Effect of the removal of yacon root astringency on taste and function

Abstract

Yacon (Smallanthus sonchifolius) root is regarded as a functional food material because it contains polyphenolrich antioxidants, fructooligosaccharides, and dietary fiber. The taste of fresh yacon root is similar to that of pear, juicy and sweet. However, a peculiar astringency is also perceived in yacon root. When astringent persimmon is exposed to ethanol (EtOH) vapor, the astringency is removed. This process is recognized as being effective for astringency removal. In this study, we applied EtOH vapor treatment for removing yacon root astringency. During vapor treatment, yacon was kept in a small chamber (3 L) containing 20mL of 10-90% EtOH solution at 20? under darkness. The removal of astringency was evaluated using decreases in soluble tannin concentrations in treated yacon juice. After 48hr of 30% EtOH vapor treatment, the amount of soluble tannins decreased to ca.14 %. Sensory evaluation revealed improvement in the smell, texture and taste. Moreover, the antioxidative activity and the fructooligosaccharide composition in the juice were retained through the treatment period. Antioxidative activity was maintained at levels above 97 %, and changes in fructooligosaccharide composition were minimal. In conclusion, we confirmed that the astringency of yacon root could easily be removed, with the treated root maintaining a healthy function.