What effect does fat and sugar have on homemade bread?

Question

I have been experimenting lately with different bread making techniques, particularly sandwich bread or 'Pain de Mie'. This differs from the previous recipes that have yeast, water, sugar, fats and salt in that it contains a lot more sugar and oil/fat - often tablespoon measurements rather than teaspoon.

These loaves have turned out really well, very soft and light and they also keep longer than the equivalent bread recipes. The dough has been quite "energetic" when rising, often to the top of the bowl on first rise, something that is generally alien to me as I have very cool kitchen.

I understand that the higher sugar content will cause the dough to rise more, but what role does the increased fat content play in this outcome?

Answer 1

Adding fat to bread dough makes it softer and makes it stay moist for longer. The first effect, a more tender crumb, is a result of fat coating gluten molecules and preventing them from forming long chains. The improved shelf life is a result of the fat not evaporating the way water does, so it stays and gives the impression of moistness. Small amounts (a few tbsp) of certain fats can also help bread dough rise more (specifically saturated fats and mono-unsaturated fats).

Sugar, of course, gives the yeast easy food to work with, which makes it more active quickly. However, larger amounts of sugar can reduce yeast activity and make it take longer for the dough to rise. Being hygroscopic, sugar can also help keep moisture inside of the bread and keep it fresh for longer.