Gadung (Dioscorea hispida) tuber starch modified by freeze moisture treatment and heat moisture treatment: a study of functional, pasting, and physicochemical properties

Abstract

Gadung starch has limitations in several functional properties and thermal stability. Modifying starch through temperature treatments such as Freeze Moisture Treatment (FMT) and Heat Moisture Treatment (HMT) potentially improves these weaknesses. This research aimed to determine the effects of FMT and HMT on the functional, pasting, and physicochemical properties of gadung starch. This study consisted of a variety of treatments, namely native starch, FMT, HMT 100°C, HMT 110°C, FMT + HMT 100°C, and FMT + HMT 110°C. The results showed that FMT and HMT treatments significantly affected the functional, pasting, and physicochemical properties of gadung starch. The combination modification treatment of FMT + HMT 110°C increased swelling volume by 1.44 times, and water absorption capacity increased by 1.37 times. This was confirmed by the formation of porous and amorphous starch granules. Modified starch also had the best heat stability, as indicated by a low breakdown viscosity of 31.00 ± 9.90 cP. FMT+HMT110°C modified treatment was the best treatment because it had more pores, cracks, and higher swelling volume. The starch crystallinity index of modified starch decreased from 35.75 to 31.58 and changed the crystallinity type from B-type to A-type. The starch modification did not cause changes in functional groups but reduced crystallinity as indicated by the smaller ratio of the bands at 1045/1022 and the higher ratio at 1022/995 from FTIR spectra. Thus, FMT and HMT could effectively improve the characteristics of gadung starch by forming heat-stable amorphous starch.

Keywords

• Starch granule
• swelling volume
• gelatinization
• crystallinity
• porous starch