By Greig McGill
Last time, in the Off Flavour Chronicles: <insert exciting montage of action shots and “eeww” faces here>. What do you mean there’s no budget for that? Bugger.
Anyway, to refresh your memory sans expensive montage, we talked about the most common faults that brewers come up against, what causes them, and what can be done to avoid or mitigate them. VDKs - most commonly diacetyl, as well as acetaldehyde, and oxidation.
This time (it’s personal?)... we’re going to talk about some of the less common, but weirder off flavours that pop up from time to time. In no particular order then, here we go!
Mineral/salty/aspirin are descriptors you might get on a beer scoresheet in competition, and you should immediately think about your water treatment, or lack thereof! A common aphorism in brewing is “if your water tastes good to brew with, it will make good beer”, and this is mostly true. However, many things can have an impact on the final minerality of your beer. Some water with high chloride content can taste great, but when used in brewing can enhance perception of malt at the expense of hops, leading to disappointment and waste of money spent on big hop presence. There are manygreatresourcesavailable on brewingwaterchemistry, but if you don’t want to get too deep, and just want to fix the basic problem, use RO water or rainwater, and add back about a teaspoon of calcium sulfate, and one of sodium chloride, as well as maybe a quarter teaspoon of magnesium sulfate for yeast health. This will give you a fairly balanced, if unscientific basis to make any style of beer with reasonable success.
Chlorine in beer is another water fault. Many councils use chlorine (or less frequently if ever in New Zealand, chloramine) to make sure drinking water is safe for brewing. Removing both chlorine and chloramine can be done easily with a catalytic carbon filter. A standard carbon filter will be good enough to remove just chlorine, and will leave your water mineral profile intact. A zero cost solution to removing chlorine is to simply let your water stand open to air for 12-24 hours, or, if you don’t mind using a bit of energy, boiling the water first for 15 minutes. Not to be confused with…
Chlorophenolic/Phenolic off flavours are sometimes pleasantly spicy, but often medicinal or antiseptic-like. Chlorophenols in particular are known for their antiseptic mouthwash-like flavours, and are caused by interactions between chlorine in the brewing water and yeast-derived phenols. They can also be artificially produced by bacterial contamination. Avoid these nasty notes by ensuring your sanitation is perfect, and there’s no chlorine in your water. Other types of unpleasant phenols can smell and taste like burnt electrical components, band-aids, or plastic. These are also commonly caused by bacterial contamination, though there are some yeasts that produce phenolic off-flavours (often called “POF positive” strains) which must be carefully managed via pitch rate, oxygenation, nutrient concentration, and temperature in order to minimise this while maximising their desirable flavour contributions. Some Belgian yeasts fall into this category.
Staleness or mustyness is usually attributable to old malt, or malt that has been pre-crushed and not used quickly. It’s another byproduct of oxidation, though tends to result in dull, stale, or musty flavours and aromas in the finished beer, leaving hop character untouched, unlike oxidation of fresh beer. Your supplier should always be able to send you the batch and age of your malt, as well as the certificate of analysis for your batch which will usually have date information present also. If you’re ordering your malt pre-crushed, consider investing in a malt mill, as even with the best of care in crushing, packing, and shipping, delays happen, and you really can taste the difference between a beer made with freshly crushed malt (which is itself fresh), and one made with the same malt that has sat around crushed for a couple of days. Try that experiment at home, in case you’re skeptical!
Cheesy flavours can come from bacterial infection, or old hops, with the latter being the most common. As hops age, their alpha acids can degrade into isovaleric acid, which smells very cheesy, and may survive the boil. The only fix to this one, assuming you’ve checked your sanitation, is to make sure you are always using the freshest possible hops. Always store your hops at the coldest possible temperature - ideally in the freezer, and consider investing in a vacuum sealer to repack leftover hops to minimise oxygen.
Hot as a descriptor is often indicative of higher than normal quantities of other alcohols besides ethanol. Aliphatic fusel alcohols are a family of higher alcohols produced during fermentation. They are often associated with hot or rough tasting alcohol flavour in beer, and are mainly caused by very warm fermentations, or unfavourable conditions for the yeast, causing them stress. These conditions include; lack of nutrients, lack of available oxygen, high wort gravity, too much CO2 presence, and/or low pitch quantity leading to excessive multiplication depleting nutrient stores. Pitch the right amount of healthy yeast into well aerated wort, with enough nutrients available, and control your fermentation temperature well and you should never have this problem. Note that a little bit of hot alcohol can be allowable, and even desirable, in big beer styles such as barleywine.
Estery beer, much like hot-tasting beer, is often a result of yeast trying to ferment in an environment that’s either too hostile, or too conducive to rapid activity, such as the top end of a yeast’s temperature range. Follow the same tips as above for hot beer if you wish to mitigate the problem of beers that taste too fruity, often in odd ways. Sometimes, high ester presence will be desirable, especially in beers that are designed for long aging, where those esters will break down into complex flavour compounds. This can add high levels of complexity to an aged beer.
Grassy/vegetal notes are often caused by too much plant matter from hops in contact with the beer for too long. While extremely high dry hop rates are practically boasted about by many in the pro brewing industry, the pros often have many ways to remove the excess vegetal matter from the beer when they’re “done” that the homebrewer doesn’t. Three days is a good rule of thumb for maximum contact time with dry hops. If you aren’t able to get your beer off of those hops after 72 hours, you may wish to investigate alternative hop products such as extracts (oil extracts replace dry hop flavour/aroma, whereas resin extracts just give bitterness) or cryo hops which have less vegetal matter.
Skunky aromas are tricky for us here in Aotearoa, as most of us don’t know what skunks smell like. Much like the Germans, when tasting bananas for the first time and observing that they tasted like Bavarian wheat beer, we can reverse engineer it from “the smell of Steinlager in green bottles that’s been on the shelf a while in the light”. Skunking, or lightstrike, is caused by the modification of isomerised alpha acids from hops by UV light at specific frequencies - mainly from sunlight. You can easily observe this by buying two cans of the freshest canned pale lager you can find, pouring one into a glass and leaving it in the sun, and keeping the other in the can, pouring it just before you taste both. You only need about 5 minutes of direct sunlight exposure and you should easily observe the difference! The simple fix for this is to keep your beer away from sunlight as much as possible. Keg it, or if you bottle, use brown glass as this filters out most (but not all) of the damaging light frequencies. Store it in the dark!
There you go brewers, a few more faults to banish from your brewing nightmares! As with most things, the world of off-flavours is vast, as there are so many ways your beautiful beer can be damaged, by yourself, or by factors you didn’t foresee. If there are any you’ve tasted and always wanted to know what causes them or how to fix them, get in touch with the friendly crew here at Brewshop.co.nz and if we have enough, they may convince me the world needs a third in this trilogy!