To get the perfect cappuccino you need a pentagonal teaspoon

Mixing coffee and milk to make cappuccino: you’ve probably always done it the wrong way. The most efficient way to obtain a perfect blend of two similar liquids, such as coffee and milk, has been found by two researchers from the universities of Mainz, Germany, and Thuwal, Saudi Arabia. First of all, you can forget the classic spoons, because what you need will be an instrument with an almost pentagonal shape and, for an optimal result, you would need two at the same time. The study is published on Physical Review fluids.

The pentagonal “spoon” and how it should be used

In the study, the researchers combined two liquids of a water-like consistency in a cylindrical container, and initially mixed them using the technique commonly used in large industrial food or pharmaceutical mixers: two cylindrical instruments that move in a circular fashion, one close to the edge of the container and one near the center. Thanks to an optimization algorithm, then, the shape of the mixers and their movement have been modified up to obtain the best possible homogeneity of the liquid.

According to the results, the optimal “spoon” would have a shape similar to a pentagon and the right technique for mixing would not be continuous, but intermittent, made up of continuous starts and successive stops. The particular combination of shape and movement found, in fact, is able to generate numerous vortices that propagate inside the fluids and act as small additional mixers. The result is liquid with up to 2.3 times higher homogeneity to what can be achieved with standard techniques.

Applications in the industrial field

Mixing fluids using agitators is a procedure used in industrial processes in the food and pharmaceutical sectors, and increasing the efficiency of the process means on the one hand obtaining more homogeneous and higher quality final products, and on the other saving energy and ingredients. While the cappuccino example fits very well with the study, however, the researchers point out that this is not the first application they had in mind: their results could be useful for making changes to traditional agitation protocols in industries. In particular, the solution found could be useful for the production of some fluids or sauces such as toothpaste or ketchupwhich become denser during the mixing process, allowing you to increase the yield while saving time and energy.