Malt in general can store for long periods of time if kept in a clean dry environment. The majority of malts are below 5.0% moisture, and quite simply at that low moisture very little can sustain life. Molds won’t grow, and many grain related insects will not be able to thrive in an environment that dry. There are some specialty malts that have higher moisture levels, and keeping all things equal, would not stand the test of time as well as malt that is below 5%.
Therefore, the best way to store large quantities of malt is in a clean, dry, silo. Not only can it be the most efficient and economical way of storing grain, but also provides the brewer the ability to maximize the malt’s “shelf life”. Larger brewers do not store malt for any length of time because they are receiving malt deliveries weekly, and for the largest breweries on a daily basis. However the smaller craft brewer, who is benefiting from volume pricing by purchasing truckload quantities can end up storing their malt for several months. This can be done easily using a silo, but there are just a few considerations or tips. First, it is a good practice to empty the silo completely a few times a year.
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This reduces the build up of chaff, which is all the dust, and pieces of debris, that are created any time you move grain. The movement of grain in a silo is such that the lighter particles will rise to the top, so if you never completely empty your silo, continuing to create chaff, you will eventually wind up with a bunch of material in the bottom that you can’t brew with. Another source of chaff build up could be from high pressures used during pneumatic unloading. Cargill recommends unloading its trucks between 3 -5 psi, which is adequate to move the grain while minimizing breakage. Also there are more insects that can easily use the fine dusty debris as a food source, therefore limiting the quantity will lessen the likelihood of getting an infestation.
You should periodically inspect your silo both the exterior and interior. Look for cracks, missing bolts, or anything that might affect the structural integrity. Take an explosion resistant flashlight and inspect the interior. Look for water marks or stains on the sidewalls, or on top of the malt indicating a roof leak. Simply taking the time to do a quick inspection will save you headaches down the road. Keep loading hoses and tubes capped off when not in use. The area around the silo should be kept clean, not only is this just a good manufacturing practice, but helps quickly reveal even the very beginnings of a hole by the telltale pile of dust on the ground.
Bagged whole kernel malt stores longer easier than pre-milled bagged malt for some of the same reasons mentioned earlier. Simple good housekeeping and manufacturing practices will go along way in preventing storage problems related to bagged malt. First of all the storage area should be kept dry, and if possible separate from the wet brewery, or any hose down areas. Bags should be off the ground either stacked on a rack or on a pallet. Storage on wooden pallets is fine as long as pallets are kept in a dry area. Spills should be cleaned up promptly. Avoid storing pallets all the way up against a wall or in a corner.
There should always be enough room for a person to walk behind the pallets. This not only allows you to keep the area clean, but also takes away the areas the pests hide and live in, too. Malt can also potentially pick up off flavors from being subjected to off odors. For example I’ve seen malt being stored in a kitchen of a restaurant, or in an area close to the delivery dock and was subjected to all the exhaust fumes from the idling delivery vehicles. I hope I’m pointing out that most storage issues can be prevented with some common sense and diligent sanitation work.
The final necessary component to help insure the quality of your malt is to implement a pest control program. Any food producing or servicing company needs a pest control program, and most are paying an outside contractor to do that work for them. Whether you choice to contract with a professional licensed pest control company, or implement an in-house plan there are a few basics that should be expected by either. A rodent program developed identifying entrance and exits into the facility, and locations of interior and exterior traps. An inspection, trap maintenance, and activity report regiment that is routinely completed and reviewed. When looking at insect prevention there are a number of chemical pesticides and applications to safely solve almost any pest issue. Again, I truly believe though, that simple good housekeeping can prevent most pest control issues.
If you do not give them a place to live or a food source to eat, the pests will find other places to go. The reason most companies contract that business out is the technician will already be certified and licensed to use some of the chemical prevention tools at their disposal such as poison baiting, spraying residual insecticide, fogging empty bins, or fumigating product. The minimum level of pest control is usually outlined by government agencies, (another good reason to contract) but a thorough assessment of the facility’s issues will dictate the level of control necessary.
To summarize, I believe the keys to storing malt safely while preserving quality are proper inventory control and maintenance. Stocks should be properly rotated and proper quantities ordered to help prevent stock from getting too old. Secondly a pest control program needs to be implemented, and most importantly the storage area needs to be dry and clean all the time.
A good resource giving a more detailed explanation of the Sanitation and Pest Control needs of a brewery is: Handbook of Brewing, 2nd Edition, Edited by Fergus Priest and Graham Stewart. Chapter 17, Sanitation and Pest Control, pgs 629 – 654