Curdling

Curdling is the breaking of an emulsion or colloid into large parts of different composition through the physio-chemical processes of flocculation, creaming, and coalescence.

[1] Curdling occurs naturally if cows' milk is left open in a warm environment to air for a few days.

[citation needed] Milk and soy milk are curdled intentionally to make cheese and tofu by the addition of enzymes (typically rennet), acids (including lemon juice), or various salts (magnesium chloride, calcium chloride, or gypsum); the resulting curds are then pressed.

[2] In hot preparations emulsified with eggs like hollandaise and custard, curdling is the undesirable result of overheating the sauce.

[3] When making cheesecake, if water is added to the cream cheese during the combining period, it will curdle.

A cheesemaker checks the set of milk curd after vegetable rennet was added to milk
A curd knife is used to cut milk curd into small cubes
A pan of curdled milk
Cheese curd prior to pressing
Silky tofu (kinugoshi tofu)