Hoezo? Ouzo!

“Hoezo” is Dutch word meaning “How so?” or “Why?”, and also the name of a popular science quiz that was on TV during my teenage years. From which I distinctly remember that we find blue foods generally yucky looking because a lot of molds are blue and that we think mirror pictures of ourselves look better because that’s what we’re used to seeing (as opposed to other people thinking non-mirrored pictures are more flattering).

The word also kind of sounds like “Ouzo” – an anise-based liquor from Greece that has the cool property of being clear until you add water, aptly named “the Ouzo effect

The Ouzo Effect

For the ouzo effect to occur we need three components: an oil, a water, and an alcohol.

The alcohol (in this case ethanol) and anise oil (also known as anethole) can be mixed. Same for ethanol and water. But anethole and water don’t mix very well: oils are generally hydrophobic.

When you add water to an anise-based alcoholic drink, such as Ouzo but other examples include Pastis and Absinthe, the liquid turns from clear to milky. By mixing these three liquids together, two of which don’t mix well, you create an emulsion: little oil micro-droplets suspended in the liquid.

Usually, oil-in-water emulsions are highly unstable, but in the case of this delicious drink* the emulsion is highly stable, making it of special interest for colloid researchers to study things like nano-droplet and micro-emulsion formations.

Or to make art:

*IMO, I know not everyone enjoys anise drinks.

Video created by:

  • Oscar Enriquez, Universidad Carlos III de Madrid
  • Daniel Robles, Universidad Nacional Autónoma de México
  • Pablo Peñas-López, Universidad Carlos III de Madrid
  • Javier Rodríguez-Rodríguez, Universidad Carlos III de Madrid

DOI: https://doi.org/10.1103/APS.DFD.2018.GFM.V0054

More details on the Ouzo effect: https://www.sciencedaily.com/releases/2016/07/160714091720.htm

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