Application Note: In-Line Dissolved Oxygen Measurement In Bright (Finished) Beer

After fermentation, rough (green) beer containing less than 10 ppb of dissolved oxygen is transferred to conditioning (aging) tanks. This allows the yeast to separate from the beer under the influence of gravity. Following aging, the beer is centrifuged, filtered, and blended before transfer to bright beer tanks. During this processing, the brewer must make every effort to exclude air, which can cause distinctive off flavors and reduced shelf life in the finished product.

Sources of air in-leakage can include leaking pump glands, worn seals, empty filter aid dosing tanks, and transfer lines and tanks not cleared of air. Older centrifuges can allow air ingress with bowl discharge if not sealed or inerted properly. Filter aid dosing pumps will inject air if the tanks inadvertently run dry. Blending water, used in high gravity brewing, must be maintained at low dissolved oxygen (DO2) concentrations to avoid an overall DO2 increase in the bright beer.

Dissolved oxygen sensors installed in-line after the centrifuge and filter, and before the filler will provide the brewer with a base level of DO2 measurement coverage. However, depending upon air in-leakage concerns, sensors can be installed at virtually any point in the process.

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