Proper aeration at the beginning of fermentation is important in producing good beer. To simplify things, yeast need an adequate amount of oxygen to ensure a healthy growth phase before they get to work turning sugars into alcohol and CO2.
Members of the Barley Legal homebrew club from Maple Shade, New Jersey, took it upon themselves to conduct an experiment comparing several aeration methods against each other. The results of their experiment were recorded for an episode of Basic Brewing Radio, which can be heard here. Spoiler alert! The results of the experiment are discussed below. For a more detailed look at the results and to hear the reactions of the participants as the experiment was being evaluated, listen to the show.
Barley Legal brewers Brett Mullin and Jim Fish brewed a wort of eight gallons with the following recipe:
Airhead Brown Ale
12 lbs. (5.4 kg) Maris Otter
1 lb. (453 g) 80L Crystal Malt
.5 lb. (267 g) 120L Crystal Malt
.5 lb. (267 g) Special Roast
.25 lb. (113 g) Chocolate Malt
.25 lb. (113 g) Carafa II
Mash for 60 minutes at 152˚F (67˚C)
.5 oz. (14 g) Northern Brewer for 60 min.
1 oz. (28 g) Fuggles for 30 min.
2 oz. (56 g) Styrian Goldings at flameout
O.G. 1.050 F.G. 1.012
After the boil, the wort was chilled and transferred into eight one-gallon jugs for fermentation. Thirty-two grams of a starter of liquid yeast was added to each fermenter, except for one, which received 2.35 grams of dry yeast. Fermentation took place at 70˚F (21˚C). Airlocks were attached to the fermenters.
The difference between the eight batches was in the way they were aerated:
– No aeration
– Wine degasser
– Dumping between fermenters
– Aquarium pump
– Pure O2
– Pure O2 – double length of time
– Dry yeast (no aeration)
It should be noted that the container-to-container beer was accidentally double pitched.
Day one: Most began activity within 1.5 hours after pitching. The first to show activity was the batch with no aeration. The wine degasser, shaken, container-to-container, aquarium pump, pure O2, double O2, and dry yeast followed in that order.
Day two: Even though Fermcap was used, all fermenters blew off. No noticeable flocculation. Trub was suspended halfway up both pure O2 fermenters.
Vigorous fermentation from most to least: Double O2, no aeration, pure O2, shake, container-to-container, aquarium pump, degasser, and dry yeast.
Day three: Kreusen starting to drop on pure O2. Aquarium pump and shaken batches began to show flocculation. All others looked the same as in day two.
End of day three: Aquarium pump appeared finished with fermentation. Shaken, pure O2, and double O2 followed.
Day four: Container-to-container is complete.
Day five: No aeration, wine degasser, and dry yeast finished.
Tasting of the samples was blind and random. Volunteers were able to sample and discuss their impressions. Those discussions were recorded for the episode. Here is a brief summary of the samples in the order they were tasted:
1. Container-to-container (double-pitched): Thin, roasty, flavors very separate from each other. No major defects.
2. Double O2: A bit sweeter than the first sample. More blended. Overall a better beer.
3. Aquarium pump: Abrupt, a tinge of alcohol, dry – not blended well.
4. Degasser: Very sweet and worty. Underattenuated. Flat.
5. Dry yeast (no aeration): Better than fourth sample, but still very sweet.
6. Pure O2: Very carbonated. Very dry. Highly attenuated.
7. Shaking: Good mouthfeel, roasty aroma, rounded flavor. Balanced. Drinkable.
8. No aeration: A “dump” beer. Flat. Sweet and under carbonated. Offensive.
Of the eight samples, the one that received double the recommended amount of oxygen and the one that was simply shaken were the overall favorites. The two were perceived as similar, with the double O2 beer being voted the best. Both were deemed drinkable and enjoyable.
As with any scientific experiment, repeatability is the key to proving the results. If the Barley Legal brewers decided to repeat their test, we’d love to hear the results. We’d also like to hear from any other homebrewers who decided to take up the challenge.