ARS | Publication request: Optimization of microwave roasting of almond (Prunus dulcis)

Submitted to: Journal of Food Processing and Preservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 5, 2012
Publication Date: N/A

Interpretive Summary: Traditionally, almonds are roasted in a forced hot-air dryer. This technique is effective but takes much longer than the alternative of microwave roasting. The goal of these experiments was to determine which microwave heating conditions (time and applied power) were necessary to produce roasted almonds that matched hot air roasted almonds at light, medium, and dark levels. At the medium roasting level, a tasting panel could not tell the difference between the microwave roasted samples and the hot air roasted samples. At all three roasting levels, the panelists could not tell the microwave roasted almonds from the hot air roasted almonds in terms of roasted flavor and crunchy texture. The information from this experiment can guide the design of both industrial and household microwave almond roasting processes.

Technical Abstract: Microwave (MW) almond roasting was investigated as an alternative to hot air (HA) roasting. Nonpareil almonds (Prunus dulcis) were roasted at 140°C 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.