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United States Department of Agriculture

Agricultural Research Service

Research Project: New Sustainable Processing Technologies to Produce Healthy, Value-Added Foods from Specialty Crops and their Co-Products

Location: Healthy Processed Foods Research

Title: Exploration of conditions for microwave roasting of almonds

Authors
item Milczarek, Rebecca
item Avena Bustillos, Roberto
item McHugh, Tara

Submitted to: Microwave Power Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: April 20, 2012
Publication Date: June 20, 2012
Citation: Milczarek, R.R., Avena Bustillos, R.D., Mchugh, T.H. 2012. Exploration of conditions for microwave roasting of almonds. Microwave Power Symposium Proceedings. June 20-22, 2012, Las Vegas, Nevada. p. 122-131.

Technical Abstract: Almond roasting is an energy-intensive process that is usually performed via hot-air convection. Microwave roasting could be a more energy-efficient alternative to hot-air roasting, but microwave roasting of almonds has not yet been thoroughly explored. Thus, the purpose of this study was to determine the effects of microwave roasting conditions on the quality of California almonds [Prunus dulcis (Mill.) D.A. Webb cv. Nonpareil]. Almonds were roasted in a Panasonic household microwave oven, nominally 1300 W. In a designed experiment, 3 variables were tested: applied power (2.8 W/g, 6.2 W/g, and 8.8 W/g), heating time (60 seconds, 120 seconds, and 180 seconds), and presence or absence of mixing. Measured response variables included internal color, percentage weight loss (due to moisture loss), water activity, and 7 instrumental texture metrics derived from a force/deformation curve. For each treatment, the coefficient of variation of the response variables was also considered, since uniform product quality is a priority in the food industry. Applied power and heating time had a significant (p < 0.05) effect on the mean values of all the response variables except the yellowness/blueness of the internal color (which was only affected by heating time) and the area under the texture force/deformation curve to the point of maximum force (which was only affected by applied power). Presence or absence of mixing only significantly affected 4 of the 7 texture metrics and the percentage weight loss; the magnitude of these effects was smaller than that of applied power and heating time. Regarding variability of the end product, applied power and heating time had a significant effect on the coefficient of variation of each texture metric associated with the first fracture of the almond. The results of this study lay the groundwork for optimization of microwave roasting conditions for California almonds.

Last Modified: 9/23/2014