Properties of beer (part 1)

As a masters student in industrial engineering at the university of Ghent I follow the course ‘Brewery technology’. After being lectured every week about the brewing process and the necessary calculations I finally got to put my acquired knowledge to the test.
I got assigned a ‘brewing day’ in which I had to performed tests on one of my favourite beers ‘Grimbergen Gold’ while maintaining the brewing process of the local beer ‘Bijloke’, brewed exclusively at the University of Ghent.


Production of Bijloke at UGent (background)

In the next blog posts I’ll explain the fundamental tests to determine the properties of beer. These tests determine the amount of Carbon Dioxide, Oxygen, alcohol percentage, living yeast cells, foam stability, bitterness and turbidity. The properties of all factory bottled beers are already precisely determined, therefore these can serve as a reference to compare with my personally found values. In reality these tests are obviously not performed on every bottle. As the entire industrial process is so precisely controlled there’s barely a chance that the pre-determined values would differ. If on the other hand the brewer decides to change the recipe or brew a new type of beer, these tests become very fundamental to know whether they’re on the right track.


Henry’s law: the higher the pressure above the liquid the more dissolved gas in solution

An important test is to determine the amount of CO2. Carbon dioxide gives beer its fizzy properties as it does in all carbonated drinks. The principle of this test is to determine the pressure in the bottle of beer according to Henry’s Law. Henry’s Law states that the concentration of dissolved gas in a liquid is proportional to the pressure in the gas in equilibrium with that liquid. This basically means that the concentration of a gas (here CO2) in the beer is proportional with the pressure of the head volume in the bottle. How higher the pressure in the gas above a liquid, the more gas is dissolved in the liquid. To perform this test, the bottle is shaken thoroughly and the maximum pressure of the gas is measured with a manometer. All this pressurized gas is then drained through a tube and into a column with a specific liquid in it. The amount of CO2 gas can then be calculated through a complex formula depending on the amount of liquid that is pushed away by the gas volume.



Henry’s Law: In a bottle or can, depending on the pressure, CO2 is dissolved in the liquid. When opening a can the pressure in the can disappears allowing the gas to escape from the liquid, making the well know “psshh” sound.

The life of a scientist isn’t always that bad as technology keeps evolving every day and allows automation for almost everything these days. It makes difficult tasks as easy as pressing a button. That is to be taken quite literally as determining the amount of oxygen in the beer only required punching a hole through the bottle cap and let the machine do its work by pressing ‘start’.

Be sure to follow up on the next blog posts for more laboratory beer tests, cheers!
~Blanckey the Brewer


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