Fermentation & Maturation
It’s so easy to enjoy cider and perry it can be easy to forget just how much hard work and magic go into our favourite drinks. With a little knowledge and armed with some fascinating new facts you can start to hone your appreciation of cider and perry to the next level.
In the third installment of his series on how cider is made Gabe Cook invites us to join him in exploring the funky and fascinating art and science of cider fermentation and maturation.
With 10+ years of experience working in the cider industry, Gabe is leading the charge for a cider revolution. AKA ‘the Ciderologist‘ Gabe is an international consultant, writer, broadcaster, and educator on all matters cider. Resident cider expert for C4’s Sunday Brunch. Gabe also chairs the International Cider Challenge.
Whether a cider maker is a multinational behemoth, an established family producer or a small-scale hobbyist, they will now all be faced with the exact same question – how to transform their juice into cider. It seems an obvious question – fermentation is the answer – but it’s not quite as simple as that. There are many options and considerations at the cider maker’s disposal at this point, and, following on from the selection of apple variety, the decisions made here will have significant determination on the overall style of cider that is produced.
The first decision is what vessel to ferment the cider in. Cider Makers tend to use neutral vessels for fermentation – stainless steel, fibreglass, HDPE plastic etc, older wooden barrels. This environment allows the innate characters of the apples (and pears), in conjunction with the yeast profile(s), to shine through.
The second decision is: does the cider maker utilise a selected yeast or rely upon the range of wild yeasts to undertake fermentation? The answer to this question is a fundamental one, frequently based upon core ideology and is often indicative of more than simply the desired flavour and aromatic profile.
The vast majority of cider made all around the world will be made utilising a selected yeast strain. For decades, specific, natural yeasts have been identified as having certain desired properties for wine and cider fermentation and have been isolated and propagated into a freeze-dried format available for purchase.
A cider maker will use a selected yeast because they want to exert some semblance of control over the fermentation and/or because there is a specific character that the yeast facilitates. The main genus of yeasts that undertake most baking, brewing and fermenting around the world are called Saccharomyces yeasts. Much of the cider made all over the world will be undertaken with a ‘Champagne’ type yeast – Saccharomyces cerevisiae – designed to convert fruit sugars into alcohol with minimal fuss and minimal flavour impact but with great consistency, crucial for any producer of scale.
The characteristics desired in a cider will vary from producer to producer, and can also depend on the nature of the fruit available and the type of consumer being catered for. Specific yeasts are used globally that facilitate these desired characteristics, which can range from low sulphur production, to aroma enhancing, to acidity reduction, to improving mouthfeel.
There are, however, many cider makers who choose to eschew a selected yeast in favour of allowing a succession of wild yeasts to undertake the act of fermentation. Living all around us are a multitude of different yeast strains. Apples coming in from the orchards will carry with them a number of non-Saccharomyces yeasts, whilst multiple wild strains of Saccharomyces strains will set up shop in the cidery building itself, adhering themselves to the mill and press.
For many, the selection and utilisation of a yeast strain holds nearly as much significance as the selection of apples variety. They want their ciders to be minimal intervention and/or to be representative of their place, their terroir. There are some people who would say that wild fermented ciders are superior to those that have been fermented with a selected yeast. I would say they’re simply different. Is a Geuze any ‘better’ than a Hefeweizen? Is a pet nat natural wine better than a methode traditionelle Cremant de Loire?
Ultimately, the selection of yeast is simply one of the tools available to the cider maker to help create variety and diversity – the joyousness of cider.
Then there is the question of sulphur dioxide (SO2). At this stage of the cider making process, it can be used as an anti-microbial agent. In conjunction with a low pH, an application of this compound can ‘bind’ to many bacteria and yeast in the juice and nullify them. This may be beneficial if one is undertaking a ‘clean’ fermentation (i.e. with a selected yeast), but is obviously less desirable if undertaking a wild fermentation. It is possible to add a ‘partial dose’ of SO2 to the juice and still enable a wild fermentation, although the full range of microflora will be diminished, with only the hardier strains remaining.
In the end, whether the yeast has been selected or not, it will be undertaking the same process – fermentation. Quite simply this is the conversion of the natural fruit sugars (fructose, glucose and little bit of sucrose) into ethanol, with CO2 as the primary by product. In the vast majority of cases, fermentation ceases when all of these sugars have been converted to alcohol. There are, of course, always exceptions to the rule, namely:
Perry – which contains a proportion of sorbitol, an unfermentable sugar, meaning that the yeasts simply cannot convert it to alcohol
Keeved cider – special process removing yeast and nutrient in the juice, so fermentation is incomplete
Cold racking – to continually rack fermenting cider/perry from one vessel to another, incrementally leaving more yeast behind until there is no viable population
Cold crashing – when a cider maker drastically reduces the temperature in a fermentation (in conjunction normally with the addition of some SO2) to stop fermentation in its track
Fermentation length depends upon the nature of the yeasts that are undertaking the fermentation, but in practice its range is from 6 days to 6 weeks (although occasionally 6 months!). Wild fermentations will often be slower owing a greater length of time to reach a viable fermenting population. These types of fermentations are often slow if undertaken in ambient cold ambient temperatures (which they tend to be from November onwards).
It’s during fermentation that some of the most common faults can occur – sulphides. These eggy, drains-y, cooked veg characters are the result of the yeast not being provided with its optimal conditions (there isn’t enough nutrient for the yeast, or the temperature is significantly too hot or told) and are undertaking a ‘dirty protest’ as a result.
When the fermentation has finished, the yeast will flocculate (word of the day) to the bottom of the fermentation vessel, to form the lees. Here they start to decompose, a process known as autolysis. It is customary for most cider makers to remove the cider off the lees through the process of racking. This is the syphoning/pumping (depending on scale) of the cider from the fermentation vessel to a new, clean maturation vessel. If allowed to sit on the lees for any great length of time, there is an increased risk of some unpleasant flavours and aromas emerging from the autolysis.
Once in its new vessel, the ‘young’ cider is given some time to recover from the rigours of fermentation, and allow aromas, flavours and textures to fully form and soften out. This is called maturation. The length of time of maturation, again, is at the discretion of the cider maker, but will generally be determined by the style of cider they wish to achieve and the fruit they are utilising.
Tannic apples will classically be allowed to mature for at least six months, but possibly up to several years. The old adage is that you “don’t tap the new season cider until you’ve heard the cuckoo”, i.e. not until the Spring following the harvest. This length of time is need for the tannins to become less harsh and bitter and to become softer, rounder and gentler in its astringency.
This length of time also enables certain types of yeast (eg Brettanomyces) and bacteria (eg Lactobacillus) to act upon the volatile phenolics within these tannic apples, creating the aromatic characters commonly associated with French and West Country ciders, namely: spicy, earthy, hay barn and “horse blanket”.
Ciders made from acid-driven apples generally require less maturation than their tannic siblings. They do not contain the bold phenolics that need time to develop, instead, the optimal qualities of these styles, namely freshness, estery aromatics and juiciness, often reach their peak within three months.
Ciders that have had little SO2 utilised in them up until this part of the process may go through a malolactic fermentation – commonly known as MLF. This is bacterial fermentation converting the zingy, fresh malic acid (naturally contained within apples), into the softer, smoother, more sour lactic acid. If, in large quantities, this can precipitate creamy, butterscotch or even yoghurt-esque flavours, which may or may not be desired by the cider maker.
Finally, the choice of maturation vessel can have an impact over the resultant cider.
For many cider makers, once again the choice will be stainless steel, plastic or fibreglass. However, there are several cider makers who utilise wooden vessels during this stage.
With a pitted surface, they harbour the aforementioned bacteria which aid maturation of the tannins, facilitate liberation of the volatile phenolics of and MLF. If the wooden vessel previously housed another alcoholic beverage, such as whisky, brandy or wed wine, then it is very possible that the previous contents could impact upon the resulting flavour profile of the cider to a lesser or, sometimes considerably great degree.
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