It’s probably best not to think about it too often, but it’s an inescapable fact: germs are everywhere. And all germs aren’t the same. Like Charlie the Tuna, some have taste. They even like beer—your beer—as much as you do. Specifically, they go for the sugars in your unfermented wort.
That mixture of malt sugars, hops, and water makes a wonderful home for yeast to grow but is also an inviting place for other microorganisms. These other organisms are waiting to devour those sugars before your yeast has had its chance to convert the mixture into beer. That wouldn’t be so bad if these uninvited guests just had a little of the wort and then went on their way. But they also give off rotten smells and bad tastes.
So how can you prevent these pesky germs from getting at your beer and spoiling it before you have a chance to drink it? The trick is to keep as many of them out of your wort asyou can, and to make it as unfriendly a place as possible for those few that do happen to sneak in.
Germs fall into three categories: bacteria, viruses, and fungi. Forget about viruses; they don’t attack beer. That leaves bacteria and fungi.
There are all sorts of bacteria. Some thrive with oxygen (called aerobic bacteria) while others thrive without oxygen (anaerobic). Some bacteria like to consume sugars such as the sugar in your beer wort; others may consume more complex compounds such as starches. Most bacteria are active only in a specific temperature range. This range could include room temperature, or even temperatures up to 120° F. In general the lower the temperature, the less active the bacteria will be.
Fungi includes molds, mildews, and wild yeasts. Most molds and mildews will give your brew a basement smell. This is never a desirable quality.
Yeast also falls into the fungus category, but you are using a specific strain of yeast to ferment your beer—one that will give your beer the desired aroma and taste. Some wild yeasts may have desirable characteristics for beer making, but don’t count on it. It is more likely that they will ferment too much of what you have, give off strange esters and aldehyds (weird aromas and headache-inducing alcohols), and then refuse to settle out of the wort, leaving it as murky as a stagnant pond.
The Battle Plan
To fight back against the enemy, you need to know where these undesirables come from.
Bacteria and wild yeasts can be found on virtually any exposed surface. This includes you, your hands, all over the outside of your body, and even on the inside. So anything you touch will potentially get contaminated.
Another way bacteria get around and can get into your beer is through the air. Bacteria and wild yeasts are most commonly transmitted on dust particles, so the longer something is exposed to the open air, the greater the likelihood that it will get contaminated. Of course, there is no need to get paranoid about all these bacteria floating around you. Over the millennia people have developed a natural resistance to the common germs around us.
Unfortunately, the same is not true for your wort; you need to take some simple precautions to prevent contaminations.
Beer can be spoiled by any bacteria or fungus that consumes sugars to survive.
The most common way to get rid of a contamination in your wort is to boil the wort for more than 10 minutes. Over the centuries, boiling has become an integral part of the brewing process. Virtually no bacteria that affects beer can survive temperatures over 170° F for more than a few minutes. Everything is fine as long as the temperature of the wort is above 170° F.
Unfortunately, if you pitch the yeast into wort at this temperature, the yeast will also get zapped. You have to cool the wort to a temperature that will allow the yeast to grow and do its work of converting the sweet wort into beer. This would be approximately 70° F for ale yeast and about 60° F for lager yeast. But as soon as the temperature drops below 170° F, you start running the risk of an contamination again.
Don’t be alarmed. If it were really that difficult to make a good batch of beer, brewing would never have been discovered all those thousands of years ago. Plus, there are some simple tricks to counter all the obstacles that nature seems to have thrown in the brewer’s path.
There is no need for you to start wearing rubber gloves while brewing. Just wash your hands before you start and don’t touch the wort with your hands once it has cooled. You also don’t have to scrub down the whole house with disinfectant. But you should disinfect all the surfaces that will come in contact with the cooled wort.
Brewing Trick Number 1: You don’t need to have everything sterile all the time. There are times when it is very important to keep sanitation at a high level, and there are other times when it is not as critical.
The most important time to keep things sanitized is while the wort is cooling and before the yeast begins actively fermenting the wort. Another critical time—but not quite as critical as the first—is when you prime the fermented wort before bottling. In fact any time you transfer the beer, such as from primary to secondary fermenter, is important.
Priming is when you add some fermentable sugars to the beer to naturally condition and carbonate it in the bottles (this also applies to kegs, if that’s where you condition your beer). Among the equipment that may come in contact with cooled wort are:
• Stirring paddles (if used after wort has cooled)
• Funnels, tubes, and hoses
• Wort chillers, hop backs
• Strainers, filters
• Primary fermenter
If this equipment is to come in contact with the cooled wort, it needs to be sanitized. There are many ways to sanitize brewing equipment, including boiling it or even using various disinfectants and cleansers.
When don’t you have to worry about the sanitation as much? Any time before the wort is boiled is not considered critical. This includes the mashing and sparging of the grains. Please, don’t misunderstand: It is still important to keep the equipment clean. You don’t want to have any bad flavors introduced because of dirt and grime, but sanitation is not as critical. This is because the time frame for mashing is so short (usually less than two hours) that any bacteria in the mash will not have enough time to do anything before they are destroyed in the boil.
Brewing Trick Number 2: Pitch actively fermenting yeast as soon as the wort has cooled to the proper temperature. This is one of the most important tricks you can perform to help prevent bacteria from over-infesting your brew.
It is very important to cool the wort quickly once the boil is completed. This allows you to pitch the yeast so fermentation can begin. You could leave the wort in the covered boiling vessel until it is cool enough to pitch the yeast. This could take eight hours or longer. As the wort cools, any airborne bacteria that got into the wort can begin their work before the yeast does. This could lead to a spoiled brew. Using a wort chiller can bring the hot wort down to yeast pitching temperature in 15 to 25 minutes.
Yeast is a living organism, and it needs oxygen to develop properly during the initial stages of its lifecycle. Oxygen-starved yeast can result in a lengthened growth stage of fermentation, increasing the chance that bacteria may become more dominant in the wort. Another problem with under-aeration is that in an oxygen-starved wort, yeast cell growth will be abnormal, and undesirable esters will be produced. These esters cause off-flavors in the beer.
The rapid boiling that took place before the wort was cooled drove off all the oxygen from the wort. The aeration of the cooled wort will dissolve oxygen back into the wort.
It is very important to remember that cool wort should be aerated, not hot wort. Wort is considered hot if its temperature is over 100° F (38° C). At the higher temperatures there can be oxidation of the wort that adversely affects the flavor of the beer. The easiest way to aerate your cooled wort is to allow it to splash when pouring it into the primary fermenter.
There are several reasons most other microorganisms tend to be overpowered once the yeast begins actively fermenting. Once the yeast is pitched into the aerated wort, the yeast multiplies quickly and consumes all the available oxygen in the wort. This means that any bacteria that need oxygen to reproduce will only be active during the short time that oxygen is available. Yeast growth also reduces the beer’s pH, further suppressing bacterial growth.
Also, as the yeast reproduces and ferments the wort, it produces alcohol. As the alcohol content increases, it will inhibit bacterial growth. In fact if the alcohol content gets too high, it will even inhibit yeast growth (this doesn’t happen with beer yeast until around 8 percent).
There are other factors that control the growth of unwanted bacteria in the fermenting wort. The bittering acids that are contained in the hops are a natural inhibitor of lactic acid bacteria. Lactic acid bacteria can give your beer a sour or even a butterscotch taste. At one time, beers that were to be stored for long periods or transported over long distances were brewed with more hops as a preservative. A good example of the preservative qualities of hops is demonstrated by India Pale Ales (IPAs), which were originally brewed extra bitter to help them survive the long trip from England to India.
Brewing Trick Number 3: Ferment the wort in a closed primary fermenter. Primary fermentation can be done in either an open or a closed container. An open primary fermenter should still have some sort of cover over it to prevent larger particles from dropping into the fermenter. However, using a closed fermenter (with a fermentation lock) prevents any airborne bacteria from floating into the brew.
This is especially important if you don’t have a place that is free from open drafts for brewing your beer. This is not to say that you should never experiment with open fermentation. On the contrary, beer has been brewed in open containers for centuries. The foam (called the kraeusen) that is formed on the surface of the beer acts as a natural insulation between the germs floating in the air and the fermenting wort. However, since the goal is to minimize possible contamination, a closed primary fermenter will provide that extra bit of security.
Since you cannot protect your wort from all bacteria, strive to make it rough for those bacteria that do happen to get in. Using all the tricks that have been passed down over the centuries:
• Boiling the wort
• Using hops as a natural preservative and bacteria inhibitor
• Sanitary brewing conditions
• Cooling the wort to yeast pitching temperature quickly
• Aerating the cooled wort
• Using a closed primary fermenter
Losing the Battle
In most cases bacteria attack the fermenting wort, and the spoilage is readily detectable. It is characterized by off smells during or after fermentation, scum that floats on the surface of the fermented wort, or yeast that fails to settle after fermentation has completed. Note that some strains of beer yeast give off a sulfury or rotten-egg smell during fermentation. This is normal, and the resulting beer is very good; the sulfury smells escape through the fermentation lock.
Other germs (usually wild yeasts) can attack the beer once it has been bottled. These will be characterized by over-carbonation of the beer. Over-carbonated beers may cause the beer to erupt into a fountain when opened or, in rare occurrences, cause the bottle to explode. This is because wild yeasts will ferment compounds that are not normally fermented by beer yeasts, resulting in the production of more carbon dioxide in the bottle than expected.
Usually there is nothing that can be done once a batch has been contaminated by some unwanted germ. If the contamination is caught early enough during the primary fermentation stage, lowering the fermentation temperature may allow you to salvage the batch from the effects of the bacteria. Often, however, you won’t notice the problem until you are getting ready to bottle the beer. If the off smells or tastes aren’t too bad, just bottle and drink the beer anyway (none of the bacteria that live in beer are harmful to people).
If the smells or tastes are more than you can handle, then you have no other course of action than to dump the batch. If a batch does go bad, make an effort to identify what type of contamination occurred and how it can be prevented in future batches. You don’t want to make the same mistakes over and over again.
Winning the War
If despite your best efforts your batch goes bad, remember: Even the big commercial breweries get an occasional contaminated batch. When that happens, they have to dump thousands of gallons of spoiled beer. So don’t get discouraged, try to figure out what went wrong, and try again. Most important, remember to have fun with your hobby. If a batch does go bad, it will make a good story to tell while your friends are drinking one of yourgood batches.