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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: Solar thermal drying of apricots: Effect of spectrally-selective cabinet materials on drying rate and quality metrics (abstract)

Authors
item Milczarek, Rebecca
item Alonzo, Jerome -
item McHugh, Tara

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: February 12, 2013
Publication Date: July 15, 2013
Citation: Milczarek, R.R., Alonzo, J.H., Mchugh, T.H. 2013. Solar thermal drying of apricots: Effect of spectrally-selective cabinet materials on drying rate and quality metrics (abstract). Institute of Food Techologists Annual Meeting & Food Expo. 169.01.

Technical Abstract: Solar thermal (ST) drying is currently not in widespread commercial use due to concerns about slow drying rates and poor product quality. ST dryer cabinets could be constructed from spectrally-selective materials (materials which transmit only certain sunlight wavelength bands), but these types of materials have not yet been systematically studied for the purpose of enhancement of ST drying of fruit. The objective of this work was to determine the effects of 5 spectrally-selective cabinet materials on the constant rate period drying rate, total soluble phenolics (TSP) content, antioxidant (AOX) capacity, and color of apricots during ST drying. Diced, unsulphured apricot pieces were used for drying. Single-layer drying cabinets were constructed from 5 spectrally-selective acrylic materials: clear (CL) – standard acrylic; ultraviolet-blocking (UV-B) – “museum glass”; infrared-blocking (IR-B) – used for skylights to transmit sunlight without overheating a room; black (B) – completely opaque; and black-infrared-transmitting (B-IRT) – visibly opaque but transparent to infrared light. Three replicate drying runs were performed. Measurements of the apricot samples, the cabinet air temperature, and meteorological conditions were taken during drying. Drying rate was significantly affected by the cabinet material type. The order of drying rates was CL (fastest drying) > UV-B > IR-B > B-IRT > B (slowest drying), with the B-IRT and CL materials yielding rates that were 43% and 83%, respectively, higher than that achieved with the B material. The difference in drying rates was likely due to observed cabinet air temperature elevation by the different materials. When samples were compared on an equal moisture content basis, the cabinet material type did not significantly (alpha = 0.05) affect the TSP content, AOX capacity, or color of the apricots. Thus, this study demonstrates that spectrally-selective materials can be used to increase the ST drying rate of apricots without adversely affecting key quality metrics of the product.

Last Modified: 10/23/2014
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