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Yeast has been used to enhance the texture, flavour and nutritional qualities of bread since ancient times. A living organism, it plays a key role due to its ability to ferment bread dough.
How yeast works
As the yeast ferments, it produces carbon dioxide, which is incorporated into the dough and causes it to rise. Fermentation also produces volatile aromatic compounds that contribute to the bread’s subtle and complex flavour profile.
Flavour
The compounds generated by the yeast during the fermentation of the dough serve as precursors to the flavours that will develop during baking and thus contribute to the bread’s subtle, complex flavour profile. Bakers’ yeast is thus at the heart of this culinary tradition. Thanks to a rich baking tradition that produces a huge variety of breads, people all over the world enjoy this healthy product on a daily basis.
Nutrition & Health
Several compounds generated during fermentation by yeast are beneficial for human health. Bakers know that modulating the fermentation time impacts the nutritional properties of bread products. Long fermentations improve the content of B vitamins in bread, especially folate, which is an important vitamin for women before and during pregnancy. Other beneficial compounds generated by yeast fermentation include certain peptides extracted from flours which have a calming effect on the nervous system. Yeast also improves the bioaccessibility of minerals present (in particular zinc, iron and magnesium) whose availability for absorption is reduced by factors intrinsically present in cereal flours (phytates). Cereals fermented by yeast thus have the advantage of having improved nutritional properties and digestibility due to the breakdown of certain constituents (proteins, fibres, sugars).
Reducing salt content in bread
Bread can be an important part of a healthy diet when consumed daily. However, it can contain significant amounts of salt. It is well known that excessive consumption of salt is one of the risk factors for cardiovascular disease. For this reason, in order to meet new consumer demand, yeast producers have developed solutions based on the potentialities of yeasts. These natural “clean label” solutions make it possible to reduce the amount of salt in breads by 20 to 40% without changing the taste or texture.
As early as 3000 BC, the Egyptians and Babylonians knew how to use fermentation to make leavened bread, but they were unable to explain this mysterious phenomenon.
It was not until the work of Louis Pasteur in 1860 that yeast was identified as the micro-organism responsible for alcoholic fermentation. He demonstrated how yeast can live in the presence or without oxygen, multiplying in the first case and causing fermentation in the second case.
Liquid yeast has a limited shelf-life and is adapted to the needs of artisanal and industrial bakers.
Compressed yeast, in the form of wrapped blocks, has a longer shelf life. Practical and economical, it is widely used.
Crumbled yeast can be weighed and dosed automatically, making it easy to use for industrial bakers.
Active dry yeast can be stored at room temperature with a good level of stability, which makes it popular in regions of the world with high temperatures and humidity. It must be rehydrated before use.
Instant dry yeast can be stored at room temperature with a good level of stability like active dry yeast. It does not need to be rehydrated before being added to the flour. It can therefore be used with the same ease as compressed yeast.
Dry yeast with reducing power (active form) is intended for pizza makers because its gas production during fermentation is moderate, which facilitates the shaping of the pizza and avoids shrinkage effects.
Deactivated or inactivated yeast has no fermenting power. The yeast membranes become completely permeable, allowing the exchange of cell contents with the dough, especially one of the components, glutathione, which has a reducing (“relaxing”) effect on the gluten.
This results in a reduction of the kneading time of 15 to 20% and therefore of the oxidation of the dough during kneading, preserving the fermentation flavours and enhancing the flavour profile of the finished product.
The 2 documents below provide general characteristics for baker’s yeast. The first document describes the “fresh yeast” form for liquid, block or crumbled yeast and the second document describes the “dry yeast” form.
These documents were first drawn up by the members of the COFALEC Technical Committee in 2006. They constitute a reference for all European yeast producers in Europe.
