Editor’s Note: A version of this article appeared in the Nov/Dec 2016 issue of The New Brewer.
How many times have you opened your malt cabinet and rummaged through a collection of zip-top bags filled with assorted base malts and specialty grains as you plan your next brew day? You recognize that some of those bags have been there, partially empty, longer than you can remember, and you’re not really sure what to keep and what to replace.
A number of factors influence grain’s degree and rate of deterioration as it leaves the farmer’s field, filters through the malting plant, survives shipping and distribution, passes through the homebrew supply shop, and, finally, lands in your home brewery. With a bit of background knowledge, you can better preserve the quality of your malt, extend its shelf life, and answer that all-important question: “Is this still any good?”
Great Malt Starts with Great Grain
Malt quality obviously starts with grain quality. As farmers deliver their harvests to the maltster’s silos, each load has to meet certain acceptability standards as defined by the maltster. Different maltsters apply different sets of inspection criteria, but most include the following.
- The barley should be bright golden in color and show no visible signs of husk damage. Most maltsters reject barley loads if samples contain more than five percent broken kernels.
- Obviously, the delivery should be free of “alien” matter such as residues of botanicals from previous deliveries by the same truck; rodent feces; rocks, metal, and other debris; stalks, leaves, and weeds; and insects. It should also be free from blight, mold, and other diseases and infestations.
- Next, the kernels should be as plump and homogeneous as possible. A kernel diameter of at least 2.5 mm is highly desirable. The bigger the kernel, the more favorable the ratio between the inner volume of the kernel (the starchy endosperm) and its enzyme-rich outer aleurone layer and the phenolic husks. Six-row barley, therefore, has a less favorable ratio of inner volume to outer area than does two-row barley. However, for the same reason, six-row barley has relatively more diastatic enzymes per unit weight. Such barley was especially developed to provide sufficient enzymes for mashes with large portions of adjuncts. Regardless of the kernels’ plumpness value, kernel dimensions should be as homogeneous as possible to ensure a uniform crush. A kernel size uniformity of at least 90 percent is desirable.
- Top-quality brewing barley should not contain 9 to 12 percent protein by weight. While insufficient protein levels can cause the finished beer to lack body, mouthfeel, and foam stability, excessive amounts can cause lautering problems in the brew house, as well as hazes in the finished beer. As a general rule, barley grown in a maritime climate, such as on the British Isles, tends to have less protein than does the same barley grown in a continental climate, such as in the Czech Republic or the Canadian Prairies.
- The optimum moisture content of incoming barley is between 12 and 14.5 percent by weight, while barley inside a silo should not have a moisture content of more than 12 percent. Therefore, most barley needs to be dried quickly before it reaches the silo. Grain that is stored too moist can become contaminated with mold and mycotoxins within just one week. Drying is usually achieved by blowing air at roughly 95 to 125°F (35 to 50°C) through the grain. A higher drying temperature could negatively affect the grain’s germination potential and enzyme viability. Grain in silos is also “alive,” which means that the plant cells continue to respire as long as there is enough moisture and oxygen in the environment. The physiological process of respiration provides the cells with energy by oxidizing carbohydrates (a depletion of plant sugars) into carbon dioxide and heat. High moisture levels can thus lead to accelerated grain weight losses through excessive kernel respiration.
- Finally, the maltster is also likely to check the germination rate of the shipment. In a good batch of barley, at least 98 percent of the kernels should be able to sprout, because kernels that cannot develop acrospires and rootlets cannot become malt.
Once the grain has met all incoming inspection criteria, it is cleaned several times. This involves removing the awns and dust, sending the grain past a magnet to remove any metal particles, and riddling the grain over successive screens of different permeability to sift out any remaining extraneous substances, chaff, kernel fragments, and debris, as well as to grade the kernels. For this purpose, sieve perforations with diameters between 2 mm and 2.5 mm are common.
In the silo, the grain continues to be aerated and cooled to a temperature of at least 55 to 60°F (roughly 12 to 15 °C), which has several advantages. This temperature range keeps respiration losses in check and suppresses the development of molds and mustiness. A temperature of roughly 40°F (4°C) all but inhibit molds. It also reduces insect growth because most insects thrive best at a temperature of 80°F (27°C). They stop reproducing at temperatures below 70°F (roughly 20°C), and they enter dormancy at 50°F (10°C). A cold grain silo also preserves the grain’s germination ability and thus extends its storage time to about 18 months. Aeration, especially with dry winter air near or below the freezing point, is optimal because it can increase the grain’s storage potential even beyond 18 months.
Malt in the Malthouse
The production of quality malt requires strict adherence to all applicable food industry standards of “good manufacturing practices” (GMP). These include the implementation of a food safety management system, commonly referred to as a Hazard Analysis Critical Control Point (HACCP) program. It involves regular quality assurance and quality control (QA/QC) analyses and controls of potential biological, chemical, and physical hazards in the malting process, from steeping, to germination, to kilning and/or roasting, to packaging. The goal is to identify and prevent—both proactively and reactively—potential food safety risks. The key features of GMP include proper staff training; periodic audits and inspections, often by third parties, of all processes and products at the various stages of production; as well as proper documentation to ensure backward traceability of any faults should they occur. Such systems also allow for the unique bar coding of each bag for online customer accessibility of each shipment’s malt analysis.
Production control involves using the right equipment for the right type of malt. For instance, it makes a difference to the flavor and aroma of caramel malts if they are produced in a kiln, which creates inconsistent results, or in a capital-intensive roasting drum, which ensures homogeneity. Finally, though this ought to be obvious, GMP rules mandate that all areas of the malting plant be kept food-grade clean.
Malt in Transit
Once the maltster releases bagged or loose malt for shipping, proper handling becomes the essential factor in preventing damage from malt’s key enemies of temperature, moisture, light, and pests. Therefore, malt bags should be strong and tear-resistant, with inner plastic liners as moisture barriers. Pallets should be made of pre-dried and pest-free material, and they should be kept away from moisture during storage, as well as when they carry malt. Shippers hired to transport malt should have a proven track record of handling cargo in their care professionally and responsibly; and distributors receiving malt shipments should have clean and dry warehousing facilities, as well as a FIFO (first-in-first-out) inventory management system.
Malt in Your Home Brewery
In the best of all possible worlds, the above precautions ensure that the malt arrives at the distributor in optimal condition. From there it is up to the homebrew supply shop and the homebrewer to adhere to a few simple rules designed to preserve the quality of the malt and extend its shelf life. Just as in the malting plant and at the distributor, the storage facility in the homebrew supply store and in the home brewery must be kept clean and dry. All malts—especially milled malts—spoil faster as the ambient moisture increases. If possible, the relative humidity in a malt storage area should be below 10 percent. Malt can tolerate a good amount of temperature variation, but an ambient temperature of roughly 50 to 70°F (approximately 10 to 20°C) or lower is ideal.
Malt bags are best stored on their pallets or in racks off the floor. They should never sit directly on the floor, which would inhibit airflow all around the bags and expose them to possible moisture pockets or puddles. Raising malt begs also makes it harder for rodents to find hiding places.
Finally, malt must be protected from insects in search of a happy meal. These critters include the ubiquitous Sitophilus granarius (grain weevil), as well as Nemapogon granellus (grain moth), Tenebrionidae (a family of so-called “darkling beetles”), and Psocoptera (also commonly known as booklouse or barklouse). Thus, vermin control is always the first order of business in a grain storage area.
Pre-milled malt doesn’t stay fresh as long as whole-kernel malt because the larger surface area of milled malt makes malt compounds more vulnerable to oxidation, rancidity, and staling—especially by the lipid-oxidizing enzyme lipoxygenase (LOX). For the same reason, milled malt is more likely to absorb ambient moisture and thus attract mold and fungi. Bugs, too, will thrive better in pre-milled malt than they do in whole malt.
As a general rule (which varies by malt type), bagged whole-kernel malt, including malt repackaged in homebrew-size plastic bags, should keep for six months to a year, provided it is kept out of direct sunlight and stored in a pest-free, cool, dry environment. Milled malt, on the other hand, should be used as quickly as possible; even if it’s properly stored, the shelf life of malt rarely exceeds three months from the time it was milled.
In terms of up-front raw material costs, purchasing malt in bulk in 50-pound or 25-kilogram bags can offer substantial savings. However, because it is essential to brew only with fresh malt, it may be wise to consider whether or not the savings are worth the potential loss in malt and beer quality. The time it takes to empty a bag should never exceed that malt’s shelf life.
For all these reasons, storing malts in an enclosed, humidity-controlled environment such as a refrigerator is a homebrewer’s best option.
Preserving Your Malt
The keys to maintaining malt quality in a home brewery are simple common-sense measures. Practice inventory control using the FIFO principle—just as commercial breweries do—to ensure proper stock rotation and keep any supply from inadvertently exceeding its best-before date. Purchase the right amounts of malt in accordance with your anticipated brewing needs. Make sure you keep pests out of your malt storage area, and, if at all possible, maintain ambient humidity controls. Your malt ultimately becomes your beer, so treat it with the same care as you would any other precious food commodity.
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Horst Dornbusch is a consultant in the international brewing industry, a multilingual author of books about beer, and a frequent contributor to Zymurgy. Thomas Kraus-Weyermann is the CEO in charge of technology and raw materials at Weyermann® Specialty Malts in Bamberg, Germany.
Photo credits: All photos by Weyermann® Specialty Malts, Bamberg, Germany.
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