Carotenoids as end-cap-active agents in lecithin cylindrical micelles

Lecithin is able to form water-in-oil microemulsions with polymer-like behavior. In most experiments on this system lecithin from natural sources (soybean, egg yolk) has been used that contains trace amounts of carotenoids. In samples in which the polymer-like phase coexists with one or two other phases, these carotenoids are only present in the polymer-like phase. The addition of small amounts (approximate to 1%) of beta-carotene to a sample in which the lecithin is disposed of carotenoids has a drastic effect on the viscoelastic properties. These observations lead to the conclusion that in this system carotenoids are likely to specifically adsorb at the end caps and work as "end-cap-active agents", which decrease the end-cap energy.