Syneresis is basically the oozing of a liquid from a gel structure while the gel is standing, or as it is being cut. It’s a serious problem that food processors have had to face and overcome in delivering quality products to meet the demands and expectations of the consumer.
“Gels” are created from a three-dimensional network of large molecules which are cross-linked with each other to such an extent that they trap water and hold it in place. The term itself is a shortened version of the word “gelatine” which was used to make some of the first jellies. You might think of the gel structure as being like a tangled fish net. The tighter the mesh and amount of entanglement, the greater will be its ability to hold water.
Looking back, tremendous strides have been made in controlling syneresis in yoghurt and other gel-based products, including pie fillings. Much of this has been due to understanding interactions at the molecular level. Such knowledge has gone a long way to generating tailor-made gelling agents designed to fit specific applications in thickening and stabilizing various products.
When the gel structure of a product like yoghurt is relatively weak, water can escape quite easily. As the yoghurt gel structure shrinks in on itself, the free water is pushed out and travels to the surface within the confines of the container. One way to prevent this moisture seepage would be to strengthen and increase the number of bonds between the large molecules that have been used to form the gel. However, this could result in a firm rubbery mass with an unpleasant texture, and an equally unappealing mouth-feel.