As we have seen in the previous articles in this series malt is produced from barley when the correct environmental conditions are provided so that the barley grain germinates. The job of the maltster is to control this germination in such a way that they deliver a package of starch and enzymes that the brewer needs to make their beer. If the germination is allowed to continue for too long too much of the starch will be utilised by the grain as an energy source to grow roots and shoots leaving the brewer with insufficient starch to make their beer. The malting process is therefore designed to control the germination of barley and this is done in three distinct phases which are:
We will look at the steeping process in more detail in this article. Barley is typically stored before malting at a moisture content of below 12% and at this level it will not germinate. The aim of the steeping process is to increase the moisture content of the grain from this low level to around 44 – 46% moisture, a level at which the grain will start to germinate. The maltster will aim to raise the moisture content as quickly as possible but without damaging the grains potential to germinate. It is very easy to over steep the grain in which case the grain can be viewed as being waterlogged and germination will stop. To prevent over steeping the maltster pays close attention to the rate at which the grain takes up water and will design a steeping programme accordingly.
Steeping is typically carried out using a discontinuous steeping process, which is where the grain is subjected to a series of what is known as wet covers and air rests. The first wet cover is where the grain is completely submerged in water for a fixed period of time, up to 10 – 12 hours. During this time the maltster will pump air into the steeping vessel to oxygenate the water. Once the first wet cover is complete the water will be drained from the steeping vessel and the grain is allowed to rest. As the grain starts to germinate it will produce carbon dioxide (CO2), which if allowed to build-up will stop germination so during this period air is again blown through the steeping vessel to remove the CO2. These two phases are known as the wet cover and air rest and this cycle is repeated two to three times during steeping so that by the end of the process the moisture content of the grain will have hit the required level for germination to have started. When the grain germinates the embryo becomes metabolically active and produces a hormone called gibberellic acid. The gibberellic acid migrates from the embryo into a layer of cells that surrounds the starchy endosperm. These cells, known as the aluerone layer, react to the presence of the gibberellic acid and start to produce the enzymes that will breakdown the endosperm.
Steeping can take up to 2 days, and by the end, the grain should have started to germinate. The sign that the grain is actively germinating is demonstrated by the grain chitting. Chitting is the name given to the formation of the rootlets. At this point the maltster will deem that steeping is complete and the actively germinating grain will be transferred to the germination vessel, which will be the focus of the next article in this series.
For earlier articles in this series click the links below: