This study was performed to investigate the quality characteristics of sweet potato(shinyulmi, yeonhwangmi and yeonmi) and chip(shinjami, juhwangmi and hayanmi) baked by far-infrared radiation.
In baked sweet potato manufacturing, baking was performed with far-infrared ray radiant oven at 250℃ for 40 minutes. Baked sweet potatoes were frozen at -18℃, and thawed by microwave oven for 3 minutes. Starch content of sweet potatoes were higher in yeonhwangmi than shinyulmi and yeonmi variety. Water binding capacity of sweet potato starches was higher in shinyulmi than yeonhwangmi and yeonmi variety. Water solubility and swelling power of sweet potato starches were increased as increasing temperature. In pasting properties of sweet potato starches, peak, trough, breakdown and final viscosity were lower in shinyulmi than yeonhwangmi and yeonmi variety. Total sugar and reducing sugar content were increased after baking. Maltose and sucrose content were increased from 3.09∼4.53 and 0.85∼1.42% to 4.16∼6.00 and 11.84∼13.18% after baking respectively. In vitro digestibility by α-amylase were increased from 26.11∼34.02% to 75.71∼82.24% after baking. Lightness, redness and yellowness were decreased by baking and thawing after freezing. β-carotene content was decreased from 198.14∼518.67 ㎍/100 g to 116.82∼212.01 ㎍/100 g by baking and thawing after freezing. In sensory evaluation, appearance, flavor, sweetness and overall acceptance were higher in baking and thawing after freezing of shinyulmi than yeonhwangmi and yeonmi variety. Overall acceptance, free sugar contents and b-value were high correlation among factors affecting sensory characteristics(p<0.05).
In sweet potato chip manufacturing, optimization of processing condition was performed in slicing thickness(1∼3 mm), baking temperature(110∼140℃), baking time(23∼31 min), concentration of sucrose solution(15∼30%) and blanching time(15∼60 sec) through sensory evaluation, color measurement and texture analysis. Optimal processing condition of sweet potato chip using shinjami was determined to be 1 mm for slicing thickness, 120℃ for baking temperature, 31 min for baking time, 20% for sucrose concentration and 45 sec for blanching time and, juhwangmi was determined to be 1 mm for slicing thickness, 130℃ for baking temperature, 29 min for baking time, 25% for sucrose concentration and 45sec for blanching time and, hayanmi was determined to be 1 mm for slicing thickness, 120℃ for baking temperature, 31 min for baking time, 20% for sucrose concentration and 45sec for blanching time. Total anthocyanin content was decreased in shinjami after baking and, was not detected in raw material and chip of juhwangmi and hayanmi variety. β-carotene content was higher in juhwangmi than shinjami and hayanmi variety and, was decreased after baking. free sugar and reducing sugar content of sweet potato chips were higher juhwangmi than shinjami and hayanmi variety. In sensory evaluation, appearance, sweet taste, hardness and overall acceptance were higher in juhwangmi than Shinjami and hayanmi variety. Overall acceptance, sugar contents, hardness and b-value were high correlation among factors affecting sensory characteristics(p<0.01).
From the results of this study, shinyulmi variety was selected for production of baked sweet potato with freezing and, juhwangmi variety was selected for production of sweet potato chip.