Dominika Zielinska's bakery by Frédéric Aguilhon / ReportagePhotosSociété nationale des Meilleurs Ouvriers de France
The baguette began life in the 20th century, just after the appearance of baker's yeast. It therefore has a direct connection to this breakthrough. Sourdough bread, on the other hand, is often a flagship product of boulangeries, after a return
to popularity brought about in the 1980s by Lionel Poilâne's famous Pain Poilâne.
But every French baker must make a choice between these two different fermenting agents.
Leavened bread is a fermented foodstuff, unlike its unleavened counterpart or buckwheat pancakes. Fermentation happens when fermenting agents (starters and bacteria) interact with fermentable sugars, which are the sugars contained within wheat (or other grain) flour, and break them down chemically.
What is yeast?
Yeast is a microscopic fungus (around 1/7,000 mm) and is therefore a single-celled organism. A piece of yeast weighing 0.03 oz. Like every living being, yeast needs to eat. It feeds on sugar, and in doing so, transforms it into different compounds.
The most well-known and widely used of these are the Saccharomyces cerevisiae (meaning beer sugar mushrooms), but many other kinds of yeast exist, too.
The result of sugar being consumed by yeast
This process differs depending on whether yeast or a sourdough starter is used.
Yeast feeds on wheat starch (a kind of sugar), releasing carbonated gas from it. Baker's yeast turns the sugar into alcohol (a very low volume which evaporates away as the dough is baked) and into carbonated gas.
Sourdough starters turn the sugar into carbonated gas and lactic (and acetic) acid, which give this bread its sour flavor.
How does fermentation act on the bread dough?
The two main outcomes of bread dough fermentation are bubble formation (the distinctive air pockets that form after baking) and the enrichment of the aromas. Like any other kind of fermentation, the process makes the food easier to digest by predigesting it.
What's the difference between a starter and baker's yeast?
Starters, the original rising product, are prepared by bakers before they make the bread. They come from a culture of yeasts and lactic bacteria that are left to develop naturally in a mix of flour and water left exposed to fresh air. Baker's yeast is an industrial product of the 19th century. It is a standardized product made by selecting and allowing certain yeast types to multiply in order to achieve a faster, more controlled fermentation.
Hot, but not too hot: the dough needs to be kept at the right temperature so the yeast can produce a good fermentation. Too cold: the microorganisms are affected by the cold. They become dormant, and the dough doesn't rise enough. Hot: the microorganisms act quickly but not in the desired way. The bread won't have the time needed to bring out its aromas, and it will go stale quickly since it also won't have the time to trap water in its glutinous network. Very hot: the yeast is cooked, the bacteria die out, and the dough doesn't rise at all.
What is gluten?
Gluten is the protein that is the building block of leavened bread. It occurs naturally in wheat (even more so in traditional wheat species). During fermentation, it binds to carbohydrates and other proteins to form a stretchy glutinous network. This network holds the bread together by trapping the gas bubbles. Without gluten, bread collapses when it is cooled.
Is gluten bad for your health? Gluten does not bring any health risks apart from risks for people with celiac disease (an acute gluten intolerance), who make up around 1% of the population. It's undeserved reputation as indigestible seems to stem largely from other factors of the bread-making process: the excessive use of additives in industrially produced bread, undercooking, and intestinal sensitivity to fermentable sugars that are more often present in white bread.
So are baguettes made using yeast or starters?
Under the official decree that defines a Baguette de Tradition Française (Traditional Baguette) under French law, both yeast and starters are permitted, either separately or together. This is left up to the preference of artisan French bakers.
This is a traditional shape (farmhouse bread) that gives free reign to the baker's creativity. Sourdough produces a small amount of gas, and the dough rises slowly, but it produces what is known as lactic fermentation, similar to what happens in yogurt or sauerkraut. This gives the bread a fuller flavor and sourness, and makes it easier to digest.
A baguette made from baker's yeast
This is a more modern type of baguette, which is easier for the baker to control since the yeast purchased is always near-identical in its composition, and the dough rises more quickly thanks to its accelerated fermentation. It has a much sweeter flavor and a subtler aroma. The baker will add aroma later while roasting the bread during the baking process.
A mix of sourdough starter and baker's yeast This is the middle ground adopted by a number of artisan bakers who are keen to take advantage of the benefits of both categories of fermenting agents. The inimitable signature aroma of sourdough and the ease of use of yeast. It's then up to the client to choose what they prefer.