Measurement of Nonenal Potential by Solid-Phase Microextraction (SPME)

Nonenal Potential, Solid-Phase Microextraction,

Abstract

The Nonenal Potential is considered an indicator for the staling characteristics of a sample. Malt extracts, worts, and beers are among the commonly analyzed materials. Its relatively high nonenal figures have made Nonenal Potential analyses easier to carry out than measurements of the free aldehydes. The often-difficult interpretation of free aldehyde concentrations as a measure of flavor stability have also contributed to the widespread use of Nonenal Potential analyses. Since the original presentation of the concept in 1990, many variations of Nonenal Potential measurement have been published, both in terms of variations of the sample digestion procedure as well as different approaches in nonenal analysis itself. Current-published methods include a variety of time-consuming and expensive steps in sample preparation, such as column chromatography and derivatization, which also may decrease reproducibility. To overcome the above-mentioned difficulties, a novel solid-phase microextraction analysis method for 2(E)-nonenal without derivatization or other pretreatment steps has been developed. The activation of 2(E)-nonenal precursors takes place in a headspace vial with 10 mL of acidified sample, pH 4.00, at 100°C for 2 h. The vial is refrigerated at 0°C and opened, Na₂SO₄ added with a magnetic agitator, and sealed. An SPME fiber is placed in the headspace solution for 1 h at 70°C. The 2(E)-nonenal adsorbed on the fiber is analyzed by CG/MS in SIM mode. Besides eliminating derivatization efforts and cost, the new method requires significantly less time compared with previously published ones. The new method has been validated testing linearity, accuracy, precision, specificity/selectivity, range, and ruggedness/reproducibility, as well as detection limit.