Emulsification enhances the retention of esters and aldehydes to a greater extent than changes in the droplet size distribution of the emulsion

The physicochemical and organoleptic properties of an emulsion depend on the way the constituents interact with one another to form emulsion droplets, interfacial region and continuous phase. The objective of this work was to evaluate the respective impact of both the emulsification and the modification of the properties of an emulsion, such as the droplet size distribution, on the partition of aroma compounds. The emulsions were prepared with sodium caseinate and the low melting point fraction of anhydrous milk fat (Φ = 0.3). Their volume-surface mean droplet size ranged from 1.8 to 0.3 μm. Results showed that the measured partition coefficients of ethyl pentanoate, isoamyl acetate, hexanal and t-2-hexenal were lower than the calculated ones from values measured separately over continuous and dispersed phases. The droplet size distribution had no significant impact on the partition coefficient of the three esters whereas, for a volume-surface mean diameter below 0.5 μm, the partition coefficients of the two aldehydes were drastically reduced. The greater retention is not related to the sodium caseinate remaining in the continuous phase of the emulsion. The formation of an interfacial area seems to govern the partition of aroma compounds in emulsions.