Removal of volatiles from beer by gas (N2) stripping coupled with high-vacuum

Engineering Session
Luis F Castro, Washington State University
Co-author(s): Carolyn Ross, Washington State University, USA

ABSTRACT: In order to study flavors and their interactions, these volatile compounds often need to be removed from their matrix. The removal of volatile compounds from complex beverage matrices like beer remains a challenge, due to the difficulty of separating these compounds from the non-volatile beverage matrix without altering their properties. The aim of this study was to develop a novel method for the removal of volatile compounds from beer. The new technique, designated nitrogen gas stripping coupled with high vacuum (NSHV), applies a vacuum to the beer sample while using forced gas (nitrogen) stripping without the application of heat. Application of NSHV to beer samples spiked with known amounts of selected volatile compounds commonly isolated from beer (ethanol, isoamyl acetate, ethyl hexanoate, myrcene, benzaldehyde) resulted in higher reduction percentages for each compound when compared to commonly used rotary evaporation. Four of the five volatile compounds studied showed >85% concentration reduction following 90 min of treatment by NSHV compared to only one compound (myrcene) showing a >70% reduction using the rotary evaporation technique. The new method was demonstrated to be a promising method for volatile compound removal from beer samples and possibly other liquid samples as well.

Luis Castro received a B.S. degree in chemistry from the University of Costa Rica in San Jose, Costa Rica. After two years of working in both industry and academia, he moved to the Washington State University, School of Food Science, to pursue graduate studies. After obtaining his M.S. degree in food science under Barbara Rasco working in the field of food safety, he enrolled in the Ph.D. program at the same institution working with Carolyn Ross. It was here that he started research on the impact of beer matrix components and their interactions on the sensory perception of beer. He is currently a research assistant in the sensory laboratory at Washington State University and is working on his dissertation to obtain a Ph.D. degree in food science.