Tuur Mertens
New Member
Beer freshness is that what makes a good beer pop. Sadly enough, for both brewers and consumers alike, beer is unresistant to the tooth of time. Noticeable staling can already occur 2-3 months from packaging when stored at room temperature. As beer starts to fade, it loses precious aromas and pleasant (hop) bitterness, all while developing unpalatable or harsh off-flavours.
The question is: does this phenomenon really concern the average home brewer?
The short answer is 'yes': a home brew will suffer the same fate as any commercially brewed beer, probably even quicker. Not much oxidation is needed to turn a price-winning home brew into a just “okay” beer. Luckily, when keeping certain codes of conduct in mind, it is more than manageable to keep your beers from tasting like wet cardboard, paper, cherry, honey, leather, horse stable, cat urine, ...
This is why I wrote a 'introductory guide to flavour stability in brewing' that delves into the ‘what’ and ‘how’ of brewing long(er)-lasting beers, with information roughly ordered from ‘easily implementable’ to ‘advanced tinkering’.
(TL;DR: Check the summary table at the end)
High relevance and easy to do
Limiting storage time (drink it fresh)
There is always the option of not giving beer the time to turn stale. Although this is more a bypassing-the-problem than a solution, it works. So always label your beers properly with a ‘packaged on’ date and drink the older beers first (FIFO method: First-In, First-Out). Make the fact that home brewers deal with small batch sizes work in your favour and keep in mind that some beer styles are more susceptible to ageing than others (e.g. hoppy beers, pilsners).
Storing dark and cold
From all the things a brewer can do to maintain freshness, this is top of the list. Firstly: Protect your beer from any damaging (ultraviolet AND visible) light; mainly the sun or fluorescent lamps. Storing beer in the dark will prevent it from getting “skunked” or “light-struck”, terms used for describing beer that tastes like skunk spray—as literally the same molecule (3-methyl-2-butene-1-thiol, a sulphur compound) is being formed by photodecomposition of hop alpha-acids. Cans and kegs will keep light out perfectly; brown bottles less so—albeit better than green or clear containers—so best to preventively keep them covered during storage.
Secondly: Keep your beer cold! This is, by far, the biggest component. Those familiar with the Arrhenius equation will tell you that a temperature rise (or drop) of 10 °C roughly equates to a doubling (or halving) of the reaction rate. Here is what this means for your beer:
Due to the difference in production size, cooled storage/transport is an area where home brewers have an edge on the ‘big guys’. However, not every home brewer possesses the luxury of having lots of refrigerated space.
Limiting oxygen downstream
Although it is hard to tell for sure, it can be reasonably assumed that limiting oxygen downstream is more relevant/significant than limiting O2 upstream. Which is why oxygen entry on the cold side (after fermentation) is likely the second biggest detractor of flavour stability that home brewers face after warm storage.
Prevent any unnecessary transferring of your finished beer, and when required, do it gently (avoid splashing/turbulence/aeration) and push with CO2 where possible. It’s best to purge any container (such as bottles, carboys, kegs, etc.) multiple times with CO2 or N2 before filling and to fill from the bottom up. Hoses and pumps can also be purged, or better, prefilled with deaerated water to expel oxygen. When bottling, always ‘cap on foam’ (by agitating the bottle slightly), so that headspace oxygen is minimized. That said, bottling by hand unfortunately often results in very high oxygen pickup, which is the reason why beers at home brew contests frequently suffer from staling.
Bottle caps are another unavoidable detractor from beer flavour stability when bottling, but not all caps are created equal. Pry-offs are better than twist-offs, which is why, for example, Sierra Nevada changed their twist-off caps to pry-offs in 2007. The liner material of the cap also matters, as some allow for more oxygen ingress than others. Then there are also specialized oxygen-scavenging caps, specially designed to combat this issue. If you want to go all-in, you can even dip the capped end of the bottle in melted wax or paraffin (perfect for e.g. barley wines); and buying a ‘dissolved oxygen’ meter can be a very valuable tool in the brewhouse (albeit expensive).
Kegged beer is less prone to oxidative ageing, because the headspace-to-beer volume ratio (initially) is much lower compared to a bottle. Canned beer has the advantage of having absolutely no oxygen ingress after sealing. Regardless of the container type, always store a beer upright and keep vibration/transportation to a minimum. This way, the beer has less chance/surface to interact with the oxygen-containing headspace, thus slowing down oxidation.
Side note: Be aware that commercially available carbon dioxide (CO2) is never pure. While even the purest commercially available grade (99.9 %) may seem “practically pure”, it is not. Force carbonation of the beer will result in a certain amount of O2 getting dissolved; enough to elicit staling. To avoid this problem, brewers can choose to carbonate their beer naturally—via e.g. spunding/bunging—with 100 % oxygen-free yeast-produced CO2.
Using healthy, vigorous yeast
Never forget that it is the yeast that makes beer, the brewer “just” makes wort. In other words: pick the proper yeast and treat it like a queen. It can make the difference between an amazing beer and unpalatable swill.
More than just creating beer, the yeast also does a great job in cleaning up aldehydes (off-flavour contributors) and scavenging detrimental transition metals (see later). Researchers were even able to chiefly remove the stale flavour from aged beer by adding fresh yeast to it. Aside from these rectifications, it will also help the beer to stay fresh over time by producing sulphur dioxide (SO2, a potent antioxidant and carbonyl binder) during fermentation and lowering the level of free amino acids and dissolved oxygen.
So, a healthy yeast and vigorous fermentation are important for flavour stability. To improve yeast performance, you may supply extra zinc and oxygenate the pitching wort (but only when cold!), and that should be the only point during the brewing process where oxygen is deliberately introduced. Keep in mind that different yeast strains have different oxygen demands. When fermentation is prematurely halting or “stuck”, it’s even worth risking oxidation by aerating the semi-fermented beer to help restart the yeast. Of course, it is better to prevent it altogether by fermenting at the recommended temperature—preferably on the lower side—and pitching enough fresh yeast (make a yeast starter or, if using dry yeast, rehydrate before pitching).
The question is: does this phenomenon really concern the average home brewer?
The short answer is 'yes': a home brew will suffer the same fate as any commercially brewed beer, probably even quicker. Not much oxidation is needed to turn a price-winning home brew into a just “okay” beer. Luckily, when keeping certain codes of conduct in mind, it is more than manageable to keep your beers from tasting like wet cardboard, paper, cherry, honey, leather, horse stable, cat urine, ...
This is why I wrote a 'introductory guide to flavour stability in brewing' that delves into the ‘what’ and ‘how’ of brewing long(er)-lasting beers, with information roughly ordered from ‘easily implementable’ to ‘advanced tinkering’.
(TL;DR: Check the summary table at the end)
High relevance and easy to do
Limiting storage time (drink it fresh)
There is always the option of not giving beer the time to turn stale. Although this is more a bypassing-the-problem than a solution, it works. So always label your beers properly with a ‘packaged on’ date and drink the older beers first (FIFO method: First-In, First-Out). Make the fact that home brewers deal with small batch sizes work in your favour and keep in mind that some beer styles are more susceptible to ageing than others (e.g. hoppy beers, pilsners).
Storing dark and cold
From all the things a brewer can do to maintain freshness, this is top of the list. Firstly: Protect your beer from any damaging (ultraviolet AND visible) light; mainly the sun or fluorescent lamps. Storing beer in the dark will prevent it from getting “skunked” or “light-struck”, terms used for describing beer that tastes like skunk spray—as literally the same molecule (3-methyl-2-butene-1-thiol, a sulphur compound) is being formed by photodecomposition of hop alpha-acids. Cans and kegs will keep light out perfectly; brown bottles less so—albeit better than green or clear containers—so best to preventively keep them covered during storage.
Secondly: Keep your beer cold! This is, by far, the biggest component. Those familiar with the Arrhenius equation will tell you that a temperature rise (or drop) of 10 °C roughly equates to a doubling (or halving) of the reaction rate. Here is what this means for your beer:
Storage temperature (°C) | Staling rate compared to room temp. storage | Estimated time before staling occurs | Examples |
0 | ¼ x | > 1 year | Fridge, bucket with ice |
10 | ½ x | 4-6 months | Fridge, cellar |
20 (room temp.) | - | 2-3 months | Living room, indoors |
30 | 2 x | 1-1.5 months | Warm room |
40 | 4 x | 2-3 weeks | Garage, attic, car trunk (sunny) |
60 | 16 x | << 3 days | Garage, attic, trunk (hot day) |
Due to the difference in production size, cooled storage/transport is an area where home brewers have an edge on the ‘big guys’. However, not every home brewer possesses the luxury of having lots of refrigerated space.
Limiting oxygen downstream
Although it is hard to tell for sure, it can be reasonably assumed that limiting oxygen downstream is more relevant/significant than limiting O2 upstream. Which is why oxygen entry on the cold side (after fermentation) is likely the second biggest detractor of flavour stability that home brewers face after warm storage.
Prevent any unnecessary transferring of your finished beer, and when required, do it gently (avoid splashing/turbulence/aeration) and push with CO2 where possible. It’s best to purge any container (such as bottles, carboys, kegs, etc.) multiple times with CO2 or N2 before filling and to fill from the bottom up. Hoses and pumps can also be purged, or better, prefilled with deaerated water to expel oxygen. When bottling, always ‘cap on foam’ (by agitating the bottle slightly), so that headspace oxygen is minimized. That said, bottling by hand unfortunately often results in very high oxygen pickup, which is the reason why beers at home brew contests frequently suffer from staling.
Bottle caps are another unavoidable detractor from beer flavour stability when bottling, but not all caps are created equal. Pry-offs are better than twist-offs, which is why, for example, Sierra Nevada changed their twist-off caps to pry-offs in 2007. The liner material of the cap also matters, as some allow for more oxygen ingress than others. Then there are also specialized oxygen-scavenging caps, specially designed to combat this issue. If you want to go all-in, you can even dip the capped end of the bottle in melted wax or paraffin (perfect for e.g. barley wines); and buying a ‘dissolved oxygen’ meter can be a very valuable tool in the brewhouse (albeit expensive).
Kegged beer is less prone to oxidative ageing, because the headspace-to-beer volume ratio (initially) is much lower compared to a bottle. Canned beer has the advantage of having absolutely no oxygen ingress after sealing. Regardless of the container type, always store a beer upright and keep vibration/transportation to a minimum. This way, the beer has less chance/surface to interact with the oxygen-containing headspace, thus slowing down oxidation.
Side note: Be aware that commercially available carbon dioxide (CO2) is never pure. While even the purest commercially available grade (99.9 %) may seem “practically pure”, it is not. Force carbonation of the beer will result in a certain amount of O2 getting dissolved; enough to elicit staling. To avoid this problem, brewers can choose to carbonate their beer naturally—via e.g. spunding/bunging—with 100 % oxygen-free yeast-produced CO2.
Using healthy, vigorous yeast
Never forget that it is the yeast that makes beer, the brewer “just” makes wort. In other words: pick the proper yeast and treat it like a queen. It can make the difference between an amazing beer and unpalatable swill.
More than just creating beer, the yeast also does a great job in cleaning up aldehydes (off-flavour contributors) and scavenging detrimental transition metals (see later). Researchers were even able to chiefly remove the stale flavour from aged beer by adding fresh yeast to it. Aside from these rectifications, it will also help the beer to stay fresh over time by producing sulphur dioxide (SO2, a potent antioxidant and carbonyl binder) during fermentation and lowering the level of free amino acids and dissolved oxygen.
So, a healthy yeast and vigorous fermentation are important for flavour stability. To improve yeast performance, you may supply extra zinc and oxygenate the pitching wort (but only when cold!), and that should be the only point during the brewing process where oxygen is deliberately introduced. Keep in mind that different yeast strains have different oxygen demands. When fermentation is prematurely halting or “stuck”, it’s even worth risking oxidation by aerating the semi-fermented beer to help restart the yeast. Of course, it is better to prevent it altogether by fermenting at the recommended temperature—preferably on the lower side—and pitching enough fresh yeast (make a yeast starter or, if using dry yeast, rehydrate before pitching).