Syneresis
The shrinking of curd as it squeezes out whey, driven by cutting, heating, stirring and acid.
Also: whey expulsion, drainage
Syneresis is the scientific name for the way a curd contracts and pushes out whey. A freshly set milk gel holds its water; once it is cut, the curd pieces begin to shrink and weep, and the cheesemaker speeds or slows this to decide the final moisture. Smaller cuts, higher cooking temperatures, longer stirring, more acid and pressing all increase syneresis, giving drier, harder cheeses. Gentle handling and little cutting keep moisture in, as for soft cheeses. Syneresis continues in the mould and the press. The same thing happens in a bowl of dahi left too long, when clear whey collects on the surface.