Saccharomyces cerevisiae, more commonly known as baker’s yeast, plays a significant role in the production of bakery products. Here we describe the path from “accidental product” to being a regularly used ingredient in the food industry.
Yeasts are single-celled microorganisms, classified as budding fungi. The scientific name of baker’s yeast combines the ancient Greek Saccharomyces, meaning “sugar fungus”, with the Latin cerevisiae, meaning “of beer”, while the German description goes back to the mid-19th century and can be attributed to the physiologist, Theodor Schwann. As the name implies, yeast is able to produce alcohol from sugar. Yeasts are quite common in nature. The various types of pure bred yeasts play an important role in food processing. These include brewer’s yeast, wine yeast, baking yeast or fermentative yeast.
The Egyptians, thousands of years ago, already used yeast in the production of beer and bread, but without knowing how it worked. The first mixture of bread ingredients and yeast was thus a product of chance. As wild types of yeast are naturally present on the surface of grapes and cereals, it could be that wine and beer were also the result of grape juice or oats that had not been immediately consumed. The first leavened bread probably came about through the accidental addition of an alcoholic drink to flatbread dough. With the invention of the microscope in 1676, it was eventually possible to analyse the microorganisms, and also the yeast. In 1859, Louis Pasteur, the father of modern microbiology, identified the function of yeast. Because of food shortages after the First World War, there was a need to find an alternative raw food material to grain, and the modern cultivation of baker’s yeast in molasses (a by-product of sugar production) as a nutrient source began. This proved to be easier and more effective than cultivation in grain mashes.
When yeast feeds on sugars from flour starch, it produces carbon dioxide. This gas expands the glutelin proteins in the flour, resulting in the slackening of the dough and also contributing significantly to the flavour development. It is the metabolism of each individual yeast cell that is responsible for the action of the yeast. Depending on ambient conditions - i.e. the water, sugar and salt content, temperatures and other parameters –results can be very different.
Much like the cells in the human body, yeast cells consist of 65 to 70% water. The nutrient composition of the remaining 30 to 35% dry matter is as follows: baker’s yeast is comparatively low in fat and carbohydrates and relatively high in protein, fibre and minerals. Furthermore, it contains high levels of essential amino acids and unsaturated fatty acids. In contrast, the sodium content is low. Baker’s yeast contains large amounts of B vitamins, which are mostly heat resistant.
Different types of yeast
Most commonly, yeast is available in blocks, cakes, sticks, granules and in liquid form. These forms all consist entirely of pure yeast cells. Baker’s yeast products may be made up of different strains. The strains, however, all belong to the genus Saccharomyces cerevisiae. Fresh yeast is usually sold in the food retail sector as 42g blocks. This quantity is sufficient to relax a dough with 500 to 1000 g flour. The unit of 42g dates back to the time when yeast was sold loose at the bakery. The baker had a 500g piece, which he would cut into 12 smaller pieces, each ideally weighing 42g. This has remained until today.
Yeast should not be confused with leavening agents, which consist of sodium bicarbonate and a suitable food acid.
The difference between "with yeast" and "yeast-free"
The term “yeast-free” is often used misleadingly. Many consumers assume that sourdough bread is automatically “yeast-free” when what is actually meant is that it does not contain baker’s yeast. In comparison to baker’s yeast, which contains a single strain of yeast, sourdough always contains (apart from bacteria) yeasts from different, natural yeast cultures.
In this context, there is currently a trend towards baking with “wild yeasts”, which are used instead of baker’s yeast. Baked goods produced in this way are inclined to be more aromatic and meet the desire for more “naturalness”.
In fact, "yeast-free" refers to:
bread raised with baking powder
sourdough breads, produced only with lactic acid bacteria. This type of bread is, however, rather uncommon.
People with yeast intolerance eagerly look out for yeast-free bakery products, like backaldrin’s Vegipan® - a special wholegrain bread, made without the addition of yeast; the relaxation of the dough happens entirely physically.
If you want to get mor involved with the subject, we recommend the following website:
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