Elution Order of the Furanoid Linalool Oxides on Common Gas Chromatographic Phases and Modified Cyclodextrin Phases

GC-MS profiling, descriptive sensory analysis, and consumer acceptance of Costa Rican papaya (Carica papaya L.) fruit purees

Volatiles of papaya purees from four Costa Rican cultivars were analysed by solid-phase microextraction and gas chromatography-mass spectrometry. A total of 83 volatiles was assigned in the purees, of which 19 were detected for the first time as papaya constituents. As revealed by multivariate statistics, i.e., principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA), the purees may be allocated to terpene- and lactone-rich ('SH-5'), ester-containing ('Criolla'), and intermediate chemotypes ('Pococí' and 'Silvestre'). Descriptive sensory analysis and a consumer acceptance test were additionally performed. Floral, fruity, and honey-like notes were perceived at significantly higher intensities in 'SH-5' puree. The latter descriptors strongly correlated with volatiles discriminating 'SH-5' in the PCA and PLS-DA, respectively. Consumer acceptance of the papaya purees differed significantly. 'Pococí' and 'SH-5' purees appear to be suitable for improving the nutritional value of blended fruit juices without impairing their sensory quality.

Meta-Analysis of the Core Aroma Components of Grape and Wine Aroma

Wine aroma strongly influences wine quality, yet its composition and its evolution during the winemaking process are poorly understood. Volatile compounds that constitute wine aroma are traditionally divided into three classes according to their origin: grape, fermentation, and maturation aroma. We challenge this view with meta-analysis and review of grape and wine volatiles and their precursors from 82 profiling experiments. We compiled a list of 141 common grape and wine volatiles and quantitatively compared 43 of them. Our work offers insight into complex relationships between biosynthesis of aroma in grapes and the changes during the winemaking process. Monoterpenes are one of the largest and most researched wine aroma compounds. We show that their diversity in wines is mainly due to the oxidative metabolism of linalool in grapes. Furthermore, we demonstrate that most of the linalool produced in grapes is converted to these oxidized derivatives.

Characterization of Volatile Components of Zingiber roseum Essential Oil Using Capillary GC on Modified Cyclodextrins

The essential oil from different parts of Zingiber roseum plants was extracted by hydrodistillation, and analyzed using enantio-GC, capillary-GC and GC-MS. Two chiral selectors, 6- tert-butyldimethylsilyl-2,3-diethyl-β-cyclodextrin (TBDE-β-CD), and 2,3,6-methyl-β-cyclodextrin (PM-β-CD) doped into 14% cyanopropylphenyl/ 86% dimethylpolysiloxane, and 35% diphenyl/ 65% dimethylpolysiloxane, respectively were compared in order to clarify the stereochemistry and enantioselectivity of terpenoids using chiral gas chromatography. The enantiomeric excess for (1R)-(+)-α-pinene, (1R)-(+)-β-pinene, and (R)-(+)-limonene were characteristic for the rhizome. In TBDE-β-cyclodextrin coated chiral columns, a significant increase in separation factor (a) for β-pinene, limonene, linalool and α-terpineol enantiomers was observed when compared with methyl substituted β-cyclodextrin. The increase in chain length of the alkyl substituents may be the possible cause for enantiomer separation in β-cyclodextrin cavity. In addition, enantioreversal of α-pinene enantiomers in 6-tert-butyldimethylsilyl-2,3-diethyl-β-cyclodextrin was noticed as a unique feature. The enantiomeric compositions of Z. roseum fruit and flower essential oils were similar, but, in contrast, the rhizome oil contained an entirely different composition. Therefore, these results aid in the authentication of the natural origin of Z. roseum essential oils.

Biotransformation of (S)-(+)-linalool by Aspergillus niger: an investigation of the culture conditions

The biotransformation of (S)-(+)-linalool by different Aspergillus niger strains was studied, using submerged shaken liquid cultures. One strain, A. niger DSM 821, was able to convert the substrate to cis- and trans-furanoid linalool oxide (yield 30% and 5%, respectively) and cis- and trans-pyranoid linalool oxide (yield 14% and 1.5%, respectively). The main metabolites, cis-(2S,5R)-furanoid and cis-(3S,6S)-pyranoid linalool oxide, have a sweet, floral, creamy odor and are used in perfumery. The culture conditions involved, such as the composition of the broth and the type and concentration of cosolvent applied and possible adaptation to the substrate during inoculation, were investigated. It was found that (S)-(+)-linalool was converted much better than (R)-(-)-linalool and that no significant chemical conversion of the substrate occurred in control flasks at pH 3.5. Three cosolvents for improving the solubility of linalool in the culture broths were compared, namely MeOH, EtOH, and acetone. The highest bioconversion yields were obtained when the substrate was applied as a diluted solution in acetone. Screening of the fungi for their biotransformation capacity was performed by solid-phase microextraction.

Gas chromatography

This review of the fundamental developments in gas chromatography (GC) includes articles published from 1996 and 1997 and an occasional citation prior to 1996. The literature was reviewed principally using CA Selects for Gas Chromatography from Chemical Abstracts Service, and some significant articles from late 1997 may be missing from the review. In addition, the online SciSearch Database (Institute for Scientific Information) capability was used to abstract review articles or books. As with the prior recent reviews, emphasis has been given to the identification and discussion of selected developments, rather than a presentation of a comprehensive literature search, now available widely through computer-based resources. During the last two years, several themes emerged from a review of the literature. Multidimensional gas chromatography has undergone transformation encompassing a broad range of activity, including attempts to establish methods using chromatographic principles rather than a totally empirical approach. Another trend noted was a comparatively large effort in chromatographic theory through modeling efforts; these presumably became resurgent with inexpensive and powerful computing tools. Finally, an impressive level of activity was noted through the themes highlighted in this review, and this was particularly true with detectors and field instruments.