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home Home > Subscribe to Ratebeer.com Weekly RateBeer Archives > Craft Beer Introduction

How to Spot a Bad Beer

A Beginner’s Guide to Acidity, Skunkiness, Floaties and other fun stuff
Craft Beer Introduction April 21, 2005      
Written by Oakes

Richmond, CANADA -

We’ve all been subject to beer that was, shall we say, not that good. This could be the recipe, or it could be that something has gone drastically wrong with the beer. This is one of the biggest obstacles that people will face in their growing appreciation for great beer. You see, beer can be a fragile product. Because mainstream beer is pasteurized, a lot of people don’t realize this. That’s because pasteurized beer doesn’t change much once it’s been bottled or canned. But a lot of craft beer is unpasteurized. Sometimes it is filtered, which reduces the risk of something going wrong (but doesn’t eliminate it), and other times the beer is “live”. Live beer is technically still fermenting. As such, it is subject to all the potential infections that can occur during the fermentation process. Another set of potential problems comes with the increase in popularity of vintage beers.

This article is intended a resource for beginners to understand some of the problems that may occur with beer, to render the end product something other than what the brewer intended. The issue will be approached in non-scientific terms to the extent that is possible. For a more scientific explanation of brewing flaws, I recommend the BJCP study guide as an invaluable resource.

Bitterness - Comes from hops, and also from roast barley in stouts. Some beers are intensely bitter, but they are almost always intended that way. In over a dozen years of beer tasting, I have only come across a beer with excessive bitterness (astringency) caused by a brewing flaw once or twice. This was due to overactive yeast in the bottle that overattenuated the malts, leaving nothing to balance the intense hop bitterness that was already built into the beer. Sometimes the beer is just plain unbalanced, but that is not a spoiled beer.

Flat Beer - As with bitterness, a lack of carbonation in beer is generally deliberate. If you’re used to fizzy pale beers, you might find a cask ale or barley wine a little shocking due to low levels of carbonation. Indeed, there is some carbonation and truly flat beer is very rare (unblended lambic, for example). Occasionally, a beer that is intended to carbonate naturally in the bottle does not, but that is very rare in professional brewing. Occasionally, a brewer may have trouble with their capping machine and the beer does not develop and hold carbonation well. This will often have a negative impact on the flavour and mouthfeel of the beer. It also increases the risk of oxidation. So, while it’s possible, lower levels of carbonation are usually not indicative of a bad beer.

Cloudy/Hazy - The visual appearance of a beer can change under certain circumstances. It can, on rare occasions, mean that the beer is bad. Usually, however, it is the result of either yeast being added deliberately, or simply of the beer not being pasteurized and/or filtered. That said, haze caused by the precipitation of proteins in the beer can sometimes have an adverse affect on flavour, and also provides a feeding ground for unwanted bacteria, resulting in one or more of the infection symptoms below.

Floaties - These are chunks of solid matter floating in your beer. Never a pretty sight. But not always bad. There are two types of floaties. The first are big blobs of protein. These look ghastly. They are essentially harmless, though. I know it doesn’t look that way and you probably agree. In the 1970’s, enough people decided that the floaties in Schlitz were such a problem that the brand took a precipitous slide from #2 beer in the US to a regional novelty. I mean, floaties killed an absolute juggernaut. But deep down, they aren’t unhealthy.

Some breweries seem more prone to floaties than others. These big blobs are often mistaken for yeast chunks, but this not to be the case. You could try filtering the beer but the problem is that something (proteins) have left the beer so the damage to the beer’s character would have already been done. The floaties won’t hurt you and the beer is still safe to drink, but it will be less than 100%.

The other kind of floatie can be found in ancient bottles of pale lager. Most domestic brands turn over too frequently, but you may see this with obscure imports, particularly if found sitting dusty and forgotten in the most forlorn corner of the store. These are generally an indicator that the beer is not fresh. It may not have deteriorated much, though, as those beers tend to be pasteurized anyway. These floaties are easily visible through the bottle so you can always check before purchasing.

Sour – There are many styles of beer where acidity is appropriate (the Lambic family, Berliner Weisse, Saison, Flemish Sour Ales, Orval). Background acidity may also be present in wheat beers (wheat gives a hint of tartness) and some stouts (famously Guinness). The acidity in stouts is a usually function of roast barley, the style’s defining ingredient. (With Guinness and a few others, a sour mash is used, but this is uncommon). These beers polarize beer lovers but sooner or later everyone comes to accept these sour beers. It may take some getting used to but be patient.

In other beers, however, acidity is almost always a sign of infection. Essentially, unwanted bacteria have infected the beer and are chewing up the remaining sugars. The intent of the brewer was that the yeast still in suspension would eat these sugars gradually in a process known commonly as bottle fermentation. Instead, the bacteria (which tend to move faster than the yeast) have gotten to the sugars first. The by-products of the yeast are alcohol and carbon dioxide. The byproducts of the bacteria are acids. The result is sour beer.

Gushers – There are two types of gushers you may experience when opening a beer. In some cases, the carbonation has built up too much, but the beer is fine. In many cases, however, the gusher will be the result of bacterial infection. In most bottle-conditioned beers, if bacterial infection occurs, the bacteria will not stop when the yeast would otherwise have stopped. So their high level activity results in pressure buildup. If you experience a gusher, it’s important to remember that it might be fine. Smell the beer and if it smells like vinegar, dump it. If it smells fine, taste it. If it tastes normal, run with it.

One conclusion you may wish to appreciate - if excess carbonation can build up in beer, treat corked beer like champagne and point it well away from anybody when open. I’ve almost had my head taken off by a few corks. Sometimes this occurs the very second the wire comes off, so take extreme caution with corked beers at all times, please.

Thinness – Related to acidity and gushers is thinness. This is what happens when a bacterial infection results in too much sugar being fermented. Typically, beer will have residual sugars that the yeast cannot break down. This is part of what gives a beer body. Bacteria often break down more than what the yeast would have, leaving behind a very thin body. Typically, this is accompanied by acidity and a gusher.

Skunkiness – This is caused by a reaction between hops and ultraviolet light. The result is an aroma not unlike a skunk. Beers bottled in clear or green glass are especially susceptible to this. The key is to keep beer out of both sunlight and UV lights in stores. Ideally, you would avoid stores that keep their beers on exposed shelves subject to supermarket lighting. Many European lagers and pilsners should be purchased in cans rather than bottles as the cans offer superior UV protection relative to even brown bottles.

Oxidation – Caused by the beer’s exposure to oxygen. Typically this is found in vintage beers, but not always. Oxidized beers taste musty, cardboardy or sherryish. Some connoisseurs favour sherryish notes in their vintage beers, while others do not. Oxidation in non-vintage beers will not be sherryish but rather cardboardy and be a result of things like an improper seal on the cap or being in a cask or keg that has been left on tap too long.

Diacetyl – Manifests itself as butterscotch or butter on the palate. This is a fermentation by-product and some yeast strains produce more diacetyl than others. At low levels, it is a trait widely considered to be desirable in many styles of beer. It is important to note than individual sensitivity to diacetyl varies widely. For some people, there is no tolerable level of diacetyl while other people simply cannot taste it at all.

DMS – The character of cooked vegetables, especially corn. DMS occurs and is usually eliminated in the boiling stage. As a rule, it is not out of place in some light lagers, but is generally considered undesirable in any beer. Contrary to popular belief, the corn-like notes are not the byproduct of actual corn in the brew. Corn syrup typically ferments right out.

Phenolic – Phenols can come from either yeast fermentation or bacterial infection. The phenols from fermentation are usually acceptable but common only in German-style wheat beers (clove, vanilla, light smoke). Phenols from infection are nasty – medicine, paint thinner, Band-Aids, bleach. Very rarely, medicinal qualities are sought by the brewer (Orval and a handful of other specialty Belgian ales) but the other bacterial phenols are always a sign of an infection.

Sulphur – Unlike in wine and cider, antioxidants are generally not used in beer. Thus, sulphur is not a desirable trait in any beer. Causes are varied, but all are brewing flaws.

Higher Alcohols – The alcohol in beer is ethanol. This is a clean alcohol taste like you will find in any other alcoholic beverage - the taste is a bit peppery and the finish is stiff. However, sometimes higher (or fusel) alcohols will be present in a beer. This can be a result of several factors, but fusels are most commonly the result of brewing from a high gravity (high ratio of sugar-to-water before fermentation). Thus strong beers are most likely to have fusel alcohols, which are more harsh and gasoline-like than ethanol. Some regular strength macrobrews have fusel alcohols as well due to a widespread industry practice called high-gravity brewing. The brewery makes a beer to, say, 8% alcohol, and then waters it down. Yes, that means X Light is often literally a watered-down version of X, which is literally a watered-down version of X Strong.

Sewage, dirty diapers, etc. – Other than the exceptions listed above, pretty much any other nasty aroma or flavour you can think of is the result of bacterial infection and the beer should be considered spoiled.

What to do with spoiled beer? As a rule, dump it. Don’t rate it. It would be considered Rateable only if you had it at the brewery (where the brewer should be held 100% responsible for quality control), in the presence of the brewer outside of the brewery, or if you’ve had the beer several times and found it to be infected on numerous occasions, indicating a chronic problem. If a group shares an infected bottle, only one rating should be entered. No need to slander a good beer’s name simply because of one bottle that just happened to be split amongst multiple Ratebeerians. That is not good form.

If the beer is a vintage beer, caveat emptor applies. No matter how many good ones you try, vintage beers should always be considered a crapshoot. If the beer is not a vintage beer, or comes on draught, send it back. Don’t pay good money for bad beer.

Lastly, if you are unsure if the beer you’re holding is infected or not, check out the other ratings. Do they talk about the same characteristics you’re finding? If not, it probably is infected. But if most people seem to agree that the beer does in fact taste medicinal and a little sour, it may just be that the brewer intended it that way.



satan165 says:

one of the most important articles ive ever read. answered many questions. thank you oakes

174 months ago

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start quote Live beer is technically still fermenting. As such, it is subject to all the potential infections that can occur during the fermentation process. Another set of potential problems comes with the increase in popularity of vintage beers. end quote