Malt Extract is a dehydrated extract of malt for use in preparing microbiological culture media in a laboratory setting. Malt Extract is not intended for use in the diagnosis of disease or other conditions in humans. Malt Extract is a clarified, water-soluble extract of malted barley. Malt Extract is a useful ingredient of culture media designed for the propagation of yeasts and molds. This ingredient is suitable for yeasts and molds because it contains a high concentration of carbohydrates, particularly maltose. The approximate percentage of reducing sugars in Malt Extract is 60 - 63%.The high carbohydrate content makes malt extract very sensitive to overheating which results in darkening of the medium it is used in. Malt Extract is generally employed in culture media at concentrations between 10 to 100 grams per litre.

Malt Agar, a medium recommended for the detection and isolation of yeast and molds from dairy products, food, and as a stock culture, contains Malt Extract. Wort Agar, used for the cultivation and enumeration of yeasts, has Malt Extract as one of the main ingredients in the formula. Several media containing Malt Extract are specified in standard methods.