Gels made from droplets are less stable than gels made from solid particles. Therefore, gels from droplets expel water much faster and to a larger extent than gels made of solid particles. These are some of the findings from recent research on the driving forces of syneresis.
Syneresis is a commonly seen process in foods, where a liquid layer of expelled water forms on top of e.g. yoghurt. Besides food products, other materials experience syneresis, such as ceramics, coatings and paints.
Fat in yoghurt
Qimeng Wu, Jasper van der Gucht and Thomas Kodger from the Physical Chemistry and Soft Matter group published their results in Physical Review Letters (from American Physical Society). In addition to droplets, which directly resemble fat in yoghurt, the researchers also investigated solid particles which showed an unexpectedly large difference between the two particle types. This may also affect other particle-based materials such as cosmetics.
Thomas Kodger explains: ‘Fundamentally, the consequences of the difference in local mobility between droplets and solid particles has not been observed before, as we show in this work, and the implications on other particle based materials are still unknown; there is much physics still to be explored.’
Way of Working
Rather than studying food products directly, the researchers created model systems to have good control over the attraction between particles and droplets and better explore the physics that occurs.