Sorption is a physical and chemical process by which one substance becomes attached to another. Sorption includes both adsorption & absorption e.g., liquids being absorbed by a solid or gases being absorbed by a liquid, cotton dipped in ink. Sorption the process in which one substance takes up or holds another; adsorption or absorption Sorption is a process in which a solute moves from a fluid to a particulate solid. The food sorption isotherm describes the thermodynamic relationship between water activity and the equilibrium of the moisture content of a food product at constant temperature and pressure. ... The typical shape of an isotherm reflects the way in which the water binds the system.