Improvement of a Method for Production of Konnyaku Powder Using Ultrasonic Treatment

Abstract

Aiming at promoting the utilization of konnyaku powder, we developed a mannan washing apparatus equipped with an ultrasonication treatment system that allows refinement of the powder on an industrial scale. Then, we attempted to determine the optimum conditions for its refinement and to improve the powder's quality using the apparatus. (1) Regarding the optimum conditions for the refinement of konnyaku powder, it was found that an ethanol concentration of 30% and a refinement temperature of 30°C were critical and the treatment by ultrasonication twice, for 10min and 5min, was most effective for the refinement. The konnyaku powder produced by the method with ultrasonication treatment showed a higher degree of whiteness than that produced without ultrasonication treatment. Furthermore, the levels of undesirable odors from the gel were markedly reduced and the appearance, viscosity and dietary fiber content were superior in the former product. In addition, the sensory attributes quality of the gel was very high in the product prepared by using ultrasonication. It was thus demonstrated that the quality of konnyaku powder was improved using the newly developed apparatus. (2) Examination by scanning electron microscopy showed that the superficial roughness as well as the hollows and wrinkles in the powder particles produced by the new method was more marked, indicating that ultrasonication treatment has significant effects in improvement of the quality of konnyaku powder. (3) The physicochemical and sensory properties of konnyaku powder refined by the present method were similar to those of konnyaku powder refined by the small-scale method described in our previous paper.