Syneresis (also spelled 'synæresis' or 'synaeresis'), in chemistry, is the extraction or expulsion of a liquid from a gel, such as when serum drains from a contracting clot of blood.
Syneresis can also be observed when the amount of diluent in a swollen polymer exceeds the solubility limit as the temperature changes.
[1] In the processing of dairy milk, for example during cheese making, syneresis is the formation of the curd due to the sudden removal of the hydrophilic macropeptides, which causes an imbalance in intermolecular forces.
In cooking, syneresis is the sudden release of moisture contained within protein molecules, usually caused by excessive heat, which over-hardens the protective shell.
Additionally, it creates unsightly moisture pockets within baked custard dishes, such as flan or crème brûlée.