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60, 90, or Otherwise: Finding the Best Boil Times

Award-winning beer comes from a 60-minute boil. So all brewers should boil for 60 minutes. Guess what? The same can be said for 70 minutes, 45 minutes, 120 minutes and so on. There is no hard and fast rule about boiling times so let’s explore how to determine what boil time is best for you and your specific batch's needs.

Understand that 15 Minutes is the Minimum

Boiling kills bacteria and sterilizes wort, making it fit for proper fermentation by yeast. For all grain brewers, boiling also stops the conversion of sugars that occurs during the mash. Without boiling to halt conversion the wort would have fewer dextrin sugars and would make for a thoroughly thinner beer than originally planned. Hot break is a process that occurs with all grain brewing when proteins and enzymes reach a certain temperature that causes them to solidify. Once the proteins solidify they form a thin string-like material that falls to the bottom of the kettle after the boil during the cooling process and can be left behind when the wort is transferred later to the fermenter. This provides clarity, helps to limit “chill haze” and prolongs shelf life -- not that delicious homebrews are around long enough to hang out on shelves. For extract brewers, and liquid malt extract specifically, the phenomenon of “hot break” has already been taken care of because the extract has already been boiled during it's production. For dry malt extract users it is lessened but still occurs. Sterilization, conversion halting, and hot break occur in the first 15 minutes of the boil. So that’s the minimum time wort should boil.

Control for DMS

DMS (dimethyl sulfide) is a chemical that produces off flavors and aromas in beer. Primarily DMS is detected on the palate as cooked corn or cabbage. That’s the bad news. The good news is that DMS is easy to avoid by boiling your wort. Caused by the heating of a chemical that naturally occurs in malt, SMM (S-methyl methionine), DMS is highly volatile, meaning it is easily expelled through the action of boiling so long as you DO NOT COVER YOUR POT. Another thing to note is that Pilsner-type malts contain eight times the SMM as other more modified malts such as pale malt. So any beer with a large portion of Pilsner malt (pilsner, saison, cream ale, weizen, etc.) should be boiled at least 60 minutes. If achieving a rigorous boil is difficult or chilling rapidly (within 30-40 minutes) is difficult, employ a 90-minute boil to drive off as much DMS as possible. Also, if you tend to worry a lot, or have had DMS issues in the past with pilsner malt, boil for 90 minutes to be safe. Pale ale malts like US-2row, Maris Otter, California Select etc. are more modified (kilned longer) than Pilsner and only need to be boiled 45 minutes to drive off DMS. If darker malts, like Munich or Vienna, or dark specialty grains are used, even shorter boiling times can be used. How short? Few have dared to find out, but below is a recipe for “30 minute American Brown Ale” that proves a 30-minute boil can be done successfully without the flaw of DMS.

Manipulate Hop Isomerization

Most of the beautiful bitterness, flavor and aroma that hops provide is created (except for dry, mash, or first wort hopping) during the boil. “Isomerization” is a fancy word for what happens when hops are in boiling wort. A less fancy word is extraction. Boiling converts the alpha acids in hops into bittering, flavor, and aroma compounds that are extracted from the hops into your wort. When you look at a package of hops, it shows you that specific hop’s AA%, or alpha acid percentage. The higher the number, the more potency that hop has. 15% is a high alpha acid hop. 5% is a low alpha acid hop. To understand hop isomerization during the boil – and to avoid very complex discussions about chemistry – think of this: hops boiled longer, 60 or 90 minutes for example, will provide more bitterness characteristics. Higher AA% hops will provide the most bittering during that time. If you want less bitterness, either boil for a shorter time or use low AA% hops. Hops boiled for only a few minutes, say 1 or 5 minutes, provide more aroma characteristics. Hops boiled in the middle, 30 minutes for example, provide flavor characteristics. Again, to manipulate what you want from hops, modify the boiling time or use hops with the appropriate AA% for your desired character. When deciding how long you should boil, take into account how long your first hop addition will boil and work from there. Most recipes call for the first addition of hops at 60 minutes, which means you’ll need to boil a minimum of 60 minutes to extract that hop’s bittering contribution to the final beer. Some recipes call for a 90-minute addition as the first addition, which will provide more bitterness. And as you’ll see in the recipe below, the first addition is a 30-minute addition of a high AA% hop, which will extract both bitterness and flavor from that hop in just 30 minutes.

Adjust for Color and Flavor Contributions

Boiling can also change a beers color and flavor profile through the Maillard reaction. This reaction darkens the wort and also provides flavors such as molasses, caramel, butterscotch, raisins, and bread and among others. The volume of the boil affects the rate at which these changes occur - a greater concentration of sugars in the boil excels the reactions. Consequently, partial volume boils (as common with extract recipe formats) and high gravity beers should expect to see quicker changes than full volume or low gravity boils. Additionally, extending the boil time to a 90 or 120 minute range will also allow more of these reactions to occur. Just remember if you extend your boil time you may want to account for the extra boil off to still meet your target batch volume.

Reduce Wort and Hit Original Gravity Target

For those brewers that do a full wort boil, the only way to get to your final volume and hit correct original gravity is to boil the wort. This will reduce the amount of wort that you claimed from your mash tun at an average rate of about .25-.5 gallons per 30 minutes. You will have to track your own evaporation rate as it changes depending on air temperature, pot dimension, boil vigor and other factors. Wort reduction also provides the needed volume and time to allow proper hop isomerization. An example of how wort reduction can help you determine boil time is this: If you get 7 gallons of wort from your mash, and have an evaporation rate of .5 gal/hr. you will need to boil 2 hours to get down to 5 gallons of finished wort 

Check What Others Do

Pale ale, porter, tripel, IPA, whatever the style of beer you plan to brew, conduct a bit of research of about that style’s color guidelines, common ingredients, and historical brewing practices. Here are some common beer styles and their recommended boil times to help you get started.

Beer Style Boil Time (Minutes) Reason
Pilsner 60-90 Modern malts are modified enough to eliminate DMS in Pilsner malt with a 60-minute boil. If you cannot chill quickly enough, lengthen your boil to 90 minutes to be sure.
Pale Ale 60 Plenty of time to reduce your wort and manage your hop additions.
India Pale Ale 30-90 A darker IPA (brown, amber or red) could be managed with a 30 minute boil using high Alpha Acid hops. For more bitterness, use a 90-minute boil and hop addition.
Porters and Stouts 60-90 These darker beers benefit from the flavor contributions of longer boils.
Black Lager (Schwartzbier) 60-90 Although it’s dark, it still uses large portion of Pilsner malt. Also the dark beer style benefits from the color and flavor contributions of a longer boil.
Barleywine 60-120 Kettle caramelization is a favorable trait in barleywine. Some recipes call for even longer than 120 minutes. Manage your volume and evaporation rates.
Saison 60-90 Often lighter in color and using large portions of Pilsner malt, these beers should be boiled at least 60 minutes.
Tripel 60-120 While these beers usually have large amounts of Pilsner malt, the longer boil is used to add layers of flavor from caramelized sugars and Maillard reactions.

Do What You Think is Best

Homebrewing is a creative adventure. Never be afraid to try something new with ingredients, process, or any part of the brewing experience. In an effort to shorten my all-grain brew day, I did the research needed to determine how short a boil could be. I chose an American Brown Ale because the darker, more roasted specialty malts reduce DMS and so I could use high AA% hops, which will provide the needed bitterness in just 30 minutes. 30-Minute American Brown Ale O.G. 1.060 IBU 38

Mash at 150 F, Extract version: Steep specialty grains at 150 for 30 minutes. Boil 6 gallons of wort to 5.5 gallons in 30 minutes adding hops according to the schedule above. Ferment for 2 weeks at 65F.