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Beer Carbonation
Principles of Carbonation
The time required to reach a desired carbon dioxide concentration depends on a number of physical factors. Temperature and pressure play an important role in determining the equilibrium concentration of carbon dioxide in solution. At equilibrium the same amount of carbon dioxide is diffusing out of the beer as is being dissolved back into solution. Increasing the pressure leads to a linear increase in the weight of carbon dioxide dissolving in the beer or water. Decreasing the temperature gives a nonlinear increase in carbon dioxide solubility in beer. Consequently, the equilibrium concentration cannot be attained without either increasing the pressure or decreasing the temperature. Thus, the closer the carbonating temperature is to 0ºC and the higher the pressure, the greater the carbon dioxide absorption.
The relationship between pressure, temperature, and carbon dioxide volumes is given in Appendix B. Fixing the temperature and pressure at appropriate settings will bring about the desired carbon dioxide concentration. For example, at 0ºC, beer containing 2.5 volumes of carbon dioxide will have a pressure of 9 psi; whereas at 16ºC, the pressure increases to 21 psi. The amount of carbon dioxide that dissolves is a function of time, with the rate decreasing exponentially as equilibrium is approached.
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