Baking usually requires the baker to preheat the oven to ensure that food cooks evenly and properly, according to Foodista. When cooking, failure to preheat the oven often results in food that is overcooked in some areas and undercooked in others. Eating undercooked food, especially meat, is unsafe because it may result in the consumption of bacteria and other pathogens.
Packaged foods typically come with cooking instructions. These instructions help the consumer cook the food correctly so it is safe to eat. Since most of these instructions ask the consumer to preheat the oven, the rest of the cooking times are dependent on that first step. Not preheating the oven changes the time needed to properly cook the food.
Preheating the oven is also important when cooking baked goods, such as cakes and pastries. This is because yeast needs a consistent temperature to rise correctly. If baked goods are put into a cool oven and exposed to gradually rising heat, they do not rise to their maximum heights.
When an oven is preheating, it is important for the cook to leave the oven shut until it is finished preheating. If the oven door is opened, heat escapes, and it takes longer for the oven to reach the desired temperature.