Influence of xanthan and agar-agar on thermo-functional, morphological, pasting and rheological properties of elephant foot yam (Amorphophallus paeoniifolius) starch

Abstract

Limited studies have been reported on the interaction of elephant foot yam (EFY) starch and hydrocolloids. Hence the present study investigated the effect of hydrocolloids (agar-agar, AAG and xanthan gum, XG) concentration (0.5, 1, 1.5 and 2%) on pasting, rheological, thermo-functional and morphological properties of EFY starch. The increase in concentration reduced the swelling index and enhanced the solubility. Peak, holding, break down and set back viscosity was highest at 2% XG than AAG. Dynamic storage modulus (G′) was higher than loss modulus (G″) within frequency range with an increase in hydrocolloids concentration. Pasting temperature reduced from 77.20 to 49.7 °C (AAG) and 77.20 to 61.56 °C (XG). FTIR exhibited differences in peak absorbance and broadness of OH and CO stretching at 3400–3200 cm−1 and 1260–1000 cm−1 upon hydrocolloids' addition. Increased AAG concentration reduced the peak temperature of gelatinization and retrogradation of EFY starch. The effect of hydrocolloids and their concentrations on the higher binding of EFY starch molecules and crystallinity has also been supported by SEM images. These results show that EFY starch with hydrocolloids can be used as a thickener. Its good binding ability may be explored for the possible applications in bakery industry and for the development of edible packaging film.