The liquid batter of pulse and rice, which is used to make food like idli and dosa, is fermented by bacteria. The puffy texture of this flour is due to the production of CO2 gas. The large holes found in Swiss cheese are caused by the large amount of CO, produced by a bacterium called Propionibacterium sharmanii. Roquefort cheese is produced by the growth of a special type of fungus which gives off a special flavour.