Effect of storage at low temperature under reduced pressure on fructooligosaccharide content and fructan exohydrolase activity in yacon tuberous roots

Abstract

The tuberous root of yacon (Smallanthus sonchifolius) is a rich source of fructooligosaccharide (FOS), which has a prebiotic effect. However, FOS significantly decreases accompanying (or FOS significantly decreases with) an increase in fructose during cool storage of harvested tuberous roots under normal pressure. The aim of this study was to investigate whether a storage condition at low temperature under reduced pressure could maintain FOS content by suppressing carbohydrate metabolism. After storage at 4? for one month, FOS in the tuberous roots stored at 0.7 atm was effectively retained. In addition, the activity of two endogenous enzymes associated with the degradation of FOS and sucrose, fructan 1- exohydrolase and invertase, respectively, was markedly suppressed at 0.7 atm. These results suggest that low-pressure storage is an effective condition for long-term preservation of FOS-rich yacon tuberous roots.