The Secondary

element: Fungi / DATE: 05/01/2020

BEFORE THE BARREL

With the regular 80% extortions one would be forgiven for thinking that whisky’s flavour emanated from just wood alone, but we believe flavour starts well before the barrel. Indeed, though many flavour differences are demonstrably derived from their unique terroirs, we are in general obsessed with getting the most natural expression of barley flavour imaginable.

That means many things: low and slow distillations, using the best malting barley possible, the substantial logistics of terroir separation and using tools such as our terroir-extractor par excellence – the mash filter. But it’s also why we don’t just bother with the industry’s simple wham-bam,“high density” fermentation, over in a flash, though it would be far more pleasing to accountants to do so.

We prefer to stretch out that process to a minimum of 120 hours – over twice the whisky industry standard – to wait for another transformation to take place: the secondary, malolactic fermentation. This, as with wine, is the conversion of harsh malic to softer lactic acid. A secondary fermentation in whisky production happens – uncommon though it is with distillers – about 60-70 hours into the fermentation process; and of course prior to distillation.

FERMENTATION FACTS

1 FARM = 75 TONNES OF MALTED BARLEY

4 X WASH BACKS = EACH FILLED WITH 85,500 LITRES OF FLAVOURSOME WORT

EACH WASH BACK PITCHED WITH DISTILLER’S YEAST
AT 21°C VIA WORT COOLER

EACH WASH BACK FERMENTS AT A THERMOREGULATED 30°C-32°C

FERMENTATION TIME = MINIMUM 120 HOURS PER WASHBACK

Neil among the wash backs

Head Brewer Neil overlooking the wash backs.

ORIGINS OF FLAVOUR

Each single farm harvest provides 75 tonnes of malted barley, each crop bearing the fruits of their own unique terroir. Brewing – that practice of regulating the interactions between water, starch, yeast to give us a wort to be fermented – has taken place in on this spot in Waterford since 1788. But today’s kit is a bit different.

Wort is liquid extracted from the mashing process (probably derived from the old English wyrt meaning ‘root’), which in traditional distilleries takes place in a gravity-driven mash tun. But in our case, we convert starch into sugar in a Mash Conversion vessel prior to filtration sophisticated Meura Mash Filter, a series of pneumatic plates that separates wort from the draff by pressure. We call it the terroir extractor, and it is at this stage – prior to distillation – where our spirit gains more mouthfeel and polyphenols. Our resulting super-pure wort contains the sugars, the most important being maltose and maltotriose, which will be fermented by the distiller’s yeast to produce alcohol.

As we are interested in natural flavour over efficiencies, we want the most floral, fruity and elegant fermented wash possible. The secondary, or malolactic acid fermentation, is an essential component of the fermentation process provided – as the name suggests – it is secondary to the primary fermentation.

And it is allowed to happen.

We start off fermenting our wash between 30°C and 32°C, and will continue for an exceptionally long time – 120 hours. During the latter stages of the primary fermentation, the yeast cell accumulates desirable esters as carbohydrate starvation forces utilisation of amino acids and peptides. These nitrogen compounds undergo transamination reactions producing higher alcohols. These higher alcohols are then formed into esters by reaction with acetyl co-enzyme A complexes within the yeast cell.

Checking the brew
Neil in the lab

Tests for pH, Present Gravity & ABV are taken every 8 hours during our long 120-hour fermentation process.

During the secondary fermentation, the pH drops: this promotes the growth of lactic acid bacteria over the harsher malic acid That, combined with the alcohol in the wash, in turn promotes autolysis of the yeast cell wall and plasma membrane. Various desirable esters and components of the yeast plasma membrane are then released into the wash – which wouldn’t have been as plentiful if we’d have called time on fermentation before this stage. The lowered pH brings about yet further ester formation.

Where minimal acid bacterial growth occurs – e.g. when a fermentation is carried out around 28°C or lower – the yeast cells do not autolyse. Indeed they appear to be relatively resistant to ester release during distillation. The final pH is then higher, so the wash distillation reactions are retarded – which is the reason we control our fermentations at a slightly higher temperature. Under Head Brewer Neil’s watchful eye, we will monitor pH, Present Gravity and ABV every 8 hours, for at least 120 hours, to ensure not only that the long fermentation process has behaved as expected, but that each individual farm batch has been treated equally; that the influence of terroir remains the key variable.

From here the wash is then distilled in our own pernickety way – low and slow, rather than some basic industry formula. But it should remain clear that for those who desire to drink a superior sprit, real flavour creation must start long before the liquid ever reaches wood; indeed flavour starts before it even reaches copper – if you care to look for it.

Ultimately it means not rushing for the sake of profit but paying attention to detail: more esters more flavours if one allows that Secondary Fermentation to occur.

Record keeping

Knowledge is power.

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