Chemical differences between brown centre and white macadamia kernels

Understanding chemical pathways of brown centre formation in laboratory induced and conventionally dried nut-in-shell macadamia kernels

“…Thus, monitoring weather to ensure nuts are harvested before wet and humid conditions, fast tracking nut processing after harvest, and improving air flow in silos would minimise brown centre formation. The variability introduced by variety and environment has been identified as a shortfall in our previous study where the results may have been masked with high within sample variability [ 15 ]. We used a single mid-late season variety of macadamia collected from one orchard to remove the variability introduced by variety and environment.…”

“…Internal discolouration is often only visible after kernel drying and roasting [ 10 , 14 ]. Oil oxidation, sugar hydrolysis and protein degradation are chemical reactions that produce compounds that may react to form brown colouration through the Maillard Reaction [ 10 , 15 , 16 ]. In roasted macadamia kernels, higher concentrations of reducing sugars have been associated with formation of brown colouration in kernels [ 17 ].…”

“…The mechanisms involved in brown centre formation of macadamia kernels particularly after roasting has been previously studied [ 14 , 16 , 17 , 22 ]. Our previous study has highlighted the nutritional and chemical differences between brown centre and white macadamia kernels where samples have been collected randomly with unknown origins [ 15 ]. However, the differences in brown centre chemistry and mechanisms explaining the brown centre occurrence developed under different postharvest conditions remained uncertain.…”