Malting Processes

What is Malt?

Malted barley, or 'Malt' as it's 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.

Barley

Perhaps the most important stage of malting is barley procurement. Bairds Malt procures more than 85% of its malting barley at harvest time.
Only malting grade barley is purchased. It is very carefully inspected on intake, dried in our own driers and segregated by variety.
Barley storage conditions are very carefully controlled and monitored and the barley is only released for malting when it has reached its optimum vigour.

Steeping

Steeping is the first stage of the true malting process and takes 2-3 days in total.

This is achieved by a series of immersions or 'wet stands' followed by 'dry stands' and this part of the process is carried out in steep tanks. During the wet stands, the water is aerated to rouse the grain. During the dry stands, air is drawn through the wet grain to keep to keep control of grain temperatures and to remove carbon dioxide. 

The moisture content of the barley is raised from typically 12% to 42-46%.

Steeping is a crucial phase of the malting process and by the end of steeping all the grains should be fully hydrated and should be just beginning to show signs of germination by the formation of tiny rootlets or 'chits'.

Germination

The Germination phase is the 'control' phase of malting. Germination continues for a further 3-5 days depending on the product type being made.

The germinating grain bed is oxygenated by providing a constant flow of humidified air. By controlling the airflow and grain moisture the maltster can control the rate of grain development and in turn meet key aspects of a customer's specification.  

The grain is turned regularly to prevent rootlets matting and to maintain a loosely packed grain bed.


 

Kilning

Kilning, the third phase of malting, dries the grain down to 3-6% moisture. This arrests the biochemical processes occurring within the grain during germination and ensures a safe moisture content for storage.

Large volumes of hot air are blown through the grain bed to dry the grain while a predetermined temperature profile is applied. By varying air flow and the temperature profile, malts of different colours can be produced with varying flavour profiles.

At the end of kilning the malt is cooled and the tiny rootlets or culm removed before analysis and storage. The final malt is analysed extensively according to malt type and customer profile.

The malt may be despatched in bulk, bags or in containers.

Peating

Peated malt is produced from conventional 2-row spring pot still malt which has peat reek introduced for several days during the kilning stage. Historically, this would have taken place as peat would have been burned to fire the kilns in parts of Scotland. The malts produced today have characteristic peaty flavours and aromas originating from the phenolic compounds imparted by the peat reek.

The malting boxes are germinated as normal until close to full modification is reached. The boxes are then kilned close to the break point before peat is added to a peat fire where it is lit and the peat encouraged to smoulder. The smoke or reek is passed through the malt bed transferring phenolic compound onto the malt. The peat fire is burned for up to 60 hours and once the fire is burned down the box is returned to the kilning phase to be dried down to approximately 4% moisture.

Roasting

Roasting is done in 4 distinct stages: steeping, germinating, roasting and cooling. At Bairds 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 colour and flavour compounds. The malt is analysed before storage and thereafter awaits dispatch to our customers.