Question

Many food items are colloids in one form or the other.

1. To which category of colloids does cheese belongs?

2. Explain how sols are classified depending upon the nature of the interaction between the dispersed phase and dispersion medium. Give suitable examples.

Answer 1

1. Cheese belongs to gel (Liquid in solid type colloid).

2. Based on the nature of interaction between dispersed phase and dispersion medium sols are divided into two categories :

(a). Lyophilic colloids : These are solvent-loving colloidal sols which are directly formed by mixing the dispersed phase with the dispersion medium. These are reversible, quite stable and cannot be easily coagulated, e.g. gum, gelatine, starch, rubber.

(b). Lyophobic colloids : These are solvent-hating sols which can be prepared only by special methods. These are irreversible, not stable and are easily coagulated on addition of small amounts of electrolytes. e.g. sols of metals and their sulphides.