Mouldy food. Moulds (grey) growing on bread and other foodstuff on a plate. Moulds are the fuzzy cobweb- like growths produced on organic matter by several different types of fungi. They begin as microscopic airborne spores which germinate on the surface of the food. The moulds then rapidly spread to form networks (mycelia) of fine filaments (hyphae). The moulds penetrate downwards into the food, digesting and absorbing nutrients.