Fluid Lactose Medium w/ Soya Lecithin and Polysorbate 20 (Twin Pack) is recommended for microbial evaluation of oral hygiene products. HM Peptone B and gelatin peptone provide nitrogen and carbon compounds, long chain amino acids and other essential nutrients for bacterial metabolism. Lactose is the source of fermentable carbohydrate. Soya lecithin neutralizes the quaternary ammonium compounds while polysorbate 20 neutralizes phenolic disinfectants; hexachlorophene and formalin.