Synthesis of a novel isotopically labelled standard for quantification of γ-nonalactone in New Zealand Pinot noir via SIDA-SPE-GC-MS.

γ-Nonalactone is a linear aliphatic lactone ubiquitous in wine, associated with coconut, sweet, and stone fruit aroma descriptors. Little research has been conducted looking at the importance of this compound to New Zealand (NZ) wine aroma. 2H213C2-γ-Nonalactone, a novel isotopologue of γ-nonalactone, was synthesised in this work for use in a stable isotope dilution assay (SIDA) for quantification of γ-nonalactone in NZ Pinot noir wines for the first time. Synthesis was carried out using heptaldehyde as the starting material, and 13C atoms and 2H atoms were introduced via Wittig olefination and deuterogenation steps, respectively. The suitability of this compound as an internal standard was demonstrated by spiking model wine at normal and elevated conditions during sample preparation, with subsequent analysis via mass spectrometry showing stability of 2H213C2-γ-nonalactone. A model wine calibration, with concentrations of γ-nonalactone from 0 to 100 µg L-1, was shown to have excellent linearity (R2 > 0.99), reproducibility (0.72%), and repeatability (0.38%). Twelve NZ Pinot noir wines, representative of a range of NZ Pinot noir-producing regions, prices, and vintages, were analysed by solid-phase extraction-gas chromatography-mass spectrometry (SPE-GC-MS). The concentrations of γ-nonalactone ranged from 8.3 to 22.5 µg L-1, the latter of which was close to the odour detection threshold of this compound. These findings provide a basis for further research into γ-nonalactone and its impact on NZ Pinot noir aroma and provide a robust method for the quantification of this compound in Pinot noir.

Influence of peeling on volatile and non-volatile compounds responsible for aroma, sensory, and nutrition in ginger (Zingiber officinale).

Industrial use of ginger after peeling results in large amounts of agro-waste. To provide a basic reference for the sustainable processing of ginger products as a spice, we investigated the differences between unpeeled ginger, peeled ginger, and corresponding ginger peel, in terms of aroma, sensory profiles, and nutrition relevant physicochemical properties. The results showed that the total concentrations of identified odor-active compounds in unpeeled ginger, peeled ginger, and ginger peel were 876.56, 672.73, and 105.39 mg/kg, respectively. Unpeeled ginger exhibited more intense citrus-like and fresh impressions compared to peeled ginger, revealed by descriptive sensory analyses. This is relevant to the high odor activity values of odorants such as ß-myrcene (pungent, citrus-like), geranial (citrus-like), citronellal (citrus-like, sourish), and linalool (floral, fresh). In parallel, unpeeled ginger contained higher total polyphenol (84.49 mg/100 g) and total sugar content (33.4 g/kg) in comparison with peeled ginger (76.53 mg/100 g and 28.6 g/kg).

Aromatic Potential of Bordeaux Grape Cultivars: Identification and Assays on 4-Oxononanoic Acid, a γ-Nonalactone Precursor.

γ-Nonalactone has been demonstrated to be a chemical marker of dried/cooked fruit nuances detected in must and wine, but little is known about its formation pathways. Therefore, on the basis of the literature, we hypothesized 4-oxononanoic acid as a potential precursor. Using dichloromethane extraction followed by gas chromatography coupled to negative chemical ionization mass spectrometry, this keto acid was identified and quantified in Merlot and Cabernet Sauvignon musts. Its concentration ranged from traces to 60 µg/L. The biotransformation of 4-oxononanoic acid into γ-nonalactone by Saccharomyces cerevisiae during alcoholic fermentation was demonstrated using labeled d6-4-oxononanoic acid. Additional experiments shed light on the 4-oxononanoic acid role as a γ-nonalactone precursor and revealed that this biotransformation was (R)-enantioselective. Sensory and distribution studies of the enantiomers revealed that the detection threshold of R and S forms were 66 and 35 µg/L and the average ratio of R/S in grape and wine was 94:6 and 65:35.

Characterization of the potent odorants in Tibetan Qingke Jiu by sensory analysis, aroma extract dilution analysis, quantitative analysis and odor activity values.

Tibetan Qingke Jiu is the most important alcoholic beverage in the daily life of Tibetan people due to its unique flavor and rich nutrients. In this study, the aromatic characteristics of Qingke Jiu were studied by sensory analysis, aroma extract dilution analysis (AEDA), quantitative analysis, and odor activity values (OAVs). Sensory evaluation demonstrated that Qingke Jiu had fruity, cooked potato, honey, sour, sweet, and caramel-like aroma. A total of 66 aroma compounds were identified by AEDA and gas chromatography-mass spectrometry, with flavor dilution (FD) factors ranging from 4 to 2048. Among them, methional, acetic acid, ethyl butanoate, phenylacetaldehyde and ß-phenylethanol appeared with the highest FD factors. The concentration of these aroma-active compounds was further quantitated by combination of four different quantitative measurements, and 17 odorants had concentrations higher than their odor thresholds. Based on the OAVs, phenylacetaldehyde, ß-phenylethanol, ethyl phenylacetate, sotolon, furaneol, methional, methionol, γ-nonalactone, ethyl 2-methylbutanoate, ß-damascenone, ethyl 3-methylbutanoate, ethyl acetate, ethyl butanoate, and acetic acid could be potentially important to the overall aroma profile of Qingke Jiu.

Age-dependent characterization of volatile organic compounds and age discrimination in Chinese rice wine using an untargeted GC/MS-based metabolomic approach.

An untargeted gas chromatography/mass spectrometry (GC/MS)-based metabolomics by XCMS-Online software combined with partial least squares regression (PLSR) was applied to characterize volatile organic compounds (VOCs) during Chinese rice wine aging and discriminate ages for the first time. Finally, seven different ages between 0 and 15 years were well discriminated by PLSR. Total 104 feature groups were isolated from all optimized candidate peaks, and 94 VOCs (including unknowns) were preliminarily identified as aging markers. Therein, alcohols, sulfides, phenols and their derivatives, small esters and acids exhibited significantly better discrimination of short-aged rice wines. Correspondingly, furans, aromatics, aldehydes, ketones, most esters and acids, discriminated the long-aged samples better. Meanwhile, the potential origins of certain VOCs were also proposed for further research. Overall, this untargeted GC/MS-based metabolomics coupled with PLSR was a feasible tool for a rapidly and globally age-dependent characterization of volatile metabolomic signals in Chinese rice wine and thus for age discrimination.

Some clues about the changes in wine aroma composition associated to the maturation of "neutral" grapes.

This paper presents a study of the influence of the harvesting date on concentrations of odorants in Moristel wines of two vintages. The wine made from grapes harvested early facilitated the accumulation of acetaldehyde (associated with low polyphenols concentrations) and higher concentrations of branched acids. A reason for these greater levels could be the lack of reduction factors (NADH or NADPH). Other changes with potential sensory consequences are the decrease of the branched acid/branched alcohol, branched ester/branched acid and branched ester/branched alcohol ratios that occurs as the grapes ripen. Besides, the variations of varietal or typical maturation markers did not have sensory importance. These results suggest that the characteristics of wines associated to the degree of maturity of grapes are mostly related to the changes in the profiles of fermentative compounds (especially acetaldehyde) induced by changes in the polyphenolic content and in the medium in which the yeast develops.

Modulating analytical characteristics of thermovinified Carignan musts and the volatile composition of the resulting wines through the heating temperature.

The impact of two temperature levels (50 °C and 75 °C) and heating times (30 min and 3 h) on the composition of thermovinified musts and wines from Carignan was investigated at the laboratory scale in 2014 and 2015. The heating temperature had a significant impact on the extraction of amino acids and a probable thermal degradation of anthocyanins was noted at 75 °C. In 2014, musts from grapes that underwent a heat treatment at 50 °C for 3 h had a similar level of phenolic compounds as those treated at 75 °C for 30 min. This indicates that the reduction of the heating temperature in some vintages can be compensated for through an extension of the heating period. Several grape-derived molecules were impacted by the rise in temperature and wines made from grapes treated at 50 °C in most cases contained larger concentrations of geraniol, ß-citronellol, ß-damascenone and 3-mercaptohexanol.

Aroma compounds and characteristics of noble-rot wines of Chardonnay grapes artificially botrytized in the vineyard.

Aroma characteristics and their impact volatile components of noble-rot wines elaborated from artificial botrytized Chardonnay grapes, obtained by spraying Botrytis cinerea suspension in Yuquan vineyard, Ningxia, China, were explored in this work. Dry white wine made from normal-harvested grapes and sweet wine produced from delay-harvested grapes were compared. Wine aromas were analysed by trained sensory panelists, and aroma compounds were determined by SPME-GC-MS. Results indicated that esters, fatty acids, thiols, lactones, volatile phenols and 2-nonanone increased markedly in noble-rot wines. In addition to typical aromas of noble-rot wines, artificial noble-rot wines were found to contain significant cream and dry apricot attributes. Partial Least-Squares Regression models of aroma characteristics against aroma components revealed that non-fermentative odorants were the primary contributor to dry apricot attribute, especially, thiols, C13-norisoprenoids, lactones, terpenols and phenolic acid derivatives, while cream attribute was dependent on both fermentative and non-fermentative volatile components.

Characterisation of aroma-active and off-odour compounds in German rainbow trout (Oncorhynchus mykiss). Part II: Case of fish meat and skin from earthen-ponds farming.

Odorous molecules in earthen-ponds rainbow trout aquaculture farming in Germany were investigated with a special focus on musty-earthy off-odorants. To this aim, fish meat and skin were extracted using solvent-assisted flavour evaporation (SAFE) and were mildly concentrated; extracts were subsequently analysed by means of one- and two-dimensional high-resolution gas chromatography coupled with mass spectrometry and olfactometry (GC-MS/O and 2D-HRGC-MS/O). Aroma extract dilution analysis (AEDA) of the solvent extracts revealed the presence of 76 odorants of which 75 were successfully identified. Thereby, rotundone (black pepper) is described for the first time as an odour-active substance in fish. Moreover, a series of compounds is described for the first time in German aquaculture rainbow trout fish, including, amongst others, (E,Z,Z)-2,4,7-tridecatrienal, (E)-4,5-epoxy-(E)-2-decenal, 4-ethyloctanoic acid, 3-methylindole (skatole), d-limonene, and indole. The analytical findings were further compared to sensory evaluation of the samples, and previously obtained data on the respective aquacultural water.