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​​​The Theory and Effect of Positive and Negative Pressure on Brewing Fermentations: Pressure Effects on Beer Fermentation​​

Karen Fortmann (1), Chris White (1), Mario Guadalupe (2), Paul Sarnoski (2), and Andrew J. MacIntosh (2). 1. White Labs, Inc., San Diego, CA 92126, U.S.A. 2. Food Science and Human Nutrition Department, University of Florida, Gainesville, FL 32611, U.S.A.​

 

Abstract
 

During yeast fermentation there are many parameters that affect both yeast growth and metabolism. Manipulation of fermentation parameters including yeast strain, fermentation temperature, nutrient content, and oxygen levels allows brewers to control different fermentation attributes, including the process rate and the synthesis of volatile compounds. An additional often overlooked parameter that can be used to control volatile production is headspace pressure (either as a pressurized or reduced pressure fermentation). This paper examines how manipulation of the headspace pressure results in a variation of the CO₂ concentration and how this can be used to influence both the production of flavor compounds and the fermentation rate. The difference in volatile production was experimentally assessed between fermentations conducted at high and low CO₂ concentrations. The formation of specific volatiles was negatively correlated with the presence of CO₂ (most strongly: acetate esters and isoamyl alcohol). The practical applications of pressure control in the context of modern brewing systems are discussed, as well as historical perspective and specific applications. ​