When brewing beer, that is not quite possible. One can taste some of the malt, to get an idea of what flavors they will carry over to the finished beer, and hops will allow that as well. But brewing is part magic. Someone once remarked: "A brewer does not make beer, only wort. The yeast makes the beer." There are so many chemical reactions that go on throughout the whole brewing process!
So last night I invited a number of friends and the New Jersey Beer Club for a small 2 night beer flavor exploration at the Stirling Hotel (next Wednesday is the second part). The first evening we explored 5 so called 'off-flavors', flavors you should NEVER find in a beer(with few style related exceptions), as they are surefire signs of errors in the brewing/packaging/tapping process, infections from various sources, etc. If you ever get a beer with such a flavor, sending it back is the only thing to do... The next evening we will present 5 flavors that can be found in normal beer, and that define styles. We discuss in a very accessible way what those compounds are, where they come from, what beers you can find them in, what beers you should not find them in.
How will this work? There will be a generic light beer with little flavor of itself. We will spike 1 liter of this beer with the concentrated and isolated flavors in 5 pitchers, plus a pitcher of unspiked beer as a reference. The compound of each flavor will be present in 3 times the taste threshold. We'll pour two thirds of each pitcher to give each 6 glasses, 1 for each flavor and the reference, and then we'll discuss each, as they have the opportunity to sample them as they explore each flavor as it is presented on its own. After this first round, we'll dilute the remaining beer by filling it up again to 1 liter, so we get to sample the flavors at 1 time the taste threshold. At that point we give a blind tasting test, so they can put their newly acquired skills to the test, and win a special beer prize!
This was a great success, and everyone went back home having learning something, after a lot of fun as we went through a bunch of quite horrible off-flavors, from creamed corn/canned asparagus over stinky feet to cardboard. Some of the group were home brewers, so they had encountered some of these, and we could give some pointers as to why those flavors appear in beer, and how to avoid them. A very common one is DMS, or Dimethyl Sulfide. Tasting and smelling like bad vegetables (asparagus and corn), it is a normal in-between step in the brewing process, and a very volatile element. So during the boiling most of this will dissipate out of the wort. Unless, of course, you had the boiling pot covered for some reason... Another one, Diacetyl, tastes like butter/butterscotch, and if encountered in a beer from a tap, almost always a sign of tap lines that are dirty and have become infected. Another 'favorite' was Isovaleric Acid, a compound that comes from oxidized iso-alpha acids that can be found in hops, and are a sign of stale or old hops. This tastes like bad cheese, stinky or sweaty feet,... A real crowd-pleaser! You can, however, get this in much softer form because of either voluntary use of wild yeast, or by contamination, specifically in sours (think lambic style beers).
As a brewer, it is important to be able to identify these bad flavors during brewing, for purpose of quality control (we would never want you to taste these in our beers, and you never will!), and to be able, if we find them, to keep the beer from being sold and to pinpoint the source of the contamination or error so we can fix it. For beer lovers, it was just fun to explore this normally inaccessible side of beer. We all are looking forward to next week, as that night we will tackle good flavors!