The difference between Dunnage Warehouse and Pallitized Warehouse

Ever wondered the difference between Dunnage Warehouse and Pallitized Warehouse? Get the answer here

The Dunnage Warehouse is a traditional type of warehouse for maturing whiskey, which is made of stone or brick and has no solid floor. They are built quite low and have thick walls. The oak casks stored for whisky maturation within a Dunnage Warehouse are stacked directly on top of each other, up to a maximum of three layers high.

Dunnage warehouses often have only one floor, but there are also those with two, three and more floors in use. Dunnage warehouses have excellent air circulation and microclimate with a higher humidity. Thanks to their thick walls and roofs, Dunnage warehouses experience less external impact than other types of warehouses.

Unfortunately, the relative costs are much higher than in a racked or palletized warehouse, partly due to the much more limited storage capacity, which offers a poor ratio of space to stored goods. These costs are further exacerbated by much higher maintenance costs. Since barrel moving equipment does not fit into Dunnage warehouses, barrels must always be moved individually and manually.

Pallitized Warehouses are modern liquor maturation warehouses made of brick, concrete or steel with a solid floor. In pallitized warehouses, the barrels can be stacked vertically in dense rows between eight and twelve layers high in long parallel rows. The drums are stored upright instead of lying down, allowing warehouse workers to move them more easily with forklifts.

How grain whisky is made
Grain whisky is made from corn or wheat. Most grain distilleries use wheat as it is currently the cheapest grain. However, it's not the traditional Scottish cheapness that applies here. When you're producing perhaps up to 100 million liters of alcohol per year, even a small difference in grain prices can have an impact on the bottom line. Grain whisky also contains a small portion of malted barley. The barley helps to kick-start the fermentation process. In whisky production, the use of artificial enzymes is not allowed, as is the case in the vodka industry.

The malted barley arrives at the distillery directly from a malting plant when it has reached the stage of the malting process known as green malt. In other words, a green sprout has just emerged and the barley grain is still alive. Grain distilleries do not spend money on drying or storage. The barley must be used as soon as it arrives at the distillery, otherwise it will mold. The malted barley is ground into flour as in the production of malt whisky. The corn or wheat grains are also ground into flour and then the flour is cooked in a giant pressure cooker to soften the starch and make it soluble.

The two types of flour are now mixed in a mash tun and hot water is added. Only one portion of water is used, whereas malt distilleries change the water three or even four times as temperatures rise. Now all the starch has been converted to sugar and the sugar water (also known as 'wort') is drained off. The protein-rich residue is used for animal feed. The sugary liquid is now drained into large stainless steel vats for the addition of liquid yeast. In just over 72 hours, the yeast has eaten the sugar and produced alcohol and carbon dioxide. The alcohol is similar to beer, called "low wines" and has an alcohol content of 8.5%. Distillation takes place on continuous distillation apparatus. These are usually called 'Coffey stills' or 'patent stills'. They run continuously 24 hours a day, 365 days a year.

Column distillation
Without the ingenious invention of the column still, the whisky industry would never have reached the heights we see today. In 1826, Robert Stein invented a distillation apparatus that was considerably more efficient than the standard copper kettles used by whisky brewers. This distillation method became popular when Irish customs officer Aenas Coffey improved on the invention and patented it in 1830. Now large quantities of very pure alcohol could be made cheaply, efficiently and quickly. However, the invention was not to be a success in his homeland, so Aenas Coffey took his invention to the land to the east - Scotland. At the time, whisky producers were under pressure from the English gin industry. They welcomed this new invention, which was named Coffey Still or Patent Still. The spirit was originally intended as a competing product to gin. An alcohol that was pure and without the, for many, overly smoky taste that was prevalent in whisky at the time.

The modernists in the whisky industry embraced the invention. Much to the anger and frustration of the traditionalists, these innovative individuals were allowed to mix grain-based alcohol (distilled in Coffey stills) with the somewhat heavier and fuller-tasting malt-based alcohol (distilled in small batches in good old-fashioned copper stills) and call it whisky! This led to somewhat tumultuous scenes in the industry, but the concept we know today as blended Scotch was born.
As we all know, the great British Empire had spread to many parts of the world and export markets were open. Emigrant Scots demanded the elixir of life in their homeland, and exporters and producers were given an unexpected helping hand by a small vine aphid, Phyloxera Vasterix, which invaded French vineyards around 1850 and destroyed all the vines. This brought the production of Cognac and brandy to a complete standstill. The middle and upper classes were now looking for other intoxicating and flavorful alcoholic experiences, and with the opportunity to sell the new product blended Scotch, the demand could be met. Scotch whisky became - and still is - a huge export.

Column distillation - how it works
The distillation apparatus consists of two columns. In one column, the fresh wash enters via an s-shaped tube. On its way down the s-shaped tube, the wash is heated by alcohol vapor returning from column two. The wash is thus near boiling point before it is brought to the top of the second column, where it begins to drip down through the second column. The second column is divided into a large number of smaller chambers separated by perforated copper plates. At the bottom of column two, steam is let in under low pressure. The steam rises and at some point meets the wash as it makes its way down the column. The alcohol in the wash, which has a lower boiling point than water, will now be separated and rise in the form of alcohol vapor. From the top of column two, the alcohol vapors are directed to the bottom of column one, where they begin to rise again. On the way up column one, the vapors must pass the pipes with the cold wash that is on its way to column two.

This cools the alcohol vapors and now condenses back into alcohol and is discharged from the column. The alcohol percentage is now up to 94.5 percent. It is an almost - but not quite - neutral spirit. A little flavor in the freshly distilled alcohol is absolutely desirable for the taste of the grain whisky that, after maturation in oak barrels, will be included in one of the many blends produced. The alcohol to be used for whisky must be a maximum of 94.7 percent. It's a simple piece of legislation. Therefore, grain distilleries "only" distill to 94.5 percent to have a small margin to run on, so that their alcohol does not have to be discarded in case they hit too high a final percentage.

The column stills may have slightly different designs, but the basic principle is the same, and they all go by the common name Coffey stills. Before this alcohol is put into barrels, it is diluted with neutral demineralized water. In some cases, it is diluted down to 68% alcohol and in other cases down to 63%. By the time the wash reaches the bottom of column two, it has turned into a waste liquid called spent lees. The high alcohols are drained off in column one and are called feints or the tail end of the distillate. The fusel oils are also drained, and both the feints and fusel oils are processed and sold. Nothing goes to waste.

The Scottish grain distilleries
Currently, there are a total of seven grain distilleries operating in Scotland.

Cameronbridge - Owned by Diageo
Girvan - Owned by William Grants & Sons
Starlaw/Glen Turner - Owned by La Martiniquaise
Invergordon - Owned by Emperador Inc.
North British - Owned by Diageo & The Edrington Group
Strathclyde - Owned by Pernod Ricard
Loch Lomond - Owned by Loch Lomond Distillers

Maturation
Alcohol for use in blends is matured according to the same rules that apply to the maturation of malt-based alcohol.
This involves maturation in oak barrels and the minimum maturation time is three years. Most commonly used are barrels made from American white oak. These casks have often served their time in malt whisky maturation warehouses. This may be the fourth or even fifth time these casks have been used. The casks don't necessarily have to contribute a lot of character and complexity, but the minimum aging time of three years must be respected. If the contents of the cask are to be included in a 12-year-old blended Scotch, for example, the minimum maturation time of 12 years must be observed, and so on. In many cases, it is - in short - a storage period to comply with current legislation.

That said, not all grain whisky is indifferent and characterless after maturation. Unfortunately, far too little grain whisky is bottled as single grain - that is, grain whisky from a specific grain distillery. It is mainly independent bottlers who occasionally bottle a gem of a cask that may even have been aged for many years.

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