Yeast extract is concentrated nutritional yeast in the form of a spread or paste. It has a pungent, savory, umami flavor and is rich in protein and glutamic acid.
Vegetarians and vegans use yeast extract to add meaty flavor to meatless dishes. The product is often thinned out with butter and enjoyed as a spread on sandwiches or toast. Other popular applications include adding it to tomato and cheese sauces, and combining it with butter to glaze roasted meats.
Well-known brands of yeast extract include Marmite, a popular but polarizing snack in New Zealand, South Africa and the United Kingdom, and Vegemite, one of Australia's most famous foods since 1923. During World War I, the British government rationed Marmite to their troops because it was a rich source of vitamin B. In 1942, during World War II, rations included Vegemite due to huge demand from Australian soldiers.
Although the Gilmour family of England became the first people to market yeast extract as a commercial good in 1902, German chemist Justus von Liebig is credited with facilitating the creation of the product. He was the first to discover that yeast waste left over from beer fermentation could be processed into paste and used as a dietary supplement.