Why is it necessary for a brewer to aerate wort?

Aeration of wort is an essential step in the brewing process primarily because it introduces oxygen into the liquid, which is crucial for yeast to thrive. When yeast is pitched into the wort, they require oxygen for cellular respiration and reproduction. The presence of dissolved oxygen enables yeast cells to undergo division and multiply, which is fundamental for establishing a robust fermentation process. A healthy yeast population during fermentation leads to more efficient fermentation, better flavor development, and a reduction in potential off-flavors that can arise from stressed yeast.

The other options touch on aspects of brewing that do not directly relate to the primary purpose of aeration. While yeast clarity and hop bitterness are important considerations in the brewing process, they are not influenced by aeration in the same direct way that yeast health is. Adding sugars is related to the malting and mashing processes rather than aeration. Therefore, providing oxygen for yeast division is the most accurate reason for why aeration of wort is necessary in brewing.