Optimization of Microwave Roasting of Almond (Prunus dulcis )

Microwave (MW) almond roasting was investigated as an alternative to hot air (HA) roasting. Nonpareil almonds (Prunus dulcis) were roasted at 140C in a convection oven for different times to achieve light, medium and dark roasting levels. Several instrumental measurements were taken, establishing targets for each roasting level. To determine the MW time/power combinations necessary to match the HA targets, a response surface experiment was conducted. Additional MW-roasted samples prepared using the optimal time/power combinations underwent both instrumental and sensory analyses. The overall sensory difference test showed that, at the medium roasting level, the MW-roasted almonds were indistinguishable from their HA-roasted counterparts. At all three roasting levels, the HA- and MW-roasted samples were not significantly different in terms of sensory roasted flavor and crunchiness. Instrumental measurements supported the sensory results. When optimized, MW roasting yields results similar to HA roasting in a fraction of the time. Practical Application The findings of this work can be used by industrial almond processors to develop large-scale microwave (MW) roasting unit operations. Also, consumers could use the optimal MW time and power combinations found in this work as guidelines for at-home preparation of roasted almonds.