Clarifying the Ouzo effect

Anyone who enjoys Ouzo or Pernod and certain other drinks like Sambuca will be familiar with the effect of adding water to these alcoholic beverages. Chemists too are familiar with this kind of cloudy emulsion formation and hope to put the effect to good use in the areas of cosmetics and drug delivery, according to Erik van der Linden and colleagues at Wageningen University in The Netherlands. Now, they have measured the stability of various emulsions prepared from commercial Pernod and compared the results to theoretical predictions of their formation. The theory seems to be at odds with the experimental results, suggesting that the predicted behavior is not quite as clear as chemists had thought. "More knowledge of the parameters that determine the stability of these emulsions, besides interfacial tension, solubility, and density difference, might lead to better control of the emulsification process," the researchers say.