I have been brewing for 10 years and often do double batches and always keg my beers. I have chronically had this issue come up when dry hopping. I don’t think it is an infection issues but please advise!
After a typical 9-14 primary fermentation I have transferred to dry hop in kegs or carboys. I like the idea that the beer is 80-90% attenuated. The gravity reading and fermentation activity suggests the beer is close to terminal gravity, although I don’t always take a reading at this point I admit. Upon adding the dry hop i see an almost immediate increase in CO2 release and subsequent fermentation activity (bubbles rising to surface) which lasts 7-12 days into the dry hop. I like to limit dry hop contact so I become stressed as of what to do. I often am legging with minimal but continued activity. This has happened on many batches over the years (IPA, pale, ambers, ext…) I have even racked to secondary and waited several days with a calm surface on the beer prior to dry hopping with the same result. Oxygen in pellets aiding yeast fermentation or infection seem likely culprits. Please advise an annoyed home brewer.