Fats play several rolls....including tenderizing. Not only how much and what kind of fat you add, but also WHEN the fat is added to the dough will affect the finished product.

When fat is added early in the mixture along with the flour, it coats the gluten and then the gluten develops in short strands for a compact crumb (almost cake-like if it's a fairly large amount of fat) and you will end up with a shorter loaf. Use the same recipe and wait to add the fat after mixing - just before kneading - or you can add the fat during kneading by coating your hands with it so the dough doesn't stick to them, and you will find you get a more open crumb and a higher-rising loaf than if it is added early. When a small amount of fat is added after mixing and before kneading, the fat increases the gas-holding ability of dough. So those are the three different times you can add the fat.

Actually, less is more when adding fat to yeast breads. If you want soft dinner rolls choose all-purpose flour over bread flour. Use high-gluten bread flour for making hard rolls. The gluten is also a factor for a soft crumb, not just the fat. By increasing the fat you have essentially "shortened" the gluten strands via fat, and also increased the calories. You can do the same thing by using a lower-gluten flour.

Fat also helps keep bread fresher longer. Lean doughs will stale much quicker (within a day) than an enriched bread recipe. This is especially true if you use coconut oil because it is also helps prevent mold development. Butter, as we all know, adds flavor.

In doughs, like a brioche, that have high amounts of butter, you may need to refrigerate it to keep the high amount of butter from melting during fermentation. These recipes are best handled while they are cold.

-Grainlady

Thanks a million grain lady! your answer has been very very helpful.