The Science of Enzyme Activity in Sourdough: What Amylase and Protease Are Actually Doing to Your Dough

There is a moment, usually sometime during a long weekend bulk when I have got a deep house playlist running and the windows cracked open because it is properly warm outside, where I start wondering what is actually happening inside the dough beyond the bubbles. The yeast and bacteria get most of the attention. But there is another layer of chemistry running quietly underneath all of it, and once you understand it, a lot of things that felt random suddenly make sense.

Enzymes. Specifically amylase and protease. If you have ever had a dough go weirdly slack on a hot July afternoon, or a loaf that tasted sweeter than expected, or a pizza base that stretched perfectly on one bake and tore on the next, enzymes were probably involved. Here is what they are actually doing in your dough and why summer is the season where it all gets interesting.

What Enzymes Actually Are (Without the Biology Lecture)

Enzymes are proteins that act as biological catalysts. They speed up chemical reactions without being consumed themselves. In baking, the ones that matter most are already sitting inside your flour from the moment you mill it. They are not added by you, and they do not come from your starter. They are native to the grain.

The two big players are amylase and protease, and they have completely different jobs. One breaks down starch. The other breaks down protein. Both of them are doing their thing from the moment your flour gets wet, and both are sensitive to time and temperature in ways that matter enormously for a summer bake.

Amylase: The Sugar Factory

Amylase breaks down the complex starches in flour into simpler sugars, mainly maltose. Those sugars are what your sourdough culture feeds on. Without amylase activity, the fermentation would stall quickly because the yeast and bacteria would run out of readily available food.

There are two main types. Alpha-amylase is fast and works across a wide temperature range. Beta-amylase is slower but more precise and produces more of the maltose that your starter's yeast actually prefers. Both are activated by water and start working the moment you mix your dough.

This matters for flavour. The sugars that amylase produces contribute directly to how your crust browns and how complex the sweetness of a well-fermented loaf tastes. A longer, cooler ferment gives amylase more time to do steady work, producing a more nuanced flavour. A fast, hot ferment can push amylase activity too hard, especially if you are using damaged starch flour, and you end up with a gummy crumb or a crust that browns too aggressively before the inside has caught up.

Protease: The Double-Edged Enzyme

Protease breaks down protein, which means it breaks down the building blocks of gluten. In moderate amounts, that is genuinely useful. Protease activity loosens the gluten network in ways that make dough more extensible, easier to shape, and more relaxed. If you have ever shaped a pizza base and it just kept snapping back, tight gluten with not enough protease relaxation is likely the culprit.

But protease is also where things can go wrong, especially in summer. Given too much time or too much heat, protease will over-relax the gluten structure to the point where the dough loses strength entirely. It goes sticky, slack and almost impossible to work with. That pizza dough you left out for six hours on a warm Saturday in July, the one that kind of dissolved when you tried to pick it up? That was protease activity running unchecked.

Whole grain flours contain more protease than white flours, which is part of why whole wheat doughs tend to feel softer and more extensible. Higher hydration doughs are also more susceptible because water accelerates the enzyme's activity. If you are running high hydration in summer, you need to keep your timings tight or shift to a cooler environment earlier than you would in winter.

Temperature Is the Control Dial for Both

Both amylase and protease are temperature-sensitive, and their optimal ranges are different. Beta-amylase works best around 55 to 65 degrees Celsius, which is actually during the oven bake rather than the ferment. But at room temperature, it is still active, just more slowly. Protease is most active at lower temperatures, typically between 40 and 50 degrees Celsius, but it will run steadily at summer kitchen temperatures of 24 to 28 degrees, especially over several hours.

This is why summer baking genuinely requires a rethink of your timings, not just for fermentation speed but for how your dough physically behaves. The dough temperature calculator is useful here because the target dough temperature affects not just how fast your culture works, but how fast these background enzymes are ticking along at the same time.

A useful mental model, borrowed from my day job in tech: think of enzyme activity like a background process running on your machine. Most of the time it is quiet and manageable. But push the CPU temperature high enough, and that background process starts consuming resources you needed for something else. Same logic applies to your dough on a hot afternoon.

How This Changes Your Summer Pizza Game

For outdoor summer pizza baking specifically, there are a few practical things worth keeping in mind.

First, if you are making a same-day dough, do not let it sit at full room temperature for longer than it needs to. Once it has passed its fermentation window, protease is still working even if the yeast has slowed. Move it to the fridge if you are not ready to bake.

Second, a slightly stiffer dough (lower hydration than you might use in winter) gives the gluten network more resilience against protease degradation. This is not always what you want for an airy, open crumb, but for pizza dough that needs to be stretched and handled at warm ambient temperature, that extra structure helps.

Third, using a portion of finely milled white flour rather than going fully whole grain for a summer pizza dough reduces protease load and gives you a bit more working time before things get too slack. I tend to save the whole wheat blends for loaves baked in cooler months when I have more control over the pace of things.

If you are the sort of person who bakes enough to want to track how your doughs are performing across different conditions and temperatures, DoughRise Pro is worth a look. The full bake history and unlimited formula saving means you can actually compare that June bake against the July one and start to see the patterns, which is genuinely how you get better at this stuff faster.

A Quick Word on Damaged Starch

One last thing that does not get talked about enough: amylase activity is massively amplified by damaged starch. Starch granules get physically broken during milling, and damaged starch absorbs water much more readily, making it far easier for amylase to break down. Stone-ground flours and some heritage grain flours can have higher levels of damaged starch, which means amylase works harder and faster in doughs made with them.

This is not a bad thing in controlled conditions. But in summer heat, with a longer ferment, it can tip into over-fermentation more easily than you would expect. If you have switched to a different flour recently and your dough is suddenly behaving differently in the heat, damaged starch levels and the resulting enzyme activity are worth considering as a variable.

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Photo by Conor Brown on Unsplash