The mashing process is a meticulous interplay between science, repetitive process and tradition. It’s a process where hot water is applied to activate natural enzymes, like Amylase, which then convert the grain’s starch into sugars that can ferment.
This article explains some of the science, time frames, and technical details involved, offering a comprehensive insight into this crucial phase of whisky production.
The objective of mashing
In the context of whisky production, the ultimate goal of mashing is to convert the starches present in grains (usually barley, corn, rye, or wheat) into fermentable sugars.
This transformation is essential because sugars are what yeasts metabolise during fermentation, producing alcohol and flavour compounds.
The mashing process
The mashing process really starts with milling, where grains are ground to increase the surface area.
After milling, the mash bill (selection of grains) is transferred into a mash tun, where the enzymatic breakdown will happen. The process typically lasts for 90 to 120 minutes, depending upon the grist composition and the targeted outcomes.
Each distillery will operate slightly different processes. But to simplify – they begin by adding the grist alongside warm water and stir. They then add hotter water and stir some more. Once ready, add even hotter water before filtering the lot out into a fermenting vessel, ready to inoculated with yeast.
Obviously, that’s a hyper-simplified way of explaining it.
The reason for stating it in such basic terms though is important. It’s just hot water and grains involved here, so how you stir, when you add, and the temperature really matters. All the enzymes are already in the grains.
Let’s delve in further…
The grains go in – What is a mash bill?
A mash bill is a term for a recipe detailing the specific grain composition to be used.
This mix could encompass various proportions of grains, including barley, corn, rye, and wheat. Some whisky styles have minimum requirements for their mashbills (e.g. Bourbon)
The choice of grains and their respective proportions in a mash bill play a pivotal role in determining the flavour, aroma, and complexity of the whisky.
The water is added – What is gelatinisation?
Gelatinisation is what happens to the starch when you add hot water. It refers to the process where starch granules absorb water and swell, breaking down their crystalline structure and making the starches more amenable to enzymatic breakdown.
This step is crucial because it allows for a higher yield of fermentable sugars, which are essential for the subsequent fermentation process.
Different grains have distinct gelatinisation temperatures, meaning that a well-strategised temperature regimen is essential. For instance, barley has a lower gelatinisation temperature compared to corn. Therefore, the choice of grains significantly influences the mashing strategy.
Enzymatic activity
Following gelatinisation, the mash undergoes enzymatic transformation. This primarily involves alpha and beta-amylases, which break down the gelatinised starch into fermentable sugars.
The higher the extent of gelatinisation, the more accessible the starches are to these enzymes, resulting in a more efficient conversion process. This is where temperature control comes in.
Typically, the process involves a step-by-step temperature increase to activate various enzymes that work optimally at different temperatures.
- Beta-Glucanase rest (40-50°C). This initial stage facilitates the breakdown of beta-glucan molecules, which could otherwise contribute to a viscous mash.
- Protease rest (50-55°C). This second stage encourages the breakdown of proteins into smaller peptides and amino acids, setting the stage for a fruitful fermentation.
- Amylase rest (60-70°C). In the hottest range, Amylase enzymes function optimally in this temperature range, converting starches into fermentable sugars.
What do we mean when we say “enzymatic breakdown”?
Two primary enzymes play a crucial role in starch to sugar conversion. Alpha moves starch into carbs, Beta moves those carbs into sugars.
- Alpha-Amylase: It breaks down starches into shorter carbohydrate chains, including dextrins and maltotriose.
- Beta-Amylase: It breaks down the shorter carbohydrate chains further into simple sugars, predominantly maltose.
By making sure the temperature is gradually increased and that optimum ranges are maintained, the maximum Enzymatic Breakdown can occur and the higher the level of sugar there is at the end of a mash.
pH levels also have a considerable influence on the efficiency of these enzymatic reactions, with the optimal range being between 5.2 and 5.8. (more on that in a minute!)
The mechanics: Mash tuns
Mash tuns vary in size and spec quite significantly. That said, all have three similar considerations. Stirring, adding water and how the end liquid, the ‘Wort’ runs off.
There is always lots of stirring involved in mashing. Some do this with ‘arms’ that rotate around the mash tun. Others have more complex helix-like shapes and through the action of continuous but slow stirring, it ensures drainage through the bed and an optimum sugar extraction during a certain time frame.
Adding the water can be as simple as spraying it in. But can be as complex as having multiple inputs to better spread the inbound liquid across multiple areas simultaneously.
Another factor is the rate of drainage. Some mash tuns have detailed designs and perforated false bottoms, others rely on far more rudimentary sets ups and on a grist with far higher husk percentage.
Why does this matter? You need as much of the contents to be thoroughly exposed as possible, in a predictable and consistent way and to allow for the distiller to be able to impact the process should they need to make decisions to keep the batch moving, track how it’s performing etc.
The mashing outcome: The Wort
At the end of the mashing process, the liquid, rich in sugars, is separated from the solid grains.
This liquid, termed “wort,” proceeds to the fermentation vessel where yeast is introduced to kickstart fermentation. The grains are sent to be up-cycled in nearby farms.
Sour Mashing in whiskey production
What is Sour Mashing?
Sour mashing is a traditional process commonly used in the production of American whiskey, including the renowned Tennessee whiskey and bourbon.
It is a technique that involves using a portion of stillage to start the fermentation of the new mash.
To comprehend the technique and purpose of sour mashing, one must revisit the basic principles of fermentation.
During fermentation, yeast cells convert sugars into alcohol, producing other by-products such as heat and lactic acid. Over time, lactic acid bacteria and other microbes naturally present in the environment can further ferment the residual sugars, enhancing the acidity of the mash and giving it a ‘sour’ character. See Fermentation article.
The purpose of sour mashing
Sour mashing serves several functions in whiskey production, including:
- pH control: Introducing a portion of sour mash helps in maintaining a consistent pH level in the new mash, creating an optimum environment for enzymatic breakdown and yeast fermentation.
- Flavour consistency: Using a fraction of a previous batch aids in achieving a consistent flavour profile, ensuring uniformity across different batches.
- Microbial stability: Sour mashing also contributes to microbial stability by fostering a lower pH environment that inhibits the growth of unwanted microbes, thereby reducing the risk of spoilage and infection.
The Sour Mashing Process
- Retaining a portion of stillage: Once a batch of whiskey is distilled, a portion of the stillage is retained.
- Integrating with fresh mash: This retained portion, rich in lactic acid and other components, is then introduced into a fresh batch of mash before fermentation.
- Controlled fermentation: The integration of stillage ensures a pH controlled fermentation environment, fostering a healthy yeast activity.
Does sour mashing make sour whisky?
Sour mashing doesn’t mean that the whiskey will be sour.
The sour mashing process imparts a complexity to the whiskey’s flavour profile. It helps create the optimum pH level to achieve the right fermentation outcome. Most major bourbon and Tennessee whiskey distillers use the sour mash technique, even though only a portion of them actively label their whiskeys as “sour mash”.
Mashing is a nuanced and critical step in the craft of whisky production, where the blend of science and experience speaks the loudest.
While it’s a technical process that can seem daunting at first, looked differently – it’s just about converting starch to sugar. Understanding the role of enzymes, precise temperature controls and how distillers manipulate variables, can shine a light on why certain whiskies taste the way they do.
You can’t make good Whisky without a good New Make, and you can’t do that without a carefully honed mash and ferment…
