Despite widespread use of citral in foods and beverages, the compound is known to degrade over time under acidic conditions, resulting in a loss of desirable flavours and formation of undesirable off-flavours.
The compound Tween 80 is already used by the food industry as a surfactant – an ingredient that improves oil-in-water emulsion stability by lowering the surface tension of at the interface between oil and water. By incorporating Tween 80 into oil-in-water emulsions it was possible to alter the stability of citral to chemical degradation, say scientists from the University of Massachusetts and flavour giant International Flavors and Fragrances (IFF) in Food Chemistry.
Approaching the same problem from a different angle, the researchers report that use of the non-ionic surfactant PGPR (polyglycerol polyricinoleate) produced so-called reverse micelles in the emulsion, and these too could protect against citral degradation in a beverage formulation.
Despite the positive results, questions remain about the applicability of the development for finished beverage emulsions: The levels of surfactants needed to achieve the results were relatively high, said the researchers, “and may be unsuitable for commercial applications due to cost, taste or regulatory reasons”.
“Future studies should examine the impact of other food grade water-soluble and oil-soluble surfactants on citral degradation in emulsions to minimize its degradation, since it may be possible to utilize lower levels than those used in this study to prevent degradation,” wrote the researchers, led by David Julian McClements from U of M.
The researchers produced micelles and reverse micelles in oil-in-water emulsions. As the concentration of Tween 80 (Sigma Chemical) increased from 1 to 5 per cent, the degradation of citral decreased. This result suggested that incorporation int micelles protected the citral from degradation, said the researchers.
The presence of reverse micelles produced using PGPR (Palsgaard) also increased the stability of citral, with the researchers noting a decrease in “the percentage of citral present within the aqueous phase of the emulsions, suggesting that citral was preferentially incorporated into the reverse micelles”.
“These results show that either micelles or reverse micelles may be used to improve the chemical stability of citral in beverage emulsions,” concluded the researchers.
Source: Food Chemistry
Published online ahead of print, doi: 10.1016/j.foodchem.2010.02.025
“Inhibition of citral degradation in model beverage emulsions using micelles and reverse micelles”
Authors: S.J. Choi, E.A. Decker, L. Henson, L.M. Popplewell, D.J. McClements