What type of bread requires a steaming process at the beginning of baking?

The steaming process at the beginning of baking is particularly significant for sourdough bread. This technique helps to create a humid environment within the oven, which is crucial for the initial stages of baking. The steam allows the bread's crust to expand and helps to develop a beautiful, crispy exterior while maintaining moisture inside the loaf. This results in the distinctive texture and flavor that are characteristic of well-made sourdough.

While other types of bread, such as white, rye, and whole wheat 5 grain breads, may also benefit from some moisture during baking, they do not require the same level of steam infusion as sourdough. In summary, steaming is essential for achieving the unique qualities of sourdough bread, making it the correct answer in this context.