When the outside of toast turns black while the inside stays white, it's usually due to a combination of factors related to the cooking process and the properties of the bread.
Heat Concentration: Toaster ovens and stovetops can generate high heat in a localized area. When the bread is placed in direct contact with the hot surface, such as a toaster oven rack or a stovetop griddle, the outer layers of the bread are exposed to intense heat. This causes the sugars and carbohydrates on the surface of the bread to caramelize rapidly, leading to browning and eventually charring (turning black).
Moisture Content: The inside of the bread usually contains more moisture compared to the crust. Moisture helps to regulate the temperature and keeps the interior from becoming overly dry. As the heat concentrates on the outer layers of the bread, it drives out moisture from the crust, promoting the browning and charring process.
Insulation: The crust acts as a natural barrier, insulating the inner part of the bread from direct contact with the heat source. This helps the inside stay relatively cooler and prevents it from browning as quickly as the outer layers.
Cooking Time: The time it takes for the outside of the bread to turn brown and eventually black is shorter compared to the time it takes for the heat to penetrate the bread and affect the interior. As a result, the surface becomes darkened before the heat has a chance to fully cook the inside.
To avoid excessive charring of the outer layers while ensuring the bread's inside is adequately toasted, you can try the following tips:
- Lower the heat or move the bread slightly away from the heat source in the toaster oven.
- On the stovetop, use medium heat and flip the bread occasionally to promote even toasting.
- Use thicker slices of bread, which can allow for better heat distribution and prevent excessive browning on the outside.
Different types of bread might also behave differently during toasting due to variations in their moisture content, sugar content, and crust thickness. Understanding how your toaster oven or stovetop works and experimenting with different settings can help you achieve the desired level of toasting without burning the outside.