High pressure treatment of bovine milk: effects on casein micelles and whey proteins.
Effects of high pressure (HP) on average casein micelle size and denaturation of alpha-lactalbumin (alpha-la) and beta-lactoglobulin (beta-lg) in raw skim bovine milk were studied over a range of conditions. Micelle size was not influenced by treatment at pressures <200 MPa, but treatment at 250 MPa increased micelle size by approximately 25%, while treatment at > or = 300 MPa irreversibly reduced it to approximately 50% of that in untreated milk. The increase in micelle size after treatment at 250 MPa was greater with increasing treatment time and temperature and milk pH. Treatment times > or = 2 min at 400 MPa resulted in similar levels of micelle disruption, but increasing milk pH to 7.0 partially stabilised micelles against HP-induced disruption. Denaturation of alpha-la did not occur < or = 400 MPa, whereas beta-lg was denatured at pressures >100 MPa. Denaturation of alpha-la and beta-lg increased with increasing pressure, treatment time and temperature and milk pH. The majority of denatured beta-lg was apparently associated with casein micelles. These effects of HP on casein micelles and whey proteins in milk may have significant implications for properties of products made from HP-treated milk.
Huppertz
Thom
T
Department of Food and Nutritional Sciences, University College Cork, Ireland.
Fox
Patrick F
PF
Kelly
Alan L
AL
D000818:Animals; D002364:Caseins / Q000737:chemistry*; D002417:Cattle; D005260:Female; D005511:Food Handling / Q000379:methods; D006863:Hydrogen-Ion Concentration; D007768:Lactalbumin / Q000737:chemistry; D007782:Lactoglobulins / Q000737:chemistry; D008823:Micelles; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000737:chemistry*; D011312:Pressure; D011489:Protein Denaturation; D013696:Temperature; D013997:Time Factors; D000067816:Whey Proteins
D002364:Caseins; D007782:Lactoglobulins; D008823:Micelles; D008894:Milk Proteins; D000067816:Whey Proteins; D007768:Lactalbumin