internal kernel discolourtion a focus for QUALITY improvement



We are continuing the focus on Brown Centre or Internal Discolouration defects in a bid to reduce waste and maximise returns to growers. An increase in Internal Discolouration defects during the 2020 season has cost SGM suppliers significantly in reduced income as well as contributing to reduced efficiencies in the factory due to the additional, laborious processing required to remove them after cracking.

Cropwatch Laboratories have reported an increase in the incidence of Internal Discolouration and Internal Disorders across macadamia kernel samples delivered for assessment during the 2020 season and are calling for more research into this problem which is thought to cost the industry at least as much as Insect Damage. 


While Brown Centre (shown above) are a main type of Internal Discolouration, Cropwatch Laboratories have identified at least eleven other types of Internal Defect in a recent report, defects include oily kernels, and bruising caused by hail or other impacts which all contribute to losses in this category.


Investing in improvements to orchard post-harvest handling and drying systems may be the best way for growers to reduce their risk of internal discolouration defects. 

While more needs to be done in the root cause of the enzymatic changes within the kernel that cause Brown Centres, it generally is well established that moisture, heat and impact management of macadamia nuts on the farm could be crucial factors in mitigating damage.


  • Install auto humidity sensors and switches on silos for more precise drying
  • Ensure fans are adequately powered for the size of silo/bin and depth of nut bed
  • Minimise contact with heat sources such as engine heat in harvester bins
  • Minimise time NIS or NIH spends in vessels without forced air such as skip bins
  • Use gentle dehusking equipment such as drag-tyre dehuskers
  • Aim for a high harvest frequency with regular harvest rounds
  • Prioritise drying ASAP after harvest
  • Dehusk, sort and dry in smaller batches
  • Adjust dehuskers for different varieties
  • Inspect equipment regularly and watch for ‘pinch points’ 
  • Place silos and holding bins inside sheds and out of direct sun
  • Duct air from a dry space, such as inside a shed, to the silo inlet

For more information talk to us or visit the Suncoast Gold Macadamias Youtube channel or Facebook Page to see how our growers are focusing on quality.

Megan Boote – Technical Officer, Grower Services, Suncoast Gold Macadamias, 2020