Quantification of hexanal as an index of lipid oxidation in human milk and association with antioxidant components

Hexanal, a secondary product of lipid oxidation, was identified as the major volatile aldehyde generated from lipid peroxidation in human milk. Hexanal was quantified in human milk using solid phase microextraction-gas chromatography/flame ionization detection that required correction for recovery based on the fat content of human milk. Alpha-tocopherol was the only tocopherol isomer in human milk found to be significantly correlated with hexanal (R = -0.374, p<0.05) and the total antioxidant capacity of human milk (ORAC(Fl) (R = 0.408, p<0.01)). Ascorbic acid content was negatively correlated (R = -0.403, p<0.05) with hexanal, but not to ORAC(Fl) in human milk. The effect of Holder pasteurization on oxidative status of human milk was determined using multiple parameters that included, hexanal level and malondialdehyde as markers of lipid oxidation, vitamins C and E content and antioxidant capacity (e.g. ORAC(Fl)). Pasteurization did not affect the oxidative status of milk as measured by hexanal level, ORAC(Fl) and malondialdehyde content. We conclude that hexanal is a sensitive and useful chemical indicator for assessing peroxidation reactions in human milk and that alpha tocopherol and ascorbic acid are two key antioxidant components in milk that contribute to protection against oxidation of milk lipids.