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Chapter: Bulk fermentation (#30)

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This adds the chapter covering the bulk fermentation
process.
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Hendrik Kleinwaechter
2022-12-30 12:42:02 +01:00
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book/wheat-sourdough/wheat-sourdough.tex
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@@ -66,7 +66,7 @@ that tastes much better than any store bought bread.
\path [line] (proof) -- (bake);
\end{tikzpicture}
\caption{The typical process of making a wheat based sourdough bread}
\label{fig:wheat-sourdough-process}
\label{j:wheat-sourdough-process}
\end{figure}
The whole process of making great sourdough bread starts with
@@ -650,6 +650,7 @@ traps the gases during the fermentation process. \cite{how+does+gluten+work}.
deteriorates over time as enzymes break down the flour. The effect
is accelerated for sourdough due to the bacteria's gluten proteolysis.
}
\label{fig:wheat-yeast-sourdough-degradation}
\end{figure}
% See https://www.figma.com/file/wTUVe6Nm2INOvT82mJhQur/Dough-strength-visualisation?node-id=0%3A1&t=fjdPvXYuJpsdQfWN-1 for
% the source of this visualization
@@ -718,9 +719,279 @@ However, if the dough is mixed too much, the compounds that contribute
to the bread's flavor, aroma, and color may be destroyed, negatively
affecting the quality of the bread.\cite{oxidization+dough}
\section{Bulk fermentation}
After mixing the starter into your dough the next stage of
the process known as bulk fermentation begins. The term
bulk is used because in bakeries multiple loaves are fermented
together in bulk. If you are a home baker you might bulk
ferment a single loaf. The bulk fermentation ends when you
divide and preshape, or directly shape your final loaves or loaf.
The hardest part when making sourdough bread is controlling
the fermentation process. Bulking long enough but not too
long is the deciding factor for making great bread at home.
Even with poor shaping and baking techniques, you'll be able
to make excellent bread, solely by mastering the bulk
fermentation process.
With a too-short bulk, your crumb will be
perceived as gummy. Your crumb will feature large pockets of
air commonly referred to as "craters". A too-long fermentation
results in the dough breaking down too much. The resulting
dough will stick to your banneton and spread while baking
into a pancake-like structure.
The key is to find the sweet spot between not too little
and not too much bulk fermentation. I'd always recommend pushing
the dough more toward a longer fermentation. The
flavor of the resulting bread is better compared to a pale
underfermented dough.
\begin{table}[!htb]
\small
\begin{tabular}{|l|l|l|l|}
\hline
\textbf{} & \textbf{\begin{tabular}[c]{@{}l@{}}Too short\\ fermentation\end{tabular}} & \textbf{\begin{tabular}[c]{@{}l@{}}Too long\\ fermentation\end{tabular}} & \textbf{\begin{tabular}[c]{@{}l@{}}Perfect\\ fermentation\end{tabular}} \\ \hline
\textbf{\begin{tabular}[c]{@{}l@{}}Crumb\\ texture\end{tabular}} & \begin{tabular}[c]{@{}l@{}}Unbaked gummy areas\\ towards the bottom of\\ the bread\end{tabular} & \begin{tabular}[c]{@{}l@{}}Crumb can be\\ perceived as\\ gummy, as most\\ gluten broken\\ down\end{tabular} & \begin{tabular}[c]{@{}l@{}}Crumb evenly baked.\\ Crumb can be perceived\\ as moist, but not\\ gummy\end{tabular} \\ \hline
\textbf{Alveoli} & \begin{tabular}[c]{@{}l@{}}Overly large alveoli\\ in the crumb "craters"\end{tabular} & \begin{tabular}[c]{@{}l@{}}Many tiny alveoli\\ equally distributed\end{tabular} & \begin{tabular}[c]{@{}l@{}}Alveoli evenly\\ distributed, no\\ "craters"\end{tabular} \\ \hline
\textbf{Taste} & Pale neutral taste & \begin{tabular}[c]{@{}l@{}}Strong acidic flavor\\ profile. Acidity\\ overweighs when\\ tasting\end{tabular} & \begin{tabular}[c]{@{}l@{}}Balanced flavor profile,\\ not too mild but also\\ not too sour. Depending\\ on starter vinegary\\ or lactic notes\end{tabular} \\ \hline
\textbf{Texture} & Overall poor Texture & \begin{tabular}[c]{@{}l@{}}Good consistency,\\ crumb is not as fluffy\\ as it could be\end{tabular} & \begin{tabular}[c]{@{}l@{}}Great combination of \\ textures\end{tabular} \\ \hline
\textbf{\begin{tabular}[c]{@{}l@{}}Oven\\ spring\end{tabular}} & \begin{tabular}[c]{@{}l@{}}Vertical oven spring,\\ mostly due to water\\ evaporating and\\ inflating the dough\end{tabular} & \begin{tabular}[c]{@{}l@{}}Very flat pancake like \\ structure after baking\end{tabular} & \begin{tabular}[c]{@{}l@{}}Great vertical oven\\ spring. Dough grows\\ more upwards rather\\ than sideways\end{tabular} \\ \hline
\end{tabular}
\caption{The different stages of sourdough fermentation and the effects on crumb, alveoli, texture, and overall taste.}
\end{table}
The worst thing you can do when fermenting sourdough
is to rely on a recipe's timing suggestions. In 99 percent
of the cases, the timing will not work for you. The writer
of the recipe probably has different flour and a different
sourdough starter with different levels of activity. Furthermore,
the temperature of the fermentation environment might be
different. Just small changes in one parameter result
in a completely different timing schedule. One or two hours
difference results in the dough not fermenting long enough, or
turning it into a gigantic sticky fermented pancake. This
is one of the reasons why the current baking industry prefers
to make solely yeast-based doughs. By removing the bacteria
from the fermentation, the whole process becomes a lot more
predictable. The room for error (as shown in figure \ref{fig:wheat-yeast-sourdough-degradation})
is much larger. The doughs are perfect to be made in a
machine.
Experienced bakers will tell you to go by the look and feel of
the dough. While this works if you have made hundreds of loaves,
this is not an option for an inexperienced baker. As
you make more and more dough you will be able to judge
the dough's state by touching it.
My go-to method for beginners is to use an \textbf{Aliquot jar}.
The aliquot is a sample that you extract from your dough. The
sample is extracted after creating the initial dough strength.
You monitor the aliquot's size increase to judge the
level of fermentation of your main dough. The aliquot
jar is extracted after creating dough strength. As your
dough ferments, so does the content of your aliquot jar. The moment your
sample reached a certain size your main dough is ready
to be shaped and proofed. The size increase you should
aim for depends on the flour you have at hand. A flour
with a higher gluten content can be fermented for a
longer period. Generally, around 80 percent
of your wheat flour's protein is gluten. Check your flour's
packaging to see the protein percentage. The actual size increase
value is highly subjective depending on your flour composition.
I recommend beginning with a size increase of 25 percent and testing
up to 100 percent with subsequent bakes. Then identify a value
that you are happy with.
\begin{table}[!htb]
\begin{tabular}{|r|r|}
\hline
\multicolumn{1}{|l|}{\textbf{Flour protein content}} & \multicolumn{1}{l|}{\textbf{Relative aliquot size increase}} \\ \hline
8-10\% & 25\% \\ \hline
10-12\% & 50\% \\ \hline
12-15\% & 100\% \\ \hline
\textgreater 15\% & \textgreater 100\% \\ \hline
\end{tabular}
\caption{Reference values for how much size increase to aim for with an aliquot jar depending on the dough's protein content}
\end{table}
The beauty of the aliquot is that no matter the surrounding
temperature, you will always know when your dough is ready.
While the dough might be ready in 8 hours in summer, it could
easily be 12 hours in winter. You will always ferment your
dough exactly on point.
\begin{figure}[!htb]
\includegraphics[width=\textwidth]{aliquot-before-after}
\caption{An aliquot jar to monitor the dough's fermentation progress.
It took 10 hours for the dough to reach a 50 percent size increase.}
\end{figure}
While the aliquot jar has enabled me to consistently bake
great loaves there are limitations to consider. It's crucial
to use a cylindrical-shaped container to properly judge
the dough's size increase. Furthermore, it is essential
to use room-temperature water when making your dough. If the
water is hotter, your aliquot due to its smaller size
will cool down faster. The aliquot will ferment slower
than your dough. Similarly, when you use too cold water,
your sample will heat up faster than the large dough mass.
In that case, your aliquot is ahead of your main dough. You
would probably stop the fermentation too early. Make sure
to keep the dough and aliquot close together. Some people even
place the aliquot in the same container. This makes sure that
both are in the same environment temperature. The aliquot
is also less reliable if your ambient temperature changes
a lot during the day. In that case, your aliquot will adapt
faster than your main dough. The readings will always be slightly
off. If you are making a large chunk of dough with more
than 10kg of flour the jar is also less reliable. The biochemical
reactions happening inside your dough will heat it.
The fermentation itself is exothermic which means
that it produces heat.
Another but more expensive option is to use a pH meter
to monitor your dough's fermentation state. As the lactic
and acetic acid bacteria ferment, more acidity is piled
up inside your dough. The acidity value (pH) can be
measured using such a meter. The more acidity the lower the pH
value of your dough. The pH scale is logarithmic meaning
that each digit change will have a 10x increase in acidity.
A sourdough dough might begin fermenting at a pH of 6,
then shortly before baking has a pH of around 4. This means
that the dough itself is 10x times 10x (= 100x) sourer
than at the beginning. By using the meter you can always
judge the state of your dough's acidification and then act
accordingly.
To use the pH meter successfully you need to find pH values
that work for your dough. Depending on your starter,
water, and flour composition the pH values to look out
for are different. A stronger flour with more gluten
can be fermented for a longer period. To find out
the pH values for your bread I recommend taking
several measurements while making your dough.
\begin{enumerate}
\item Measure the pH value of your sourdough starter before using it
\item Check the pH after mixing all the ingredients
\item Check the pH before dividing and pre-shaping
\item Check the pH before shaping
\item Check the pH of your dough before and after proofing
\item Check the pH of your bread after baking
\end{enumerate}
If the bread you made turned out successful with your values
you can use them as a reference for your next batch. If the
bread didn't turn out the way you like, either shorten
the fermentation or extend it a little bit.
\begin{table}[!htb]
\begin{tabular}{|l|r|}
\hline
\textbf{Step} & \multicolumn{1}{l|}{\textbf{pH Value}} \\ \hline
Starter ready & 4.20 \\ \hline
Mixing & 6.00 \\ \hline
Dividing/preshaping & 4.10 \\ \hline
Shaping & 4.05 \\ \hline
Before proofing & 4.03 \\ \hline
After proofing & 3.80 \\ \hline
After baking & 3.90 \\ \hline
\end{tabular}
\caption{Example pH values for the different breakpoints of my own sourdough process}
\label{table:sample-ph-values}
\end{table}
The beauty of this method is its reliability. Once you found
out your good working values, you can reproduce
the same level of fermentation with each subsequent dough.
This is especially handy for large-scale bakeries that want
to achieve consistency in each bread.
While this method is very reliable there are also certain
limitations to consider.
First of all the pH values that work for me likely won't work for
you. Depending on your own starter's composition of lactic
and acetic acid bacteria your pH values will be different.
You can use the values shown in table \ref{table:sample-ph-values}
as rough ballpark figures. Regardless you need to find values
that work for your setup.
Another limitation is the price. You will need to purchase
a high-tech pH meter. Ideally, a meter featuring a spearhead.
This way you can directly poke the meter deep into the dough.
At the same time, automated temperature adjustments are a
feature to look out for. Depending on the temperature
the pH value varies. There are tables you can use to
do the adjustment calculations. More expensive meters
have this feature built-in. The pH meter loses accuracy
over time. For this reason, you need to frequently
calibrate this. The process is cumbersome and takes time.
Lastly, you need to carefully rinse the pH meter before
using it in your dough. The liquid surrounding the
head of your pH meter is not food-safe and thus should
not be eaten. I rinse the meter for at least one minute
before using it to measure my dough's fermentation stage.
The last method to judge the state of bulk fermentation
is to read the signs of your dough. The more bread you are
made the more accustomed you will become to this process.
Look out for the dough's size increase. This can sometimes
be a challenge when your dough is inside a container.
You can help yourself by marking your container. Some bakers
even use a transparent rectangular bulk container. You
can use a pen to mark the initial starting point. From there
on you can nicely observe the size increase. Similar to the
mentioned aliquot jar look out for a size increase that works
for your sourdough composition.
\begin{figure}[!htb]
\includegraphics[width=\textwidth]{bulk-finished-dough}
\caption{A dough in a good state to finish bulk fermentation. Notice
the tiny bubbles on the dough's surface. They are a sign that the dough
is inflated well enough.}
\end{figure}
Look out for bubbles on the surface of your dough. They
are a good sign that your dough is inflated with gas. The
further you push the bulk fermentation the more bubbles
will appear. If you overdo this stage the dough becomes leaky and
the bubbles will disappear again.
Take note of the dough's smell. It should match the same
smell of a ripe starter shortly before collapsing. As mentioned
before, your dough is nothing but a gigantic starter. You
can also proceed and taste your dough. It will taste like
pickled food. Depending on the acidity you can judge how
far the dough is in the fermentation process. The final bread
will taste less sour. That's because a lot of acid evaporates
during baking.\footnote{More on this topic later.
Just by baking longer and/or shorter, you can control
the tang of your final baked bread. The longer
you bake the less sour the final loaf. The shorter
the more acidity is still inside the bread. The resulting
loaf will be sourer.}
When touching the dough it should feel tacky
on your hands. The dough should also be less sticky
compared to earlier stages. If the dough is overly
sticky you have pushed the fermentation too far.
If you pushed the bulk fermentation too far you won't be able
to bake a free-standing loaf with the dough anymore. But don't
worry. You can move your dough into a loaf pan, or use parts
of the dough as the starter for your next dough. When using
a loaf pan make sure it's properly greased. You might have
to use a spatula to transfer your dough. Allow the dough
to proof for at least 30 minutes in the loaf pan before
baking it. This makes sure that large cavities induced
by the transfer are evened out. You could push the proofing
stage to 24 hours or even 72 hours. The resulting
bread would feature an excellent very tangy taste.
\section{Controlling fermentation}
This chapter is still pending and will be added soon.
\section{Stretch and folds}
This chapter is still pending and will be added soon.