Beer Brewing

Home Malting
Building a Malting Machine
Kiln Drying

Beer brewing has been a hobby for years. My brother and I have checked out different approaches to beer brewing, including home-malting and a semi-automatic brewing installation. In 2001 I founded the AMIV BRÄU , a student brewery for the students union (AMIV) at ETH Zürich.

Home brewing - from scratch

Home Malting

In our effort to brew the all-selfmade beer, we have started out making malt from barley. We checked out different methods using pots, nets, bags, fruit dryers, a hairdryer - just to conclude that malting is a delicate business. We found that if a malting process is to be reproducible, parameters like humidity, temperatures and time spans must be tightly controlled. This lead to the construction of a malting machine and a 'kiln dryer'.

Malting requires the following steps:

Two-row barley of seed-quality is soaked in water for roughly four hours. This lets the grains swell and they start to grow.
Next the water is removed and for 20 hours, the heap is regularly turned so that the temperature distribution remains even.
The first two steps are repeated for about four days, until the grains reach a certain water content.
For another three days the barley grows until radices of a grain-length are formed.
The last step is kiln drying. Here, the grains are dried for roughly 20 hours at a high air flow rate, according to a specific temperature profile. Low temperatures at the beginning dry the grains and stop the growing process. Temperatures up to 100 degrees Celcius towards the end lead to a light roasting.

The reason why barley is malted is that enzymes are built during the growing process. These enzyms (mainly alpha- and beta-amylase) help cutting starch into simpler sugar molecules during the mashing. Sugar, as opposed to starch, can be fermented by yeast.

A machine for the boring task

As soaking, drying and turning the grains for several days is boring and prone to forgetting, we constructed a machine that does the job. A plastic barrel holds the grains. Holes allow the water to enter and leave the barrel. A motor lets the drum rotate at a slow speed, so the grains are turned at regular intervals. The water level is controlled by electric valves. A floater switch serves as an 'emergency shut-off' for the water to avoid floods and alike. The machine is controlled by a PIC microcontroller with an LCD display. The software allows to adjust the timing of the process.
The machine is filled with barley and when started, works on its own for a week.

raw barley is filled into the drum

reloading the machine

The machine gets refilled with raw barley

malting machine

malting machine

The machine during a soaking period

malt machine controller

barley after soaking for a week

Left: This box contains a PIC microcontroller and controls the motor and the water valves
Right: Barley grains after a week of soaking and germination

Kiln drying

A typical drying profile starts with a high air flow at roughly 30 degrees Celsius. The temperature slowly rises to 50 degrees after 15 hours. After that a faster increase leads to around 80 degrees. The last four hours are usually at the roasting temperature around 80-110 degrees, depending on the required type of malt.
To get a reproducible malt quality, temperatures must be tighly controlled. Our installation uses an old electric oven that is controlled by a PC software that implements a PID controller. Temperatures are measured with a calibrated PT100 element. The airflow is guaranteed by a vent.

roasted barley

screen shot of the oven controller software

Left: The barley is put into the oven for kiln drying
Right: A PC software controls the temperature curve of the oven. The temperatures are kept within +- 1 degree Celsius of their goal value

malting oven

malting oven - finished

Left: The oven in action. The barley is kept on three hordes made from metal meshes
Right: Roasted barley after the temperature profile is completed

After the roasting, the radices of the grains must be removed. This is done mechanically in a metal box where the grain is spinned quickly by an electrical drill and a paint stirrer.

brew-ready malt

brew-ready malt

Finished malt, after the dry radices have been removed