Off-flavors in beer
A famous VW ad from the sixties titled "Lemon", created by the great Bill Bernbach, ends with the following line: "We pluck the lemons; you get the plums."
This sentence pretty much sums up one of the most important jobs our brewers do - to make sure that only the best Staropramen beer leaves the brewery.
In order to detect off-flavors in beer proper training and years of experience are needed. Every brewer has to pass sensory training where they exercise their palate to detect the flavors and aromas that water, malt, hops and yeast give to beer. This is accomplished in a number of ways. One of them is using special kits that contain ready-to-use liquid forms of various flavors and aromas commonly found in beer. The other is simply tasting beer and keeping notes during the entire brewing process.
Brewers usually start with a general idea of what they are actually trying to accomplish with the beer they are brewing and what will it taste like once it reaches the consumer. This is the conceptual part where they are looking at how the ingredients fit together and which ones will perhaps be more pronounced than the others. Sometimes, brewers simply have to adjust the water chemistry, malt or hop bill to reach the desired beer profile. However, problems do occur. It is part of the brewing process. In a way, it is even exciting because it can feel a bit like detective work. What is the problem? Why did it happen? How can we make it go away? Once the problem is detected, the cause has to be eliminated. For instance, if the beer tastes grassy the cause might be that the malt was stored poorly so it picked up moisture. If the beer tastes yeasty it means that it is either too young or that the yeast is unhealthy. Oxidation is the most common beer off-flavor, the one that all brewers are diligently fighting to keep out of the brewing process (except for one part where oxygen is more than welcome). If exposed to oxygen, beer will develop a wet cardboard flavor. Beer with off-flavors can also be skunky, cidery, vinegary or taste like green apples, cooked vegetables, chloride, alcohol, to name a few. It has to be noted that some off-flavors are welcome in certain beer styles. Such is the case with diacetyl, the taste of buttery popcorn, which is acceptable in small amounts in some Czech lagers.
Ingredient selection, storage, equipment sanitization, brewing, each part of the process matters. Still, sometimes things can go wrong because beer is a living thing. This is where all the training, experience and brewery quality control procedures come into play. To borrow from Bernbach, this is how we pluck the lemons.