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Part 4: Malt - The Key Ingredient in Beer

January 27, 2012 | Comments: 0 | Views: 183

In part 3 of this article series the process of steeping the barley grain was described. We will now move onto the description of germination. Once steeped the grain enters a phase of rapid growth known as germination. When I say rapid I mean rapid in the plant kingdom! Overall the germination phase of malting can take anywhere between 4 and 7 days depending upon what the maltster is trying to make.

During the process of germination the grain is converting its stored energy reserves, starch, into simple sugars which it utilises for energy to grow into a new plant. Thus the germination phase of malting can be described as a process of watching grass grow and no matter how dynamic and exciting I might try and make it sound that is essentially what is occurring.

As has already been mentioned malting is just a process of controlling the germination of the barley grain and during the active germination phase the maltster can do this by controlling the temperature that the grain is germinating at, the moisture content of the grain and the airflow through the grain.

Germination is a very active state for any seed and a number of biochemical reactions occur as the seed grows into a plant. All these reactions generate heat and therefore the temperature of the seed, or in this case the barley grain, can increase dramatically. In a traditional floor maltings the temperature of the grain is controlled by spreading the grain in a thin layer on a cooling stone or slate floor. Because the layer of the grain is very thin and is sitting on a stone floor the heat that is generated by the germinating grain is easily dissipated. However in a modern maltings where the tonnage of grain being processed is significantly higher the depth of the grain bed is much deeper.

To give you an idea of the difference, in a traditional floor maltings the depth of the grain can be up to 30 cm, in a modern maltings the grain bed depth can be up to 1.5 m deep! In this type of environment the temperature of the grain bed can rapidly increase from the ideal of 18 - 20ºC to 25 - 30ºC. If it does so this can severely impact on the germination process and in some cases stop germination altogether. To control this, the germination vessel is designed to have a perforated floor so that cool humidified air can be pumped through the grain bed to keep the grain cool and moist. The other reason for pumping air through the grain is that as the grain germinates it produces carbon dioxide. If the carbon dioxide is left to build up it can also stop germination and so by pumping air through the grain the carbon dioxide is removed, along with the heat, from the grain bed.

During germination the grain grows roots and shoots as it starts to develop into a barley plant. These roots and shoots will intertwine and can therefore link together to form a solid mat of germinating grain. This is not ideal so during germination the maltster has to make sure that they turn the grain regularly. In a traditional floor maltings this job is done by a man physically turning the grain with a malting fork and rake. A very hard and physically demanding job. In a modern maltings this is done by mechanical turners. Trust me moving 250 tonnes of germinating grain by hand is not something you would want to do.

As the grain germinates a number of enzymes are synthesised and these start to penetrate into the starchy endosperm of the grain. The enzymes start to degrade the cellular structure of the endosperm to reveal the starch granules. If the grain was allowed to grow into a barley plant the enzymes would break the starch down into simple sugars and these would be utilised in plant growth. However, this would not be good for the brewer as they want the sugar so that they can convert it into alcohol in their brewery. Therefore the maltster has to carefully control germination so that the enzymes are synthesised and the early stages of cellular breakdown are initiated but the all important starch granules are left relatively untouched. In fact the maltster is measured by the brewer on how well they do this. If the extract potential, that is the level of fermentable sugars that can be extracted from the grain, is low the brewer will penalise the maltster.

There are a number of methods by which the maltster assess how well they have controlled the germination process. One of the key measures is something known as malting loss. Malting loss is what is lost during the malting process as a whole, but much of it can be controlled during germination. It is used as a measure of yield and it can be quite surprisingly high. For a brewer the roots and shoots that grow during germination are of no use, and are actually bad for beer quality, so will be removed at the end of the malting process. They are therefore counted as a loss. The carbon dioxide produced by the grain during steeping and germination is essentially a loss.

Poor handling during the process can also lead to physical loss of grain from the process. If all these causes of grain loss are added up then the malting loss can be quite large and a maltster will try to limit this to no more than 15%. That is for every 100 tonnes of grain going into the process up to 15 tonnes can be lost, that is quite a significant number if you consider how much grain costs to buy! However, this number can also been seen as a quality consideration as well. For example if the malting loss is very low then it can be suggested that the grain has not germinated very well and so the quality will be poor. For the maltster the malting loss is therefore a compromise between minimising the loss of grain and maintaining quality.

Germination is a very complex stage of the process and the skill of the maltster is in judging the correct time to stop and move into the next stage known as kilning, which we will consider in the next article.

Daniel Cooper gained his degree and Ph.D in brewing science and has 15 years of research and production experience in the brewing and malting industries. He has published work in both trade and scientific journals as well as writing about brewing science for a number of consumer magazines. More of his work can be found at http://www.homebrewtechniques.co.uk

Source: EzineArticles
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