Quality changes in macadamia kernel between harvest and farm-gate

Abstract

Significant loss of macadamia kernel quality occurred on a commercial farm during sorting and storage of nuts-in-shell before nuts were consigned to a processor. Nuts-in-shell should be dried as quickly as possible and on-farm handling minimised to maintain optimum kernel quality.

Shelf Life of Tropical Canarium Nut Stored under Ambient Conditions

“…Macadamia originated in the sub-tropical rainforest of eastern Australia, and is a rare example of a nut from the tropics grown commercially in plantations [11][12][13][14][15][16][17]. Brazil nuts have also become an important industry for countries along the Amazon River such as Brazil, Peru and Colombia, however, Brazil nuts are harvested from the forest floor rather than plantations [18].…”

“…In other crops postharvest handling methods have been developed to reduce waste in the postharvest chain and maintain quality and nutritional attributes, [12][13][14][15][16][17]33]. Nuts are prone to rancidity because of high content of unsaturated fatty acids.…”

Maintaining high moisture content of macadamia nuts-in-shell during storage induces brown centres in raw kernels

“…Browning of horticultural products is a common problem during postharvest storage; for example, browning of litchi pericarp stored at ambient temperature and of apple skin while in cold storage . Browning of kernels is also an important postharvest issue in nut crops such as almonds, hazelnuts and macadamia and is often associated with roasting . However, browning can also occur in raw kernels, for example, walnuts and hazelnuts .…”

“…Macadamia ( Macadamia integrifolia and M. tetraphylla and hybrids) is an important horticultural crop in Australia, South Africa, Hawaii, Kenya, Brazil, and other countries. Macadamia kernel quality and shelf life depend on harvest management, efficient drying, appropriate storage and postharvest treatment . Kernel brown centres, also termed ‘internal browning’ or ‘internal discolouration’, is an internal quality defect of macadamia kernels sometimes accompanied by an ‘off’ odour and flavour.…”

“…Nuts‐in‐shell should be partially dried on‐farm to approximately 10% moisture content for transport, then further dried to 3% at the processors before cracking . Prolonged storage of nuts‐in‐shell at high moisture content has been associated with reduced kernel quality; for example, nuts‐in‐shell remaining at 15% moisture content 14 days after harvest produced kernels with significant levels of shoulder damage, weight of pieces, unsound kernels and after‐roast darkening . Maintaining nuts‐in‐shell at high moisture content can cause discolouration; for example, brown patches on the surface of cashews are thought to be related to prolonged storage of nuts at high moisture content…”