Optimization of Purification Process of Konjac Glucomannan by Response Surface Methodology

The fat, protein and other compounds in konjac powder limit the application of konjac glucomannan. Konjac glucomannan with relatively high purity could be applied in food, medicine and other sectors. This research aimed to optimize the ultrasonic assisted purification process of glucomannan from konjac powder with ethanol. The significance effects of five relevant factors including the ratio of konjac powder to ethanol, ethanol concentration, ultrasonic time, power and temperature were analyzed based on single factor analysis of variance. The first three aforementioned factors were selected for further analysis their significant effects on the purity of glucomannan. Moreover, the relevant factors were optimized via response surface model fitting. The final optimized parameters were as follows: 1:102 (g/mL) for the ratio of konjac powder to ethanol, 73% ethanol, 55 min ultrasonic time, 175 W ultrasonic power, 50 ℃ ultrasonic temperature. The content of konjac glucomannan under the process condition was 88.1%, which was close to the predicted value, and the purification process of glucomannan from konjac powder was feasible. The structure of the samples before and after optimization were measured by infrared spectroscopy and X-ray diffraction with no significant difference. The content of konjac glucomannan in the purified konjac powder by this process was significantly higher than that in the unpurified one, and the structure was less affected. Results from this study could provide theoretical support for efficient utilization of konjac glucomannan and development of relevant functional products.