Antifoam can be a number of products. Some are silicone used and there are newly approved Antifoam for the beer brewing industry that are hop derived. They all basically have an effect on surface tension, and more specifically protein stability. In brewing beer the fermentation foam is of concern and becomes loss in primary fermentation. I think for the whiskey mashes its a combo of heating the mash and residual dissolved co2 coming out of solution as it comes to temp in the boiler. Also as the mash is further heated more mash proteins are precipating out of solution from the temp increase and we see that as frothy foam. Just like bringing pasta up to boil really. Antifoam allows for increased efficiency of vessels. You can fit more, lose less to foaming, and gain more control. However like mentioned, why not make it without Antifoam and use techniques already in existence that are proven and do not adulterate the mash?

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