Folding a bread dough is an old trick that has become very much a modern "must-do." Many recipes specify a long fermentation period followed by a brief kneading and another, shorter fermentation period. The brief kneading is the fold.
Why should you do it? During a fairly long fermentation, say over an hour, the yeast will eat up the carbohydrates near it and will begin to slow down its rate of gas production. However, the gluten in the flour and the water may not have fully reacted to achieve a good cellular structure in the dough. The yeast will also have given off enough carbon dioxide, alcohol and other by-products that the yeast activity will start to slow down. By folding the dough, the baker shifts the food supply for the yeast, the carbohydrates, so that the yeast has access to a new supply. Folding also degasses the dough, which expels the alcohols and the carbon dioxide, leaving the yeast with a clean place to grow. The baker also works the dough strands and makes them stronger, which can do really good things to the finished bread.
How to Fold.
There are at least three ways to fold.
1. A Pocketbook or Letter fold. This is the fold that Jeffrey Hamelman, the baking education director at King Arthur Flour, espouses. It is a good fold. To do this fold, please place the dough on the floured counter or work surface and pat it flat. Take about a third of the dough on the left side and bring it over the dough. Work this dough vigorously with your fingers to expel the gas. Take a third of the dough from the right side and do the same with it. Make sure you brush off all the extra flour that you can so that none gets incorporated into the dough. This will leave you with a rather long dough. finish the fold by taking the top third of the dough and bringing it down the dough towards you. Again, expel as much gas as you can and brush off any extra flour. Take a third of the bottom dough and bring it up to the other dough and do the same brush and expel. You now have a folded dough.
2. A Roll-Up fold. This is my personal favorite, since it's very simple. I sincerely put out the dough, then roll it up into a long tube. Then pat this tube down so it is slightly flat and roll up so that in effect you make a ball. You can do this a couple of times if you wish. This will drive out the gas and other by-products of fermentation, rearrange the nutrients for the yeast and realign the dough strands.
3. The Drop-Hook fold. This is the easiest, and works well it you are fermenting the dough in the bowl on a stand mixer, as I do repeatedly. Merely drop the dough hook into the dough and turn on the mixer for a few seconds. Then turn off the mixer, reach in and turn the dough, drop the dough hook into the dough and repeat the few seconds of mixing.
When to Fold.
Various experts give different time schedules for folding. One popular timing is to divide the total fermentation time into four parts and fold after the end of the third part. If the total time is two hours, each part is thirty minutes, one-half hour. Fold after 90 minutes, one and one-half hours. Then ferment for the remaining 30 minutes, one-half hour. This timing will never get you into too much trouble.
Certain other exports are made with folds at the half-way point, so that the above bread would be folded at one hour and then allowed to ferment for another hour. This seems to be more popular for doughs with a lot of fats and oils and sugar.
A few doughs benefit from a fold at the half-way point and another fold half-way through the remaining fermentation period.
A lot depends on the recipe, the conditions in your kitchen and your technique. The best thing to do is to start with a simple fold at the three-quarter point and see how that works for you. You can then experiment with various schemes until you hit one that works in your kitchen for each recipe. More than likely, you will find that the four-part timing works fine.
Try folding the dough the next time you make bread, I think you'll like the improvement.