High pressure-induced denaturation of alpha-lactalbumin and beta-lactoglobulin in bovine milk and whey: a possible mechanism.
In this study, high pressure (HP)-induced denaturation of alpha-lactalbumin (alpha-la) and beta-lactoglobulin (beta-lg) in dairy systems was examined. In both milk and whey, beta-lg was less baroresistant than alpha-la; both proteins were considerably more resistant to HP-induced denaturation in whey than in milk. HP-induced denaturation of alpha-la and beta-lg increased with increasing proportion of milk in mixtures of milk and whey. Addition of a sulphydryl-oxidising agent, KlO3, to milk or whey increased HP-induced denaturation of beta-lg, but reduced the denaturation of alpha-la. Denaturation of both alpha-la and beta-lg was prevented by adding a sulphydryl-blocking agent, N-ethylmaleimide, to milk or whey prior to HP treatment, highlighting the crucial role of sulphydryl-disulphide interchange reactions in HP-induced denaturation of alpha-la and beta-lg. Removal of colloidal calcium phosphate from milk also reduced HP-induced denaturation of alpha-la and beta-lg significantly. The higher level of HP-induced denaturation of alpha-la and beta-lg in milk than in whey may be the result of the abscence of the casein micelles and colloidal calcium phosphate from whey, which facilitate HP-induced denaturation of alpha-la and beta-lg in milk.
Huppertz
Thom
T
Department of Food and Nutritional Sciences, University College Cork, Ireland.
Fox
Patrick F
PF
Kelly
Alan L
AL
D000818:Animals; D002130:Calcium Phosphates / Q000032:analysis / Q000737:chemistry; D002364:Caseins / Q000032:analysis / Q000737:chemistry; D002417:Cattle; D003102:Colloids / Q000737:chemistry; D005033:Ethylmaleimide / Q000494:pharmacology; D007768:Lactalbumin / Q000737:chemistry*; D007782:Lactoglobulins / Q000737:chemistry*; D008823:Micelles; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000737:chemistry*; D011312:Pressure; D011489:Protein Denaturation; D000067816:Whey Proteins
D002130:Calcium Phosphates; D002364:Caseins; D003102:Colloids; D007782:Lactoglobulins; D008823:Micelles; D008894:Milk Proteins; D000067816:Whey Proteins; D007768:Lactalbumin; C020243:calcium phosphate; D005033:Ethylmaleimide