Modification of gadung (Dioscorea hispida Dennst) starch by ultrasonication and freeze moisture treatment

Gadung starch (Dioscorea hispida dennst.) has several weaknesses related to its low functional properties and stability. Physical modifications of ultrasonication and Freeze Moisture Treatment (FMT) can be an alternative to improve the functional properties by forming cracks and cavities in starch. Hence, this research aimed to obtain modified gadung starch with better functional and physicochemical properties through ultrasonication and FMT. The combination of ultrasonication 30 min + FMT 70 % produced the desired characteristics. This includes the functional properties of starch, which revealed that swelling volume increased by 1.19-fold, solubility increased by 1.17-fold, and Water Absorption Capacity (WAC) increased by 1.31-fold. The stability of the starch paste was better, with a decrease in Breakdown Viscosity (BV) from 3093.50 to 2408.00 cP. The physicochemical properties exhibited that the surface of the starch granules had cracks and cavities, the starch was more amorphous, and the crystallinity decreased from 35.75 to 32.06 and the smaller ratio of the bands at 1045/1022 from 1.412 to 1.396 by FTIR spectra. However, the treatments did not cause changes in crystallinity type (B-type) and functional groups. Therefore, the combination treatment of ultrasonication and FMT effectively improved the properties by forming amorphous gadung starch.