Olive Pomace, a Source for Valuable Arabinan-Rich Pectic Polysaccharides

Cell wall polysaccharides account for nearly one third of olive pomace dry matter produced by the environment friendly biphasic system. These polysaccharides are mainly cellulose, glucuronoxylans, and arabinan-rich pectic polysaccharides, in equivalent proportions. The structural features of pectic polysaccharides are unique concerning the arabinan moiety due to the occurrence of a beta-(1 -> 5)-terminally-linked arabinose residue. This odd feature tends to disappear with olive ripening and can be used as a diagnostic tool in the evaluation of the stage of ripening of this fruit, as well as a marker for the presence of olive pulp in matrices containing pectic polysaccharides samples. These pectic polysaccharides have the ability to form elastic gels with calcium. The critical gelling calcium and galacturonic acid concentrations are higher than that observed for commercial citrus low-methoxyl pectic material. Nevertheless, they present a syneresis occurring for much higher calcium concentration and, consequently, show a much larger zone in which homogeneous gels are formed. In addition, olive pomace pectic polysaccharides gels are more resistant to temperature than the low-methoxyl pectin/calcium gels. These properties show that olive pomace can be a potential source of gelling pectic material with useful properties for particular applications.