Morphology and functional properties of corn, potato and tapioca starches

In this study, morphology and functional properties of commercial native corn, potato and tapioca starches were evaluated. Morphological study with light and scanning electron microscopy revealed that these starches had unique granule characteristics. The starches were observed to be almost insoluble in water at 20 °C but upon heating to 70 °C, they were solubilized in water to an extent of 3.89, 13.49 and 14.36% for corn, potato and tapioca starches, respectively. Among these, corn starch held less water as compared to potato and tapioca starches. The viscosity of starches was almost same at low concentration (0.1%, w/v) but increased curvilinearly with the increase in concentration to 0.5% in ascending order for tapioca, corn and potato starches and at high concentration (5%, w/v) they showed shear thinning behaviour. Corn starch exhibited high viscosity stability to shear. The pasting curves of starches during cooking, using rapid visco-amylograph indicated that corn showed higher degree of crystallinity since it gelatinized apparently at higher temperature. Other pasting properties of starches like peak viscosity, final viscosity and breakdown were higher for potato compared to corn followed by tapioca but the setback tendency gave an opposite trend. Potato starch gelled at lower concentration followed by corn and then tapioca starches. Texture profile analysis results showed that potato starch gel was harder, sticky, gummy and chewy than that of corn and tapioca starch gels. The moisture sorption isotherm described with the help of GAB equation revealed that potato starch had higher heat sorption and monolayer moisture content compared to corn and tapioca starches.