FUNCTIONALITY OF GUM-ARABIC - FRACTIONATION, CHARACTERIZATION AND EVALUATION OF GUM FRACTIONS IN CITRUS OIL-EMULSIONS AND MODEL BEVERAGES

Gum arabic, the exudate from Acacia senegal, has been fractionated by size exclusion chromatography (SEC) and by hydrophobic interaction chr omatography (HIC). Five SEC fractions and two HIC fractions have been evaluated in orange oil emulsions and also in model beverages. Compari sons were made on an equal nitrogen and/or equal weight basis to contr ols. Amino acid and other analyses of the whole gum and its fractions have also been performed. While the higher protein, higher mol. wt fra ctions make the best emulsions, all fractions, except the lowest mel. wt fraction (similar to 5% of the whole gum), make reasonably good emu lsions and perform well in model beverage. Although the protein conten t of this last SEC fraction (lowest mol. wt) is comparable to that of the whole gum, the fraction made a very poor emulsion. Since the zeta potential of the droplets in all these emulsions is the same, the diff erences in emulsion stability can be attributed to non-electrostatic f actors. The data support a picture of gum arabic as a very complex, po lydisperse glycoprotein, polydisperse in mol. wt and particularly in p rotein composition. Gum arabic, an excellent emulsifier, is endowed wi th a particularly good combination of many molecular species differing in size and composition.