Structural characterisation of polysaccharides from roasted hazelnut skins.

Two polysaccharide fractions sequentially extracted with water 1W and alkali 1A, were isolated from the hazelnut skins. The monosaccharide composition together with the FTIR and NMR analyses, indicated that both fractions are formed from a mixture of polysaccharides. The fraction 1W consists of methyl-esterified pectic polysaccharide with rhamnogalacturonan I blocks, branching with arabinose side chains, and with 1,5-, 1,3,5-arabinan and galactan polysaccharides. The fraction 1A is a mixture of deesterified rhamnogalacturonan I and 1,5-, 1,3,5-arabinan and 4-O-Me-glucuronoxylan polysaccharides. The presence of unsaturated galacturonic acid and the heterogeneity of the molecular weights, which M ranged between 3.6 and 39 kg mol, indicated the pectin degradation during roasting.