Determination of 2-methoxy-3-alkylpyrazines in carrot products by gas chromatography/nitrogen-phosphorus detection

The 2-methoxy-3-alkylpyrazines in 6 types of carrot products were determined by a stripping-selective trapping procedure followed by purge-and-trap gas chromatographic analysis with an NP detector. The aroma threshold of one of the principal pyrazines, 2-methoxy-3-sec-butylpyrazine, in a carrot medium was 0.19 ng/g. The concentrations of this compound in whole-carrot products were 0.43 (fresh), 0.291 (canned, cooked), and 0.224 ng/g (frozen). A diced, cooked, and freeze-dried product contained 0.070 ng/g. All of these products contained only this pyrazine. In contrast, a shredded, bagged product contained 2-methoxy-3-isopropylpyrazine as the sole pyrazine (0.32 ng/g), and a sliced, dried product contained a mixture of 3 pyrazines: 2-methoxy-3-sec-butyl- (0.109 ng/g), 2-methoxy-3-isopropyl- (0.176 ng/g), and 2-methoxy-3-isobutylpyrazine (0.029 ng/g). The pyrazine concentrations in most of these products (except the freeze-dried product) exceeded the threshold value.