Abstract: The invention provides sponges (foams) produced from hydrocolloids by the expansion of gels of these. The foams have properties which can be varied, such as water absorption, biodegradibility, pore size and structure. Edible products can be produced which may contain an edible plasticizer, a sugar or sugar substitute and possibly also a flavoring agent or taste enhancer. The novel sponges are produced by preparing a gel of a hydrocolloid, and either sealing it in a closed vessel with a liquid of similar composition, pressurizing the vessel and abruptly releasing the pressure, followed by freeze drying, or by incorporating in such a gel a suitable microorganism, such as a yeast and inducing fermentation in the presence of a suitable nutrient medium, so that the carbon dioxide formed results in the expansion and foam formation, which is processed to the final product. The sponges-foams of the invention are such, that the initial network of the gel is maintained.