What it does
Kappa forms a firm, brittle gel and needs potassium. Iota forms a soft, elastic gel that recovers after shearing and needs calcium. Lambda does not gel at all; it thickens. The sulphate groups carry a negative charge, which is why it reacts specifically with the positively charged regions of casein. That reaction is the reason a very low level does in a dairy system what a much higher level of another hydrocolloid cannot.
Where it works
Dairy above all: suspension of cocoa in flavoured milk, body in ice cream, gel strength in a dessert, and melt control in an analogue cheese. Also water binding in cooked meat.
Where it does not
It hydrolyses at low pH under heat, so a product that is both acidic and retorted will lose the structure it was given. It is also poor as a standalone emulsifier: it stabilises what is already emulsified rather than emulsifying it.
What it interacts with
Potassium and calcium change the gel entirely. Locust bean gum with kappa gives a more elastic, less brittle gel than either alone, which is one of the oldest and most useful synergies in the field.
