What is Malt?
Malted barley, or ‘Malt’ as it is most commonly known, is a wonderful package of starch, enzymes, protein, vitamins, and minerals plus many other minor constituents that provide the brewer and distiller with their main raw material.
60-65% of the weight of malt is un-degraded starch and malt contains all the key enzymes for starch degradation during the mashing stage of both the brewing and distilling process. These enzymes produce fermentable sugars to supplement the other key nutrients for yeast growth that malt provides. These include amino acids, vitamins, and minerals.
The Malting Process consists of 4 stages which are steeping, germination, kilning and roasting.
The purpose of steeping is to increase the moisture in the grain from around 12% to approximately 45%.This is achieved through successive immersions and air rests over a period of 2-3 days. During this process, the grain begins to germinate and therefore produces heat and carbon dioxide. In the immersion cycles, the grain is immersed in water and air is blown through the wet grain to keep the level of dissolved oxygen in the water high enough so as to not stifle the developing embryos. In the air rests, the carbon dioxide is removed.
Due to the varying degree of moisture tolerance of the different grains, steeping is a crucial step in the malting process. When the steeping process is complete, all of the grain should be evenly hydrated and show signs of germination.
The Germination phase is the ‘control’ phase of malting. Germination continues for a further 4-5 days depending on the product type being made. The germinating grain bed is kept at temperature and oxygenated by providing a constant flow of humidified air through the bed at specific temperatures. The grain is turned regularly to prevent rootlets matting and to maintain a loosely packed grain bed. The maltster manipulates the germination conditions to vary the type of malt being manufactured.
Kilning, the third phase of malting, dries the grain down to 3-5% moisture and arrests germination. Large volumes of hot air are blown through the grain bed. By varying air flows and kiln temperatures, malts of different colors can be produced with varying flavor profiles. At the end of kilning the malt is cooled and the tiny rootlets removed before analysis and storage. The final malt is analyzed extensively according to malt type and customer profile. The malt may be dispatched in bags, in containers or in bulk.
Roasting is done in 4 distinct stages: steeping, germinating, roasting and cooling. At GWM Malt, grain spends 34-46 hours in steep tanks where we aim for a target moisture of 42-44%. The grain is transferred to germination which lasts for around 4 days in Wanderhaufen style streets. This is a semi continuous moving batch germination process. Once germination is complete, the green malt is then transferred to the roasting drum.
The roasting takes place in two roasting drums. The average roasting time is 2 ½ – 3 hours with an air on temperatures of up to 460˚C. Our roasters take a batch size of 2.4 – 3.5 tonnes. The roasted malt is then transferred to the cooler and spends 35 – 60 minutes there in order to drop the temperature to <15˚C and fix the color and flavor compounds. The malt is analyzed before storage and thereafter awaits dispatch to our customers.