Profiling the volatile carbonyl compounds of barley and malt samples using a low-pressure assisted extraction system

Abstract

In this work, an analytical methodology for the analysis of volatile carbonyl compounds in barley and malt samples is presented. A simple low-pressure extraction system for volatile compounds was developed. This analytical tool enabled the extraction of volatile compounds directly from barley or malt solid samples (15 min extraction, 10.0 g sample) to an acceptor derivatizing liquid solution, thereafter analyzed by HPLC-DAD-ESI-MS/MS. The low-pressure conditions, pressure of 20 ± 2 in. Hg vac. (33.7 ± 3.7 kPa), enabled to increase the efficiency of the extraction process of some volatile compounds up to 3-fold comparing to normal conditions. Also, no heating procedures were applied, avoiding possible sample degradation and adulteration. Barley and different malt samples, namely pilsner, caramel, chocolate and black, were evaluated. Relevant differences were observed in the volatile carbonyl compounds profile between the samples analyzed. Specialty malts showed richer volatile profiles comparing to barley and pilsner malt samples. Some marker compounds, such as hydroxyacetone and furfural responsible for caramellic, burnt and bready flavours, could be assigned for the most intensely roasted malt samples. In comparison, 2- methylbutanal and 3-methylbutanal were characteristic for caramel malt. The results herein obtained showed that this analytical methodology could be a valuable analytical tool in the characterization, as well as in the quality control of these important raw materials during the malting and roasting processes.