Adding Water to a Boil
Q: Brad Smith Has stated a 90-minute boil is recommended for boiling off dimethyl sulfides (DMS). My pot is only 8 gallons (30 L) so 90 minutes results in too little wort into the fermenter. Is it OK to add water along the way during the boil?
— Peter Young • Sault Sainte Marie, Michigan
A: Brewers, and those of us brewers who write about brewing, have all sorts of rules of thumb to help guide us through our brewing journeys. Boil time is one such rule. Some brewers say to boil for a least an hour to allow all of the things required in the boil to occur, and others skip straight to what works best for them and use that as their rule. Just guessing here, but Brad Smith probably has figured out that a 90-minute-long boil works best for his brews. A real dilemma with long boils, however, is excessive evaporation and energy consumption.
Adding water during the boil and/or at the end of the boil can certainly be done to help you hit your volume and gravity targets while hitting that 90-minute target. But long boils may do more than drive off DMS and water; they lead to flavor development, wort darkening, and contribute to beer oxidation through the creation of peroxide radicals that survive wort production.
As a starting point, you can slowly dial back the boil time if you are not having issues with DMS. At a minimum, you may be able to shave off a few minutes to your brewing day, and, in the process, you may discover that the shorter boil improves your beer flavor since different systems do better with different boil times.
Boil duration, intensity, and evaporation rate has been a topic of significant interest for the last 25+ years, and continues to be investigated because of the amount of energy consumed during this stage of the brewing process. Today, there are several high-temperature, thermal processing methods to sterilize wort, precipitate wort proteins and polyphenols, isomerize alpha acids, convert S-methylmethionine to DMS, and strip DMS from wort with either very minimal or no wort boiling. All of these methods incorporate some sort of wort stripping technique to remove DMS from the wort during the process and/or right before wort cooling. These methods will undoubtedly become more common in the future as concerns about energy consumption continue to intensify. Today’s rule of thumb may soon become another historical brewing technique.
