Doppelbock 4 way tasting experiment Published January 13, 2013 at 650 × 411 in Another Doppelbock and oxygen tasting experiment The 4 beers that were tasted. From left “no yeast/no O2”, “no yeast/O2”, “yeast/ no O2” “yeast/O2”. The picture was taken during the foam stability test. The two samples on the right were poured 1 min after the samples on the left were poured.