Calcium bridges in fatty acid/pectin assemblies

Pectins are anionic polysaccharides arising from plant cell walls. Due to their charge, modulated by the degree of esterification, they are sensitive to cations, a property that is widely used in food science. Besides their gelling properties in bulk systems, little is known as regards their effect on interfacial films that constitute dispersed systems such as emulsions and foams. On the contrary, fatty acids are well known to form more or less condensed films at interfaces in the presence of calcium. By means of basic tools such as Langmuir Balance and a Brewster angle microscope, we demonstrate that pectin molecules are able to bind through calcium bridges to fatty acid films formed at the air–water interface. The interfacial behaviour of these new aggregates is controlled by the degree of charge of pectin and the calcium concentration.