Let’s talk about autolyse, gluten development and fermentation in breads. I am going to focus on gluten based flours (wheat flours). Another notably long post.
Some background information – When water is added to flour, there are a couple main things that begin to occur. Two proteins – glutenin and gliadin begin to link together to form gluten. This process will occur naturally without any intervention. Natural enzymes in the flour will be activated. One primary function of the enzymes is that they will begin to convert starches in the flour into sugars. There are very few natural sugars in the flour. This will become important once we add yeast and/or starter. Whole wheat flours are predominantly starch. White flours are almost 100% starch.
The autolyse process was developed by Calvel as a means to shorten the amount of mechanical mixing needed by commercial bakeries – thus reducing dough oxidation. The process, by definition, is only flour and water. It does not include salt or yeast/starter. It’s primary goal is to naturally start gluten development. It is typically 20-30 minutes in length. Today, there are people leveraging extended autolyse periods. This is intended to be a non fermentive process.
Once yeast and/or starter is added, fermentation begins. Fermentation is a yeast / bacterial process. Fruit/flower waters are dominantly yeast based, where SD starters contain a balance of yeast and lactic acid bacteria (LAB). Yeast fermentation differs from bacterial fermentation. Yeasts consume sugars and create two primary byproducts – carbon dioxide (CO2) and ethanol (alcohol). The LAB also consume sugars (different ones from the yeast) and produce lactic and/or acetic acids. Acids are sour to the taste. Lactic acid is yogurty sour and acetic acid is vinegary sour. (Acetic acid is vinegar).
Of all of these, during fermentation, the baker is typically most aware of only one – CO2. The CO2 gets trapped by the gluten in the dough – causing the dough to expand (rise). We make most judgements based on this.
We do need to consider gluten for a moment as it plays the other critical role in this process. Gluten develops naturally over time. Traditional mechanical mixing of a dough somewhat forces the proteins in the flour to link together and will develop the gluten in a short few minute period. Hand kneading or the slap and fold methods are also relatively aggressive methods of developing gluten structure. They are the hand equivalents of machine mixing. Common now is the method of using stretch and folds. This takes advantage of the natural development of gluten over time. The dough is typically mixed until all flour has been incorporated. It is allowed to rest – typically 20-60 minutes. Gluten will form and the dough is then stretched several times to create structure to the gluten and develop strength. It is followed by another rest (more gluten develops) and another series of stretches. Over several repetitions, the gluten will be fully developed. The other end of the spectrum are no knead doughs. In this case, the dough is mixed, with a very very small amount of yeast or starter and simply allowed to rest for a very extended period. This method relies totally on the natural development of gluten. Gluten can be developed quickly (5 minutes) or slowly (10 hours) or anywhere in between. I strongly recommend that every baker should make a no-knead bread at least once – just to gain the understanding of how much bread will make itself.
My personal view is that the autolyse process adds value when using methods that are intended to develop gluten quickly. It adds much less value to a S&F or no knead process. It may help with whole grain flours – even extended times – but perhaps more because it helps soften the bran.
We also need to talk a little about flours. Wheats are categorized into 2 dominant categories – hard and soft wheats. Very simply, hard wheats are generally higher in protein and gluten content, while soft wheats are lower in protein and gluten. There are hundreds of wheat varieties grown in a wide variety of conditions. Each wheat harvest will be different. It is good to note that wheat itself is a large variable in baking. Hard wheats typically become bread/strong flours. Soft wheats become cake/pastry flours. The all purpose flour category was created to provide a medium protein/gluten flour. It is made by blending hard and soft wheats or by using lower protein hard wheats.
So – why is this important? One of our primary goals in dough development is gluten structure and strength. The amount of gluten strength possible is directly determined by our choice in flour. Higher protein/gluten flours simply have more gluten. There are also two main characteristics of doughs – dependent also on the flour choice. They are extensibility – the ability of the dough to stretch and not tear – and elasticity – the ability of the dough to return to it’s original shape. These are also strongly related to flour choice. Different gluten levels will produce different outcomes. A simplistic view – less gluten will produce a softer more tender crumb where more will create chewer textures.
A little about hydration (ratio of liquids to flours by weight) too. No two flours are exactly alike. Two things worth noting – tyically, the higher the gluten content a flour has, the more water it can absorb. Whole grains may absorb more water because of the added bran, but may also absorb less if they are lower in gluten content. There is no absolute rule here. An ancient grain, like einkorn fir example, is higher in protein, but not specifically in gluten. By generic thought, we might consider it a high protein whole grain flour capable of higher absorption. The reality is that it is not. This will also vary from batch to batch.
What this means – a baker trying to follow a recipe that is 80% hydration may have an entirely different experience when using an all purpose flour vs. a high protein hard whole wheat flour or high gluten white flour. It is very relative to your flour choice.
Back to fermentation. As the dough ferments, the yeast will produce CO2. Trapped by the gluten, the dough will begin to expand. How much it can expand will be determined by how elastic and extensible the dough is and by how strong the gluten is. This is all related to the choice of flours.
Enzymes are still working – still converting starches into sugars, they are also changing the gluten structure over time – reducing elasticity and increasing extensibility. Alcohol is being created and in the case of sourdoughs, lactic and/or acetic acids are being produced. Other acids and flavor compounds are being created. It’s a magical process.
Changing fermentation rates.
We can change how fast this process occurs by controlling a few simple things.
First – the amount of yeasts. Pretty simply – more yeasts will consume more sugars in a given period of time and produce more CO2 – the dough will rise more quickly. To slow it down, we simply add less yeast/starter.
Starters add a second dimension – bacterial fermentation- making breads sour. Changing the amount of starter we add also changes the amount of bacteria we add.
This will change the rate at which the dough acidifies. Ironically – shorter fermentations (more starter / more yeast / more bacteria) tend to make less sour breads. How we manage our starter also plays a role – we can make it more yeast active or more bacterial active – but that’s a whole different discussion.
Second – temperature. Temperature has a direct correlation to the rate of fermentation. This is true for the enzyme activity, the yeast activity and the bacteria activity. Cooler = slower and warmer = faster. There is a physical limit to temperature variation. Below freezing – things stop. Over ~140f (60c), the yeasts and bacteria will die. The practical limits are 35-85f (2-29c). Over 85f (29c) will work, but typically non desirable flavors will develop. The optimal fermentation temperature for breads is often viewed as 78f (25c).
Cold retardation is somewhat the slow motion button for fermentation. It simply slows everything down. The bacteria in sour doughs will remain slightly more active than the yeasts. It is a great tool for making doughs match your schedule. Fridge temp will greatly influence what occurs. Warmer fridges will often result in the dough rising where colder ones may seem to stop all rising – it is still fermenting.
We tend to think in terms of two temperature options – room temp or the fridge. There are a wide range of choices in between – be creative. Similar to gluten development, fermentation can be rushed (1.5 hours) or greatly extended (72 hours).
Hydration also plays in here. Higher hydration (wetter) doughs will ferment more quickly and the higher hydration will slightly weaken the gluten
For reference – Salt strengthens gluten and slows fermentation.
There are most commonly two steps – the bulk fermentation and the final proof. These are terms somewhat introduced by larger bakeries where dough was mixed in large batches and initially fermented in bulk. It is then divided and shaped and a final proof is done prior to baking. Fermentation is occurring from the time water and yeast/bacteria are added to the flour and does not stop until the dough reaches 140-145f and the yeasts and bacteria die or you exhaust the sugars in the dough (this will not happen in regular bread baking).
How to know when a step is complete – this may be one of the most interesting questions a baker needs to answer. Let’s try to put some of the pieces together. First – as a dough ferments it develops flavor. The longer it ferments, the more flavor it has. This is good. Also, for sourdoughs, the more acidic (sour) it may become. This may be viewed as good or bad, depending on your personal preference. Just to note – even regular yeast based doughs that have very extended fermentation times will acidify.
Sugars in the dough are being produced by the enzymes and being consumed by the yeast and bacteria. CO2 is being generated and trapped and our dough is rising. There is a general rule – “until the dough has doubled in volume”. General rules are exactly that – general. The reality – the gluten strength, elasticity (ability to expand) and elasticity (wanting not to change) all determine how much a dough can physically expand. Lower gluten flours may only increase by 75%. Very high gluten flours may triple in volume.
The enzymes are also working to change the gluten – both weakening it and making it less elastic and more extensible. If we are judging solely by volume, we are looking for the point where the dough has reached its maximum expansion.
There is no specific value in this method, other than it is a useful visual way to determine dough readiness. What I mean by this is that fermentation should really be viewed more as a time based process and not a specific increase in dough volume. The same fermentation benefit is achieved if the dough is left to fully rise or if we periodically degas the dough. Time is the critical component. We can actually extend fermentation times by degassing the dough periodically throughout the fermentation.
So – we want the dough extensible so that when it is baked, it will achieve it’s maximum volume. If we wait too long, the gluten will weaken and eventually collapse. This is known as over proofing – we simply fermented too long. Many lower gluten doughs have overproofed while waiting for them to double.
This is where the infamous finger poke test arrives on the scene. Another somewhat general guideline. What it is intended to do. Poke your finger into the dough about 1/2″, remove it and see what happens. Flouring your finger before poking higher hydration doughs will help. We are judging multiple things. Remember, as the dough ferments the gluten becomes weaker, it has expanded under pressure from the CO2 and may be approaching it’s limit, it is becoming more extensible and less elastic. When we poke, we watch the dough response after we remove our finger. If it fills in quickly (returns to it’s original shape) – it is still quite elastic. If it slowly fills in, ideally we have found that sweet spot between elastic and extensible. If it stays, we have lost elasticity. Too long and the gluten may collapse. We must also remember that every flour has somewhat different characteristics and will react differently. Wetter doughs will tend to appear less elastic. This is not a foolproof method. Err on the side of a fermentation that is a little too short rather than a little too long.
I actually have no simple answer here – you really need to consider your flour, the dough hydration and the temperatures to estimate how long it will take. This is a horrible answer for a new baker.
We subsequently divide and shape the dough into loaves. Shaping is also another duscussion. Shaping will, just like the stretch and fold – restrengthen the gluten. However, it remains less elastic and more extensible.
The fermentation continues and we watch the dough rise again. If the temp remains unchanged, It will increase in volume more quickly than during the bulk ferment… Often in about half the time. Again – if it peaked at 75% during the bulk ferment, the same will be true here. It is the best predictor of what to look for here. Try to bake just as it is approaching its peak. Too long and you risk it loosing strength and collapsing. If you’re looking for big oven spring, bake when it has reached 2/3 or 3/4 of it’s peak. Do note that the shape of the container may impact your perception of how much a dough has increased in volume. Again, the final proof is really a function of time. The finger poke works the same here.