Galacturonic acid

Oxidising the carbon-6 alcohol of D-galactose into a carboxyl group creates galacturonic acid, a member of the uronic acid family. Pectins are built largely from it, and it also turns up in plant gums and bacterial cell walls. Its carboxyl groups let pectin chains cross-link with calcium into the gels that set jams, and food chemists track its release when they measure pectin breakdown during ripening or processing. The compound thus sits at the heart of fruit texture science, linking cell-wall chemistry to the firmness shoppers feel.