Chemical differences between brown centre and white macadamia kernels

Nuts are susceptible to many quality issues, including discoloration defects in kernels. These discolouration defects can affect their market value and result in significant economic losses to both growers and processors. In macadamia, this quality issue is called brown centres and has been related to storage at high temperatures and moisture concentrations. However, the chemical differences between brown centre and white macadamia kernels have not previously been studied. We aimed to determine the chemical differences between macadamia kernels with brown centre defects and kernels that were white and cream coloured. We used brown and white kernel samples from 20 commercially processed batches of macadamia. From each batch, we selected brown centre samples and compared their chemistry with white kernel samples from the same batch. We compared the moisture concentration, sugar concentration, nutrient concentration, fatty acid profile and peroxide value of brown centre defect and white kernel samples. Our results showed that brown centres had a higher moisture concentration compared with white kernel samples (5.16 % vs 2.91 %, respectively, P