IBUs and using a Hopback

[GregR]

Does anyone know how using a hopback affects IBUs? An equation, or some correction to add to a standard IBU equation?

Thanks!

[crassbrauer]

It shouldn't affect the amount of bittering units in your beer much at all, if any. What's the temperature of your beer when your sending it through the hopback? If yours is placed between the wort kettle and wort chiller as is usually the case, your wort is still hot but obviously not actively boiling; therefore, the primary goal here is to extract the oils and not isomerize the bittering compounds. Isomerization is the only way to increase your IBUs. You might consider whirlpool hopping in conjunction with dry-hopping as an alternative to a hopback, because the bacteria on hops are not wort spoilers, and you avoid excess hot-side aeration by doing so.

[GregR]

Ah, thanks for the tip. Yeah, true, it's not "boiling" wort, so probably not going to affect my IBUs. Not sure why that didn't occur to me right off. :P