LIPOXYGENASE AND PEROXIDASE ACTIVITY OF MACADAMIA KERNEL AFTER THERMAL PROCESSING

The objectives of this study were to determine the activities of lipoxygenase and peroxidase enzyme present in roasted and unroasted nuts of four Australian macadamia varieties and to investigate possible relations between them. Extracted crude enzyme was partially purified with ion exchange chromatography. Activity of each enzyme was measured by spectrophotometric methods with suitable substrates. Results indicated that ‘Daddow’ variety exhibited highest lipoxygenase (LOX) and peroxidase (POX) activity. Roasted samples showed lower activity than unroasted samples in all four cultivars and there was no clear correlation between LOX and POX activity for all cultivars studied. The result indicated that high protein content fraction had high enzyme activity for both LOX and POX. In addition enzyme activity varied between cultivars. Roasting deactivated POX and LOX and consequently, rancidity was inhibited.