For all-extract brewing, boiling (along with hop and yeast selections) is a big factor in the overall character of your beer. But maybe you’ve wondered, “Why boil at all? I use hopped extract kits!” Or maybe you know boiling is needed to kill bacteria in the wort but still wonder how long the boil should be, and why. Well, there are three main reasons to boil the wort: The first is to make a physically stable finished product that won’t become hazy too quickly with age. The second is to get the goodness out of the hops and into the beer. The third is to evaporate undesirable substances called malt “volatiles.” Dimethyl sulfide (DMS), which smells of cooked corn, is often the most critical to remove.
There’s a fourth, albeit less critical reason: to fill your home or apartment with the delightful, captivating aroma of the brew kettle.
“Stabilizing” the wort means to alter its makeup, making it less prone to change over time. Three big causes of unwanted changes are bacteria, enzymes, and proteins.
Room-temperature wort containing bacteria from the air, your water, or any other source will probably change over time as bacteria discover the nutritional value of your wort. If enough bacteria gather to change the wort’s taste, smell, or appearance, then it becomes contaminated, ruining its flavor. Boiling “resets” the living bacteria count to zero. If you work quickly and with sanitary equipment after the boil, inevitable contamination will be kept in check until the yeast make beer. Beer can defend itself.
For all- or partial-mash brewing the enzyme activity that was desired in the mash would, if not halted through boiling, continue in the fermenter. Dextrins would continue to be converted to fermentable sugars, and you’d likely end up with a thinner, more alcoholic beer than planned. This is an aging process, changing the beer from your intended design.
Finally, wort contains many kinds of proteins that slowly degrade and change the appearance and flavor of the beer. The more of this protein you can eliminate from the wort, the less likely you are to have unpredictable and unwanted changes in your product over time. Boiling for about 15 minutes completely halts enzyme and bacterial action, and longer, vigorous boils will cause much of the unstable proteins to drop out of the wort as “break” material.
Outfitting for the Boil
To begin you’ll need a pot to serve as your brew kettle and a spoon you can use to reach to the bottom of the pot when it’s full of boiling wort. Your pot should have a volume about one-quarter to one-third greater than the volume you expect to boil. It’s important to be able to do a full, vigorous boil, and it’s important to keep the boiling, sugary wort inside the pot.
For a five-gallon extract recipe many instructions call for a wort volume of two gallons at the end of the boil. The wort is then added to three gallons of chilled water. With this method you should have at least a four-gallon pot. This allows you to start the boil with about three gallons of wort, to be reduced during the boil to about two gallons.
If you don’t have a brewpot yet, you have at least two choices to make: how big and what material. Your choices include enamelware, aluminum, and stainless steel. Whichever you choose, a good rule of thumb is to buy the heaviest pot you can afford. High-quality enamelware pots are hard to find, unlike small, paper-thin aluminum and stainless pots, which are everywhere.
Prices range from about $20 for 15-gallon enamelware to $60 for six-gallon heavy aluminum to $150 for a 10-gallon, aluminum-clad stainless unit. Thicker pots and those with aluminum-clad bottoms are better choices if you want to avoid scorching, a common problem in the boil that not only makes cleanup a big chore but also affects beer flavor.
Finally, a very real consideration is the Aroma Factor. Some non-brewers have a genetic flaw that makes the smell of the brew kettle intolerable. If you haven’t brewed in the house yet, you may want to try it first with available or borrowed gear to determine if those who live with you will ever permit it indoors again. Having to brew outside can add to your equipment requirements. This extra cost is called the Aroma Factor.
Turn Up the Heat
If you’re brewing with extract, it’s important to avoid scorching when adding the syrup to the water. When the water begins boiling, take the pot off the heat and stir in the extract. Continue stirring until the extract is completely dissolved, then return the pot to the heat. Any syrup or dry extract sitting on the pot bottom may stick to it before it dissolves, so keep stirring for a while. It’s important to continuously watch the pot during this reheating — changes occur quickly as the wort begins to boil.
Just before the wort boils, you should see a thin, uniform layer of foam develop on the surface. Without your complete attention a boilover is possible within the next few minutes. Reduce the heat when you see this layer form. If you get surprised and are using an electric range, you’ll need to remove the pot from the heat completely because the hotplate doesn’t cool very fast after it’s shut off. It’s a good idea to have a pair of potholders handy and a nearby place to set the pot.
After a few minutes of very gentle boiling, the foaming problem will go away. At this point you still need to watch for boilovers, but the problem is much less severe. The goal is to maintain as vigorous a boil as possible, without the risk of boiling over. The strong agitation of the wort and the bubbles moving to the surface both provide what’s needed for a strong protein break and a stable, quality final product.
Until this point the wort is referred to as “sweet wort.” Now it’s time to change that by adding hops. Hops actually have three very important things to offer:
- Resins add bitterness used to balance the malty sweetness all beers would otherwise have.
- Tannins help to drop out those nasty proteins that cause unwanted haze in your beer.
- Oils add aroma and flavor to the beer.
The one hop resin that’s most important for bittering is called alpha acid. Look at the label on any package of hops at your supply store, and you’ll see the alpha acid content given as a percentage by weight. The numbers on bittering hops range from four to 14 percent, and you may see labels such as “6.3% alpha acid” or “7.8% AA.” The larger the number, the more bittering resin the hops contain.
The alpha acid content alone doesn’t determine how much bitterness will be added to your wort, though. Alpha acid itself is not very soluble in wort. Boiling helps extract the resin from the rest of the hop and convert it to a soluble form. Only the percentage extracted and converted remains in the finished beer. The percentage of alpha acid extracted increases with a longer boil time and decreases with higher gravity wort. After an hour or so of boiling, nearly all the resins extracted from the hops will have been converted to soluble bittering material.
For wort having an original gravity between 1.050 and 1.060 and boiled for one hour, you can expect the percentage of total alpha acids extracted to be 20 to 30 percent. This extraction is called hop utilization and also depends on what form of hops you use (pellet, whole, or plug). In general pellet hops will provide the highest values, partly because they disintegrate into fine particles in the boil. Whole-leaf hops provide the lowest utilization.
It’s generally accepted that it takes a vigorous, 60-minute boil to get conversion of the hop resins to a soluble form and to ensure enough violent activity in the kettle to get a good protein hot break. Most recipes will specify either 60-minute or 90-minute boils, with 90 minutes being common for all-grain worts, primarily due to the need to coagulate proteins.
The bittering hops can be added at any time near the onset of boiling. But when doing 90-minute boils, add the kettle hops about 15 minutes into the boil to avoid unpleasant bitterness from over-boiling the hops. However, adding a few hop
pellets before the wort begins to boil will help prevent boil-overs in the early stages of boiling. Later in the process things are a bit different; hop pellets can cause boil-overs when added to a vigorously boiling pot of wort. It’s a good idea to add a little, wait for the foam to settle down, then add a little more, and so on.
Looks Like Rabbit Food
At first brewing with pellet hops may seem processed and unnatural. There’s a practical problem with whole leaf hops though: They tend to plug things up. Your brewer’s supply shop should have straining bags (hop bags) to solve this problem.
Hop bags are available in both reusable, washable nylon or throwaway gauze. You fill a bag with the appropriate amount of hops and tie it shut with a drawstring. Just drop the full bag into the kettle and pull it out with tongs at the end of the boil, before chilling. When using hop bags some brewers like to increase the recommended hop weight by about 10 percent to compensate for poorer extraction.
Whole hops don’t cause as much initial foaming, but you still need to add them carefully at the start of the boil. Because it can be more tedious to separate or weigh out whole leaf hop additions, it’s a good idea to have everything ready before you start the boil. It helps to weigh the hops into paper or plastic sandwich bags prior to the brew session. If you don’t have a set of scales, then whole hop plugs are especially handy for getting good hop weight estimates. The plugs can be readily split using a sharp knife.
In Grain We Trust
If you haven’t used specialty grains yet, you need to! Find an exciting grain/extract recipe and get a thermometer. The idea is simple. As with any extract recipe, all or most of the fermentable sugar will come from the extract. Grain is used to provide color, aroma, flavor, complexity, and fun. Any grain used mainly for these reasons is called a specialty grain. Some folks just call them “dark grains,” even though they aren’t all dark.
Several different techniques for using specialty grains work equally well. Here’s an easy one:
- Put all the grain into a pan large enough so the grain only fills it about halfway. Run your tap until the water is as hot as it gets (probably about 140° F), then cover the grain with enough water to get a very thin, easily stirred mixture.
- Put the pan on very low heat. Temperature control isn’t critical, but try to keep it around 150° F and definitely below 170° F. Time the heating of your brewkettle water so it will be just boiling by the time the grain has steeped for 30 to 40 minutes.
- After a 30 to 40 minute steep at this temperature, carefully pour the grain mixture through a large kitchen strainer or pasta screen into the kettle water. An important goal is to get as much water into the kettle as possible, with no grain. Boil the water and add your extract as you normally would.
Another technique is to put all the grain in a grain (straining) bag (also at your supply shop), and drop the closed bag into the kettle as it’s being heated. Remove the bag when the water temperature is about 170° F, and drain it into the kettle. This might be easier and less messy for you, but you’ll get a little less from the grain. As with hop bags, you may want to increase the grain weight by about 10 percent when using a straining bag. Keep good records and find out for yourself.
Finishing with Flair
Recipes will almost always specify when all hop additions are to be made, usually in minutes from the end of the boil. Again, the hop resins are extracted and made soluble by a good 60-minute boil. But the hop oils, which contribute flavor and aroma, are driven off almost completely by such long times in the boil. Therefore aroma hops are usually added in the last 20 minutes or less of the boil. In fact some brewers add aroma hops only after the burner is shut off and the boil has stopped. If you add your finishing hops this way, cover the kettle completely and let it sit quietly for about 10 minutes.
One important but often misunderstood element of cooling wort is the difference between aeration and oxidation. After the boil is complete, the wort (now called the “hopped wort”) should be cooled as quickly as possible then transferred to your fermenter. But before you decide how you’ll do this, you should know what’s good for the wort and what’s not. When the liquid is above 140° F or so, any air mixed into the wort may oxidize it, and that’s bad.
The chance for oxidation is greater with increased agitation of the wort at higher temperatures. Now, don’t worry about a little sloshing around in the kettle. But avoid pouring hot wort from one container to another or allowing hot or warm siphon flow to drop and splash. This may damage the product permanently, degrading the beer’s flavor and how well it ages.
When the wort is at pitching temperatures, 75° F and below, air mixed into it simply dissolves, and that’s good. The yeast will use all the dissolved oxygen they can get, and you can’t dissolve too much with common methods. Those methods include pouring the cool wort back and forth from one bucket to another, agitating as much as possible (with your long spoon), and using an aquarium air pump with tubing and aerator.
It’s very simple: If the wort is above 140° F or so, avoid any splashing. If it’s 75° F or below, agitate and splash it as much as possible.
Cooling the Wort
You have three main goals in cooling the wort. First, lower the temperature as quickly as possible through the 80° to 100° F danger zone, where the wort is most vulnerable to contamination. Second, get a strong, fast, healthy start to the yeast. The sooner the yeast produce alcohol and increase the acidity of the wort, the sooner it becomes an unwelcome place for bacteria. Third, produce a good cold break — that’s when more of those unwanted proteins drop out of the wort.
Depending on your time and esources, you may choose to cool using the bucket-in-the-bathtub method, a copper coil chiller, or any other method suggested in books, by friends, or by your supply shop. Remember though, once you’ve finished the boil everything that comes into contact with the wort must be sanitized. The “hot side” of your brewery may be a grungy garage, but your “cold side” containers, tubing, and other gear must be clean and sanitary.
Your Work is Done
Even if you consider boiling the wort a tedious task, it’s a step you shouldn’t skip. Not only is there a lot happening in that kettle, but the boil provides many options for fine-tuning the brew. Making quality wort is the brewer’s Job One. After that it’s pretty much up to the yeast to make the beer. Give them the best raw material you can.