A sampling and analysis method for the determination of 21 phenolic compounds in smoke samples from biomass combustion has been developed. The smoke is used to make smoked foods, following an artisanal procedure used in some parts of the Canary Islands. The sampling system consists of a Bravo H air sampler, two impingers, each one containing an aqueous solution of sodium hydroxide 0.1 mol L−1, followed by a silica gel trap. The variables optimized to reach the best sampling conditions were volume of absorbent solution and sampling flow. Under the optimum conditions, 100 mL of absorbent solution of NaOH 0.10 mol L−1 and 2 L min−1 for the sampling flow, sampling efficiencies are higher than 80%. Analysis of phenolic compounds was carried out by headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography–mass spectrometry (GC-MS). Five different fiber coatings were employed in this study. By means of a central composite design, extraction time, salt concentration, and pH of the solution were optimized: 65-μm carbowax–divinylbenzene, extraction time 90 min, concentration in NaCl of 35% (m/v), and pH 2 yielded the highest response. Detection limits of phenol and their alkyl derivatives, guaiacol and eugenol, are between 1.13 and 4.60 ng mL−1. 3-Methoxyphenol, 2,6-dimethoxyphenol, and vanillin have detection limits considerably higher. Good linearity (R2≥0.98) was observed for all calibration curves in the established ranges. The reproducibility of the method (RSD, relative standard deviation) was found to oscillate between 7 and 18% (generally close or lower than 10%).
Smoked foods Phenolic compounds Headspace analysis Solid-phase microextraction Central composite design Gas chromatography–mass spectrometry
This study was supported by the projects: AGL 2002-02149 financed by Dirección General de Investigación del Ministerio de Ciencia y Tecnología (Spain); and CAL02-075-C3-3 financed by Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (Spain).
Clifford MN (1993) In: Macrae R, Robinson RK, Sadler MJ (eds) Encyclopaedia of food science, food technology and nutrition, vol 6. Academic Press, San Diego, p 4150Google Scholar