What is hot side aeration (HSA) and should I be concerned about it?
Ever since an article was published in a brewing technical journal in the late 1980s there has been a long debate about “hot side aeration” or HSA. This is the unintentional aerating of the mash liquid or wort while it is hot. There is some evidence that this may cause chemical reactions that can contribute to premature staling of the beer after it is bottled or kegged. However, there is countering evidence that the effects may be very limited and especially of little or no consequence to homebrewers. Whether or not this is truly an issue, many homebrewers in general avoid unduly splashing the mash liquid and wort until it is chilled. It is clear that HSA is not a problem during boiling when the ability of the wort to absorb oxygen is nearly zero. Once the wort is chilled and before fermentation begins, oxygen is desirable for healthy yeast reproduction, which is why aeration is recommended at that time but not otherwise.
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- What is hot side aeration (HSA) and should I be concerned about it?
