Free Monoterpene Isomer Profiles of Vitis Vinifera L. cv. White Wines

Monoterpene compounds contribute floral and fruity characters to wine and are desired by grape growers and winemakers for many white wines. However, monoterpene isomers, especially monoterpene enantiomers, have been little explored. It is possible to identify and quantitate 17 monoterpene isomers in 148 varietal wines from eight grape varieties; Chardonnay, Gewürztraminer, Muscat, Pinot gris, Riesling, Sauvignon blanc, Torrontes, and Viognier in two vintages by Headspace solidphase microextraction multidimensional gas chromatography mass spectrometry (HS-SPME-MDGC-MS). Results obtained from general linear models and discriminant analysis showed significant differences for the isomer profiles and enantiomer fractions among the eight grape varieties and four wine styles. The high R² values from the fitted line show low variation in enantiomeric differences based on variety. These results provide an overview of the monoterpene isomers of wide varietal wines, and support that isomer profiles and enantiomer fractions could differentiate our wines by varietal and wine style.

Determination of Volatile Flavour Profiles of Citrus spp. Fruits by SDE-GC-MS and Enantiomeric Composition of Chiral Compounds by MDGC-MS

INTRODUCTION

Citrus fruits are known to have characteristic enantiomeric key compounds biosynthesised by highly stereoselective enzymatic mechanisms. In the past, evaluation of the enantiomeric ratios of chiral compounds in fruits has been applied as an effective indicator of adulteration by the addition of synthetic compounds or natural components of different botanical origin.

OBJECTIVE

To analyse the volatile flavour compounds of Citrus junos Sieb. ex Tanaka (yuzu), Citrus limon BURM. f. (lemon) and Citrus aurantifolia Christm. Swingle (lime), and determine the enantiomeric ratios of their chiral compounds for discrimination and authentication of extracted oils.

METHODOLOGY

Volatile flavour compounds of the fruits of the three Citrus species were extracted by simultaneous distillation extraction and analysed by gas chromatography-mass spectrometry. The enantiomeric composition (ee%) of chiral camphene, sabinene, limonene and β-phellandrene was analysed by heart-cutting multidimensional gas chromatography-mass spectrometry.

RESULTS

Sixty-seven (C. junos), 77 (C. limon) and 110 (C. aurantifolia) volatile compounds were identified with limonene, γ-terpinene and linalool as the major compounds. Stereochemical analysis (ee%) revealed 1S,4R-(-) camphene (94.74, 98.67, 98.82), R-(+)-limonene (90.53, 92.97, 99.85) and S-(+)-β-phellandrene (98.69, 97.15, 92.13) in oil samples from all three species; R-(+)-sabinene (88.08) in C. junos; and S-(-)-sabinene (81.99, 79.74) in C. limon and C. aurantifolia, respectively.

CONCLUSION

The enantiomeric composition and excess ratios of the chiral compounds could be used as reliable indicators of genuineness and quality assurance of the oils derived from the Citrus fruit species. Copyright © 2017 John Wiley & Sons, Ltd.

Optimization of a sample preparation method for multiresidue analysis of pesticides in tobacco by single and multi-dimensional gas chromatography-mass spectrometry

A selective and sensitive multiresidue analysis method, comprising 4 7pesticides, was developed and validated in tobacco matrix. The optimized sample preparation procedure in combination with gas chromatography mass spectrometry in selected-ion-monitoring (GC-MS/SIM) mode offered limits of detection (LOD) and quantification (LOQ) in the range of 3-5 and 7.5-15ng/g, respectively, with recoveries between 70 and 119% at 50-100ng/g fortifications. In comparison to the modified QuEChERS (Quick-Easy-Cheap-Effective-Rugged-Safe method: 2g tobacco+10ml water+10ml acetonitrile, 30min vortexing, followed by dispersive solid phase extraction cleanup), the method performed better in minimizing matrix co-extractives e.g. nicotine and megastigmatrienone. Ambiguity in analysis due to co-elution of target analytes (e.g. transfluthrin-heptachlor) and with matrix co-extractives (e.g. δ-HCH-neophytadiene, 2,4-DDE-linolenic acid) could be resolved by selective multi-dimensional (MD)GC heart-cuts. The method holds promise in routine analysis owing to noticeable efficiency of 27 samples/person/day.