For brewers and bartenders, identifying off-flavours in beer is an extremely important skill. For Cicerone candidates, it’s a requirement in order to pass the exam. Arguably the hardest part of the exam, it’s responsible for the majority of failed candidates. Training for this section as an Australian is difficult – organised events are rare and ordering off-flavour kits online is expensive.
Thankfully, it just so happened that while I was in Vancouver recently, the Cicerone Certification Program was hosting a guided off-flavour training course at the CRAFT Beer Market, a well-known bar in Vancouver’s Olympic Village district. I figured that this course would not only be personally beneficial, but the subsequent article would allow anyone interested in hosting their own training course to know exactly what the official standard of required knowledge is like.
The course was hosted by Advanced Cicerone Bobby Wood, who manages breweries in Washington state. As an introduction, we all did the ‘jellybean test’, which involved chewing on a red-coloured jellybean with our noses pinched, then releasing our noses to experience the full flavour of the jellybean. As expected, nothing could be tasted with noses blocked, but as soon as they were released, a huge cinnamon flavour hit. Bobby’s point was clear – the nose is an important part of flavour detection.
That nicely segued in to a review of some basic aroma sampling techniques, using our control beer for practice. Interestingly, no fancy glasses were involved, just a simple plastic cup which we were instructed to swirl heartedly before each technique. These included the distant sniff from 15-20 cm away, short sniffs (“like a bloodhound”), a two-second long sniff, and a covered sniff, which involves covering the beer glass with one’s hand, swirling and then taking a short sniff.
Next, we tasted our control sample. Enough beer should be drunk so that “the tongue floats,” which allows all the taste receptors to be engaged. We were also reminded that the ‘tongue map’ model was a myth. The trick with tasting was to not affirm what the aroma told us, but rather try to pick up things that we could not distinguish by smell. This includes bitterness, mouthfeel, carbonation and alcohol. Finally, we practised retronasal detection – taking a small breath in through the nose, tasting the beer, swallowing, then exhaling out the nose, all whilst keeping the mouth closed. Despite being told not to, someone in the class managed to choke while attempting this.
Finally, it was on to the tasting. Our six samples, labelled A-F, each had an isolated flaw, dosed to three times the detectable threshold (the same as in the Cicerone exam). Although we were provided with a control, we were encouraged not to use it unless we were really having difficulty. This was to allow us to determine flavours independent of any other influence, as well as to not rely on a control comparison which may not exist in the real world. For each taste, we wrote our own tasting notes for the first few minutes before consulting with the rest of the class, to avoid any bias towards certain aromas and flavours.
Part 1: Brewing/Fermentation Flaws
A: DMS (Dimethyl sulphide)
Smells like: Barnacles on a saltwater dock in the sun (to me, at least).
Tastes like: Creamed corn, canned cabbage, sketchy milk or rotting vegetables.
Caused by: Primarily malt, secondarily wort spoilage bacteria. DMS comes from SMM, a compound found in all malt but predominant in lighter malts. As the malt is heated, for instance during malt kilning or during the boil, the SMM converts to DMS, which then volatises.
In any situation where the wort is hot enough to convert SMM to DMS, but isn’t hot enough or given enough time for DMS to volatise, it will be present in the beer. This can happen not only during a short boil, but also afterwards, where warm wort temperatures can produce DMS but won’t volatise it, avoided by fast chilling.
Smells like: Melted butter, movie theatre popcorn. In fact, it used to be added to movie theatre popcorn before it was realised how carcinogenic it was – giving movie theatre staff a condition called popcorn lung.
Tastes like: Oily and waxy, like that scene in The Simpsons where Homer drank a candle.
Diacetyl is produced naturally by yeast but, given enough time, is then reabsorbed and converted to a colourless, flavourless compound. If the diacetyl is not absorbed, the yeast may be weak, too highly flocculent (drops out too quickly), or has not been given enough oxygen or time.
The longest stage in the diacetyl production and reabsorption process is that which converts a precursor compound (alpha-acetolactate) to diacetyl. So, it may only be present in beer once it has been bottled, but can be tested for prior.
Pronounced like: According to Bobby, “assa-towel-hide” (has to be done in Canadian accent).
Smells like: A sour-powder coated Warhead lolly, green or sour apple.
Tastes like: Green or sour apple, latex paint, pumpkin, rubber gloves.
Caused by: Primarily due to too short a fermentation. Yeast forms assa-towel-hide as a precursor to ethanol. It can also be formed by oxygen in packaged beer, however this isn’t required knowledge.
Part 2: Handling/Serving Flaws
D: T2N (Trans-2-Nonenal)
Smells like: Cardboard box, a ripped paper sticker.
Tastes like: The time I ate printer paper as a small child.
Caused by: Oxidation of malt components during mashing, boiling or other processes in the brewhouse, then magnified with improper aging. After fermentation, beer becomes oxidised faster in warm environment. For instance, oxidation may begin to occur after three months refrigerated, but only one month at room temperature and only a few days at 30°C.
Smells like: Skunk spray (according to every North American in the class), stale marijuana (funnily enough also what my hostel smelled like), wet coffee grounds. The aroma is easy to become accustom to, so one’s first instinct is generally correct.
Tastes like: Heineken.
Caused by: Exposure to UV light, natural or fluorescent, within minutes. The light breaks down bittering compounds in the hops (isohumulones), producing 3MBT after a series of chemical reactions.
It’s prevented by packaging in brown bottles, cans and kegs, but can occur in beers packaged in green or clear bottles, such as Corona or Heineken. In some cases, it’s also prevented by using tetra-hop compounds that do not contain isohumulones and are immune to the effects of UV light.
Smells like: Cheap white wine, vinegar.
Tastes like: Balsamic vinegar, pickles, with a slick mouthfeel. Chemically, this off-flavour was a combination of diacetyl and acetic acid.
Caused by: Bacterial contamination, predominantly in draft lines.
With all our samples tasted, we were invited to ask questions and revisit the beers we had difficulty with. Overall, the class lasted just over an hour, and served as a great crash course for the required Cicerone knowledge. If the opportunity comes up, I’d highly recommend this off-flavour course, or any others, to those in the industry looking to expand their knowledge.