Barley Malt

Controlled germination

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If barley is wetted in a container or on a special floor and stirred to keep oxygen levels high it will germinate. This produces high levels of alpha amylase which converts the starch to sugar. This process is called malting and the product is malt. This is an ancient process for producing a sugary solution for making cheap beverages such as whisky and beers.

After malting barley can be used in two ways. It can be dried and sold as dried malt. Often with a high temperature treatment that caramelises some of the sugar to give a pleasant-tasting flavouring also known as 'malt'. This may be extracted with water to give a 'malt extract'. Dark beers (eg Guinness) are made from malt which has been heated so much it has almost burned black, hence the dark colour.

After malting the grains do not just contain sugar. Before heating they also contain a lot of alpha amylase. This enzyme can convert still more starch to sugar. This is used in several processes. For example:

Malting barley is a quite complex skill and requires all the grains to germinate more-or-less simultaneously. This is largely controlled by malting a single variety at a time, often after cold treatment. Gibberelic acid, an enzyme, is sometimes added to trigger germination. Good varieties will germinate quickly (ie NOT be dormant) and produce a maximum quantity of sugars after malting. Some varieties are good close to harvest but then become poor whilst others are the reverse. Consequently most maltsters will run on one variety at a time for long runs and only use varieties tested and approved by the Institute of Maltsters.


A rough guide.
The traditional British ale is made from the sugary solution by a vigorous quick fermentation where the yeast is in suspension through most of the liquid. It is clarified by settling and other ancient processes unlike the cheap filtered product. Proteins in the barley make it cloudy so specific varieties with very low proteins are required (even for filtration) to produce a clear beer. Most prized are those with a protein level of under 1.4%N, which are hard to produce and command a large premium. Currently one of the best malting varieties available is Maris Otter. It is very hard to grow well.

Lagers are produced by a cold slow fermentation where the yeast sits mostly on the bottom. Protein cloudiness is less of a problem but a good 'head' is. They thus require a protein level of 1.6%N to 1.7%N (to produce the protinaceous head), which is easier to produce at higher yield levels and more fertile soils with 'ordinary' malting varieties. In my opinion it is of indifferent taste compared to a genuine British ale.