Questioning dip hop advice

Q. I have been reading about dip hopping and am wondering why flush the fermenter the dip hops are in with CO₂ before adding wort? Also, why avoid agitating the dip hops? I ask because I’ve been adding dip hops to wort already in the X3 fermenter and then crashing to yeast pitch temperature using glycol and a counterflow chiller, so there’s exposure to oxygen and agitation in the sense the hops sink through the wort. It’s been working for me, but if adding hops first > CO₂ flush > closed wort transfer works better, I’m all ears.
David Lutman
via email 

Mr. Wizard says …

I don’t know when carbon dioxide flushing and minimizing agitation were first suggested as part of the dip hopping method, and I can only guess that this idea stems from the general concern about oxidation of hop and beer compounds associated with dry hopping. One significant difference between dip hopping and dry hopping, however, is that dry hopping involves adding hops to beer, whereas dip hopping involves adding hops to wort, where oxidation of beer flavor compounds is not yet a concern.

If you are interested in giving the purge suggestion a whirl, it may be something you discover makes a difference in your dip-hopped beer. It sounds like your current dip hopping method is producing good results, but brewers are always looking for ways to continue improving the liquid we all love.

I have written and talked more about dip hopping in the last few years than I ever imagined, mainly because the method is so straightforward. In 2023, we shot a BYO+ video where I reviewed what dip hopping is and how brewers were using the method. In that video, I mentioned a simplified variation of the original method described by Kirin — which actually includes agitation — where pellet hops are added to the cone of a fermenter, purged with carbon dioxide to drive air from both the hops and the headspace above, and then followed by the addition of hot water from the bottom of the tank. Unfortunately, I cannot locate the original reference to the carbon dioxide purge that I mentioned back in 2023. 

I am also somewhat skeptical about the benefits of CO₂ purging when it comes to dip hopping because of the absence of beer compounds at this stage. Oxidation of hop compounds is certainly possible, but hot water is used, and the steep is not too different from the oxygen exposure that hopped wort experiences in whirlpool vessels.

Your question raises a broader issue — the power of skepticism. Questioning advice is healthy. In my opinion, healthy skepticism gives critical thinkers a filter that prevents unproven ideas from suddenly turning into “facts.”