Last week someone asked me how to convert yeasted bread or other formulas so the leavening is done by sourdough rather than bakers yeast.
Good question, but I realised I couldn’t explain it in 5 minutes. It takes a bit of background knowledge first to make sense of it.
Let me first qualify that, there are some types of leavened breads, cakes, pastries, etc that are perfectly fine as they are with yeast leavening. But this person has a bakers yeast allergy so in this case the exercise is needed. Having said that, the species – saccharamyces cerevisiae – bakers yeast – is naturally present in artisan sourdoughs. Generally its population is somewhat small but it’s presence is a fact. However, it is generally regarded as different to industrially cultured bakers yeast since commercial yeast is strain specific. We might ask the question how does bakers yeast come to be there, but for this post we will safely sidestep that for another time.
Of course the final characteristics of many of these products will be markedly different after the change to sourdough is made.
So, what is the background that needs to be considered? Firstly, many of these enriched sweeter products are better without the tangy flavour of complex organic acids characteristic of sourdough. Many will benefit with a bit more flavour complexity but it’s important for them not to be burdened with too much acid. So how can we take advantage of the leavening power of sourdough but control the acid production?
Artisan sourdoughs are essentially an ‘ecosystem’ and like all ecosystems its an environment to a whole host of microorganisms. Each group has a particular environmental preference. In fact, that’s exactly how bakers maintain their sourdoughs, by controlling the influencing parameters such as:
- temperature range
- water level/hydration
- ash content of the flour
- time frames
- seeding quantities (amount of starter and sourdough to the flour weight)
Since this home baker was specifically interested in croissants, our exercise will focus on croissants. It’s a more complicated example but we may tackle other examples later and as time permits I will post them. We need to consider more specifically – time frames – hydration – and for some recipes temperature. Of these – time, hydration level, seeding quantity and temperature are the most influential for our croissant formula conversion.
Spicher & Stephan – two German scientists specialising in sourdough microbiology and biochemistry have done lots of work describing sourdough fermentation. It’s apparent from their work that the early fermentation in artisan sourdoughs favours yeast activity. Intense acid production needs more time and occurs in the latter stages of sourdough maturity.
For croissants we want to encourage yeast growth and gas production to aerate our dough but limit acid production to the very latter stage of final proof. Even then we want to be careful not to allow the sourdough to become excessively mature for croissants. In order to achieve this we will make a two stage sourdough with short fermentation times – 6 hours each stage . This will mean yeast activity and carbon dioxide production will predominate without excessive maturity. The sourdough will then be added to the final dough with the remaining ingredients. This dough will be made cold by using cold or chilled water and allowed to ferment at a cold temperature overnight in the fridge.
Cold dough is important to maintain the consistency of the dough and butter so they can be sheeted with a rolling pin and still maintain the layers. It’s important to keep it cool to prevent gas forming by the yeast activity and prevent the butter being too soft since butter has a low melting point.
See the recipe for more details.
The rest of the process to making croissants is almost the same as if you were using yeast except that the final proof will take longer.
After the overnight ferment in the fridge we need to make some preparation. First, we should prepare the unsalted butter that will be used to laminate the dough to achieve the flakiness characteristic of croissants. Preparation involves sheeting the butter into a uniform thickness using a rolling pin. Using a rolling pin push the butter together. This will involve force on the butter pieces to bind them. Some small amounts of flour on the bench and pin can be used to aid release. It’s important to achieve the right size to be completely enrobed in the dough without excess amounts of dough on the sides or edges. The size of the butter sheet is important to get the best distribution of butter to dough and avoid as much as possible areas of dough without a butter layer. This will ensure the correct number of layers over the whole dough square or sheet and reduces waste when it comes to the final dimensions on setting out the croissant triangles.
See the diagram below on how to set out the butter sheet and dough to get the best distribution and fit using the “French” method.
The next step is to sheet the dough with the butter enrobed into three times it’s length so a fold can be made. This will produce three layers of butter and still keep it enrobed in the dough. We call this a “half turn”. See below
After each fold the dough will need to be chilled in the fridge for an hour to keep the butter solid but pliable and the yeast activity retarded. This method requires two half turns and a “book turn”. Repeat the above to make two (2) half turns. See below for a book turn.
Making a book turn will increase the layers of butter to thirty six (36) which will impart excellent lamination and flakiness. A helpful tip is to pin the dough a little thinner and longer than you would to make a half turn to get that 4th fold in the book turn.
After refrigeration the dough should be pinned out to 3-4 mm evenly thick. Then cut into triangles. See below
Use a knife and a rule to mark out triangles with a base of 11cm and a length of 22cm. A small cut in the middle of the triangle base helps when rolling them up to get some splaying of the triangle base corners. When rolling the pieces up make sure there is no flour (dust) on the surfaces – if so give them a brush. rolling croissants starts from the base end. There are two ways to complete the roll – roll away from you or roll toward you. It doesn’t matter which as long as they are even, relatively tight, without excess pressure to rupture the dough and butter layers. Remember they will be getting warm by now as the dough has spent some time unrefrigerated on the bench.
Place them on the tray with the points on the bottom to hold their shape and allow to prove for several – 3-4 hrs – at a temperature no more than 28° C to prevent the butter melting.
Egg wash and bake at 180-190° C. Allow to cool and enjoy.
My final comment is that you’ve seen that making croissants requires several steps – the faint hearted may shy away from trying as it seems a little burdensome. It really isn’t as difficult or as time consuming as it may seem. After all much of the time involved is resting in the fridge. Besides that, all things that are worthwhile are a bit more than simple but realise this…….. if a software engineer can do it…… anyone can!