Torula yeast is a species of yeast that is used as a food additive because it has a meat-like flavor when cooked. It is used as a replacement for MSG to give foods a stronger umami flavor, a taste associated with the savory component of cheese, meat and mushrooms.
Torula is a kind of fungi, just like other yeasts. It is grown in vats and fed byproducts from the wood or sugar industry. It is able to eat these leftovers and convert them into glutamic acid, which is perceived as umami, and nucleotides that boost the glutamic acid's flavor. It has been well known for years that glutamic acid plus nucleotides lends foods a strong savory character. MSG has a similar effect on foods but is considered less natural by many in the organic food movement despite being derived from seaweed. Traditionally, dashi and veal stock were used as sources of umami flavoring, but torula yeast is now the least expensive option in processed foods.