The Results of Different Heating Temperatures on Activities of Bioactive Proteins in Human Milk

Background: The most utilized pasteurization method in donor human milk banks is Holder pasteurization (heating 62.5 degrees C for 30 min). However, many bioactive proteins are heat sensitive and are inactivated. Research Aim: To determine the results of a range of heating regimes on the activities of xanthine oxidase, lactoperoxidase and lysozyme, the concentrations of immunoglobulin A and lactoferrin, as well as bacterial inactivation. Method: This prospective, cross-sectional, intervention study was designed to measure the influence of heating temperatures on bioactive components in donor human milk. Milk samples were processed at 40, 50, 55, 62.5, 75, 127 degrees C and the activities of the enzymes, and the concentration of immune proteins, were measured. Results: No bacterial colonies were detectable, using standard culture methods, after heating above 50 oC. All proteins studied retained over 60% concentrations or activities when the pasteurization temperature was 50 oC or lower, while their concentrations or activities were lost at higher temperatures. For lactoferrin, the residual concentration was above 80% when heating temperature was under 55 degrees C, while only 20% remained after Holder pasteurization. Both xanthine oxidase and lactoperoxidase had little residual activity when temperatures were above Holder pasteurization. Lysozyme retained a greater proportion of residual activity than other proteins, following heating at all temperatures. Conclusions: The concentrations or activities of immune proteins and bioactive enzymes decreased when heated above 50 degrees C. The results of this study can be used to design temperature control guidance during alternative methods of pasteurization.