The past couple posts have focused on the importance of getting the right amount of air into cupcakes, but aeration is important for other baked goods, too. In bread, the amount of air in the dough when it enters the oven also affects rise and texture. This is most directly controlled by the proofing step that happens after shaping and before baking. For this experiment, we under- and over-proofed bread to see how it baked up.
Experiment Overview
Goal: To see and taste a difference in bread that’s under- or over-proofed
Recipe: Hokkaido Milk Bread from What to Cook Today
Method: Prepare bread dough as instructed through the first rise. Shape the dough, then bake either immediately, after proofing for 45 minutes, or after proofing for 2 hours. Bake, cool, and taste.
Results: As the proving time changed, we noticed differences in
– Poke test results
– Dough size
– Bake time
– Bun shape
– Bread crumb
– Bread texture
Conclusions: Perfectly proofed dough bakes up with a smooth surface and light texture. Under-proofed bread tends to split along the side and have a dense texture, while over-proofed bread can become wrinkly and spread too much.
Testing Method
Ingredients and Equipment
As listed in Hokkaido Milk Bread recipe, no mix-ins.
Baking the Bread
- Prepare the bread dough as written in the recipe through the first rise. Preheat the oven to 350°F and line three baking sheets with parchment.
- Punch down the dough, then remove 9 portions of dough, 25g each. Shape each bun into a sphere by tucking the edges to the center, turning the seam side down, and rolling the bun against the work surface. Place three buns on each baking sheet and cover with plastic wrap.
- As soon as the buns are shaped, the dough should spring back completely if poked. Brush one sheet of buns with egg white, then bake until golden, about 17 min. Remove to a rack to cool completely.
- 45 min after shaping, the remaining buns should have expanded a little in size. An indentation poked into the bun should fill back slightly. Brush another sheet of buns with egg white, then bake until golden, about 16 min. Remove to a rack to cool completely.
- 125 min after shaping, the last buns should have expanded even more. An indentation poked into the bun should not fill back. Brush these buns with egg white, then bake until golden, about 15 min. Remove to a rack to cool completely.
- Once all buns are cooled to room temperature, slice and taste!
Results
To better understand these results, I suggest checking out the earlier posts about leavening and yeast.
Keep in mind that this experiment focuses on the last proof before the dough goes into the oven. Many bread recipes (like this one) let the dough rise twice, once after kneading and once after shaping, but other bread recipes might have fewer or more rises. (Number of rises affects crumb—the more rises, the finer the crumb.) Because the dough gets punched down before it is shaped, over-proofing is not really a problem during the earlier bulk ferments unless the bread ferments for so long the yeast deplete their food. (Check out the post about yeast to learn more about this.)
Poke test results
As I mentioned in the Method, we can use the poke test to gauge whether bread dough is proofed. Firmly poke the dough as if you were trying to get someone’s attention. Right after shaping, the indentation quickly springs back all the way. With time, the indentation fills back more slowly, and a small hole remains. If the dough is over-proofed, the indentation will not fill back at all. I demonstrate the poke test in my challah video here.
Remember that yeast actively produce gas as they feed on sugars in bread dough. The gas fills and expands individual cells within the dough to raise the bread, kind of like how Mr. Fredricksen filled millions of individual balloons to lift his house in the movie Up.
When we punch down and shape the dough, we redistribute the yeast, making sure they have access to the fresh food they need to continue creating gas. So right after shaping, the yeast are making plenty of gas. If we poke it, the dough springs back quickly as gases build up inside. It’s like how the balloons have the strength to rip the house off its foundation when Mr. Fredricksen first fills them.
As time goes on, however, the balloons lose air, and Mr. Fredricksen’s house sinks lower and lower to the ground, eventually landing on the ground forever. Similarly, yeast lose vigor over time as they deplete their food sources. When the dough is perfectly proved, the yeast are reaching their limit. If we poke the dough, the yeast only muster up enough gas to push back a little. And if the dough is over-proofed, they’re no longer creating the amount of gas they need to fill the indentation back up.
Dough size
The longer the dough proofed, the larger the buns became. As you can see, these expanded from about 1-1/2 inches across to 1-5/8 then 1-3/4 inches. Keep in mind that when a recipe tells you the dough should “double in size,” it should not expand twice in size in all three dimensions, since that would be an eight-fold increase in volume. If you want to get mathematical about it, the cube root of two is about 1.25, so we’re looking for about a 25% increase in each dimension. Then again, not all doughs will double in size by the time they’re ready. Usually, I feel confident baking the dough if there’s been a noticeable increase in size. And again, you can use the poke test. Either way, it’s important to use more metrics than just time — remember that yeast activity rates vary depending on the environment. If your kitchen is a little warm or a little cold, your proofing time will change. The times given in a recipe should only be used as a guide.
Bake time
As the proofing time for the buns increased, their bake time decreased. As I described in the Method, the bake time decreased by about a minute as the dough proofed for longer. In this experiment with baking powder in muffins, we saw that batters with more air bake faster than batters with less air. Similarly, in these buns, the ones that proof for less time and start off with less gas heat up more slowly, so they need to bake longer to attain the same color.
Bun shape
As you can see below, the differences in the baked buns are striking. Most obviously, the under-proofed buns split dramatically along the sides. The over-proofed buns are flatter and wrinkly.
Remember that most of the air in bread dough comes from yeast. Yeast eat the sugars around them in the dough and produce gas as a byproduct. This gas inflates the bread dough, and in the oven, it expands to raise the bread even further. Yeast also work more quickly as they warm up in the oven, and they eventually die at higher temperatures.
Because yeast also reproduce as they eat and produce gases, the longer our dough proofs, the more yeast there are, the more food they eat, and the less food remains in the dough around them. This is why we punch down and knead the dough a bit after the first rise—we want to redistribute the yeast and move them to fresh food.
In our under-proofed buns, the yeast have barely made a dent in the food around them before we put them in the oven. It’s like we dropped them at a buffet and told them they only had five minutes to eat. Naturally, the yeast stuff themselves as quickly as they can, which means they also produce a lot of gas very quickly. In fact, by the time the outer crust of the bun sets, the yeast in the center are still cranking out gas, and the buildup of pressure gas splits the outer crust of the bread and forms a crack.
In the over-proofed buns, the yeast have created an excess of gas. They’ve taken their time at the buffet and stuffed themselves so full it hurts. As we saw in our over-creamed cupcakes, excess air creates a lot of problems. For one, the dough doesn’t have enough structure to support all the gas, so it doesn’t hold its shape—you can see that the over-proofed buns have flattened more than the other two.
Once the over-proofed dough enters the oven, the problems compound. As the gas expands even further, it stretches the dough holding it in place, ultimately tearing the dough and causing the structure to collapse. This created a wrinkly surface in these buns, and in more extreme cases, it can result in a deflated loaf.
Bread crumb
The differences in proofing time they led to different bun shapes also created different crumbs. As you can see, the under-proofed buns have the tightest crumb, especially in the center, and the over-proofed buns have an open crumb. Remember that the holes in the crumb are pockets occupied by air.
Because the under-proofed buns didn’t start off with much air, the bubbles didn’t expand much before the bread set. This is especially true at the center, where the rise was constrained when the outer crust set. On the other hand, in the over-proofed buns, the bubbles started off with a lot more air, so they expanded to a larger size. (The crumb reminds me of these muffins with doubled sugar.) These buns were not over-proofed enough to deflate dramatically.
Bread texture
The texture of the buns reflected their crumb. The under-proofed buns were dense, while the over-proofed buns were most tender in this experiment. However, more extreme over-proofing could have resulted in more structural collapse and a noticeably denser texture.
Conclusions
Although proofing is more of a waiting step, getting the timing right is essential to baking bread with a good rise and texture. Under-proofed dough is prone to unseemly splitting, and the baked bread is dense. Over-proofed dough loses its definition, its surface wrinkles, and it can deflate. As your dough proofs, watch the clock, but only use time as a guideline. To check whether your dough is ready, make sure it’s visibly increased in size or use the poke test. It is better to err on the side of under-proofing, but if your dough is severely over-proofed, you can just punch it down, which removes the air, re-shape, and let it proof again as long as food remains available to the yeast.
References
Corriher, Shirley O. Bakewise; Scribner: New York, 2008.
Figoni, P. How Baking Works, 3rd ed.; John Wiley & Sons, Inc.: Hoboken, 2011.
“How to Know Your Dough Has Properly Proofed.” Cooks Illustrated.