Novel emulsifiers from olive processing solid waste

• Solid olive processing waste yields efficient emulsifiers.
• The emulsifying extracts comprise of hydrocolloids and smaller molecules.
• The composition and structure of the emulsifying extracts has been studied.
• The emulsifiers show synergy between larger and smaller molecular components.
• Olive waste, a major pollutant, could be a source of hydrocolloids.

Emulsifiers fit for use in oil-in-water emulsions have been extracted from solid olive processing waste, using aqueous solutions under parallel and tandem extractions. SEC–MALLS/RI/UV and FTIR results showed that these products comprise of polysaccharide agglomerates, proteins and their hydrolysis products, among other constituents. The materials obtained using direct extraction at pH 7 and pH 5 of the alcohol-insoluble solid waste are effective emulsifiers for acidic and non-acidic model food emulsions, while their zeta potential values are negative at both pH. Dynamic interfacial tension measurements at the water/oil and water/air interface demonstrate surface activity. Significant differences in the dynamics of adsorption of different extracts and in their equilibrium interfacial tension are related to their emulsifying capacity and emulsion stability. SEC data of the centrifuged emulsions' serum show that most macromolecular components are interfacially adsorbed. When tested as emulsifiers, the dialysis-isolated macromolecular populations alone are moderately efficient emulsifiers, as compared to the full extracts. Smaller molecules present in the extract appear to provide a synergistic effect in the overall emulsification capacity. The above suggest that olive waste, a major pollutant in the Mediterranean and in other areas, could be used as to reclaim high added value food hydrocolloids.

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