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Yeast Extract Analysis

Yeast are microscopic, single-celled organisms in the kingdom fungi. They have had an enormous impact on human culture since before recorded history, and long before we knew about microscopic, single-celled organisms. They play a central role in baking and fermentation, making possible both bread and alcoholic beverages. Yeast cultures are also processed to make yeast extracts as a food source themselves, and are used as a culture medium for growing micro-organisms.

Minerals
- Yeast extracts are rich in potassium. A serving size of 6 g of yeast extract contains 156 mg of potassium, 4 percent of the recommended daily potassium intake. A serving also contains 9 percent of the recommended daily intake of sodium, though this nutrient is rarely deficient in most people's diet. Extracts contain lesser amounts of other minerals including magnesium, selenium, iron, calcium, phosphorus and zinc, but all less than 4 percent of the recommended daily intake for a recommended serving size.
Vitamins
- Yeast extract contains high concentrations of some vitamins, but is deficient in others. It's very high in thiamin, riboflavin, niacin and folate. It does not contain appreciable amounts of vitamins A, C, D or K. A suggested serving contains 4 percent of the recommended dietary intake of vitamin B6. It does not naturally contain any vitamin B12, though some yeast formulations are supplemented with this nutrient.
Protein
- A 6-g serving of yeast extract provides about 2 g of protein. An analysis of the amino acids that constitute the protein indicates that glutamic acid is the most prevalent, followed by leucine, arginine and valine. A 6-gram suggested serving size provides 3 percent of the recommended daily protein intake.
Growth Media
- Yeast extract can be a food source for humans in the form of marmite, for example. (Most British people have a jar of marmite yeast extract somewhere in their kitchen. Americans may not be as familiar with this product.) It's also a nutritious food source that microbiologists use to feed hungry colonies of microbes. Microbiologists choose their growth media carefully. Yeast extract makes an excellent medium for Escherichia coli. It makes a poor medium for Staphylococcus aureus. These two organisms are very common agents of food-borne illness, so identifying a good medium for growing them in cultures plays an important role in combating food poisoning.

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