Aroma release from gum arabic or egg yolk/xanthan-stabilized oil-in-water emulsions

The partitioning and release of limonene and trans-2-hexenal from oil-in-water emulsions was evaluated by applying static headspace gas chromatography. Experiments were carried out on gum arabic/xanthan (GA/X) and egg yolk/xanthan (EY/X)-stabilized emulsions. The dispersed phase (φ0 = 0.05 and 0.20) was composed of sunflower oil, while the oil droplet size (d32) ranged from 0.8 to 12.5 μm. The type of emulsifying/stabilizing system influenced the thermodynamic component, as expressed by the air–liquid partition coefficient (Ka/l) values at equilibrium (37 °C), of the release of limonene only. Increase in lipid fraction decreased the release of both aroma compounds. The oil droplet size had no significant impact on the partition coefficients of trans-2-hexenal, whereas for a lipid content of 20% (v/v) and GA/X stabilizing system, the partition coefficient of limonene was considerably reduced. Additionally, information on the aroma compound diffusion through the liquid–gas interface was obtained by calculating the initial slopes of the time–release curves. Both aroma compounds diffused more slowly through the GA/X-stabilized emulsions compared to EY/X-stabilized systems, while the release rate of limonene was significantly decreased when oil droplet size was increased. This behaviour was attributed to changes in viscosity as well as to reinforcement of xanthan network because of the presence of gum arabic. On the other hand, the nature of the interfacial film and the extent of oil droplet interactions in the EY/X-stabilized emulsions is considered to be responsible for their lower ability to retain the two aroma compounds. Odour assessment experiments were also conducted and the results were found to partially correlate with gas chromatographic results.