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United States Department of Agriculture

Agricultural Research Service

Title: Thermal and dielectric properties of sweetpotato puree

item Fasina, O
item Farkas, B
item Fleming, H

Submitted to: International Journal of Food Properties
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2003
Publication Date: 10/20/2003
Citation: Fasina, O.O., Farkas, B.E., Fleming, H.P. 2003. Thermal and dielectric properties of sweetpotato puree. International Journal of Food Properties. 6(3):461-472.

Interpretive Summary: The sweetpotato is a highly nutritious but under-utilized vegetable. We have done research on the pureeing and conversion of the roots into value-added products which has required knowledge on the thermal and dielectric properties of the puree. Our results showed that increases in temperature from 5 to 80C significantly increased the values of certain thermal properties of the puree. Dielectric properties also were influenced by temperature, as well as by frequency. Results from this study will be useful to engineers in designing of processing and handling equipment for sweetpotato puree.

Technical Abstract: Pureeing of sweetpotato (SP) is carried out to enhance the conversion of the roots into value-added products. During processing, production and home utilization, the puree is often heated (conventional cooking or microwaved), hence the need to measure these properties of SP puree. Thermal (specific heat, thermal conductivity, density and thermal diffusivity) and dielectric properties (dielectric constant and dielectric loss factor) of SP puree were determined within a temperature range of 5 to 80 deg C. Increase in temperature increased the specific heat and thermal conductivity and decreased density and thermal diffusivity of the puree. Both temperature and frequency (900 to 2500 MHz) significantly affected the dielectric constant (60.54-73.02) and dielectric loss factor (16.50-29.53) of SP puree. At the two frequencies (915 and 2,450 MHz) used in industrial food processing, calculations showed that the penetration depth was not significantly affected by temperature at 2450 MHz, while at 915 MHz, the penetration depth decreased with temperature.

Last Modified: 06/27/2017
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