Effect of cookingon the fructooligosaccharide content of yacon root

Abstract

Yacon (Smallanthus sonchifolius), a vegetable which originates from the Andean region in South America, was introduced to Japan about 20 years ago. Yacon root is known to be a good source of fructooligosaccharides (FOS). However, the effects of cookingon the FOS content in roots have not been sufficiently investigated. In this study, roots of four species of yacon (Peru-A, Sarada-Otome, Andesu-No-Yuki and Sarada-Okame) were cooked by several methods, such as boiling, microwaving, and steaming, and FOS was extracted from the treated roots and evaluated. Furthermore, the effects of peelingand gratingon FOS content in the root were investigated. The followingresults were obtained: 1) Yacon FOS decreased markedly by storage at 4°C for 1month, 2) FOS decreased by heating at 100°C after peeling and grating, 3) FOS in species, except for Sarada-Otome, was little influenced by treatment with 1% acetic acid for 1 hour, 4) FOS dramatically decreased with deep-fryingand was little influenced by heatingby methods such as boiling, microwaving, baking and steaming, and 5) Yacon extracts from Sarada-Otome containing 4% FOS had decreased emulsifying activity and increased emulsion stability. These findings suggest that high concentrations of FOS from yacon root could be obtained by usingsuitable cookingconditions.