It's an improved MC medium. MC medium is a medium made of soybean peptone and beef paste powder, which is used to count the colonies of lactic acid bacteria in lactic acid bacteria drinks. Soybean peptone, beef paste powder and yeast extract powder provide nitrogen source, vitamins and growth factors; Glucose and lactose provide carbon sources for fermentable sugars; Lactic acid bacteria ferment sugar to produce acid, so that calcium carbonate around the colony is dissolved to distinguish lactic acid bacteria; Agar is the coagulant of culture medium; Neutral red is the pH indicator.