What are yeast extracts and what are they used for

Yeast extracts are a generic name for various forms of processed yeast products made by extracting the cell contents (removing the cell wall); they are used as food additives or flavoring agents, or as nutrients in bacterial culture media. They are commonly used to create savory and fresh taste sensations and can be found in a wide variety of packaged foods, including frozen foods, crackers, snack foods, gravies, stock, etc. Yeast extracts in liquid form can be dried into a light paste or dry powder.
Yeast extracts and fermented foods contain glutamic acid, an amino acid found in meats, cheeses, fungi and vegetables, including mushrooms, broccoli and tomatoes. According to Joe Dixon, a former member of the USDA’s National Organic Standards Board, some consumer groups claim that certain food ingredients, such as autolyzed yeast and hydrolyzed protein, are MSG in disguise. Large food retailers dispute this.

Autolyzed yeast

Autolyzed yeast (containing cell walls) or autolyzed yeast extract consists of a concentration of yeast cells that are allowed to die and break down, so the yeast’s endogenous digestive enzymes break down its proteins into simpler compounds (amino acids and peptides).
Yeast autolysates are used in AussieMite, Mightymite, Vegemite (Australia), Marmite, Promite, Oxo (Ireland, New Zealand, Canada, South Africa and the UK), Cenovis (Switzerland), Vitam-R (Germany) and Maggi sauces. Bovril (Ireland and UK) switched from beef extracts to yeast extracts in 2005 and for much of 2006, but then switched

The general approach to producing yeast extracts on a commercial scale for food products such as Vegemite and Marmite is to add sodium chloride (salt) to the yeast suspension to make the solution hypertonic, which causes the cells to shrivel; this triggers autolysis, in which the yeast self-destructs. The dying yeast cells are then heated to complete their breakdown and the shell (yeast with thick cell walls) is then separated. Removing the cell walls concentrates the flavor and changes the texture.
Yeast extracts are used as flavor enhancers in a variety of processed foods.

Hydrolyzed yeast

Hydrolyzed yeast or hydrolyzed yeast extract is another form used as a flavor enhancer. Exogenous enzymes or acids are used to hydrolyze proteins. When combined with sodium, it mimics MSG.