The word yeast derives from Proto-Germanic *jest, meaning “to boil, foam, froth”, and is related to fermentation. Brewer’s and baker’s yeasts are long-known natural products. They consist of living cells of fungi. Baker’s yeast comes as block yeast, granulated yeast, liquid yeast or dry yeast.
The effects of yeast have been known for over 5,000 years. In the past, good baking results were achieved with sourdough and “mysterious fermentation”, but no one really knew what fermentation was. It was not until the 19th century that Louis Pasteur discovered that microorganisms were responsible.
Yeast has been commercially produced since the 18th century (or, in some cases, even the Middle Ages). The main raw material is molasses, a by-product of sugar production.
Yeast can live both in the presence as well as in the absence of oxygen. When there is oxygen, the yeast multiplies. When there is no oxygen, fermentation occurs. The duration of the fermentation influences taste.
Today, yeast is mainly produced industrially by means of complex processes. There is constant research and technological development in this field. Selected raw materials during production ensure a high quality of yeast.
A driving force
In essence, yeast is about the leavening power and wholesomeness of bread and pastries. The aim is to make bread and pastries with “porous” dough, and this is how it works: yeast cells produce gas (carbon dioxide) from sugar that is present in the dough. The gas is held in the dough, causing the dough to increase in volume (rising). This process is responsible for the airy texture. The resulting structure is fixed during baking.
Flour also naturally contains microorganisms. The existing (wild) yeasts and bacteria that produce vinegar and lactic acid are cultivated during sourdough production. This gives a characteristic “sourdough bread taste”.
Wild yeasts vs. cultivated yeast
Bread made with wild yeast needs more time (20 – 24 hours), but stays fresh longer and offers even greater eating enjoyment. Furthermore, a longer “standing time” increases digestibility in several respects: single undesirable substances are broken down, and the availability of others (e.g. magnesium and calcium) is improved.
Cultivated yeast (baker’s yeast) has strong leavening action and ensures a fine taste in bread and pastries. Special varieties are then bred to provide sufficient leavening in yeast doughs that contain plenty of fat.
Occasionally, fresh yeast pastry might cause indigestion. Those who suffer from histamine intolerance may be sensitive to yeast and have a reaction to the contained glutamic acid.
Effects on the body
Yeast is relatively rich in B vitamins and proteins. Still, the small amounts of yeast we consume and the loss of nutrients during baking must be taken into account.
Special medicinal yeasts can act as probiotics against diarrhoea and help to strengthen our intestinal flora e.g. after antibiotic treatment.
Tips for storing fresh yeast
To prevent it from external influences, a yeast cube should be stored in the refrigerator in a lidded jar (e.g. a jam jar) for a maximum of one week. Fresh yeast can also be frozen and then dissolved with water and a little sugar.
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