Because muffins are small, they are generally baked at relatively high temperatures so they develop browning before their interiors overcook. In general, muffins bake for 15 to 20 minutes. Loaves, on the other hand, have a much greater volume-to-surface-area ratio and require longer baking at a lower temperature. We tested several fruit and nut muffin recipes, as well as a plain one, baking each in 8 1/2 by 4 1/2-inch pans at a range of oven temperatures and times.Our findings?
To convert a muffin recipe to make a loaf, set the oven rack in the middle position, decrease the oven temperature by 50 degrees, and bake until a toothpick inserted in the center of the loaf matches the visual cue (either “with few moist crumbs attached” or “clean”), 60 to 70 minutes. Recipes with sugary toppings like streusel should be tented with foil during the last 20 to 25 minutes to prevent them from getting too dark.