(Off) flavours

If you think being a biersommelier is all about trying the newest and best beers and drinking all kind of nice stuff, think again … Training for becoming a biersommelier puts beer and flavours in a whole new perspective, and unfortunately not all is nice.

As I mentioned before, the flavours of beer can be affected by a whole range of things, in a positive and negative way. Of course there are the basic ingredients, the different kinds of malt and grains, the myriad of hop aromas and flavours, the differences the yeast strains make, even the water makes a difference. But there are also spices, sugars, fruits and other things you can add to your beer as well as bacteria and other things to make your beer sour for example. Then there is the way you brew the beer, on high or low temperatures, adding the hops early or late, using a filter or whirlpool or not, lagering, barrel-aging, multiple fermentations, bottling, canning, fermentation on the bottle, keeping your brewery clean (or not). After that there is the way you treat the beer, do you keep them in a continuously stable environment or are the temperatures changing rapidly? Do you keep your beer in the basement or a fridge, standing up, lying down? Do you clean your taps regularly, and how long do you keep a keg on your tap? Do you use carbon dioxide to tap or do you have a handpump? Do you use nitrogen?

If this all happens according to the plan of the brewer and the taste of the beer comes out as intended, it should be fine. But as a biersommelier you also learn how to recognize off flavours, because some off flavours might indicate an infection or another issue at the brewery ór the pub and can help to solve it more quickly as a particular off flavour could point in the general direction to look for the cause of the problem. Like the taste of baby puke might indicate mold in the mash while the taste of butter might indicate filthy taps. It could also help a brewer figure out why their beer tastes differently than they intended it to be and what they can change to improve.

The term off flavour has a certain implication of negativity, but not all off flavours are bad or unwanted in all beers. Sulphur can be very unpleasant, but gives a certain freshness in small amounts in pilsners. Most off flavours have several potential causes. Dyacetyl (buttery) might indicate a filthy tap, but it’s also a flavour you get during fermentation (and can disappear again with a dyacetyl rest before lagering), and in Czech pilsners it is not a fault, but a wanted flavour. So in most cases off flavours are just an indication and naming them could help to make the beer or the treatment of the beer better.

Recognizing them is an important part of the work of a biersommelier, so of course we also have to keep training that. And I can tell you, that is one nasty business. We trained 20 off flavours from Aroxa in the last month with a group of other sommeliers and brewers. The off flavours we used were from Aroxa an went waaaay over the tasting threshold. The tasting threshold is when the amount of the flavour is enough for most people to recognise a flavour to name it. The first ten flavours we trained were:

2,4,6-trichloroanisole, acetic acid, butyric acid, dimethyl sulphide, ethyl phenylacetate, ferrous sulphate, hop oil extract, isobutyraldehyde, styrene, trans-2-nonenal.

A musty basement or cork aroma is associated with a high degree of consumer rejection. It mostly indicates an infection. Acid aromas and flavours can be wanted in sour beers, if they are not it might indicate an infection of the brewery with certain bacteria. Baby puke aromas and flavours mostly indicate mold in the mash. Cooked corn could indicate too short a cooking, but can be wanted in small amounts in some beers. Honey (not in honey beers) is an aging flavour. It comes áfter the cardboard and leather aging flavours and indicates the beer is really old.
A note: Most beers, if they were good to begin with, are not a health hazard and do not become a health hazard after aging and expiring, it’s just that the taste is not what the brewer had in mind for this beer. The date you see on beer therefore always indicates until when the brewer will guarantee the wanted flavour.
Metallic tastes indicate a metal infection, it could be that the beer just touched certain metals. Mind you that cans are made of materials that do not interact with beer and do not give of that metal flavour. Hop oil is added to a lot of beers to enhance flavours. In small amounts it’s just fine, but people stop drinking the beer because it seems off when there is too much hop oil in it. It then tends to become musty and chemical. The same goes for the green grains flavour, which is mostly wanted in small or large amounts in every beer. Plastic flavours are associated with a high degree of consumer rejection as well and might indicate defective CO2 gas, or contamination by packaging materials.

The second ten flavours were:

2,3-butanediol, 3-methyl-2-butene-1-thiol, 4-vinyl guaiacol, dimethyl trisulhpide, guaiacol, hydrogen sulphide, isoamyl acetate, isovaleric acid, methional, trans-trans-2,4-heptadienal.

Dyacetyl or butter flavoured tends to be the most dreaded one, although it can be a wanted flavour in small amounts in for example Czech pilsners, because it gives a bit more body to a beer. It is produced during fermentation, so can point towards a short lagering. But it’s also an indication of a filthy tap or contamination with a lactic acid bacteria. The skunk aromas (or weed aromas which is a more familiair smell for Dutch people than skunk) are formed by a reaction of hop bitter acids, vitamins and sulphur compunds under the influence of light. Some big brewers have chemically altered their hops so this won’t happen, but for all other beers, they will get this smell after some time in light, no matter if that light is artifical or from the sun. It’s the perfect reason to use cans for beers. I think it’s sometimes a wanted flavour though, in my experience it’s quite common in Corona for example. 4-vinyl guaiacol or 4-VG is thé characteristic aroma of Weizen. It’s like cloves. It can be produced in low levels in the wort production, but more likely it’s the result of a specialty yeast strain. Fried onion aromas are formed during storage of packaged beer. Some hops impart this aroma when used for dry-hopping. Smoky fish in your beer can be desirable in some ales and is the signature flavour of Rauchbier. Cooked or even rotten egg aromas are produced by yeasts during fermentation and maturation and is present in all beers. It’s an off flavour in a too high amount, but a signature flavour in Burton Ale (Ah! That explains a lot!).
Banana or pear drops is also present in all beers, and is a signature flavour for Weizen beers. Pear drops can indicate overly excited yeast though, due to too high temperatures during fermentation. Stale cheese or sweaty socks are due to a breakdown of the alpha-acids in hops. It is imparted to beer by use of high hopping rates of degraded hops (as in hops that were already old before using in the beer) or hop extracts. Sometimes it is caused by wild yeasts, like Brett. Mashed potato is an indicator of autolysed yeast, and could come from re-used yeast, but can also be due to over-pasteurization. Last but not least rancid oil aromas are formed in adjuncts during storage as a result of lipid oxidation.

Needless to say, these trainings were quite the experience. And we’ll repeat them again at least twice in 2020.

Would you be interested to join us in a off flavours training?


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