Inhibition of citral degradation in model beverage emulsions using micelles and reverse micelles

Coral is a flavour component that is widely used in the beverage, food, and fragrance industries. Citral chemically degrades over time in aqueous solutions due to acid catalysed and oxidative reactions, leading to loss of desirable flavour and the formation of off-flavours. We examined the influence of surfactant micelles (Tween 80) in the aqueous phase and reverse micelles (polyglycerol polyricinoleate, PGPR) in the oil phase on the oil-water partitioning and chemical degradation of citral in medium chain triglyceride oil-in-water emulsions. The percentage of citral in the aqueous phase of the emulsions increased with increasing Tween 80 concentration, which was attributed to its incorporation within surfactant micelles. The rate of citral degradation decreased as the Tween 80 concentration was increased from 1% to 5% w/w in both aqueous solutions and in emulsions, suggesting that citral was protected from degradation once it was incorporated into micelles. The presence of reverse micelles (5% or 10% w/w PGPR) in the oil droplets decreased the percentage of citral present within the aqueous phase of the emulsions, suggesting that citral was preferentially incorporated into the reverse micelles. In addition, the presence of reverse micelles increased the chemical stability of citral, possibly because a greater fraction remained within the oil droplets. These results show that micelle or reverse-micelle structures may be used to improve the chemical stability of citral in beverage emulsions. (C) 2010 Elsevier Ltd. All rights reserved.