August 14, 2015 by fhsteinbart
You may or may not remember a piece I wrote not too long ago about how to do an experiment. I suggested keeping to a simple yes/no style called a Case Study in which I brewed a 10 gallon batch of beer, then split the batch into two 5 gallon batches. One batch was locked down with an airlock, while the other simply had a loose fitting lid placed on the top of the fermentor. With everything else being the same, the only difference should be whether there is a difference between open and closed fermentation. I did a triangle test with members and guests of the Oregon Brew Crew and 25 out of 26 people correctly identified the odd beer out of the test. That’s 96.15% positive correlation which is extremely significant. The only unexpected result was the change in color on the open fermentation being approximately 4~5 SRM, while the closed fermentation is about 7~8 SRM. Some conjectured that the oxygen may have acted as a bleaching agent as found in hydrogen peroxide, but there shouldn’t be enough molecular oxygen available from the atmosphere to do that. I thought it might be that there were Melanoidin reactions taking place in the closed fermentor from enzymatic reactions that weren’t taking place in the open fermentor. This could be from Amadori rearrangement during fermentation or some other Maillard reaction. So now we are left with more questions than answers, and this is one reason scientific inquiry is so important in the field of brewing. So what we need to do now is both a longitudinal study of open vs. closed fermentations from more brewers, and a cross sectional study looking at different yeasts and seeing how each yeast performs with open vs. closed fermentations to understand what variations, if any, exist between strains and see if the results are reproducible within the same yeast. If anyone have any suggestions, please feel free to post your comments here, and maybe we’ll do another great experiment!