Why does my loaf deflate in the oven?

A question I am often asked is why does my loaf deflate when I put it in the oven?

Your loaf looks fabulous, you put it into the oven and when you fetch it out it has deflated and is half the size it was when it went in. This is a really disappointing thing to happen.

Don’t worry, this is an issue that is easy to solve.

The problem is that the loaf has overproofed.

Understanding the stages of making a loaf:

The stages of making a loaf are:

  1. Mixing
  2. Developing the dough (by using the stretch and fold method, or by kneading)
  3. Fermenting the dough, allowing it to rise and become filled with air
  4. Gently shaping the dough
  5. Proving the dough until it is ready for the oven
  6. Scoring (aka slashing) the loaf
  7. Baking and steaming the oven
  8. Cooling

It is at point 5 that the problem lies. It can be really hard to judge when the loaf is ready for the oven.

What happens during fermentation?

During fermentation (stages 3 & 5) enzymes break the damaged starch molecules in the flour down into complex sugars and then into simple sugars (these are the enzymes that would do the same job if the grain was allowed to grow in the ground). The yeast then feasts on the simple sugars and expels carbon dioxide and ethanol. The carbon dioxide disperses through the dough and where it finds an air bubble it expands as a gas pushing against the gluten network that was developed and strengthened during the stretch and folds or the kneading of the dough. This creates pockets in the dough and rises the bread.

As bakers we learn to watch for the signs of fermentation. In the first round of fermentation when the dough is sat in a bowl this fermentation can go quite wild. the dough can double or even triple in size and as long as we haven’t added an excess of yeast or left the dough in a warm kitchen for far too long all is well. The dough still has some sugars left for the yeasts to continue to feast on.

Shaping the dough

We then shape the dough and leave it to ferment a second time. This is when we need to be more watchful.

If we have shaped the dough well, (take a look at this video for help with this), giving the loaf good structure and surface tension, then as the yeasts get to work the loaf starts to expand again, upwards rather than outwards.

Overproofing the dough

If we leave the loaf too long in a warm kitchen at this point then the yeast can begin to exhaust the sugars in the dough and the carbon dioxide can begin to push the gluten beyond its structural limits. At this point the dough may look well risen in the pan and look as if ready to bake when in reality it should have been baked perhaps 10, 20 or 30 minutes earlier.

If we put the loaf in the oven when it looks like we want it to look when it comes out it is highly likely that it is over proofed. The loaf has already reached its limits and when we put it in the oven the loaf will just deflate. The slightest knock and the carbon dioxide pockets in the loaf will push against the pushed to the limit gluten structure and the whole thing will collapse. If the dough is over proofed oven spring can’t happen and the dough’s structure collapses rather than springs.

The ideal point at which to bake a loaf is when it has risen but the dough still feels like it has some surface tension and that there is still potential in the loaf to grow some more.

What happens in the oven?

When you put a loaf in the oven chemical reactions continue to take place and the most important of these is ‘oven spring’.

The yeast has a last frenzied chance to eat some of the sugars as the dough reaches the yeast’s optimum temperature of 38 C and before it dies at 55C. This additional yeast activity is limited but it does have a slight contribution to the oven spring.

The most important contribution to oven spring is that the trapped carbon dioxide expands further in the heat pushing against the gluten network and rising the loaf further – oven spring.

This is why it is important that the loaf hasn’t already achieved its optimum rising before you put it in the oven. If it looks like a perfectly risen loaf (the size that you were hoping it would get to), then the chances are you left it too long before you baked it.

You want the dough to still have a bit of energy left so that it can have that last rise in the oven.

How to solve the problem of the deflated loaf

Next time you bake a loaf try putting it in the oven 10 minutes before you normally would. In other words, put the loaf in before you think it is ready to go in. Take a look at this video, which shows you what to look for in a loaf that is ready for the oven.

Remember to steam your oven. Steam allows oven spring to happen. If you don’t steam your oven the crust of your loaf dries out before the oven spring can happen.

To steam your oven you can use a plant mister to spray water on the sides and the floor of your oven as you load the loaf and as you are closing the door (avoid spraying a glass oven door or the oven light or they may explode with the shock of the cool water). Alternatively you can place a roasting tray in the bottom of the oven with a few bolts and nuts in the bottom and preheat with the oven. When you load the loaf pour in a cup of hot water into the roasting tray and close the oven door. This will produce a lot of steam for the first ten minutes of the bake. Be careful to stand back when steaming the oven so that you don’t burn yourself. Only add enough water to steam the oven for the first ten minutes. You want the oven to be without steam for the reminder of the bake so that the crust can crisp up.

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