All-Grain Brew Day Walkthrough (IX: Aeration)


A standard wort oxygenation setup. A regulator sits atop a cylinder of welding oxygen. The oxygen passes through a HEPA filter on it’s was to the aeration stone, made of sintered stainless steel.

This is the nineth installment in the All-Grain Brew Day Walkthrough, which started with a post on strike water preparation.


Aside from cleanup, the last two things a brewer does on brew day is to aerate the wort and pitch the yeast. Pitching an adequate amount of yeast, and “feeding” it with an adequate amount of oxygen, will ensure an orderly fermentation. An orderly fermentation is one that starts in a reasonable time, proceeds smoothly, and reaches a reasonable final gravity.

Altering the pitching rate or aeration level in your beer can affect its aroma and flavor. If you lower the pitching rate below what is optimal, the yeast need to reproduce more to reach the proper density to ferment the wort. Since esters are primarily given off in the growth phase, under pitching leads to more estery beer. In a like manner, under aerating the wort also increases ester production. These effects are most easily seen in yeast strains that produce a lot of esters and other fermentation byproducts. Most estery English ale yeasts, “spicy” Belgian yeasts, and wheat beer yeast strains “clean up” noticeably when the pitching rate is increased above the optimal rate and the wort is well aerated. The effect is harder to notice in cleanly fermenting yeast strains.

In most cases, it’s best to pick a yeast strain with the fermentation characteristics you desire rather than trying to stress a yeast into producing more esters, or taming its fermentation byproducts through overpitching.

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