Global demand for tree nuts has grown by around 50% in the past decade, with global trade of around 5.3 million tons per year. Macadamia is a tree nut crop considered a gourmet food for its delicate flavour, crunchy texture, and high oil content. Macadamia nuts are susceptible to a quality defect that produces a brown internal discolouration, known as brown centres which renders the kernel unsaleable. This defect cost the Australian macadamia industry AU$23.3 million between 2009 and 2019. Brown centre formation in macadamia kernels has been associated with improper storage under wet conditions and high temperatures, however, no study has examined the chemical differences between raw kernels with the brown centre defect and white macadamia kernels. I aimed to evaluate the chemical differences between the unsaleable kernel with brown centre defect and saleable high-quality white macadamia kernels in this thesis. There were two studies: in the first study, I compared brown centres and white kernels from mixed sample of nuts from a different cultivars, sites and postharvest handling conditions. However, in the second study, I carefully controlled the postharvest drying of macadamia nuts in the laboratory. I used nut-in-shell from one variety (849) and one site, all harvested at the same time, to reduce background variation in nut chemistry.