Dropping macadamia nuts-in-shell reduces kernel roasting quality.

Area of Science:

• Agricultural Science
• Food Science
• Postharvest Technology

Background:

• Macadamia nuts-in-shell experience impacts during postharvest handling, potentially damaging raw kernels.
• The impact of dropping on roasted macadamia kernel quality remains largely unknown.
• This study investigates the effects of dropping macadamia nuts-in-shell on kernel quality after roasting.

Purpose of the Study:

• To determine the effect of dropping macadamia nuts-in-shell on roasted kernel quality.
• To assess how moisture content, number of drops, and receiving surface influence kernel damage.
• To identify the relationship between postharvest handling and roasted macadamia kernel characteristics.

Main Methods:

• Macadamia nuts-in-shell were subjected to dropping under varying conditions (moisture content, drop number, surface).
• Dropped and control samples were dry oven-roasted at 130 °C for 20 minutes.
• Kernels were evaluated for color, mottled color, and surface damage.

Main Results:

• Dropping nuts-in-shell at 3% or 20% moisture content increased dark roasted kernels.
• Mottled kernel color increased when nuts were dropped sequentially at 20% then 10% moisture onto a metal plate.
• Surface damage significantly increased with dropping, particularly at 3% moisture onto other nuts or at 20% then 10% moisture onto a metal plate.

Conclusions:

• Postharvest dropping induces hidden cellular damage in macadamia kernels, manifesting during roasting.
• This cellular damage facilitates non-enzymatic browning reactions, leading to darker roasted nuts.
• Optimizing handling practices, including minimizing drops and improving equipment, can reduce kernel damage and post-roast darkening.