title: Maintaining high moisture content of macadamia nuts-in-shell during storage induces brown centres in raw kernels.
abstract: 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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore DC, Queensland 4558, Australia. dwalton3@usc.edu.au
authors.forename: David A
authors.initials: DA
authors.lastname: Walton
authors.forename: Bruce W
authors.initials: BW
authors.lastname: Randall
authors.forename: Marie D
authors.initials: MD
authors.lastname: Le Lagadec
authors.forename: Helen M
authors.initials: HM
authors.lastname: Wallace
mesh_terms: D000383:Agriculture / Q000379:methods; D003116:Color; D018556:Crops, Agricultural / Q000737:chemistry* / Q000254:growth & development; D018857:Food Packaging; D005519:Food Preservation; D063427:Food Quality; D061353:Food Storage; D006358:Hot Temperature / Q000009:adverse effects; D039106:Macadamia / Q000737:chemistry* / Q000254:growth & development; D015416:Maillard Reaction; D009754:Nuts / Q000737:chemistry* / Q000254:growth & development; D011786:Quality Control; D011793:Queensland; D014867:Water / Q000032:analysis*
chemical_list: D014867:Water
keywords: brown centres; kernels; macadamia; moisture content; nuts; storage