivation of plasmin and denaturation of beta-lg were first order reactions, with the rate of inactivation of plasmin being greater than the rate of denaturation of beta-lg. The predominant mechanism involved in the denaturation of plasmin in the temperature range 65-80 degrees C was its interaction with beta-lg (kr at 60 degrees C, 0.0526; Ea, 176 KJ/mol). At the point of complete inactivation of plasmin approximately 45% of the beta-lg remained undenatured. Thermal inactivation of plasmin through other mechanisms was negligible. The association of beta-lg with the casein micelles at 60 degrees C had a rate constant of 3.71 x 10-5 min-1 and an Ea of 259 KJ/mol; thermal denaturation of beta-lg was of much less importance, with a rate constant at 60 degrees C of the order of 1 x 10-10 min-1 and an Ea of 250 KJ/mol. On denaturation of all beta-lg in the system, a maximum of approximately 55% was associated with the casein micelles. The effect of heating on the subsequent hydrolysis of beta-casein indicated that the level of plasmin activity was the most important factor affecting proteolysis, while the interaction of beta-lg with the casein micelles had limited effect. Overall, thermal stability of plasmin in milk is very much dependent upon its interaction with beta-lg.
Collections Ireland -> University College Cork -> PubMed

Full list of authors on original publication

Alan L Kelly, Jorge C Oliveira, Anthony Crudden

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Alan L. Kelly
Total Publications: 63