Presenter: Gustavo Charry, MillerCoor, Milwaukee, WI. Coauthor(s): Maritza DeJesus-Echevarria and Fernando Perez, University of Puerto Rico-Mayaguez Campus, Mayaguez, Puerto Rico.
Volatile compounds such as higher alcohols, esters, and aldehydes are formed by the yeast, as by-products of their metabolism, during the beer fermentation process. The most widely used technique for the identification of volatile compounds is gas chromatography–mass spectrometry (GC/MS) and headspace sampling. Recently, headspace solid-phase microextraction (HS/SPME) technology has been used because it is a relatively simple, fast, sensitive, and solvent-free technique that enables extraction and concentration steps to be performed simultaneously. GC/MS/FID and HS/SPME parameters, including fiber type, absorption, equilibration time, desorption time, salting-out effect, and others were optimized. Results evidenced the importance of proper control over extraction conditions to ensure precise quantification of compounds. Concentrations found in local beer for the compounds of interest, acetaldehyde, ethyl acetate, 1-propanol, 2-methyl 1-propanol; 2-methyl 1- butanol, 3-methyl 1-butanol, isoamyl acetate, 2-phenyl ethyl alcohol, and 2-phenyl ethyl acetate, were with the 0.32-43.7 ppm range. The results also showed that the reproducibility of the technique depends on the compounds, where alcohols have higher values (RSD mean value 5.01%) than esters (RSD mean value 2.3%) and aldehydes (RSD 4.4%). The simplicity of the validated development methodology could be used as a regular quality control procedure for beer.
Gustavo Charry started his focus in the food industry in Bogotá, Colombia, where he studied chemical engineering at the University of Los Andes. His passion for the brewing industry started in Mayaguez, Puerto Rico, where he obtained his M.S. degree in food science and technology in 2009, and led to a common project between the university and the local brewery. He worked as a researcher in Cervecera de Puerto Rico for two years, focusing on beer flavor development during fermentation. Gustavo jointed MillerCoors Milwaukee brewery in 2010, working as a quality engineer focused on flavor stability.