Structural characteristics of pectic polysaccharides from olive fruit ( Olea europaea cv moraiolo) in relation to processing for oil extraction

Abstract

In the olive oil industry technical enzyme preparations are used as processing aids to improve the extraction yield and product quality. In order to obtain more insight in the mechanisms by which these enzyme preparations lead to a higher yield and a better quality, the effect of these preparations on the structure of the pectic polysaccharides present in the cell wall of olive fruit was investigated. Four pectin-rich fractions were isolated from the cell wall material of non-enzyme treated and enzyme treated olive fruit by successive extractions with cold buffer, hot buffer, chelating agents and diluted alkali and analysed. The results revealed that the use of technical enzyme preparations during processing mainly affected the pectic material present in the cold and hot buffer fractions. The structures of the arabinose-rich pectic polysaccharides solubilised by extraction with chelating agents and diluted alkali were barely affected by the use of enzyme preparations. The changes of the buffer soluble pectic material were reflected by a decrease in methyl esterification, a change in molecular weight distribution and a degradation of the (1→4)-linked galactan chains. No differences were observed in the composition of the arabinan chains. Also, the structural features of the polysaccharides present in the vegetation waters, the liquid by-product of olive processing, were studied. The sugar composition indicated the presence of mainly material of pectic origin in the vegetation waters. As a result of enzymatic processing the degree of methyl esterification decreased, the profile of the molecular weight distribution changed and the (1→4)-linked galactan chains were degraded as was also shown for the buffer soluble pectic polysaccharides.