Effect of fermentation time on the quality of modified gadung flour from gadung tuber (Dioscorea hispida Dennst.)

Gadung (Dioscorea hispida Dennst.) is one of the tubers in Indonesia that has the potential as a food source. However, due to the low nutritional value and high content of cyanide acid, these tubers cannot be consumed directly. Therefore, proper processing techniques are needed to improve the nutritional value of gadung tubers. The aim of this study was to investigate the effects of fermentation time on the quality of modified gadung flour in a reasonably short time. Soaking and submerged fermentation processes were applied. It was found that modified gadung flour can be used as a wheat flour substitution under the following conditions: water to gadung mass ratio of 50 for 120 min (soaking process) and initial bacteria cell number of 1.21 x 10¹¹ cells of Lactobacillus plantarum at the temperature of 32°C for 36 h (fermentation process). The result showed that protein, cyanide acid, starch, amylose, and amylopectin contents were 7.63%, 6.66 ppm, 75.27%, 38.18%, and 61.82%, respectively, while physicochemical properties, such as swelling power, water solubility, and flour whiteness degree were 6.75 g/g, 0.56%, and 71.43%, respectively.