BACKGROUND
Kernel brown centres in macadamia are a defect causing internal discolouration of kernels. This study investigates the effect on the incidence of brown centres in raw kernel after maintaining high moisture content in macadamia nuts‐in‐shell stored at temperatures of 30°C, 35°C, 40°C and 45°C.
RESULTS
Brown centres of raw kernel increased with nuts‐in‐shell storage time and temperature when high moisture content was maintained by sealing in polyethylene bags. Almost all kernels developed the defect when kept at high moisture content for 5 days at 45°C, and 44% developed brown centres after only 2 days of storage at high moisture content at 45°C. This contrasted with only 0.76% when stored for 2 days at 45°C but allowed to dry in open‐mesh bags. At storage temperatures below 45°C, there were fewer brown centres, but there were still significant differences between those stored at high moisture content and those allowed to dry (P < 0.05).
CONCLUSION
Maintenance of high moisture content during macadamia nuts‐in‐shell storage increases the incidence of brown centres in raw kernels and the defect increases with time and temperature. On‐farm nuts‐in‐shell drying and storage practices should rapidly remove moisture to reduce losses. Ideally, nuts‐in‐shell should not be stored at high moisture content on‐farm at temperatures over 30°C. © 2013 Society of Chemical Industry