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​33. Carbon dioxide solubility in wort and beer

Alex R Speers, Dalhousie University, Halifax, N.S., Canada

 

ABSTRACT: Carbon dioxide (CO₂) is a key component of beer; however, the amount of CO₂ within beer is dramatically affected by temperature and pressure. The CO₂ level in a beer is dependent on CO₂ solubility, which in turn is affected by temperature, containing pressure, and beer composition. There is a substantial gap in the literature as to how substances in wort and beer affect CO₂ solubility. In fact, the origin of various pressure-temperature solubility charts contained in ASBC’s Methods of Analysis or MBAA’s Beer Packaging: A Manual for the Brewing and Beverage Industries are largely unknown and poorly referenced. This is especially problematic as there are discrepancies between the most commonly used charts, and explanations for these differences are not readily apparent. This presentation details the findings of an exhaustive literature search through electronic and pre-electronic cited literature. The methods used to create these charts will be discussed, including the assumptions reported by the original authors. ASBC and MBAA solubility charts and those generated by simple formulas will be compared to each other and to the van ‘t Hoff equation, which describes how gas solubility is affected by temperature. The influence of other variables unaccounted for in the aforementioned solubility charts will be reported. Specifically, the effect of ethanol (0–8.3 g/100 g) and solids (0–13 g/100 g) on Henry’s constant in water, model worts, and beers will be presented. Reports concerning CO₂ solubility made outside of the brewing literature and their applicability will be noted. Finally, measurements in our laboratory concerning the time at which freshly fermenting wort reaches CO₂ saturation will be compared to predictions based on measured sugar, alcohol, pressure, and temperature levels.

 

Alex Speers is a professor in the Food Science program at Dalhousie University, Halifax, NS, Canada. Born in Creston, BC, he gained B.S. (Agr.), M.S., and Ph.D. degrees in food science at UBC. At “Dal” he instructs students in brewing science, quality assurance, and product development. In the past, Alex has been employed in the Quality Assurance departments of both Labatt and Molson Breweries. His current research interests include various aspects of the brewing process, including fermentability, yeast flocculation, fermentation modeling, extract calculations, and the properties of (and problems created by) beta-glucan and arabinoxylan polymers. He has organized and/or presented brewing workshops in Australia, China, America, and Canada. Alex also organized the International Brewers Symposium: Yeast Flocculation, Vitality, & Viability in Boston, MA, in 2009 sponsored by MBAA. Alex has spent sabbaticals at CUB/Fosters in Melbourne and the Columbia Brewing Company in Creston. He is a past chair of Editorial Board of the MBAA Technical Quarterly. Alex belongs to several professional societies and is a member of the editorial boards of Food Research International, JASBC, JIB, and the TQ. He has published or presented more than 150 papers and edited and was recently named a Fellow of the Institute of Brewing and Distilling and awarded the W.J. Eva Award by the Canadian Institute of Food Science and Technology.