Characterization of the structural and emulsifying properties of sugar beet pectins obtained by sequential extraction

In this study, we examine how the extractant type used and extraction steps effect the structural and emulsifying properties of the resulting sugar beet pectins (SBPs). Using ammonium oxalate and sulfuric acid as the extractants, two oxalate-extracted pectins (denoted OEP1 and OEP2) and four acid-solubilized pectins (denoted AEP1, AEP2, AEP3 and AEP4) were sequentially extracted and characterized regarding their structures and emulsifying properties. All six pectins shared common features such as having a high galacturonic acid content and a low methylation degree, however, OEP1 and OEP2 not only had lower amounts of ferulic acid (FA) and protein but their molecular sizes were also smaller in comparison to the remainder. Moreover, the oxalate-extracted sample series was significantly different from the acid-extracted sample series in regards to amino acid compositions. Due probably to the hydrophobicity of the proteinaceous components and the lower contents of FA and protein, OEP1 failed to stabilize oil-in-water emulsions containing 15% middle chain triglyceride (MCT). In contrast, AEP1-4 were shown to have better emulsifying activities, producing fine emulsions under favorable conditions (e.g. pectin concentration 1.5%). The d(43) values of the emulsions prepared at a 1.5% concentration of AEP2, AEP3, or AEP4 did not markedly change throughout the period of storage (28 days) at 30 degrees C, whereas the AEP1 emulsion was relatively less stable. The correlation between emulsifying properties and the structures among the acid-extracted pectins highlights that the extraction sequence plays an important role in the resulting compositional and emulsifying properties of SBP.