Effect of high-pressure treatment on denaturation of bovine lactoferrin and lactoperoxidase.

Lactoferrin and lactoperoxidase are whey proteins with biological properties that may provide health benefits to consumers. These properties are vulnerable to potentially denaturing conditions during processing. High-pressure treatment is an appealing alternative to the traditional heat processing of foods because it exerts an antimicrobial effect without changing the sensory and nutritional quality of foods. In this work, the effect of high-pressure treatment on the denaturation of lactoferrin and lactoperoxidase present in skim milk and whey, and as isolated proteins in buffer, was studied over a pressure range of 450 to 700 MPa at 20°C. Denaturation of lactoferrin was measured by the loss of reactivity with their specific antibodies using a sandwich ELISA. Denaturation of lactoperoxidase was determined by measuring the loss of enzymatic activity using a spectrophotometric technique. No substantial inactivation of lactoperoxidase was observed in any treatment assayed. The concentration of the residual immunoreactive lactoferrin after each pressure treatment was determined, and the data were subjected to kinetic analysis to obtain D and Z values. Denaturation of lactoferrin increased with pressure and holding time, and D values were lower when lactoferrin was treated in whey than in milk, and lower in both whey and milk than in phosphate buffer. Thus, protein is denatured more slowly in buffer and in milk than in whey. Denaturation of lactoferrin in the 3 media was found to follow a reaction order of n=1.5. Volumes of activation of about -34.77, -24.35, and -24.09 mL/mol were obtained for lactoferrin treated in skim milk, whey, and buffer, respectively, indicating a decrease in protein volume under pressure.