Spirit Blue HiVeg™ Agar

Principle And Interpretation

Lipids, including fats and oils, are highly reduced. When a lipid is catabolized, it has the potential to yield more pairs of electrons per gram, and thus more energy, than either carbohydrates or proteins (1). This process is brought about by the enzyme lipase, and the organisms possessing the enzyme lipase are called lipolytic organisms. Growth of lipase-producing microorganisms can contribute to flavour defects in milk and high fat dairy products. Some of the free fatty acids released by the action of lipolytic enzymes have a low flavour threshold and can impart a rancid flavour at low concentrations. Spirit Blue Agar is prepared according to the formulation of Starr (2) is recommended by APHA (3) for detection and enumeration of lipolytic microorganisms. It is a basal medium to which lipoidal substrate is added for the detection, enumeration and study of lipolytic microorganisms. Formulations in practice before Starr which included dyes as indicators of lipolysis were sometimes inhibitory to the microorganisms. Starr showed spirit blue to be inert and an ideal indicator of lipolysis, visualized as clear halos around colonies. Spirit Blue HiVeg™ Agar is prepared by using vegetable peptones in place of animal based peptones which make the media free of BSE/TSE risks. HiVeg™ hydrolysate and yeast extract in the medium are sources of carbon, nitrogen, vitamins and minerals. Spirit blue is a dye which acts as an indicator of lipolysis. The lipase reagents recommended as the lipid source are cotton seed meal, cream, olive oil etc. A satisfactory emulsion can be prepared by dissolving 10 gram acacia or 1 ml polysorbate 80 in 400 ml warm distilled water, adding 100 ml cotton seed or olive oil and agitating vigorously to emulsify.