Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2005
Publication Date: 12/1/2005
Citation: Coronel, P., Truong, V., Simunovic, J., Sandeep, K.P., Cartwright, G.D. 2005. Aseptic processing of sweetpotato purees using a continuous flow microwave system. Journal of Food Science. 70:E531-E537. Interpretive Summary: The utilization of sweetpotatoes in the food industry often involves processing the roots into purees that can be used as a functional ingredient in various processed food products. Preservation of the purees by freezing, canning, or other conventional thermal processing has been applied. However, due to high viscosity and low heat conductivity of the purees, conventional thermal processing methods usually result in poor product quality and high nutrient losses. On the other hand, frozen puree requires considerable investment in distribution and storage, as well as a lengthy and poorly controlled defrosting treatment prior to use. Alternative technologies providing rapid and uniform heating such as microwave energy for producing shelf-stable products could help overcome these problems. This study was undertaken to determine the technical feasibility of producing shelf-stable sweetpotato purees using an industrial microwave heating systems operating at 915 MHz. We demonstrated that aseptically packaged sweetpotato puree was successfully produced using a pilot-plant scale of a continuous-flow microwave system. The resulting product packed in flexible plastic containers had the color and apparent viscosity comparable to the untreated puree and was shelf-stable to the time of the report, at least three months, with no detectable microbial counts. This process can be applied to several other vegetable and fruit purees, and consistently high quality products can be packaged into virtually unlimited sizes (up to 55-65 gal). To the best of our knowledge, this is the first report of aseptically packaged vegetable purees processed by a continuous flow microwave heating system.
Technical Abstract: Sweetpotato purees (SPP) were aseptically processed using a continuous flow microwave system to obtain a shelf-stable product. The dielectric properties of SPP were measured, and the dielectric constant and loss factor were within the range of the published values for fruits and vegetables. Small-scale tests were conducted in a 5 kW microwave unit to determine changes in color and viscosity with different thermal treatments. The results of these tests showed that color values (L*, a*) and viscosity did not change significantly compared to the untreated control. Pilot-scale tests were then conducted in a 60 kW microwave unit where the product was heated to 135 deg C and held at that temperature for 30 s. The pilot scale test produced a shelf-stable product with no detectable microbial count during a 90-day storage period at room temperature. This is the first report of aseptically packaged vegetable puree processed by a continuous flow microwave heating system.