Concentration and Purification of Yacon (Smallanthus sonchifolius) Root Fructooligosaccharides Using Membrane Technology

Yacon is a perennial plant originating from the Andean region whose roots have been receiving increased attention due to their high content of prebiotic fructooligosaccharides (FOS). Apart from many health benefits, FOS have interesting characteristics as food ingredients, so are used as sugar substitute, and their extraction from yacon roots may be an alternative to commercially available FOS. This work evaluates membrane technology for concentration and purification of FOS from yacon root extract, combining ultrafiltration (UF) with nanofiltration (NF), with and without the use of discontinuous diafiltration (DF). After UF, 63.75% of the saccharides from the initial feed were recovered in total permeate. DF did not largely influence FOS retention during NF (it increased from 68.78% without DF to 70.48% with DF), but decreased glucose and fructose retentions, from 40.63 to 31.61% and 25.64 to 18.69%, respectively, which was desirable, allowing greater purification of FOS in the retentate. The yield of total saccharides in the final retentate after combined UF and NF processes was 50.89% and of FOS was 51.85%, with 19.75% purity. The results indicate that the combined UF and NF is a promising technique for concentrating yacon saccharides, but more diafiltration steps are required for the improvement of FOS purity.