Grape seed and apple tannins: Emulsifying and antioxidant properties

•Tannins were used as emulsion stabilizers alone.•Native tannins did not stabilize emulsions.•Results obtained with oxidized tannins were similar to those obtained with poly(vinyl alcohol).•Even oxidized, tannins exhibited a high antioxidant activity.•Oxidized tannins are both emulsion stabilizers and antioxidants. Tannins are natural antioxidants found in plant-based foods and beverages, whose amphiphilic nature could be useful to both stabilize emulsions and protect unsaturated lipids from oxidation. In this paper, the use of tannins as antioxidant emulsifiers was studied. The main parameters influencing the stability of emulsions (i.e. tannins structure and concentration, aqueous phase pH, and ionic strength) were identified and optimized. Oil in water emulsions stabilized with tannins were compared with those stabilized with two commercial emulsifying agents, poly(vinyl alcohol) (PVA) and polyoxyethylene hydrogenated castor oil. In optimized conditions, the condensed tannins allowed to obtain a stability equivalent to that of PVA. Tannins presented good antioxidant activity in oil in water emulsion, as measured by the conjugated autoxidizable triene (CAT) assay.