There is a lot about the process that we can overlook when we get caught by the desire to be impressed by the initial sight of the loaf: the color of the crust, the way the crust crackles, the punctured bubble on the surface, the way the loaf expanded into the weakness we created with the slash of a blade. The enzymes and pH matter.
What does the flavor of bread come from?
With yeast, an alcoholic fermentation occurs. Sugar is converted to alcohol and CO2. With bacteria, a lactic fermentation occurs. Sugar is converted to lactic acid and lactic form of aromatic molecules. Mature levains are heterofermentative, meaning they create a number of end products (ie. acetic acid, gas or CO2, lactic acid). In The Bread Baker’s Apprentice, Peter Reinhart’s says, “What we call sourdough bread should more correctly be called wild-yeast bread, as it is natural wild yeast that leavens the loaf and not all wild-yeast breads taste sour. More importantly… it is not even the wild yeast that makes the bread sour, but the acids produced by the various bacteria that inhabit the dough. These acids lower the pH level of the dough, creating a wake of flavors in the process, most notably the distinctive sourness we associate with sourdough bread. This is the microbial world, quite active beyond our sight, constantly changing the medium, the bread dough in which the organisms live.”
The flavors come from lactic and acetic acids produced by inevitable environmental bacteria, which are working on the flour’s sugars along with the yeast. Different bacteria make different flavors. Same flour, different environment, different bacteria, different tasting loaf. Bake often. Share often.
Be wild. Be constant to change. Live.
What is the difference between levain and starter?
Bakers sometimes use levain and starter interchangeably. Levain is typically referred to as the portion of the starter that is used in the final dough, but if this is the only purpose for the starter, then the starter can be levain as well. The labelling I care to make is naming and feeding her. In Latin America, levain or starter is known as masa madre.
What is amylase?
Amylase is an enzyme that cuts the starch into simple sugars. Amylase works well between 4.5-6.5 pH. When amylase cannot work (outside desired pH range), there cannot be more sugar created which means no more fermentation. In other combination of words, amylase activity improves the conversion of complex sugars into simple sugars that yeast are then able to feed on and produce alcohol and CO2.
With rye flour, we want large quantities of starter to manage the enzymatic activity because we don’t want too much amylase activity, or what is sometimes known as “starch attack.” (See: Why is the rye bread gummy?) At 85ºC/185ºF, amylase is destroyed.
What is protease?
Protease is an enzyme that cuts protein chains, sometimes referred to as gluten. Proteases are important for bread-making because they have a softening effect on dough. They are present in small amounts in flour as well as in yeast and bacteria. As dough acidifies, protease activates. Protease works well between 3.5-4.5 pH. At a pH of 4, there is maximum protease activity. This activity results in smaller protein chains and loose amino acids. Too much protease activity will destroy the gluten structure you might need right before the dough goes into the oven. Free protein increases maillard reaction as captured in crust color.
What is pentosane?
Pentosanase increases the softness in bread by increasing the elasticity of the gluten. Pentosanase is active between 3.5-4.5 pH. Pentosane can absorb 4-10x its own weight, increasing water holding capacity in bread, therefore, reducing staling! When dough viscosity increases, the gas in the dough can increase the volume.
What is phytase?
Phytase destroys phytic acid and is active at a pH level below 4.5. Phytic acid fixes to minerals. Yeasted whole wheat bread is not optimal for health because there is not enough acidity to break down phytic acid to release minerals for our absorption. (The reason there has become a preference to soaking nuts and seeds before eating or what is sometimes referred to as “activated” carries the idea to remove phytic acid to aid in maximum absorption of nutrients!) More nutrient absorptions when the pH level is below 4.5. Sourdough breads are more than just about enjoyment of flavor, they also help us absorb the nutrients in wheat.
Temperature is important.
At temperatures between 20-30ºC (68-86ºF), the curve of yeast and bacteria activity is proportionate: 1ºC change in temperature changes activity by 7%. At temperatures below 10ºC (50ºF), there is no bacteria activity, while yeast activity is present, but low. Cooler dough temperatures and lower hydration encourage acetic acid production. Higher dough temperatures and higher hydration encourage lactic acid production.
Temperature during fermentation influences the yeast and bacteria activity, the length of time the dough spends in certain pH ranges, the amount of enzymatic activity, the amount of starch or protein break down, how much free starch and protein is available at time of baking.
As the dough goes into bulk fermentation, the stage after mixing, the wild yeast performs best at 24-26ºC (75-78ºF). This is sometimes referred to as desired dough temperature, or DDT. The easiest way to influence DDT is altering the water temperature. To learn how much to adjust the water temperature, record the temperature of your environment, flour, water, and dough after mixing. In the summers, I use ice to lower the temperature of the water or I refrigerate some water.
Notes on pH and why it matters.
The measuring device of pH is negatively charged to measure H+, which mostly represents its reaction with the acid molecule which has a “-” charged. (However, high protein flour and whole grain flours can take up the “free” H+ in a dough, so when measuring the pH, the pH is mistakenly higher. If taking the pH of the dough, take note of the small buffering effect of higher amounts of “wholeness” in the wheat.)
pH determines enzymatic activity. It establishes the rhythm of the process. How much time and how active amylase and protease are affect the appearance and potential enjoyability of the loaf while phytase activity affects your health!
With a decrease in pH, glycemic index drops. The lower pH doesn’t allow amylase to keep working, lowering the GI because there is less free starch and therefore sugar. Increasing fiber can also help decrease GI. Fibers fix water, meaning less water for enzymes. The lower the GI, the less fat production in our bodies, so eat sourdough breads and breads with fiber! Phytase becomes active at a pH below 4.5, destroying phytic acid, meaning a higher bioavailability of minerals and more nutrient absorption.
With a lower pH, breads ability to stay mold free and textural shelf-life increases. More time for enjoyment. Una masa madre es como un yogi, puede estirar el tiempo.
Since everything here is a side note, here’s another: at pH of 4.3, we call the loaf, pain au levain.
What is protein quality?
It’s not just the “gluten” percentage of a flour that matters. The relationship between elasticity and extensibility. The gluten can be “strong” but in what ways it is strong will affect the dough. With a higher elasticity and lower extensibility, the baked loaf will have a rounded bottom edge and may not break at the top surface. When the relationship is more ideal, the loaf will open well at the score and sit relatively flat on the bottom edge. A really extensible loaf with little elasticity may yield a flat loaf when baking.
The size of the mixing bowl matters.
When the mixing bowl is small, there isn’t enough time and room for the dough to relax between mixing/folding.
Why do we degas the dough?
CO2+H20 = HCO3-H (carbonic acid)
When there is too much carbonic acid in the dough, fermentation activity slows. Degassing lowers the carbonic acid (HCO3-H) and as the HCO3-H “regroups,” CO2 is produced again.
What about no knead breads?
Mixing creates oxidation in dough. To develop gluten, a certain amount of oxidation is necessary. When gluten molecules are oxidized, sulfhydryl groups on certain amino acids produce disulfide bonds which contribute to the crosslinking of the gluten molecules, forming the gluten matrix. If the dough is over-oxidized, some of the compounds that contribute to the color, flavor, and aroma of the bread are destroyed and the quality of the bread is diminished. With this being said, if decreasing mixing time, increase fermentation to create a good gluten structure. Salt is also an anti-oxidative ingredient. It’s better to add after the first mixing and before second adding of water (See: why do some bakers encourage water in stages).
Why do some bakers encourage water in stages?
Extra water after the first mix is for extensibility and defining final dough temp. Not having all the water up front can make it easier to manage enzymatic activity and to have a chance for the grain to tell you its current absorption capacity.
How much levain should I add to the final dough?
Large amounts of levain doesn’t impact the “quotient fermentaire,” (QF) but it does impact the pH and and enzymatic activity. QF can be described as the ratio of lactic to acetic acid. In some rye breads, large amounts of levain are used to lower the pH quickly to prevent “starch attack.”
A young levain has a pH of 4-4.2, while a mature levain has a pH of 3.7-3.9. If you had the same amount of time for fermentation, you would need 30% young levain versus 20% mature levain.
Most bread consumers prefer a QF between 3-4.
What is the purpose of scoring/slashing the dough?
Scoring allows us to participate and assist in the aveoles/coalescence structure of the dough. Scoring provides a weakness in the crust structure to direct direction of pressure created from expansion of gas. When the dough has been retarded, the scoring affects the coalescence less than a direct method (no retard) because the crust is less brittle, has dried out a little. Without proper strength from gluten in the bread, coalescence or the merging of air pockets doesn’t happen as much because the pressure moves through the crust without merging. Merging aveoles or coalescence increases the perfectly irregular look of the crumb. (It is easier to merge aveoles when there is some 2nd speed mixing because the walls of the aveoles are thinner and easier to collapse. Bake with high heat to break aveole.)
What is starch damage?
The milling of wheat causes physical damage to a proportion of the starch granules of the flour. The level of starch damage directly affects water absorption and dough mixing properties of the flour. Damaged starches hydrate quickly and provide fermentable sugars for yeast. Native starch is usually 82-85% of the flour while damaged starch is 15-18%. Native starch fixes 0.4x its own weight in water while damaged starch fixes 4x. When there is too much damaged starch in the flour (and thus the dough), when you bake, the starch gelatinizes earlier and the volume is less when baking. Gelatinized starch “sets” at a lower temp. High hydration, increase maillard reaction, and small loaf volume indicate too much damaged starch can include.
Why is the rye bread gummy?
In 100% rye breads, pH must be below 4.5 or else bread will be very dense. pH must be above 4 or bread will be too slack. A pH between 4.2 and 4.5 pH is ideal. When baking, starch swells and amylase destroys starch. Too much amylase and starch attack results in a gummy, collapsed rye. Below pH 4.5, amylase is inactive. Remember that GI and starch attacked are linked to amylase activity, which can be controlled by pH. A large seeding and starter that has been refreshed multiple times is helpful in making rye breads. It’s good to target the rye dough at just below 4.5 immediately after mixing.
I want to add beer to the dough.
At levels past 12% alcohol addition into dough, fermentation activity slows because wild yeasts do not thrive environments high in alcohol. Boil and cool the beer before adding to dough. Flavor only will allow for the dough to ferment easier.
Enjoy the forum on acidity affect on gluten strength on thefreshloaf.com for other ways to understand pH and enzyme activity.