Skip to main content
ARS Home » Southeast Area » Raleigh, North Carolina » Food Science Research » Research » Publications at this Location » Publication #103192
Title: RHEOLOGICAL AND PHYSICOCHEMICAL PROPERTIES OF STARCHES FROM MOIST- AND DRY-TYPE SWEETPOTATOES

Author
item Walter Jr, William
item TRUONG, V - NCSU
item WIESENBORN, D - NCSU
item CARVAJAL, P - NCSU

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2000
Publication Date: 7/1/2000
Citation: Walter, Jr., W.M., Truong, V.D., Wiesenborn, D.P., Carvajal, P. 2000. Rheological and physicochemical properties of starches from moist- and dry-type sweetpotatoes. J. Agric. Food Chem. 48:2937-2942.

Interpretive Summary: Sweetpotato cultivars and experimental selections exhibit a wide range of textural properties when cooked. These characteristics have been described from a sensory standpoint as mouthfeel attributes ranging from moist to dry (characteristic of white potatoes). Although starch makes up a significant part of the dry matter of sweetpotatoes, its effect on texture of cooked sweetpotatoes is unknown. The purpose of this research was to find out if the physical properties of purified starches were related to the textural properties of cooked sweetpotatoes. To conduct this research we isolated and analyzed starches from sweetpotato cultivars and experimental selections representing three sweetpotato texture types (moist, intermediate, and dry). We then compared starch properties to the texture of cooked sweetpotatoes as determined by taste panels. We found that, although differences in physical properties were observed for sweetpotato starches, there was little relationship between these properties and sensory texture characteristics of the cooked roots. This indicates that factors other than starch properties are responsible for texture of cooked sweetpotatoes. For plant breeders, these results mean that parameters other than starch properties must be developed as an index of the textural properties for newly developed sweetpotato cultivars.

Technical Abstract: Although starch makes up from 50 to 70% of sweetpotato (SP) dry matter, its role in cooked texture is unknown. The purpose of this research was to characterize starches from SP cultivars and experimental selections (C/S) with a wide range of textural properties and investigate the relationship between textural properties and starch characteristics. Shear stress measured by uniaxial compression of cooked SP cylinders served as an objective measure of SP texture. We isolated starches from C/S representing three SP texture types: moist - Jewel and Beauregard; intermediate - NC10-28 and NC2-26; dry - NC6-30 and NC8-22. We measured the following parameters of isolated starches: amylose content by colorimetric and differential scanning calorimetric (DSC) methods; swelling power, solubility, gelatinization enthalpy (deltaH), and pasting properties by Brabender Amylograph (BA) and Rapid Viscoanalyser (RVA). Pasting temperatures for SP C/S measured by BA and RVA were significantly correlated. Due to high shear degradation in RVA, RVA viscosities of starch solutions were from 5- to 12-fold lower than corresponding BA viscosities. There were no statistically significant differences among the C/S for amylose or deltaH. However, significant C/S differences in swelling power, solubility, and pasting properties were observed. Although differences in some rheological and physical properties were observed for C/S starches, we found that shear stress was statistically correlated only with DSC onset temperature (r = 0.78), indicating that, with the exception of DSC onset temperature, the physical and compositional properties measured in this study do not significantly contribute to the texture of cooked SP C/S.