By Greig McGill

A long time ago, Stu McKinlay (of Yeastie Boys and SOBA founding member fame) and I had a good natured back-and-forth thing going on Twitter. #FreshIsBest (me) versus #FreshIsNotBest (Stu). I’d link to it, but I finally rage-quit twitter, so that’s a bit tricky! Now, to be fair, we both had our tongues firmly in our cheeks at the time, and neither of us cared that we both meant basically the same thing. That is, most beers should be consumed fresh in general, but there are many counter-examples, and sometimes the definition of “fresh” is when the brewer considers the beer ready. I can already hear Stu yelling “or the consumer”, and you know, he’s right! Just don’t tell him that.

We often talk about fresh being best in beer. But then we also go nuts for barrel aged, and vintage beers. Every homebrewer has a story of a beer they made which seemed somewhere in the ordinary-to-terrible spectrum, but then it improved hugely with some age. So which is it? Well, both!

Aging in beer is simply the result of chemical reactions over time. There’s nothing magical about it, and without a massive lab full of equipment (or even with…) it’s near impossible to know exactly how much age will put the beer in the optimum state for you to enjoy it. Instead, imagine you have a case of twelve identical beers, and you age them for up to twelve years, drinking one on your birthday each year. You will drink twelve completely different beers, and there will be one of those beers you like more than the others. That’s the sweet spot for that beer, for your palate.

So, how do you know where that sweet spot will be? You can’t. But what you can do is use knowledge of what happens during the aging process in order to make some educated guesses about when you’re most likely to enjoy the beer the most. But just in case, always buy (or make) enough so you have some margin of error! I mean… more beer is good, right?

To begin with, oxidation is the most dominant chemical reaction that occurs during aging. Oxygen interaction with different compounds in the beer will produce many different flavour and aroma compounds. Few of these are “all bad” or “all good”, but instead will add complex notes which generally benefit some types of beer in small doses but become unpleasant at higher concentrations.

All packaged beer contains some oxygen. This is picked up at various stages in the brewing process, and packaging, and is referred to by brewers as TPO - total packaged oxygen. Most brewers aim to keep this under 50ppb (parts per billion), though some will tolerate up to 150ppb, and for some barrel aged or similar beers it might be a lot higher. Canned beer is notoriously higher in TPO due to the difficulty in fully purging a can of atmosphere and filling it under pressure, then seaming the lid without any oxygen pickup. Due to this, I generally do not recommend aging beer packaged in cans. That said, if TPO in a can was, say 150ppb, and TPO in a bottle was 30ppb, most bottle crown seals exchange gas with atmosphere at a rate of around 7 ppb per day at an ambient temperature of 21C. In other words, in theory, the bottle would equal the can in around 17 days in terms of TPO, right? Well, not quite. It’s a little more complicated due to storage temperatures, degree of dissolution in the beer, remaining active/scavenging yeast, and other poorly understood factors. The generalisation is that well stored bottles will generally degrade in a more graceful way than well stored cans, where all that oxygen is in there and reacting from day one. Like all general rules, there are plenty of exceptions! When possible, always use your own palate on a fresh sample of a packaged beer before deciding whether you think it will age well.

The major dominant products of oxidation in beer are (E)-2-Nonenal (previously called trans-2-nonenal) and phenyl-acetaldehyde. (E)-2-Nonenal is commonly perceived as a papery/cardboardy and phenyl-acetaldehyde as sweetish and honeyed. The perception of these compounds may change depending on their concentration and interaction with other components of the beer. You may enjoy some of these compounds in varying amounts as the beer ages, despite their general perception as aging faults.

Of course, other things happen as beer ages. Generally, iso-alpha acids degrade over time, and so hop-derived bitterness will fall. Esters produced by the yeast will also break down, reducing perceived fruity flavours, and allowing other lower level characters to shine through more clearly. Delicate hop aromatics will degrade fairly swiftly, although terpene compounds will initially intensify, giving a small window where more “dank” or catty type hops may actually seem to grow stronger before fading back. Finally, malt proteins will break down slowly, decreasing perceived body in the beer.

Now you can start to apply some of this information in order to make informed guesses in terms of what will age well, and what will age poorly. Got a nice hoppy NZ pilsner with a delicate but pleasant tropical hop character? Drink it yesterday. How about a big American-style double-IPA that was a little aggressive on the bitterness? Well, maybe that bitterness will die back along with the more aromatic aspects of the hops, leaving a medium bodied variant of a decent US style barleywine! Of course, there are always the classics recommended for aging - imperial stouts, strong Belgian styles, and English-style barley wines.

So what about pre-aged beer? That is, beer that a brewery has aged for you, in barrels, tanks, kegs, or just held bottle stock for vintage releases. This generally falls into two categories. Either the brewer has determined that the beer is now at the perfect age to drink it when they choose to release it, or that the beer will continue to age and either improve or change in an interesting way with time. Most will tell you their expectations on the packaging, but many will leave it to the consumer to decide.

When aging beer, it’s best to remember that all chemical reactions progress more swiftly at warmer temperatures. You will have much more control if you set a place for aging your beers which is cooler, rather than warmer. Too warm, and you’ll get rapid production of (E)-2-Nonenal, producing a stale tasting beer. Too cold, and aging will progress very slowly indeed. Around 12C is ideal.

Hopefully you can apply the information in this article and be rewarded with many great drinking experiences. Just don’t forget to taste your cellared stocks at regular intervals, and if it’s tasting incredibly good, consider that now is the time to drink the rest. It’s possible that it might get even better still, but in my experience this is fairly rare. Good luck!