Study deepens emulsion-flavour release understanding

Researchers from the University of Thessaloniki investigated the release of the flavour compounds limonene and trans-2-hexenal from emulsions formulated using gum arabic or egg yolk/xanthan gum.

"Gum arabic as well as egg yolk are two very common emulsifiers used in many food formulations and their impact on aroma release from emulsions stabilized with xanthan gum has not been systematically investigated so far," they wrote in the journal Food Research International .

The research could have implications for food formulators looking to extend or enhance oil-in-water or water-in-oil emulsions, like salad dressings, beverages, dips, sauces, desserts, and yoghurts.

Flavour release from such emulsions is complicated by the two-phase systems since the flavour/ aroma compounds may be distributed in the oil phase, the aqueous phase, and/or the interface.

Whipping up new data Emulsions composed of sunflower oil in water, and stabilised by gum arabic/xanthan (GA/X) and egg yolk/xanthan (EY/X) were tested and the flavour release of limonene and trans-2-hexenal.

An increase in lipid/oil fraction was found to decrease the release of both aroma compounds, according to data obtained using static headspace gas chromatography.

Moreover, both compounds diffused quicker through the egg yolk/xanthan-stabilised emulsion than the gum arabic/xanthan-stabilised emulsion.

"This behaviour was attributed to changes in viscosity as well as to reinforcement of xanthan network because of the presence of gum arabic," stated the Greek researchers.

This quicker diffusion of the aroma compounds through the egg yolk/xanthan-stabilised emulsion indicated a lower ability to retain the aroma compounds.

The researchers cite the nature of the interfacial film and the extent of oil-droplet interactions as the reason for this observation.

"Lipid/water phase ratio fraction influenced the release of both aroma compounds, while the increased surface area, resulting from oil droplet size reduction, enhanced the release of limonene but had no effect on trans-2-hexenal," stated the researchers.

"Additionally, the nature of the oil-water interface as well as the interactions which may take place between macromolecules present in the aqueous phase are possibly more related to the higher retention degree of limonene in gum arabic than egg yolk containing emulsions," they concluded.

The taste of success Taste is a key driver in the €3.2 trillion global food industry and a greater understanding of the physiology of consumers, could lead to strong market advantages.

Researchers from Agri-Food Canada recently reported in the Journal of Food Science that the release of flavour from food is dependent on the oil content of the emulsion.

"It appears that the hydrophobic flavour release profile in oil-in-water emulsion could be optimised by appropriate alteration of emulsion composition," stated the Agri-Food Canada scientists.

Not only did the researchers provide significant evidence for the relationship between emulsion oil content and flavour release, they also report a new technique for measuring flavour release that offers a "rapid, simple and sensitive instrumental approach in real time."

The technique, a modification of gas chromatography, enabled the researchers to evaluate the effect of protein, oil and aroma concentrations on flavour release from model emulsions.

Source: Food Research International Published online ahead of print, doi: 10.1016/j.foodres.2008.04.004 "Aroma release from gum arabic or egg yolk/xanthan -stabilized oil-in-water emulsions" Authors: S. Karaiskou, G. Blekas, A. Paraskevopoulou