Diagnosing Beer Problems: Tips from the Pros

Some of us might ignore obvious flaws in our homebrews, chalking it up to equipment limitations, other time commitments or the “relax, don’t worry, have a homebrew” rule. But if you’re serious about reaching the level of winning homebrew competitions, amazing your significant other or even landing a full-time brewing job, then it’s time to diagnose your beers and learn how to fix them. This issue’s pros will get you started.

Brewer:  Matt Cole, Rocky River Brewing Company in Rocky River, OH

Brewers often use the phrase “cleanliness is next to godliness.” This is something all brewers must accept and respect. The best of the best religiously check and recheck their work, adhering to strict sanitation and proper cleaning procedures. However, problems do arise and we must understand how to pinpoint and address them. Here are some possible problems that can arise in your brewery.

DMS can produce unpleasant sulfur tones similar to cooked vegetables or creamed corn. The most common occurrence of DMS is produced during malt kilning, wort boiling and wort cooling. DMS is released during boiling as a gas, which is dissipated into the atmosphere. This is the reason for
a vigorous rolling boil of at least 60 minutes. Improper cooling techniques also lead to DMS production. Force-cooling the wort helps establish a more complete break (reduced trub levels) and reduces DMS development. The wort must be cooled rapidly, within 45 minutes to reduce DMS precursors.

Another common beer problem is oxidation. Oxygen quickly stales finished beer, yielding papery-tasting compounds, reducing malt character, accelerating diacetyl formation in beers that have not been aged properly and dulling hop character. While yeasts are good antioxidants, they cannot overcome the large amount of oxygen that is picked up during shoddy brewing and racking techniques. Oxygen and aeration are two distinctive things. It is important to comprehend which is which.

Aeration is the addition of oxygen to the cooled wort. Oxygen must only be applied when the temperature is cooled below 75 ºF (24 ºC). Aeration of hot wort causes the oxygen to chemically bind to wort compounds. These oxygen compounds can then oxidize the alcohol and hop compounds into off flavors and aromas such as papery, cardboard or sherry-like flavors. Mash pH is critical for proper enzymatic reactions and appropriate hot and cold breaks. Final runnings are also critical to monitor — discard any last runnings that drop below 1.008–1.010. These runnings may have a high level of polyphenol content and can lead to bad taste and haze in your beer.

Also, oversparging or sparging too hot can lead to the extraction of polyphenols and tannins from the malt. Care must be taken to keep sparge temperatures under 175 ºF (79 ºC) or off flavors can occur. Likewise, beers contaminated with bacteria may rapidly go turbid and develop a biological haze depending on the bug, though clean beers when stored for an extended period of time may also become cloudy and deposit a haze. Sugars like honey and molasses tend to develop haze over time if they are not used properly. This is due to the presence of complex proteins and polyphenols.

Besides running your beer through a filter, there are an assortment of ways to get a brighter brew. One approach is a vigorous rolling boil of at least 90 minutes, preferably 2 hours, supplemented with an addition of Irish moss or an equivalent kettle fining. Be sure to whirlpool in the kettle by stirring the wort in a circular clockwise motion at the end of the boil. This will help precipitate proteins and hop solids to settle in the center of the kettle. Many homebrewers use a “chore boy” wrapped in a muslin sack to trap solids. There are also various fining agents that can be added after fermention to help clarify the brew. The two most popular are isinglass and gelatin. These agents help bind with positive charged proteins, pulling them out of solution and falling to the bottom.

A preventative method is to choose a yeast strain that is highly flocculent. These strains tend to fall out quickly and naturally. The yeast will go dormant and fall to the bottom of the vessel, and will have a tendency to drag any remaining haze factors with it.

Brewer: Brian Lottig, Great Lakes Brewing Co. in Cleveland, OH

One major flaw that can be diagnosed in “bad beer” is diacetyl. Diacetyl is a flavor-active compound that is a natural by-product of amino acid metabolism during fermentation. The flavor and aroma of diacetyl have been described as buttery, butterscotch and stale milk. If any of these qualities are evident in your beer, chances are you have a diacetyl issue. In a standard fermentation, yeast produces alpha acetolactate during cell growth and later absorbs diacetyl and converts it to less flavor-active compounds, namely 2,3 butanediol and acetoin. For this reduction to take place, active yeast is required late in fermentation.

Removing beer from the yeast too early can leave diacetyl behind. If you are lucky enough to have temperature control, letting the temperature rise about two thirds of the way through fermentation will usually increase yeast metabolic activity enough to absorb most of the diacetyl present in the fermentation. A strong, viable yeast is needed for this. A sluggish fermentation will generally lead to low yeast in suspension and poor diacetyl removal. This is one of the reasons why preparing an adequate yeast starter is so crucial — not only does a fast fermentation limit bacterial growth, it can also limit diacetyl production. Esters are another common beer problem. A few practical means of decreasing the level of esters would be to one, increase the amount of aeration at pitching, two, increase the trub content in the wort and three, pitch a larger volume of yeast.

Another flaw homebrewers should learn to detect is oxidation. This is a chemical reaction that begins during the brewing process and continues throughout the life of the beer. While oxygen is critical at the beginning of fermentation to promote cell growth, it is detrimental at any other stage of the process. At its worst, an oxidized beer will have a papery or grassy aroma and flavor. To limit the extent of oxidation, you should avoid low mash-in temperatures — below 145 ºF (63 ºC) — sparge and transfer gently and fill bottles or final containers with minimal agitation. Even though you may package with active yeast, the yeast does not absorb all of the oxygen that is picked up during sloppy filling.

Issue: July-August 2005