Identificação e quantificação de compostos carbonílicos livres e ligados em cervejas artesanais

Abstract

Beer is one of the most consumed alcoholic beverages in the world, with Brazil being the third largest producer. The composition of beer, as well as its production process, leads to the formation of chemical compounds that can change the taste and stability of the final product, such as carbonyl compounds. The presence of these in the drink can also cause damage to human health. This work aimed to identify and quantify free and bound carbonyl compounds present in real samples of craft beers. The samples were acquired in commercial establishments in the city of Salvador - Bahia and submitted to the analysis of 15 carbonyl compounds (formaldehyde, acetaldehyde, acrolein, propionaldehyde, crotonaldehyde, methacrolein, butyraldehyde, benzaldehyde, valeraldehyde, cyclohexanone, hexaldehyde, heptanal, octanal, nonanal and decanal) by high performance liquid chromatography (HPLC). The method was validated through the evaluation of selectivity, linearity, detection limit, quantification limit, precision and accuracy. To analyze the free carbonyl compounds, the derivatization reaction was carried out in 50 mL of the previously decarbonated sample, concentrated hydrochloric acid was added (up to pH<2) and 10mL of the derivatizing agent (2,4-dinitrophenylhydrazine) at 0.5%. The sample was placed under ultrasound (20 min) to complete the reaction. After derivatization, each sample was concentrated by solid phase extraction (SPE) using C18 cartridge. The analytes retained in the cartridge were eluted with acetonitrile (1.0 mL) and injected into the chromatograph. For the analysis of bonded carbonyl compounds, sodium hydroxide 1N was added to 50 mL of the sample to adjust the pH ≈ 11 and stirred for 30 min. After stirring, the sample was derivatized according to the procedure adopted for the analysis of free carbonyl compounds. Analyzes were performed by liquid chromatography with array diode detector (HLPC-DAD). The method showed good linearity (R2≥0.9990). The limits f detection ranged from 1.69 (octanal) to 6.13 µg L-1 (metacrolein), while for the limits of quantification, the variation was between 5.62 (octanal) and 20.45 µg L-1 (methacrolein). Repeatability and intermediate precision were satisfactory, with relative standard deviations below 16.9% (methacrolein) and 16.9% (hexaldehyde), respectively. In the analyzed samples, the concentrations found for free carbonyl compounds ranged from 7.30µg L-1 (acrolein) to 2896.97µg L-1 (acrolein). For the bonded carbonyl compounds, the variation was between 11.20 µg L-1 (octanal) and 2270.05µg L-1 (propionaldehyde). The proposed method presented satisfactory results that demonstrated the ability to identify and quantify free and bound carbonyl compounds, in different concentrations, in craft beers.