Spray-Drying of Amylase Hydrolyzed Sweetpotato Puree and Physicochemical Properties of Powder

Spray-drying, which has been used for commercial production of functional ingredients from several fruits and vegetables, has not yet been studied for sweetpotato processing. Thus, the objective was to determine the effects of viscosity reduction of sweetpotato puree with alpha-amylase, maltodextrin (MD) addition, and inlet air temperature on the physicochemical characteristics of spray-dried sweetpotato powder. A face-centered cube design was used to evaluate the effects of amylase level (0, 3.75, and 7.5 mL/kg puree), MD concentration (0%, 10%, and 20%), and inlet air temperature (150 ◦C, 190 ◦C, and 220 ◦C) on powder characteristics. Model-fitting using response surface methodology was performed to examine the effects of independent variables on the moisture content, color, water absorption, solubility, particle size, bulk density, and glass transition temperature. The data were fit to a full second order polynomial equation. However, only the linear and quadratic terms proved to be significant for most dried powder attributes. MD significantly increased powder solubility, altered the hue value, and raised the glass transition temperature of the powder. Pretreatment with alpha-amylase resulted in a lower glass transition temperature and a decrease in particle size. Overall, results show that good quality sweetpotato powders can be produced using this drying method, with potential applications in food and nutraceutical products.