The differences between some bread dough recipes, with and without oil are subtle but important.
Our Deli Rye Bread and Thin-Crust Pizza recipes call for such small amounts of oil (1 tablespoon of oil and 4 cups of flour for the bread; 1 tablespoon of oil and 3 cups of flour for the pizza) that you might wonder if it’s necessary. When we made batches of these recipes both with and without the oil, the differences were subtle but important. The pizza crust without oil was less tender on the inside and less crisp on the outside. The rye bread without oil had a slightly tough, chewy crust.
Fats work as tenderizers in breads by coating some of the proteins that form gluten, preventing them from hydrating and linking up to form large networks that would lead to toughness. When it’s present in high percentages (think of ultratender breads such as brioche and fluffy dinner rolls), fat’s effect is obvious, but it’s still important in smaller amounts, reducing toughness for a more tender interior and a more delicate, crispier exterior.