Baking with sourdough has a number of advantages. The bread is moister, stays fresher for longer, is less crumbly, has a better texture and a richer aroma and acidic taste. The bread is also less sensitive to mould. Making a sourdough involves mixing wheat and/or rye flour with water into a loose dough which then stands and rises. Within the sourdough is formed lactic acid, acetic acid and aromatic compounds of the natural micro-organisms called acid bacteria.