How malt is made

 

Malting is the controlled germination of cereals, followed by a termination of this natural process by the application of heat. Further heat is then applied to 'cure' the grain and produce the required flavour and colour. A basic rule is that for malt to be made, the barley must be capable of germination, so maltsters source their barley with a minimum germination of 98%.

Barley image 1 before steeping

Barley image 2 after steeping with the root chit just showing.

Barley image 3 with germination almost completed, showing the green malt with its longer root growth.

A simple way to consider it is that a barley kernel is composed of three parts:

Dorsal

Cross section through a barley grain, with the embryo stained red by tetrazolium dye, showing that it is capable of full germination.

a) The embryo, or germ, which will eventually grow into the roots and shoots of the new plant.

b) The endosperm, comprising of hard insoluble starch, which is the food reserve to be used by the growing germ of the grain. Once hydrated, the embryo causes enzymes to be produced that break down the cell walls in the endosperm, releasing starch granules for subsequent breakdown during the brewing process. This change is called the "modification" of the barley corn. The process must be controlled by the maltster, otherwise the enzymic conversion will continue, and the soluble stach will be further converted to sugars, to feed the growing barley plant. This must be avoided, to prevent loss of useful brewing extract.

c) The husk, formed by two overlapping halves, which cover the grain surface, to protect the germ and endosperm.

The maltster's task is to get the endosperm modification to a certain point, and then stop the process, "locking it up" by the use of heat. The brewer will then "unlock" the process when he mashes his milled malt, and completes the conversion to sugars which will feed the yeast to produce alcohol, whilst other characteristics in the malt produce strong contributions to the quality of the final beer.

It is very likely that malting, as part of a brewing operation, was the first use of biotechnology by man. The development of brewing cannot be factually dated, but it is likely that the earliest process was the fermentation of raw grain, an accidental discovery. The next discovery was likely to have been the use of bread to produce a fermentable drink. Dr Briggs in "Malts and Malting" cites a Sumerian reference to kilning malt for brewing, which has been dated to around 2500 BC. We can therefore be reasonable sure that some form of malting was in use four thousand five hundred years ago, and that the basic process is relatively unchanged.

Although the use of the natural process of change within the grain, which is the basis of malting, has a very long history, only in the last fifty years have maltsters gradually taken complete control.

That change has been brought about by the breeding and selection of the barleys best suited to produce malt, the knowledge of the physical and chemical changes that take place during the malting process, and the development of techniques for their most effective control.

The modern maltster is able to source the correct malting barley, and with a skilful use of water, air, heat and time can produce a wide range of malts which can differ in flavour, colour and many other parameters as specified by the maltster's customer.

In the UK most of the grain used for malting is barley, but a small quantity of wheat is also malted for specific purposes. For the purpose of this explanatory note all references will be to the malting of barley.

In the UK the significant stages of a maltsters' operations can be identified as follows:

1)Intake of the grain from the grower to the maltsters' facilities, after a careful evaluation of each load.

2)Prompt drying of the intake grain to a safe storage moisture, of below 14%.

3)Storage of the dried grain, for at least a sufficient length of time to allow it to overcome, after drying, the natural condition of germ dormancy, (perhaps six weeks plus).

4)Screening of the barley to produce an even size corn, and to remove dust etc.

A Steep filling with grain.
5) Two or three immersions under water (or 'steeping') of the evenly sized grain, followed by drainage of the water, and a rest in air, to take place over a period of two to three days. This simple process is where the Maltster's skill comes into play. The correct combinations of water/air/water/etc must be given to result in the moisture content of the grain being raised to the required level of around 46%, and without 'drowning' it! At around 35% moisture content the embryo within each kernel of barley will start to germinate, but this is insufficient moisture to allow the complete modification of the starchy endosperm that the maltster desires. The starch content of the original dry grain is about 80% of its weight.

6) The germination process commences during the air rests towards the end of

             Saladin Box with germination underway
Germination underway in a Saladin Box
IMAGE LOADING
A loaded Germination Vessel which also is a kiln.

the steeping stage, and when the moisture is raised to the figure the maltster has predetermined, the steeped grain is transferred to a germination vessel. In traditional maltings this was the 'germination floor', where the grain was turned by shovel to prevent heat build up. Modern maltings use a range of vessel designs, which allow air to be blown through the grain bed from the underside. Often the air is humidified to help with temperature control, and to ensure that the grain does not dry out. The modern vessels will also incorporate a gentle mechanical turner, to keep the germinating grain loose, which at this point is called 'green malt'. This stage of the process can last between four to six days, depending on the final malt type. Once sufficient enzymes have been produced within the grain to allow breakdown of the cell walls of the starch and its modification, but before the endosperm can be converted into a food source for the awakening roots and shoot that will form the new barley plant, the maltster stops the modification by applying heat.

 

Empty Germination Vessel showing turners.

 

A Kiln being Loaded.

7)The Kiln is where the modified green malt is transferred to, when the maltster considers the process of germination should be terminated. In the past this decision would have been taken whenever the malt was ready, but in modern malting regimes these cycles are predetermined, and the great skill of the maltster is correctly steeping the barley, so that it always is ready to load to kiln at the correct cycle time.

On the kiln the malt is first dried, and then 'cured', the latter taking place at a higher temperature, which stops all changes within the grain. Kilning is a complex procedure, which only uses variable combinations of air-flow and heat, but under very tight control. The temperature/air flow profile varies depending on the malt being made, and would be quite different, for example, for a lager malt compared to an ale malt. Kilning is still a high energy user. Historically, in traditional floor maltings with no energy saving devices, it could take as much energy to make a tonne of malt as it took to make a tonne of steel! Modern malting plant technology has reduced that to less than half.

The maltster's kilning expertise produces the final components that have been specified by the customer, the simplest of which is the colour of the malt.

The kilned product is now called malt, and is now in a stable form,

IMAGE LOADING
The Finished Kiln.

with a moisture content of between 3% to 6%, dependent on its use. However, it cannot be used straight from the kiln.

8)Malt from the kiln is put through a machine known as a deculmer, to remove the 'culm' or small rootlets that have emerged from each kernel during germination. Malt culm is a co-product for the maltster, which can be sold as an animal feed, as it has a higher protein content by weight than the original barley.

9)The malt is then put into store for a specified period before being screened and then sent to the customer.

UK maltsters have spent considerable time and effort in ensuring that their malt production is carried out to a very high standard, which is auditable. The world's first malt assurance scheme, Assured UK Malt, is detailed on this website click here for more details.

Risk analysis is well understood, and the MAGB has drawn up a Hazard Analysis Critical Control Code of Practice Click here to load an Adobe Acrobat version of the guide

A glimpse of some of the changes in malting technology...Click Here to see both a traditional floor and a modern tower maltings

Back to the top