IMPROVED SHELF LIFE AND QUALITY

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-Measurements for the brewing industry

We know that improper amounts of oxygen present in various stages of the brewing process will greatly affect the final taste. Accurate oxygen analysis allows the brewer to control the process so that the shelf life of beer can greatly be extended. A brief review of where to measureoxygen is provided in this article, followed by some helpful information on how to best make oxygen measurements in-line, in-package and whilst using portable analysers. Finally, some technicaldetails are provided explaining the benefits of using electrochemical sensors for oxygen measurements.Understanding of the importance of oxygen measurements at each step of the brewing process and how to best apply various solutions for making measurements will lead to improved oxygen measurements in the brewery.

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xygen is of interest to the brewer for at least threereasons. Firstly,the character of beer (clarity, colour, odour and taste) is partly determined by the quantity of oxygen available to the yeast during fermentation. Secondly,the beer produced is subject to oxidation and therefore should be protected from the atmospherethroughout processing and in the package. Thirdly, aluminum can manufacturers specify upper limits on the concentration of air in canned beverages due to a risk of corrosive attack from oxygen. Expert tasting panels can easilyrecognise beers which have been oxidised. Noticeable changes take place within two hours after packaging when dissolved oxygen is too high. Physically the changes areaccompanied by a decrease in colour type (the beer becomes reddish) and chemically by adecrease in sulphur dioxide, an increase in diacetyl, and an increase in acetaldehyde. These aresufficient reasons to make the control of dissolved oxygen levels of prime importance in the brewery.The most detectable off-flavour that arises from oxidation is a “cardboard” or “wet paper” taste produced by the reaction of polyphenols. Careful beer handling in the brewery can result in packaged dissolved oxygen values of less than 100 ppb. At this level the shelf life will be greatly extended.It is critical to accurately controloxygen levels at various steps in the production process since improper amounts of that might be present will greatly affect the taste of the final product. Furthermore, oxidation is an additive process so all steps from fermentation to the final package must be taken into account to maximise the beer’s shelf life and taste. Table 1 shows the expected oxygen levels throughout the brewing process.It is not enough to simply knowthat oxygen measurements are important. It is critical to ensure that correct measurements aremade using in-line, portable orlaboratorybased analysers. In addition, a clear understanding of the benefits of electrochemical oxygen sensor technology Chris Klein
Beverage Market Manager, started withHach Ultra in 1998 as a Regional Sales Manager in the USA. In 2000 he was promoted to Key Account Manager for Soft Drinks and Bottled Water in the Americas. Since 2005 he has been the Beverage Market Manager and currently works at Hach Ultra’s global headquarters in Geneva, Switzerland. Contact: cklein@hachultra.com Picture 1: Orbisphere 3650 Portable Oxygen Analyser. Frank A. Dunand
Dunand has been the author of 15 technical papers in the analytical chemistry field beforejoining ORBISPHERE in 2002. He currently holds a position as Senior Product Manager at Hach Ultra heading ateam managing all ORBISPHERE andPOLYMETRON products. Contact: fdunand@hachultra.com

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·BBII1/2008