Identification and characterisation of water and alkali soluble oligosaccharides from hazelnut skin (Corylus avellana L.)

Hazelnut skins are a good example of agricultural by-product with the potential to become a valuable source of functional ingredients. In this work, the fibre from hazelnut skins was extracted by using water and alkali solution and characterised by a suite of analytical tools (MALDI-FTICR, nano LC-Chip-Q-ToF and gas chromatography). Over thirty complex free oligosaccharides, composed mainly of galacturonic acid and N-acetylgalactosamine, were characterised for the first time in the present study. Their concentration ranged between 16 and 34 mg per g of extract. The oligosaccharides isolated from this agricultural by-product are mainly hexose oligosaccharides (potentially galacto-oligosaccharides,) and xyloglucans. The identified composition could justify the bioactive activity of the extracts, namely prebiotic activity, previously demonstrated.

► Hazelnut skins are an abundant and inexpensive source of natural oligosaccharides.
► Oligosaccharides were characterised by mass spectrometry and gas chromatography.
► About 20 mg/g of galacto-oligosaccharides, and xyloglucans were measured in skins.