P-4
Results of field analysis of carbon dioxide quality in retail dispense
Presenter: Chris Duffell, Domnick Hunter Ltd., Gateshead, United Kingdom

Carbon dioxide (CO(2)) is used in the beverage industry for brewing, carbonation, packaging and dispense. In recent years there has been increased awareness of the importance of CO(2) quality and its effects on beverage products, particularly in retail dispense where the drink's manufacturer has little or no control over CO(2) quality. Carbon dioxide should be considered as an ingredient and hence needs strict quality guidelines to protect the customer from flavor and appearance defects or physiological detriment. Also the scale of the problem needs to be quantified. Quality guidelines for CO(2) used in the beverage industry are published by bodies such as the International Society of Beverage Technologists (ISBT) and European Industrial Gas Association (EIGA). These guidelines are intended to offer protection against naturally occurring CO(2) impurities that could result in flavor defects of the beverage. Contaminants may also affect the appearance of the foam head and hence presentation of the beer. Impurities are also controlled by regulation for the prevention of physiological detriment. In-line purifiers have been designed which act as a final multi-layer barrier filter against trace impurities in a CO(2) gas supply. In addition, in-line purifiers also help protect beverage quality by removing trace contaminants that may have been introduced inadvertently during the storage and distribution of the gas from its source to the point of use. The performance of these purifiers has already been verified by introducing contamination to beverage grade CO(2) to provide an inlet challenge in excess of the ISBT specification. The data presented shows that removal of typical contaminants including aromatic hydrocarbons and sulfur-containing compounds can be achieved by the multi-stage purifier. These results were all verified by an independent third party. The unit cannot adsorb lighter compounds with fewer than three carbon atoms (corresponding to contaminants with molecular weight below approximately 30 g), as they are too small. This paper presents findings of carbon dioxide quality obtained from cylinders and bulk tanks in use in the field. Data are presented from field trials where a carbon dioxide purifier has been used in real-life installations for a number of months and then desorbed to check the quality of the CO(2) processed. Filter elements from production plants have also been analyzed as a comparison between large-scale and retail dispense gas quality. In summary, it has been shown that carbon dioxide contamination is evident in the real world and that guidelines should be adopted, perhaps even adapted into a standard, to ensure quality of one of the major ingredients.

Chris Duffell completed his masters degree in astrophysics from Cardiff University in 1997. He then began employment at the National Engineering Laboratory in Scotland as a project engineer researching fluid dynamics for the oil and gas industry. Chris achieved chartered physicist status from the Institute of Physics in 2000. He then joined Strathclyde University to continue his research into flowmeter development. His Ph.D. project was entitled "Application of optimization techniques to the design of ultrasonic transit-time flowmeters." Upon completion of his Ph.D., Chris began employment with domnick hunter ltd, in Newcastle, as senior development engineer in the filtration division. His work now involves product verification and development. The Science Council awarded Chris chartered scientist status in July 2004.