DRY MILLING
F O R D I S T I L L E R Y O P E R AT I O N S WRITTEN BY ERIC MARCOTTE
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P H O T O S P R O V I D E D B Y S T E D M A N M A C H I N E RY C O M PA N Y
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he Old Bushmills Distillery in Northern Ireland is the oldest licensed whiskey distillery in the world, with its license issued in 1608. So what has changed over time? In a word—efficiency. The steps necessary to convert raw grains into the myriad of beverages millions enjoy today remain largely the same. However, the processes have been refined and streamlined leading to considerably more efficiency.
MILLING
TYPES OF MILLING MACHINES
Let’s take stock of the steps to produce some of these products beginning with milling. Milling breaks up cereal grains so that water can penetrate and facilitate the cooking process. Grinding grains is the process of increasing surface area. More surface area gives water and enzymes a better opportunity to penetrate the grain. By grinding the grain, you not only create many more particles that are smaller and more accessible, you actually increase the surface area of that grain exponentially. The optimal size of the ground material varies according to the distiller, but the science behind the opinions includes making particles so fine that they allow maximum access for hydrolysis of starch. Another school of thought proposes larger particles are the way to go for better yield. Whether fine or coarse, the idea is to expose the starch to water in a way that won’t cause handling problems. If the mash is too hard to dewater then the distiller may lose liquid containing alcohol, decreasing yield. Particle size distribution analysis of the meal should be done on a regular basis. When the distribution falls outside specifications, the mill should be adjusted.
Grinding of corn, rye and malted barley in distilled liquor production calls for equipment performance typically required in food plants. The grain must not be overheated in the grinding process, as this could affect the final product flavor. The ground grain must also be uniform, relatively coarse and contain as little flour, or dust, as possible to prevent handling and dewatering problems. Generally a hammer mill is used for corn, wheat and rye, a roller mill for malted barley, and a cage mill can be used for all four.
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HAMMER MILLS Hammer mills use rectangular pieces of hardened steel attached to a shaft rotating at a high speed inside the milling chamber. The rotating “hammers” accelerate the grain into breaker plates lining the housing of the mill. Next, the grain encounters a changeable screen with a “close tolerance” gap between it and the rotating hammers. WWW.ARTISANSPIRITMAG.COM