Adsorption

The adhesion of molecules of liquids, gases or dissolved substances to the surfaces of solids — distinct from absorption, in which molecules actually enter the bulk medium. Food technology exploits adsorption everywhere: activated carbon adsorbs pigments from sugar syrups, chromatography separates flavours by selective adsorption, catalysts for oil hydrogenation work through adsorbed reactants, and packaging films are chosen partly to avoid adsorbing desirable aromas from the product. Understanding which compounds stick to which surfaces, and how tightly, lets processors purify, separate and protect with precision — surface chemistry as a manufacturing tool.