Yeast extract has replaced monosodium glutamate, or MSG, as a taste-booster in most processed foods because it appears to be a natural ingredient on food labels. However, yeast extract contains the same concentrated free glutamic acid as MSG. The increasing use of yeast extracts in foods ranging from soups and sauces to meats and canned fish is due to its distinctive taste, resulting from the peptides and amino acids formed by autolysis of yeast protein.

Canned and Frozen Soups

Yeast extract is a clear and water-soluble product formed after the enzymes in the yeast cells autolyze, or dissolve the proteins in the yeast. There are light versions of yeast extracts used in light-colored foods such as bouillon and chicken broth and darker versions for heavier soups. Canned and frozen soups contain yeast extracts to enhance their taste and highlight the flavor of meaty or cheesy ingredients. It is a practice widespread throughout the food industry, and yeast extracts can also be found on the ingredient labels of processed soups proclaimed natural and without MSG, including those sold in nature food stores.

Research by Vanderbilt University has found that although the Food and Drug Administration does not prohibit the use of yeast extract, even when the name is used to disguise the presence of MSG, the quantity of free glutamate it contains poses problems for MSG-sensitive individuals who experience its effects as toxic.