Brewing Priorities: Full Boils By: Tom Ayers
This week I’m going to continue my discussion on brewing priorities. As a recap last week I discussed the importance of proper fermentation temperature control. This week I’m going to discuss the next item I have listed as a top brewing priority, Full Boils.
Over the next several weeks I’m going to walk through, in detail, each of these items continuing this week with #2:
Have you ever heard the term “Homebrew Twang”? Have your friends ever said there is just something odd about your brew and that all your beers have the same taste? This is often a result of brewing in concentrated volumes and can be exasperated by boiling extract in concentrated volumes. This can be resolved by using full boils. As a side note, if you cannot do a full boil adding most of your extract late in the boil can help reduce the twang.
But first things first, what equipment is needed to do a full boil? That’s easy, a big old pot and enough power to boil the full volume. In terms of a pot you need at least 20% more than the max volume you intend to boil. Assuming you are planning to do a 5 gallon batch for an hour with a 9% evaporation rate per hour you need a pot of around 6.5 gallons (7 to be safe). That is because your starting volume will be about 5.5 gallons to boil off 9% down to 5 gallons, plus you need a 20% buffer to guard against boil overs. I personally prefer to use a much larger pot. See my article on making a keggle, this is a great option.
Secondly, you need the power to bring 5.5 gallons to boil. Some gas stoves can do this, and even some electric stoves. I’ve used my electric stove with the pot over two burners to achieve a boil of 5.5 gallons. Of course one of the logical steps many brewers make is moving outdoors and using a propane camp burner. A little more advanced option is to go electric. If you’re up for it I highly recommend the electric option.
Full boils do several beneficial things for the homebrewer including
When boiling at a concentrated volume and adding your extract for the full length of the boil you risk kettle caramelization. This occurs because the thick, sugary extract in a lower volume of water (e.g. 2-3 gallons) is highly concentrated. In the kettle this thick sugar water is more likely to caramelize in the kettle. This is what contributes to the Homebrew Twang I referred to earlier. Additionally, sugars can scorch in a highly concentrated boil. Once these sugars scorch, not only do they affect the flavor, but they are unfermentable. This can also be avoided by late extract additions to boil. For these same reasons the extract will darken and the resulting beer will be darker than the desired outcome had a full boil been used. Of course you can adjust for this by using lighter specialty grains and extract, but the level of flexibility is limited as changes to grains and extracts will also affect the resulting flavor of the end beer.
Hop utilization will improve with full boils. What this means is the number of IBU’s (International Bittering Units) contributed to your beer will be greater with a full boil. Hop utilization is reduced because the wort is thicker and less soluble. This stops the hops from isomerizing at proper levels, therefore lower amounts of IBU’s are in the end beer. The alternative is to use more hops or higher alpha acid hops to achieve the same numbers of IBU’s.
Lastly, the risk of contamination is reduced. When doing partial boils the brewer must add several gallons to the boiled wort after the boil is over. You can separately boil the additional water and I highly recommend you do so. But anytime you add water post boil you are risking contamination. With a full boil the entire volume is boiled together and therefore sanitized together and there is no need to add anything extract except the yeast.
As you can see there are many advantages to full wort boils. Ultimately, you will achieve a better beer on par with many of the commercial examples available. However, note I have placed several alternatives to using a full wort boil if you are unable to do so.
As always, if you’d like more homebrew information, follow me on twitter @Tom_Ayers. If you have any questions, comments, or topic requests send me an email at AyersBrewing@gmail.com and I’ll be sure to respond. Until next week, cheers and happy brewing!