Multi-volatile method for aroma analysis using sequential dynamic headspace sampling with an application to brewed coffee

Abstract

A novel multi-volatile method (MVM) using sequential dynamic headspace (DHS) sampling for analysis of aroma compounds in aqueous sample was developed. The MVM consists of three different DHS method parameters sets including choice of the replaceable adsorbent trap. The first DHS sampling at 25°C using a carbon-based adsorbent trap targets very volatile solutes with high vapor pressure (>20kPa). The second DHS sampling at 25°C using the same type of carbon-based adsorbent trap targets volatile solutes with moderate vapor pressure (1–20kPa). The third DHS sampling using a Tenax TA trap at 80°C targets solutes with low vapor pressure (<1kPa) and/or hydrophilic characteristics. After the 3 sequential DHS samplings using the same HS vial, the three traps are sequentially desorbed with thermal desorption in reverse order of the DHS sampling and the desorbed compounds are trapped and concentrated in a programmed temperature vaporizing (PTV) inlet and subsequently analyzed in a single GC-MS run. Recoveries of the 21 test aroma compounds for each DHS sampling and the combined MVM procedure were evaluated as a function of vapor pressure in the range of 0.000088–120kPa. The MVM provided very good recoveries in the range of 91–111%. The method showed good linearity (r2>0.9910) and high sensitivity (limit of detection: 1.0–7.5ngmL−1) even with MS scan mode. The feasibility and benefit of the method was demonstrated with analysis of a wide variety of aroma compounds in brewed coffee. Ten potent aroma compounds from top-note to base-note (acetaldehyde, 2,3-butanedione, 4-ethyl guaiacol, furaneol, guaiacol, 3-methyl butanal, 2,3-pentanedione, 2,3,5-trimethyl pyrazine, vanillin, and 4-vinyl guaiacol) could be identified together with an additional 72 aroma compounds. Thirty compounds including 9 potent aroma compounds were quantified in the range of 74–4300ngmL−1 (RSD<10%, n=5).