Submitted to: Lebensmittel Wissenschaft und Technologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/2007
Publication Date: 11/14/2007
Citation: Grabowski, J.A., Truong, V., Daubert, C.R. 2007. Nutritional and rheological characterization of spray dried sweetpotato powder. Lebensmittel Wissenschaft und Technologie. 41:206-216. Interpretive Summary: Processing of sweetpotatoes into spray-dried powders is an approach to convert this highly nutritious vegetable into a functional ingredient. Recently, we reported that spray-drying of sweetpotato puree is technically feasible using alpha-amylase to reduce puree viscosity and maltodextrin to facilitate drying. Further physicochemical characterization of the produced powders is needed to determine potential applications of sweetpotato powders in processed food products. Thus, nutrient analysis and rheological characterization of sweetpotato powders were performed. Results indicated that spray-drying significantly reduced the amount of beta-carotene and ascorbic acid in the final product. Additionally, the all-trans form of beta-carotene was further transformed to the cis-isomer during dehydration. The viscosity of reconstituted powder solutions was much lower than that of the puree at the same solid concentration. Maltodextrin greatly increased the dispersibility of powder particles in solution and contributed to decreased viscosity. Reconstituted sweetpotato slurries did behave similarly to pre-gelatinized starch solutions. Thus, sweetpotato powder has the potential to be utilized as a functional ingredient for enhancing natural color and flavor, and acting as a thickening ingredient like pre-gelatinized starches in food systems. However, the nutrient retention of spray dried sweetpotato powders would have to be further improved to make the powders more attractive to food product developers and consumers.
Technical Abstract: Spray drying feasibility of sweetpotato puree is enhanced using alpha-amylase treatment to reduce puree viscosity and maltodextrin addition to facilitate drying. To better determine potential applications of powders produced with various levels of amylase and maltodextrin, nutrient composition and rheological properties of the hydrated spray dried sweetpotato powders were examined and compared with sweetpotato puree. Proximate composition, beta-carotene, vitamin C, and mineral analyses were performed. Steady shear rheology of reconstituted powder solutions was also evaluated at different temperatures and shear rates. Spray drying significantly reduced the '-carotene and ascorbic acid contents. Additionally, the all-trans form of beta-carotene was further transformed to the cis-isomers during dehydration. The viscosity of the reconstituted solutions was much lower than that of the puree at the same solid concentration. Rheologically, the reconstituted sweetpotato slurries behaved similarly to pregelatinized starch solutions. Thus, spray dried sweetpotato powders have a potential to enhance food systems as a thickener despite the need for increased nutrient retention.