In both types of muffins, the fat is responsible for providing a
soft structure, thus avoiding a dry mouthfeel. Fats can help to
distribute the gas during the mixing process (Brooker, 1996) and
the small fat crystals aid the gas cell stability (Brooker, 1993). Fats
improve tenderness, moistness and mouthfeel in baked products.
Depending on the type of fat, particular textural properties are
obtained. Using oil instead of butter lends greater volume to the
final product, since the proteins in the flour are better wrapped in
the fat and, thus, it is more difficult to develop the gluten network.