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Oxygen Measurements in Breweries
Oxygen, and more importantly the absence of oxygen is critical during beer brewing and the filling process. Reliable O2 sensors can conserve resources and make a difference in beer quality.
The yeast that turns the sugar in the wort to alcohol and CO2 needs oxygen to grow. This is why oxygen is added during the brewing process when the wort is transferred to the fermenter and the yeast is added. The oxygen content is usually regulated to values of 6 – 8 ppm. After fermentation however, there are only traces of oxygen left in the beer.
Oxygen in the final product can negatively affect the beer’s flavor stability and shorten its shelf life. This is why in all the following process steps up to the filling into bottles the uptake of oxygen must be avoided. This is usually achieved by purging tanks, pipes, and the bottles the beer will be filled in with gas, CO2 or nitrogen, to create an oxygen free environment. In the final product the dissolved oxygen content should be as low as 0.0 – 0.5 ppm.
Especially during the filling process there is a high risk that oxygen is taken up. Therefore, in bottling plants sampling is conducted to test bottles for the dissolved oxygen content in the beer or gaseous oxygen in the headspace.
Even before the brewing process oxygen plays a vital role in the propagation of the yeasts used later for fermentation. Breweries grow and then store the yeasts until it is needed. To ensure reliable and reproducible quality of the yeasts the propagation process must be closely monitored. Oxygen probes are used to measure and control the aeration in the propagation tanks and in the exhaust air.
Want to know more about oxygen measurements in yeast propagation at brewery scale?
Like in yeast propagation the aeration level in the fermenter – when the wort is inoculated with the yeast – must be closely monitored and controlled, to ensure proper yeast growth and avoid unnecessary use of resources.
After fermentation the in-line measurement of oxygen traces with trace oxygen probes in the product as well as in the purged tanks can ensure an oxygen-free production process and guarantee the highest product quality.
In the bottling plant non-invasive optical oxygen sensors offer a convenient method for quality control. Sensor spots can be integrated in sampling bottles and then sent through the bottling system. Afterward, the oxygen content in the filled and capped bottle - in the product as well as headspace - can be measured through the bottle wall, without having to pierce the lid and have the risk of introducing atmospheric oxygen. These simple, straightforward oxygen measurements can indicate if a readjustment in the gas amount for bottle purging is necessary.
Even though it is not so common, beer sometimes is also filled in PET bottles. In plastic bottles, the oxygen permeation through the bottle material over time must also be considered. PreSens has developed a special system with sensor caps containing oxygen sensors, that allow analyzing the oxygen uptake over longer time periods.
In-line O2 Measurements with OXYPro®
The OXYPro® series steel probes are available for different measurement ranges and therefore perfectly suited for in-line monitoring at different stages in the brewing process, from yeast propagation to the filling plant tanks. The probes are directly connected to the control unit, have a standard PG 13.5 thread and can easily be integrated in Varivent valves with an adapter. They stand CIP and SIP and are almost maintenance free.
Testing Product and Headspace O2 with Oxygen Sensor Spots
Oxygen sensor spots for non-invasive measurements can be integrated at different heights in bottles before filling and closing. The spots can then be read out from the outside, and it is possible to determine the oxygen content in the product and the headspace quickly and easily. PreSens offers small benchtop oxygen meters that can be set-up everywhere or portable, completely stand-alone devices, if you choose to be more flexible.
Watch our video on sensor spot integration in bottles:
Oxygen Permeation Measurements in PET Bottles
PreSens non-invasive sensor spots and oxygen-sensitive caps can be used to conduct long-term measurements to determine oxygen permeation in PET bottles.