Mint oil is a very popular flavouring agent in food formulations, but its complex mixture of volatile and labile components makes it very sensitive to degradation. This has led to formulators micro-encapsulating the ingredient.
According to findings published in Food Chemistry by researchers from Jiangnan University, Hua Bao Food Flavour and Frangence (Shanghai) Co. Ltd., and the University of California, Davis, microemulsions may offer a valid alternative to protect mint oils in food formulations.
The most effective formulation used a combination of two surfactants, AOT [sodium bis(2-ethylhexyl) sulfosuccinate] and CrEL [Cremophor EL - polyoxyl (35) castor oil], in a one to one ratio.
Particle sizes in the oil in water microemulsion were around 20 nanometres, and a mint oil encapsulation efficiency of around 78 per cent was achieved.
“The formation of a microemulsion with mint oil as the oil phase was highly dependent on surfactant types and composition,” explained the researchers. “It was found that the mixed surfactants of AOT and CrEL, enhanced the microemulsion formation and decreased the amount of surfactant required compared to the other mixed surfactants,” they added.
“The results indicated that a microemulsion of mint oil/AOT and CrEL/ethanol/water, may be a promising dispersion for the protection of mint oil in food products,” they concluded.
The use of microemulsions as carriers of ingredients was discussed by Dérick Rousseau, PhD, from Ryerson University in Canada told attendees at the IFT International Food Nanoscience Conference in New Orleans in 2008. While micro emulsions are thermodynamically stable, meaning they are formed almost instantly on mixing, and they also do not separate over time, they do have draw-backs, said Rousseau.
Innovation is handicapped by the limited choice of food grade surfactants, he said. The use of surfactants like triglycerides is not possible since the triglycerides are typically relatively large and inflexible.
Dr Rousseau's research group has developed a combination of ingredients, including water and propylene glycol, triceprylin (a relatively short triglyceride), and Tween 80 as the surfactant. Ingredients such as plant sterols and resveratrol are being added to these microemulsions.
Source: Food Chemistry
Volume 115, Issue 2, Pages 539-544
“Formation and characterisation of mint oil/S and CS/water microemulsions”
Authors: F. Zhong, M. Yu, C. Luo, C.F. Shoemaker, Y. Li, S. Xia, J. Ma