Abstract
In this work, a gas-diffusion microextraction (GDME) methodology was optimized and validated for the analysis of selected staling aldehydes (furfural (FURF), 2-methylpropanal (2-MP), 2-methylbutanal (2-MB), 3-methylbutanal (3-MB), and acetaldehyde (ACET)) during natural and forced aging of beer. The methodology was optimized considering time, temperature of extraction, and derivatizing agent. Using 4-hydrazinobenzoic acid (HBA) as a derivatizing agent, the performance of the method was evaluated by assessing several parameters such as detection limits (ranging from 1.2 to 1857.7 µg/L for 2-MB and ACET, respectively), quantification limits (ranging from 3.9 to 6192.4 µg/L for 2-MB and ACET, respectively), recoveries (higher than 96%), intraday and interday precisions (lower than 3.4 and 9.2%, respectively), and linearity (r2 ≥ 0.995). During beer aging, higher content of Strecker aldehydes and FURF were found, while no significant variations in ACET levels were observed. In general, the aldehydes content assessed for beers stored at 37 ± 1 °C for 7 and 14 days mimics that observed for beers stored at 20 ± 2 °C for 3 and 6 months, respectively. Lower temperatures of storage (4 ± 1 °C) delayed the development of staling aldehydes. Based on PCA analysis, the content of staling aldehydes and beer color were responsible for 91.39% of the variance among the analyzed samples, and it was demonstrated that these are key parameters to discriminate fresh from aged beers. The results herein presented showed that the proposed analytic methodology is a valuable strategy for the characterization and quantification of important staling aldehydes in beer with a potential application in the quality control of beer during storage.
Highlights
Beer is a complex matrix of more than 3000 different compounds in an aqueous environment
In the last 10 years, different extraction techniques have been applied for the analysis of carbonyl compounds in alcoholic beverages, such as headspace solid-phase microextraction (HS-SPME) [17,18] and stir bar sorptive extraction (SBSE) [19,20]
The study was conducted in model solutions (5%, v/v), and blank experiments were carried out to evaluate the possible conversion of ethanol into acetaldehyde by the application of temperature (40 ◦C) during the extraction procedure
Summary
Beer is a complex matrix of more than 3000 different compounds in an aqueous environment. Our research group has applied the gas-diffusion microextraction (GDME) extraction procedure for the identification of several carbonyl compounds in different liquid and solid matrices ([23,24,25,26]). This technique consists of the extraction of volatile analytes through a permeable membrane to an acceptor solution, combined with a derivatization step (acceptor solution containing the derivatizing agent). The validated procedure was applied to investigate the impact of storage time and temperature on the concentration of several aldehydes (ACET, FURF, 2-MP, 2-MB, and 3-MB)
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