AVH Association – 7 th Symposium – Reims, March 2000 ABSTRACT The use of novel mass spectrometric techniques, off-line coupled to chromatographic techniques is described in order to obtain molecular mass information of compounds present in complex mixtures of oligosaccharides. Such information could be quite useful in studies where pure and well-defined enzymes are used to study the che- mical fine structure of polysaccharides. Post source decay fragmentation using a Matrix- assisted laser desorption/ionisation Time of flight Mass Spectrometer may result in more detailed structure information of oligosaccharides without laborious purification protocols. In addi- tion to the valuable contribution of HPAEC in the separation of complex oligosaccharide mix- tures, alternatives for the separation of oligosac- charides having alkali-labile substituents are suggested. INTRODUCTION Polysaccharides are important constituents of plant cell walls and represent the bulk of plant biomass. They determine quality attributes of fresh fruits and vegetables (ripeness, texture etc.) and their processing behaviour in the manufacture of foods. Polysaccharides are also predominantly present in by-products of the agro-industry (beet pulp, potato fibre, wheat bran, etc). Much research is focused to reveal the relationship between the chemical structure of the various classes of polysaccharides (e.g. pectin, hemicellulose, and cellulose) and their corresponding functional properties (e.g. stabili- sing, suspending, thickening, gelling, water-hol- ding capacities). Such knowledge is essential for the food industry to come to improved or novel processes and/or products and to extend the use of (components derived from) agricultural by- products in food or feed application. The common way to establish the chemical structure of polysaccharides is starting with the determination of their sugar (linkage) composi- tion, the presence of non-glycosidic substituents like methyl esters and acetyl- and feruloyl groups. However, it is recognised that, in addi- tion to these chemical characteristics, the sequence of the composing sugar moieties within a complex polymer or the distribution of the various substituents over the polymer back- bone play a major role in determining the phy- sical properties of the polysaccharides. Furthermore, the interaction of the various classes of such complex polysaccharides (with each other and with proteins, etc) within the cell wall is of immense importance for the final behaviour of the plant material. These interac- tions also determine the enzymic modifica- tion/degradation by both endogenous and added enzymes. Therefore, specific strategies are being developed to obtain more information on the precise chemical structure of the native polysac- charides. NMR spectroscopy is gaining interest since information about sequences of building blocks can be recognised within a polymer (e.g. pectins: Neiss et al., 1999) although this is quite difficult for more complex/heterogeneous mole- cules. For many years, we are using pure and well-characterised enzymes to obtain oligomeric fragments from polysaccharides in a very defi- ned way. These fragments fit better within the analytical range of chromatographic, spectrome- tric and spectroscopic methods. Following the full characterisation of unknown oligomeric fragments, (hypothetical) structures of the star- 39 HPLC of oligosaccharides: New developments in detection and peak identification Henk SCHOLS, Mirjam KABEL, Edwin BAKX, Piet DAAS, Gert-Jan van ALEBEEK, & Fons VORAGEN Wageningen University, Laboratory for Food Chemistry, The Netherlands