Kinetics of Heat and Mass Transfer and Color Development of Pre-Treated Sweet Potatoes During Frying

Abstract

The potential utilization of sweet potatoes in the production of fries was examined. The influence of various pre-treatments (blanching, freezing, osmotic dehydration, and air-drying) on moisture loss, color development, and temperature rise in the product was investigated. Pre-treated sweet potato disks were fried in pure canola oil at 170C for 0.5 to 5 min. Temperature rise within the product was similar for all pre-treatments except for samples frozen prior to frying. The maximum temperature range recorded was 166.7C to 168.6C for both the top and bottom surfaces. Air-drying, freezing, and osmotic dehydration (OD) in 3% NaCl solution accelerated moisture loss during frying. Both the frying time and pre-treatment influenced moisture content of the core, and final values ranged between 66.2% and 78.7%. Pre-treated samples had higher L, a*, and b* values, which became significant with longer frying periods and resulted in improved product color. Air-drying and OD may be considered as pre-treatments in the production of sweet potato fries.