GC-MS and HPAEC-PAD characterization of pectic oligosaccharides (POS) derived from hydrolysis of citrus and apple pectins

Trabajo presentado al XVI Scientific Meeting of the Spanish Society of Chromatography and Related Techniques, celebrado en Sevilla (España) del 2 al 4 de noviembre de 2016.Pectins are one of the most structurally complex families of polysaccharides in nature and are isolated on an industrial scale mainly from apple and citrus peels. Besides, these pectins are widely used as functional food ingredient. Pectic oligosaccharides (POS) are obtained by depolymerisation of pectins by chemical, enzymatic and combined methods. POS include various types of oligomers, i. e. oligogalacturonides (OGalA), galacto-oligosaccharides (GalOS), arabino-oligosaccharides (AraOS), rhamnogalacturono-oligosaccharides (RhaGalAOS), xylo-oligogalacturonides (XylOGalA) and arabinogalacto-oligosaccharides (AraGalOS). The structural characterization of POS is very difficult however different chromatographic methods have been developed for their characterization such as HPAEC-PAD and GC. Therefore, the aim of this work was to characterize by GC-MS and HPAEC-PAD of POS obtained by enzymatic hydrolysis of citrus and apple pectins using two commercial enzyme preparations. POS were obtained by enzymatic hydrolysis of 1% (w/v) of commercial citrus and apple pectin using 16 U/mL of Glucanex 200 G and 4 U/mL of Viscozyme L preparations. Depolymerisation reactions were followed by HPLC-SEC-RID and GC-FID. Then, optimal conditions of hydrolysis were selected and POS formed were characterized by HPAEC-PAD and GC-MS. According to the results obtained by HPAEC-PAD maximum POS formation was achieved at 30 min of hydrolysis ranging from to 448.9 to 929.3 mg/g pectin. Digalacturonic and trigalacturonic acid were identified among other minor compounds. Molecular weight of POS varied from 0.2 to 9.6 kDa (HPLC-SEC-RID). GC-MS allowed determining m/z ions 217, 332 and 540 corresponding to galacturonic acid fragments in all samples. In addition, m/z ions 423, 321 and 277 derived from ß-cleavage fragmentation of uronic acids were reported in small abundance. Citrus and apple pectins behave similarly, however the two enzymatic preparations studied produced different chromatographic profiles of POS.This work has been funded by MINECO of Spain: Project AGL2014-53445-R.Peer Reviewe