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?