Effects of Citric Acid Concentration and Hydrolysis Time on Gembili (Dioscorea esculenta) Starch from Indonesia

In this study, we investigated the effects of various citric acid concentrations and hydrolysis times on the physical and chemical characteristics of gembili (Dioscorea esculenta) starch. The gembili starch was hydrolyzed using citric acid at concentrations of 0.1, 0.2, and 0.3 M for 6, 12, 18, and 24 h. The recovery yield was between 90.67% and 96.03%, with the highest amylose and resistant starch, following starch hydrolysis, at a citric acid concentration of 0.1 M and hydrolysis time of 12 h (C1-12). Starch hydrolysis using 0.1 M citric acid increased the oil holding capacity, while the water holding capacity remained the same for all treatments. During hydrolysis at concentrations of 0.2 and 0.3 M, solubility increased, whereas swelling power decreased. The L* value and whiteness index increased at citric acid concentrations of 0.2 and 0.3 M, respectively. The starch exhibited type-A diffraction patterns and polygonal morphology in all treatments. Pasting properties analysis indicated no significant differences with the same citric acid concentrations, except for pasting temperature observations with the value between 77.65°C to 80.95°C. Thermal properties analysis revealed that the onset temperature value was significantly different in the native and citric acid-hydrolyzed starches. Particle size distribution analysis indicated a wider range of particle sizes at increasing concentrations of citric acid. Fourier transform infrared spectroscopy analysis indicated a lack of new peaks after the modifications. The results of this study provide information on the effects of acid hydrolysis on the functional properties and health benefits of gembili starch.