Managing the drying process is essential to obtain tasty crunchy kernel. When the macadamia nut is first harvested, moisture content is around 27%. This has to be lowered to around 4% to crack effectively.
Stage 1 drying is dropping the moisture content to around 14%. At this level those moulds causing kernel discoloration cannot survive. Forcing cool dry air through the macadamia nuts is ideal. In practice this usually means blowing ambient air through the macadamia nuts in a purpose-built drier, or leaving nuts in a breezy spot in onion bags. Macadamia nuts could also be laid out in shallow layers if the volumes are small, eg. on an old wire-wove bed. Indoors in a controlled environment is better, and avoid getting direct sunlight on the nuts. Rake over nuts regularly to ensure even drying. This process may take 6-8 weeks in N.Z. Macadamia nuts will not dry below around 14% without going to stage 2.
Stage 2 drying (or 'curing') is forcing warm dry air through the macadamia nuts. For the home grower this may mean drying nut-in-shell in a small space with a dehumidifier over several days or longer. When relative humidity gets down to around 30% then some nuts should begin rattling in their shells. If heating to about 30 degrees can be added, drying is accelerated.