the invention provides sponges 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 .