Malting process

The malting process converts raw grain into malt. The malt is mainly used for brewing or whiskey making, but can also be used to make malt vinegar or malt extract. Various grains are malted, the most common grains used are barley, sorghum, wheat and rye. There are a number of different types of equipment that can be used to produce the malt. A traditional floor maltings germinates the grains in a thin layer on a solid floor, and the grain is manually raked and turned to keep the grains loose and aerated. In a modern malt house the process is more automated, and the grain is germinated on a floor that is slotted to allow air to be forced through the grain bed. Large mechanical turners keep the much thicker bed loose with higher productivity and better energy efficiency.

The grain is received at the malt house from the farmer. It is taken in from the field and cleaned (dressed) and dried if necessary to ensure the grain remains in the best condition to produce good malt.

The barley is tested to check for suitability for malting and to prevent dead or unfit barley from entering the process. Some of the typical quality checks include:

Barley received at the Malt house with a moisture of more than 13% must be dried before it can be safely stored without loss of germinative capacity (GC). The moisture is removed by circulating heated air (up to 50 °C) through the grain and can either be performed using dedicated grain driers or as a batch process using a kiln. High temperatures or over-drying will damage or kill the barley embryo and the grain will not germinate after steeping. The dry barley can safely be stored for up to 18 months without fungal growth or loss of grain vigour.

The aim of barley cleaning is to remove foreign matter (straw, chaff, dust and thin corns) found in the incoming grain, leaving only the grain most likely to produce a good malt. Magnets are used to remove metals from the grain, in turn reducing the possibility of sparks, which could lead to a dust explosion. Rotating and shaking sieves are used to remove unwanted foreign matter either larger (straw and un-threshed ears) or smaller (sand and thin corns) than the normal barley grain. During the sieving process an aspiration system removes the dust and chaff. De-stoners or shaking screens are used to separate small stones from the barley. The stones, which are more dense than the barley, move out the top of the machine and the cleaned barley exits at the bottom. Half corn separators may be used to remove broken kernels. Half kernels need to be removed as only the one half will germinate and produce enzymes. At the end of the cleaning process the grain is weighed to determine the cleaning losses (the difference between the weight of grain received and the weight of the grain after cleaning) and it is transferred to a silo for storage.

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Wikipedia