Mar 7 2016
Cooks are aware of the fact that often lumps are created when powder is dissolved in a liquid, like that witnessed in the case of polenta in water or semolina in milk.
The cooks are not aware of the fact that physicists spend most of their time to learn what happens in those lumps.
In a recent paper featured in EPJ E, researchers from the École Supérieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI), France, have explained their theories following extensive research on the wetting of soluble polymer substrates by solvent droplets, such as water.
In this article the focus is mostly on the first phase of powder dissolution, as water enters every single pore of the powder called the imbibition phase, and not on the latter dissolution phase. Similar experiments conducted in the field focus on understanding the mechanisms of how a water droplet propagates on a layer of water-soluble polymer as time goes by. The amount of solvent present in the substrate differs as the droplet begins to spread. The manner in which the droplet spreads differs based on the variations in the substrate composition on the droplet’s edge.
As a result scientists are now able to understand the two reasons why specific powders such as flour, which contain extremely lengthy polymer chains, are hard to dissolve. At the microscopic stage, spontaneous imbibition is arrested due to changes in the softness of the material as a result of melting the polymer by the solvent. This results in converting the substrate into a gel and reducing the spreading speed of the droplet. Hydration results in increased solvent affinity for the material to be wetted and the spreading ability of the droplet.
Spreading of the solvent increases based on an increasing amount of solvent reaching the substrate. Researchers still need to detect the accurate size of the pores and grains or the size distribution of the pores and grains that have to be finely adjusted to increase the imbibition and then the subsequent dissolution stage.
Source: http://www.springer.com/