Most of the time, the cider or perry in your glass will be a delightful, flavoursome joy of a drink. But what happens when it goes wrong? And why does it go wrong in the first place? In this article, I’ll be taking you through some of the common, and less common faults, found in cider and perry. We’ll explore some of the biochemistry behind what’s happening and talk about how they can be prevented. But this isn’t a guide for cider makers (at least, not alone). This is about empowering you as a consumer to know what’s going on in your glass, and why sometimes it’s just not as good as it should be.
Landlady of the Station House in Durham, and bottle shop and tap room Fram Ferment. Certified Cider Pommelier.
One of my strongest memories of cider is of one I tried after closing time at a festival I was working at. A friend had been sent by the cider bar manager to pick a box of cider and bring it to the hospitality truck we were sitting in to warm us up on what had been a very busy, but freezing, night. The errand-runner had no idea what they were looking for and so picked a box at random.
It was the most disgusting thing I’d ever tasted in my life. Rotten eggs, dead rats, and hairy goats. In hindsight, I’m now certain it had every fault in the book. If that had been my first experience of full juice cider, I’ve no doubt it would have put me off for life.
A fault is a flavour (or visual appearance) in a finished cider that is not considered desirable. The vast majority of faults in cider are due to microbial action of one kind or another, but what we can taste or smell is a volatile chemical compound. Mostly, they are not harmful to humans – just simply unpleasant. [1]
On the face of it, cidermaking is a much simpler process than brewing. A brewer determines the eventual flavour of the drink by manipulating ingredients, temperatures, timings and choosing yeast strains. A cidermaker’s job is subtler: to provide an environment that encourages the yeast (whether a selected yeast chosen and pitched by the producer or wild yeasts from the juice, press, and cider house) to ferment in the manner the cidermaker chooses; and to suppress any microbes and control any environmental factors that might cause problems. (There are of course many other choices to do with fruit variety, quality, fermenting vessel, and so on, all of which will also impact on the eventual flavours in your glass and which Gabe Cook explores here.)
As we will discuss, many faults arise from similar issues in the cidermaking process, so it’s reasonably common that, where there is one fault, there may be several. As a drinker, it is worth being able to identify and name faults. It means that when you dislike a cider, you can identify whether it’s a stylistic dislike, or a defect.
So let’s consider common faults in more detail:
Acetic acid is one of the most common faults you’ll find in cider and perry. I can virtually guarantee that if you are interested enough in cider and perry that you are reading this article, nerding out on faults, you will have tried an acetic cider.
It’s also one of the most hotly debated. Many ciders, especially those from the West Country and Spain, do contain acetic acid in perceptible amounts [2], and some people are used to it and enjoy it. Some argue that acetic acid in very low quantities [3] adds to the character of the cider. However, there is also a vocal school of thought that says that any perceptible acetic acid is undesirable and off-putting to new drinkers.
Acetic acid in UK ciders is usually the fault either of bacteria from the acetobacter family, or apiculate (airborne) yeasts. These microorganisms are found everywhere, in the atmosphere, and on the legs and bodies of fruit flies (aka beer flies aka vinegar flies). Acetobacter require aerobic conditions (i.e. they need oxygen) to grow and live, and hence grow on the surface of ciders exposed to the air, forming jelly-like sheets that are the beginnings of a “mother” for vinegar production.
Acetobacter metabolise the alcohol produced by yeasts in the cider to acetic acid. Because they require oxygen to do so, the simplest way of ensuring that a cider remains clean of acetic acid is to store it in an oxygen free environment – i.e. keeping fermentation and storage vessels topped up with little headspace and airlocks topped up with water. It’s really important for the cidermaker to monitor this, as over the slow fermentation and maturation period there will be some volume lost from the cider – through evaporation if it’s a porous fermentation vessel, for example.
There is, however, another biochemical pathway to finding acetic acid in your glass, involving malolactic fermentation caused by lactic acid bacteria [4]. This group of bacteria is often encouraged by the cidermaker to convert malic acid into lactic acid (which can help soften some sharper notes in the cider and give a softer mouthfeel) but can also sometimes convert citric acid into acetic acid. This is the mechanism usually thought to be at work in Spanish ciders, and is also common in perries, as pear juice tends to be higher in citric acid than cider.
Here, I fear, I will be straying into controversy. Brett – the affectionate name for the Brettanomyces family of yeasts – can be used deliberately in cider making, as has become fashionable again in beer. So to list it here in a summary of faults will undoubtedly rub some people up the wrong way. Nonetheless, it is named as a fault by many respected people within cider, and so I feel duty bound to cover it as a fault
As a yeast, Brettanomyces, like its brothers the Saccharomyces yeasts feeds on the sugars in the apple or pear juice, and excretes alcohol and carbon dioxide. However, as with all microorganisms, this yeast doesn’t stop there and also produces aromas such as the elegantly named 4-ethylphenol that are likened to barnyard, horse stable and, if in high enough concentration, “notes of manure”. [5]
Because Brett is found commonly in the juice, or living in the pores of wooden barrels, in small quantities these aromas can be sought after, and are associated with certain styles of cider – particularly those of the West Country. However, in greater concentrations these can be strong flavours which can be off-putting to many who then, unfortunately, permanently associate them with “dry cider” or “scrumpy cider”. [6]
Sulphites, used properly will suppress the growth of Brett as well as other organisms. However, some cidermakers who choose not to use sulphites may deliberately introduce Brett, or ferment or age in vessels that harbour Brett, such as wooden barrels.
As a consumer, it is a fault that it is worth being aware of and worth understanding why there is debate. As for how much is too much? Well, I guess that’s up to the agreement of a competition judging panel, or your own preferences. [7]
Mouse is a fault that many cidermakers dread. And yet, 40% of the population can’t taste it – a quirk that is due to the way it reacts at different pH levels. Those of us with more acidic saliva are less able to taste mouse. Of those that can taste it, it can be very variable the degree to which they can taste it.
Those that can taste it strongly find it unmistakeable, and often completely unbearable – a dry, stale, biscuity, flavour likened to the bottom of a mouse’s cage (I can only assume that, given taste is majority aroma, people have sniffed the bottom of a mouse’s cage as opposed to actually licking one…), that overwhelms the taste of the cider itself and lingers in your mouth. As a retronasal (back of nose) aroma, it can only be detected once the cider is in your mouth.
It’s thought to be chemicals called 2-acetyl tetrahydropyridine, or ethyl tetrahydropyridine, generated by species of either lactobacillus bacteria or Brettanomyces yeasts, under aerobic (oxygenated) conditions in the presence of alcohol (ethanol) and another chemical called lysine. This might explain why a fermentation can seem to be going well, and then all of a sudden after some maturation time it develops mouse. [8]
Nothing can be done once a cider or perry goes mousey. There is no cure or way to hide the mouse. Let us take a moment to mourn the death of what may have been an excellent cider.
There are two routes by which your cider could have gone wrong, if what you can smell in your glass is solventy – especially nail polish remover-y.
One mechanism involves the formation of film yeasts from the Mycoderma, Pichia, Hansenula or Candida groups of yeasts. These yeasts sit on top of the cider where it is exposed to oxygen as a thin, whitish or greyish film. [9]
As they grow, they break down some of the alcohol, form ethyl acetate and/or amyl acetate, and become increasingly, bullyingly, unpleasant, as well as making the cider seem thinner in body and more insipid generally. [10]
That said, the cider can sometimes be rectified if the film yeasts have not developed too far by – and I appreciate I may start to sound like a broken record here – by the cider maker topping up the fermentation vessel so that oxygen is excluded.
Alternatively, our old friends, the wild apiculate yeasts can also form ethyl acetate during early fermentation. If a “farmhouse” style cider is showing signs of ethyl acetate from very early on, this is the more likely cause.
Meanwhile, in those sweet ciders sitting at the less acidic end of the spectrum (e.g. French or French style keeved ciders) you may notice an aroma much like very fake fruit flavours – foam banana sweets or raspberry flavouring, or “sherry-like” aromas.
This could be bacterial in origin – Zymomonas anaerobia or Zymomonas mobilis pomaceae. These strains of bacteria ferment the sugars that remain in the cider, but instead of alcohol, they convert it to acetaldehyde. [11]
More commonly in the UK, where ciders have been stored without additional SO2 and with exposure to air, a purely chemical reaction can occur – tannins self-oxidise using aerial oxygen which then liberates hydrogen peroxide, which in turn oxidises the ethanol directly to acetaldehyde.
Let’s talk next about sulphur. Or, more accurately, about Hydrogen Sulphide.
This is actually pretty common – it’s that overly-Burton-Snatchy, rotten egg type aroma. But, before we go any further, we need to make sure we’re all clear on the difference between Sulphite and Sulphide. Look closely, there’s one letter different, and it’s a very important one.
Sulphite with a T refers to the sulphur added by the cidermaker in the form of SO2, often in the form of sodium metabisulphite. When dissolved in water this becomes sulphurous acid and is used to suppress unwanted bacterial action, especially at the point of pressing, and often also when bottling or moving between vessels at the cidery.
Sulphide, on the other hand, refers to Hydrogen Sulphide – H2S.
It’s this volatile chemical that you can smell when you are smelling rotten eggs – in the case of eggs, it’s because of the break-down of proteins in the egg as it rots. [12]
In the case of cider, it’s left over from a series of chemical reactions. Either: the yeasts are breaking down amino acids in order to utilise the nitrogen contained within them, thus liberating sulphide ions contained within; or there is an excess of sulphide produced by the series of reactions used by the yeasts to make their own amino acids to grow and survive.
Amino acids are the Lego bricks used to make proteins – so without the presence of sulphur within cider, the yeast cells will struggle to grow, and thus to produce alcohol.
Sometimes, however, the balance of production and use of these sulphide ions is a little out of whack, and it’s at this point that it combines with the positively charged hydrogen ion (H+) found in acidic solutions (you may remember that all cider is at least slightly acidic) and becomes hydrogen sulphide – H2S.
There are many reasons why the balance might be wrong. Where juice is low in nitrogen – for example, in an old, never-fertilised orchard – it can increase the yeast’s ability to form H2S. High levels of the element sulphur in the orchard meanwhile can make it into the juice and thus increase the amount of H2S. Certain strains of yeast will naturally produce more or less H2S than others.
In practical terms, at low levels sulphides are common in cider, often associated with bottle conditioning – perhaps because the yeast at that point is under a little more strain, or because any sulphur can’t escape from the bottle until opening. However, unless it’s very bad, often it’ll blow off within a few minutes of pouring the cider. If it’s especially bad, however, it might be worth taking back to the bar.
Oxidation: Oxidation of tannins in fruit are what turn apples brown when you cut into them and expose it to air. As such, it’s inevitable that a certain amount of oxidation will occur when making cider, and it can be used wisely to help manage tannins in the eventual product. However, if allowed to go too far, the cider will have an overly dark, orangey colour, and is likely to be faulty in other ways as well – such as having a stale, musty aroma or acetic acid.
Discolouration from metals: Very old equipment may contain iron or copper. If the cider comes into contact with these (e.g. while pumping into the bottling machine), metal ions can dissolve in it. When the cider then meets the air, these metal ions will react with oxygen in the air and change colour – in the case of iron to reddish or black and copper to green/blue. This is effectively the same reaction as rusting/corroding. [13]
Hazes, cloudiness, floating particles, perry “brain”: Almost never harmful, most visual defects are simply offputting. They can be caused by a variety of factors, including the precipitation of tannin over time, the growth and subsequent settling of yeasts, precipitation and coagulation of pectin into a gel, etc. You will most often notice these kinds of defects in bottled cider, when simply pouring carefully after storing vertically should allow the sediments to stick to the bottom. [14]
Sometimes, a maker may disgorge, or repackage a product that has formed a sediment, but this is not always a guarantee that it will not precipitate further, especially in the case of perries which are notorious for continuing to form flaky, snowglobe-like sediments over time. However, if the cider or perry tastes and smells good, there is unlikely to be any reason to be concerned.
For a long time, CAMRA has taken the same approach with cider as it has with beer – that the best cider is unpasteurised, “live” cider. More recently, with the updated definition, the emphasis has shifted to looking at juice content, and one of the reasons for this is because pasteurisation and sterile filtering are very useful techniques for cidermakers, and thus publicans and retailers, given the risks of packaging their cider and subsequently finding that there were infections that have developed in bottle or BIB.
Although, if not done carefully, pasteurisation does run the risk of giving a “cooked”, or slightly dulled flavour to some people’s palates, most people can’t taste the difference when it’s done carefully, allowing the cidermaker to reduce the risk of subsequent fault development, especially in ciders which are back-sweetened or contain residual sugars.
Meanwhile filtering, where the cider is pushed through a very fine plate with holes smaller than the size of the yeast and bacteria cells, may also, when carried out carelessly, strip out larger polyphenols (tannin), as well as some of the aroma compounds. This will have an impact on the flavour and texture of the final drink. Hence, it should be done with intention and purpose. [15]
As a consumer, it’s really worth educating yourself around faults in cider. As much as cidermakers, generally, will do their best not to knowingly release ciders that are faulty, if you as a consumer know what is acceptable in a cider, and what is not, you can advocate for the ciders sold in your local bars and pubs to be better.
All too often, thanks to a lack of knowledge in the pub trade about cider, we can assume that “it’s supposed to taste like that”. I will be the first to admit that for a long time I didn’t know cider could be faulty. When I didn’t like a cider, I assumed that it was just my personal preference, and that it was supposed to taste like that. I have sold ciders over the bar in the past, that now I would take back if I was served them.
In an ideal world, consumers would simply never have to worry about this. When was the last time you tried a wine (let’s exclude natural wines here) that was vinegary, or mousey? Wine can get very similar faults, and yet you very rarely come across them as a consumer, because every level from producer to wholesaler to bar will be filtering those faulty wines out before they reach your glass. It’s a process that requires the knowledge, at the least, that something can taste “not right”, even when you’re not sure why.
In reality of course, mistakes happen, there isn’t always the level of understanding of faults, or good storage practice that we would like at the various stages from production to sale, and faulty products will always slip through the net, but this is even more true with cider than it is with cask ale or wine. Hence, by us as CAMRA consumers knowing what we’re tasting, we can advocate for better standards, in the same way as we advocate for better quality beer as well. In turn, if the overall availability, not just of cider, but of delicious, non-faulty cider is increased, we reduce how many people are put off cider entirely by a faulty cider that they should never have been given.
Heartfelt thanks to Andrew Lea, Barry Masterson and Albert Johnson for proof-reading and ensuring scientific accuracy.
[1] Lea, A. G. H. 2014. Cidermaking. From Bamforth, C.W. & Ward, R.E. (eds.) The Oxford Handbook of Food Fermentations. Oxford University Press.
[2] Lea, A.G.H. 2003. Cidermaking. From Lea, A.G.H. & Piggot, J.R. (eds). Fermented Beverage Production. Springer Science + Buusiness Media. New York.
[3] Perception thresholds for acetic acid are between 750-1000 mg/L. Bartlett, T. Acetobacteraceae: Acetic acid bacteria. In Thomas, K. (ed.). Advances in Cider & Fruit Wine Technology. 2011.
[4] Lea, 2003.
[5] The same biochemical pathway can also be used by lactic acid bacteria (lactobacillus) to produce the same results. Andrew Lea notes in correspondence with the author that it is difficult, and indeed, largely irrelevant, to determine which microorganism is responsible in most instances.
[6] Jolicoeur, C. 2013. The New Cidermaker’s Handbook. Chelsea Green Publishing. Vermont.
[7] Cider Faults – Beer Judge Certification Program. Accessed by the author December 21.
[8] Jolicoeur, 2013
[9] Whitehead, D. 2013. Identifying and tackling film yeasts and ethanal production. From Thomas, K. (ed.). Advances in Cider and Fruit Wine Technology.
[10] Bartlett, 2013
[11] Lea, 2003
[12] Jolicoeur, 2013
[13] Jolicoeur, 2013
[14] Lea, 2003
[15] Ibid
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