Tag Archives: optimisation

Maximizing Whisky Yield: Part 3 – improvements to the brewing equipment – small changes can make a big difference.

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In this final post on whisky wash process optimisation I will cover the mechanical changes I advised and helped to implement with the new craft whisky distillery whom I have been supporting.

By inspection when I started with this client it was clear that just a handful of minor equipment changes should be able to greatly reduce their process time and with this, for the reasons I highlighted in my first post, significantly boost their yield from malt to sugar.

  • Swap out their heat exchanger (HX) for one with a larger surface area

  • Install pipework to allow for recirculation of the mash tun

  • Install pipework to allow for the recirculation of the hot liquor tank

  • Add inline temperature measurement between the HX the fermenters (FV’s)

None of the above issues stopped us making good quality wash, but the time required to make a batch when I started was around 8-9 hours which is far too long for whisky wash where you need active enzymes from the malt to survive into the fermenter to enable full fermentation and thus maximal yield.

Step 1 – upgrade the heat exchanger

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Sadly the heat exchanger which had been installed had not been correctly sized and was simply not capable of cooling the wort from 64-67 C down to the required 25-28 C for fermentation. A quick fix to this was in place when I arrived, in the form of a copper coil in the underback, but this required the wort to be cooled batch-wise to 40 C before it could be pumped through the HX and hit the desired fermentation temperature. This was adding hours to the process time. Through my contacts I was able to get sizing data and source a pre-loved plate HX from a brewery in Essex to enable the wort can be cooled in one pass.

Step 2 – adding recirculation to the mash tun and hot liquor tank (HLT).

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I still remember the guiding words my first Head Brewer gave to me when I started my brewing apprenticeship. He said “The two most important aspects of brewing are cleanliness and temperature control.” Simple advice which I now pass onto anyone that I train. Whilst I found a manual way to mix the HLT in the early days of this project, having recirculation yields an even temperature across the HLT, an important consequence of which is be able to get an accurate measurement of the mash water. Together this means hitting out mash temperature +/- 0.5 C for every batch now This really matters both to yield, quality and process time. With a whisky mash you start running off just as soon as you know the starch conversion is ‘complete’ which is determined using an iodine test. The sooner the starch is converted the sooner you can start running off the strong worts. Achieving the desired mash temperature every time clearly helps.

When I started there was no recirculation facility on the mash tun either, which made this a two man operation with buckets. This is great for your biceps, but is slower and less effective at producing a clear wash than a steady pumped recirculation flow. And as Bradley Wiggins proved in the 2012 Tour de France, winning a race is often about making a lot of small gains, which when added together become significant enough to put you out in front. In addition the manual recirculation method really requires two people, and wash preparation should really be a single person operation.

Step 3 – adding in-line temperature measurement on the chilled wash line

The final change required to make this a single person operation was to add in-line temperature measurement for the chilled wash. Early on, one of us controlled the wash / cooling water flow rates whilst the other monitored the temperature of the wash entering the FV with a thermocouple. Perfectly accurate, but again an unnecessary use of manpower and thus extra cost.

Final position.

Together these changes have reduced the batch time by a massive three hours. The rate limiting step is now getting the HLT for third water up to temperature in time. There is now time for one person to set up a distillation at the start of the day, move over to brewing a batch of wash with time left within a normal working day to shut down and wash the pot ale out of the still, leaving it ready it for the next day.

Before optimising the mash temperature and introducing third water we were seeing brewhouse yields of around 70%. Now they are consistently above 95%. In parallel, the manual effort and man hours of input to achieve this have been grossly reduced since the start of the project. A very satisfying result for everyone.

That completes my three posts on the project to define and optimise a new craft whisky wash process.

Post 1 – The key differences between beer wort and whisky wash manufacture

Post 2 – How process parameters were determined and yield optimised.

This post – How minor equipment changes significantly reduced the batch time.

If you would like help starting a new micro-brewery or distillery, or if you have an existing operation you would like to to optimise wrt time or yield and you are based in the North of England then give me a call.

Maximizing Whisky Yield: Part 1 – Key Differences and Optimization in Wash Production

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This is the first in a series of three posts detailing how I worked with a new English whisky distillery to define and optimise their wash production.

Background

In November 2023 I was called by a new craft whisky distillery to help them with two distinct processing problems: stuck mashes and incomplete fermentations. However this soon grew into a project to optimise the yield of their wort production.

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Structure

This first post explores the key differences between wort production for beer and wash production for whisky. Both are sugar solutions derived from malted barley but understanding the key differences between the two methods is vital to the quality of the end product.

The second post covers how I defined the process control parameters from scratch using ‘on the hoof’ experimentation on the live process (a skill I developed working in a production based tech support roles in the chemical industry).

The final post (link to follow) looks at changes we implemented in the brewing equipment. What I arrived on the project the brew kit had already been installed, but some minor low cost changes have significantly reduced the process time, which in turn have positively impacted both quality and yield.

Part 1 – What are the key differences between wort (beer) and wash (whisky) production?

Why are the processes different?

The primary driver of whisky wash production is yield. Because the optimal ABV of the fermented wash is around 8.5% ABV, the quantity of available sugar left in the weak worts after the end of the sparge would be considerable if a beer wort method were used – in this case the weak worts at the end of run off would be 1.050-1.055 (approx 140 g/L sugar content). Additionally, it is desirable in beer to have unfermented complex sugars in the final beer to give body and a residual ‘sweetness’. Beer worts typically show an attenuation* of 75-80%. If your aim is to maximise the yield of alcohol per tonne of malt both of these factors would be considered a loss to yield. With whisky production, the optimal yield is 415 litres of pure alcohol per tonne of malt input.

It is always important to remember that the (desired) flavour of whisky is defined by the process by which it has been made. And since the nature of the process was fixed before the underlying consequences on the biochemistry of the process were fully understood it is important to (1) follow traditional methods to give the traditional/desired flavour; (2) understand and manage the shortcomings or “features” of these methods to achieve a consistency of yield to, and quality of final product.

*percentage conversion of sugars to alcohol

Malt colour-gradientMash temperature

Traditional wash production uses a mash tun, and normally you would think that this would limit you to an isothermal mash. But with whisky wash production a pseudo step mash is carried out by initially mashing at a low temperature (ideally just above the gelatinisation temperature for the quality of malt, which varies by the season). This favours the production of immediately fermentable sugars. It is then sparged at 75 C to both wash out the sugars already formed and also to raise the mash temperature to activate alpha-amylase thus form and extract complex sugars also.

Run off method

To maximise sugar extraction during sparging, most of the strong worts are run off before the sparge is started. Often the liquor:grist ratio is higher in wash production which means there is more volume to run off. This step needs to be carefully designed to avoid running off too much liquor which could lead to a stuck mash.

No wort boil

Wash is run off directly into the fermenter, it is not boiled. There are a number of consequences to this:

  • Lactic acid bacteria (LAB), present on the surface of all barley malt remain viable and active in the fermenter – they are not denatured by a boiling stage. This needs to be accounted for (see below)

  • In a well run process, active enzymes – amylases but also importantly limit-dextrinase – transfer with the wash into the fermenter

  • Because the wash has not been boiled (which causes vigorous mixing) or recirculated in the copper the wash in the fermenter cannot be directly sampled to gain a representative sample for SG / OG control.

These consequences all need to be managed if you are to achieve product consistency and high yield.

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Managing lactic acid bacteria (LAB).

As soon as the wash is formed, LAB start acting on the maltose to form ethyl lactate. Because they convert sugars which could form alcohol this can have an economically significant effect on the yield. For this reason, yeast is pitched into the strong worts, early in the transfer into the FV. The aim is for the yeast to out compete the LAB and minimise losses of sugar to ethyl lactate at the start of the fermentation.

The fruity flavour imparted by ethyl lactate is an important characteristic of whisky so careful management of the fermentation is required to ensure that the level is consistent from batch to batch. At the end of the yeast fermentation, LAB are able to metabolise other oxygenates, such as malic acid to form ethyl lactate. To ensure flavour consistency the length of time that the fermentation is left to stand post completion of yeast action needs to be controlled. It is normal in small scale whisky production for multiple batches of wash to be required to fill one cask with spirit. Because of the impact of five day working not usually possible to allow every fermentation to run for the same length of time, and from this come the terms ‘shorts’ and ‘longs’ describing wash fermentations which have been been completed and distilled within the week or run for longer over a weekend. Each cask of spirit should contain the same proportion of shorts and longs and thus production should run to a regular pattern each week.

Malt enzymes in the fermentation

It is essential for the enzyme limit-dextrinase (from the malt) to remain present and active in the fermentation. For this to happen, the time that the wash remains hot post saccharification needs to be minimised i.e. you need to run off and cool the wort as quickly as possible once starch conversion is complete. It is this enzyme which breaks down the unfermentable sugars in the wash into fermentable sugars which allows a far higher attenuation by the yeast. A typical whisky wash has an OG of 1063, without limit-dextrinase the fermentation would end at an SG of around 1013, with it present the fermentation continues to an SG of 996-1000.

Wash SG control

Ideally the FV (often called a wash back) needs to be able to be recirculated so that the wash gravity (SG) can be accurately measured and controlled, at very least during process commissioning. Remember that wort gets progressively weaker during its transfer, and thus the FV is stratified ‘by design’ and thus non-homogenous. Recirculation could not easily be retro-fitted to the kit I was working on, so I developed and proved an alternative method which I will discuss in my next post.

3rd water

Once all the wash has been collected, the mash bed is sparged again, at a higher temperature still, and this liquor is used for mashing the next batch of malt. This liquor is called 3rd water.

  • First water – liquor used to mash the grist.

  • Second water – sparge liquor sent forwards to the FV.

  • Third water – second sparge liquor containing residual sugars, recycled into the following batch.

In a large distillery, the 3rd water is likely to be used within the hour. In a craft distillery it is likely you will only be making one or two batches of wash per day so you need want to hold some of your 3rd water overnight. What is key here is to keep it above 70 C so it remains free of the effects of bacterial or wild yeast contamination. However, for anyone familiar with smaller scale brewing you know you want your mash water at or close to strike temperature (usually 70-74 C) at the start of the day anyway so it is normal to heat it to 10 C above this the night before knowing it will come in about right the next morning in a well insulated hot liquor tank.

Improving your margin…by maximising your batch size.

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We are living in a challenging time for the small scale brewer. Raw material and energy costs are at an all time high, yet our customers has less disposable income. To maintain your margin without sacrificing quality one, excellent method is to max out the capacity of your brewery. This article is aimed at small brewers, not those with vessels to hold their last runnings to use as the start of the next sparge and the like.

Which vessel is going to limit you?

This is the first question you need to ask – which of your vessels is going to limit your output? Assuming you brewery equipment was bought at the same time, it is unlikely that your mash tun will be your limiting factor. This is likely to have been designed to brew ABV’s higher than your core range beers. So you need to know the volume and thus working capacity of your copper and your fermenters.

It is easy to estimate the volume of these vessels. Most coppers are cylindrical and thus the total volume is easily calculated.

Volume of a Cylinder = Π . r2 . h

The volume of flat bottomed fermenters can be calculated the same way, but if you are lucky enough to have cylindroconical fermenters you need also to calculate the volume of the cone at the base and add this to the volume of the cylindrical section.

Volume of a conical section = Π . r2 . ⅓H

But of course there is a difference between the total volume and the ‘working’ or useable volume. For a copper this is 80% of the total volume. For a fermenter it will be in the range 80-90% depending on variety of factors.

How to maximise the capacity of your copper

Wort-Boiling

There are two options here. If you don’t want to alter your recipe then to maximise the volume that your copper can safely boil you can reduce the foaming that occurs at the start of the boil. As the proteins from the malt denature and drop out of solution they act as nucleation points for the bubbles of the boil and other proteins aid foam stability. This can lead to a deep head of foam during the first 10 minutes of the boil. There are commercial antifoaming agents which can be added at this stage of the boil, but you may not know that the natural product versions of these are actually a hop extract. So if you add around 5% of your hop bill just before the start of the boil (i.e. First Wort Hops) these will reduce foaming without you adding cost or anything artificial into you beer.

Another option would be to consider taking a small step towards high gravity brewing. You can aim for a pre-boil gravity 10-20% higher than your designed post boil gravity, knowing that you can liquor back at the end of the boil either directly post boil, or during the transfer.

How to maximise the capacity of your fermenter

Filling fermenter - foam

Here again, foam management is key to maximising your capacity. Medium and larger scale breweries would normally fill their fermenters from the bottom to minimise foam formation. As well as increasing capacity it also aids head stability in the final beer. Think of the foam capacity of beer being a fixed value over the whole life of the beer, from manufacture to the customers glass – the more foam you form in the process, the less potential for foam (head) there is in the final beer. In bottom fill operations the wort is oxygenated in-line on the way to the fermenter. However in micro breweries oxygenation is often achieved by top filling the fermenter, allowing the splashing of the work to entrain oxygen and thus avoid the need to buy bottled oxygen.

If you top fill your fermenters to oxygenate the wort the volume of foam can be considerable and limit the capacity of the fermenter. Here an antifoam agent such as Murphys FD20PK or AB Vickers Foamsol can be added during the first 10% of the transfer to dramatically reduce the foam and thus increase your fermenter capacity. I was recently able to increase the fermented volume at a brew-pub client by 7% using this approach.

None of the concepts I have highlighted above require the purchase of any additional equipment. It is not uncommon for a brewery to increase it’s capacity by buying double sized fermenters and filling with two batches of wort each day, but this is likely to mean employing extra staff or paying overtime – so whilst it will increase your capacity, the impact on your margin will be minimal in comparison to the simple optimisation methods I’ve detailed above.

The best approach

When you have decided which process stage you want to focus upon, the best approach is to make a number of step wise changes towards what you have estimated as your maximal capacity. But remember that each increase will need to be in increments of cask volume (i.e. 42 litres for an extra Firkin or 21 litres for a Pin). Gaining an extra 3/4 of a cask does you no good at all!

If you would like help maximising the batch size of your microbrewery, then please give me a call.  Similarly, if you would like someone to brew on your kit to cover times of peak output or to cover holidays (without having to employ an additional person full time) then this is another service I am pleased to offer.