C. botulinum Isolation Agar Base is recommended for rapid, selective isolation of Clostridium botulinum from food samples. This medium is formulated as per the recommendation of APHA. Botulinal toxin is heat-labile. Therefore the test samples and cultures should be maintained at refrigeration temperatures. The pH of the toxic material should also be maintained at a slightly acidic pH since botulinal toxin is less stable at alkaline pH. Egg yolk emulsion added in the medium helps in detecting lecithinase, lipase and proteolytic activity. Lecithinase degrades lecithin present in the egg yolk producing an insoluble, opaque precipitate in the medium surrounding the growth . Lipase break down free fats present in the egg yolk causing an iridescent (oil on water) sheen to form on the surface of the colonies.