Enhancing the potential of oligosaccharides from corncob autohydrolysis as prebiotic food ingredients

Milled corncobs were treated with hot, compressed water under a variety of operational conditions to cause the hydrolytic degradation of arabinoxylan. Hemicellulose-derived products (substituted oligosaccharides and monosaccharides) and non-saccharide compounds were found in the reaction media. Liquors obtained in hydrothermal treatments carried out under optimal conditions were concentrated and subjected to crossflow ethyl acetate extraction (three stages) and ionic exchange (with Amberlite IRA 400 or Amberlite IRA 96) to decrease the content of non-saccharide components. The various streams involved in the whole process were assayed for composition, and material balances were formulated for the best situation. The highest purification degree corresponded to operation with Amberlite IRA-400, which led to a final isolate (made up of monosaccharides, substituted oligosaccharides and nonvolatile, non-saccharide components) containing 88.7 weight percent of saccharides and 11.3 weight percent of non-saccharide components (mainly made up of phenolic substituents and melanoidins). The recovery of soluble oligosaccharides accounted from 23.3 weight percent of the raw material, whereas the yield in substituted xylooligosaccharides reached 45.5% of the amount corresponding to the stoichiometric conversion of the polymeric components contained in the raw material.