Optimization of Modern Analytical SPME and SPDE Methods for Determination of Trans-2-nonenal in Barley, Malt and Beer

摘要

Trans-2-nonenal is an aldehyde contributing to an unpleasant off-flavor and odor of rancid butter in stored beer. The automated solid-phase microextraction technique (SPME) coupled with gas chromatography (GC) and solid-phase dynamic extraction (SPDE) coupled with gas chromatography were optimized and introduced to determine trans-2-nonenal in barley, malt and beer. Five types of SPME fibers coated with different stationary phases (100?μm PDMS, 65?μm PDMS/DVB, 85?μm CAR/PDMS, 50/30?μm DVB/CAR/PDMS, 85?μm PA) and two needles (PDMS, PDMS/AC) were compared and tested for their efficiencies in the headspace (HS) SPME and SPDE determination of trans-2-nonenal in barley, malt and beer. The highest extraction efficiency of HS-SPME was achieved with the PDMS/DVB fiber, and addition of 1.5?g of NaCl, extraction time was 20?min at 60?°C. The highest extraction efficiency of HS-SPDE was obtained with the PDMS needle, 15 extraction strokes at 60?°C and addition of 1.5?g of NaCl. Trans-2-nonenal was identified with the method of HS-SPME coupled gas chromatography-mass spectrometry (GC–MS); the samples were analyzed using the HS-SPME-GC-coupled gas chromatography-flame ionization detector (GC-FID) technique.