
What is Mashing & Milling?
The process of whisky-making is a harmonious blend of science and tradition, and mashing and milling are critical stages in transforming grains into fermentable sugars—the foundation of any whisky. After malting, where enzymes are activated to convert starches into sugars, the grains are milled and mashed to extract these sugars, preparing the liquid for fermentation. These stages greatly influence the efficiency of sugar extraction and ultimately the character of the whisky.
Milling: Preparing the Grains
Milling is the process of crushing malted barley (or other grains in some whiskies) into a coarse powder known as grist. This step is critical because it determines how well the grain will release its sugars during mashing.
The Structure of Grist
Grist consists of three main components:
- Husks: The outer covering of the grain, which helps filter the mash during lautering (the separation of liquid wort from solid grain residues).
- Flour: The finely ground starch content that dissolves quickly and releases fermentable sugars.
- Grits: Coarser particles that contribute to gradual sugar release and prevent clogging during lautering.
Precision in Milling
- The ideal grist ratio is typically 20% husk, 70% grits, and 10% flour.
- Over-milling creates too much flour, leading to clogging in the mash tun, while under-milling reduces sugar extraction efficiency.
Milling is therefore not just about crushing grains but ensuring a balance that supports smooth mashing and efficient fermentation.
Mashing: Extracting the Sugars
Mashing involves mixing the milled grist with hot water in a large vessel called a mash tun. This step extracts the fermentable sugars from the grains, producing a sugary liquid known as wort. The mashing process occurs in three or four stages, with water added at progressively higher temperatures.
Stages of Mashing
- First Water: Hot water (around 64°C/147°F) is added to activate enzymes like amylase, which break down starches into maltose (a sugar). The wort from this stage is the richest and is drained for fermentation.
- Second and Third Waters: Warmer water is added to extract remaining sugars from the grain bed. These subsequent worts may be combined with the first or used in a future mash.
Temperature and Enzymes
The temperature during mashing is critical:
- 64-65°C (147-149°F): Activates enzymes while preventing denaturation, optimising sugar conversion.
- Higher Temperatures: Extract additional compounds, including proteins, which can influence mouthfeel.
Enzymes like alpha-amylase and beta-amylase play key roles:
- Alpha-Amylase: Breaks down complex starches into smaller sugar chains.
- Beta-Amylase: Converts these chains into maltose and glucose, fermentable sugars that yeast can metabolise.
Lautering: Separating the Wort
After mashing, the liquid wort is drained through the grain bed. The husks act as a natural filter, ensuring the wort is clear and free of solid grain particles. The residual grain, known as "draff," is typically repurposed as animal feed, ensuring minimal waste in the whisky-making process.
The Influence of Mashing and Milling on Whisky
The precision of mashing and milling directly impacts the quality and flavour of whisky:
- Sugar Yield: Proper milling and mashing ensure maximum extraction of sugars, crucial for fermentation efficiency and alcohol yield.
- flavour Development: The quality of the wort influences the final flavour. A clean, well-balanced wort provides a solid foundation for fruity, malty, or smoky flavours.
- Mouthfeel: Over-extraction during mashing can introduce proteins and tannins, affecting the texture of the whisky.
Innovations and Traditional Techniques
Many distilleries continue to use traditional mash tuns made of copper or stainless steel. However, some modern facilities employ automated systems for precision and consistency. These innovations ensure that the delicate balance of milling and mashing remains efficient without compromising quality.
Conclusion
Milling and mashing are essential steps in the whisky-making process, where science meets tradition. Milling prepares the grains for optimal sugar extraction, while mashing unlocks the sugars necessary for fermentation. These processes not only set the stage for alcohol production but also significantly influence the flavour, aroma, and texture of the final product. Whether crafted in a centuries-old distillery or a modern facility, the meticulous care given to milling and mashing ensures that every drop of whisky is a testament to the art of distillation.
Cheers to the journey from grain to glass! 🥃