Development of a sensitive non-targeted method for characterizing the wine volatile profile using headspace solid-phase microextraction comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry

Future understanding of differences in the composition and sensory attributes of wines require improved analytical methods which allow the monitoring of a large number of volatiles including those present at low concentrations. This study presents the optimization and application of a headspace solid-phase microextraction (HS-SPME) method for analysis of wine volatiles by comprehensive two-dimensional gas chromatography (GC×GC) time-of-flight mass spectrometry (TOFMS). This study demonstrates an important advancement in wine volatile analysis as the method allows for the simultaneous analysis of a significantly larger number of compounds found in the wine headspace compared to other current single dimensional GC-MS methodologies. The methodology allowed for the simultaneous analysis of over 350 different tentatively identified volatile and semi-volatile compounds found in the wine headspace. These included potent aroma compound classes such as monoterpenes, norisoprenoids, sesquiterpenes, and alkyl-methoxypyrazines which have been documented to contribute to wine aroma. It is intended that wine aroma research and wine sensory research will utilize this non-targeted method to assess compositional differences in the wine volatile profile.     

Beyond the characterization of wine aroma compounds: looking for analytical approaches in trying to understand aroma perception during wine consumption

The volatile compounds present in wines are responsible for the quality of the wine aroma. The analysis of these compounds requires different analytical techniques depending on the type of compounds and their concentration. The importance at sensorial level of each compound should be evaluated by using olfactometric techniques and reconstitution and omission studies. In addition, wine aroma is influenced by other factors such as wine matrix, which could affect the compounds’ volatility, decreasing or increasing their concentration in the headspace above the wine. Moreover, when a wine is consumed, several oral physiological variables could affect aroma perception. The focus of this review is to outline the most recent advances in wine aroma analysis and the most innovative techniques in trying to elucidate the main factors that influence wine aroma perception during consumption.     

Influence of Triazole Pesticides on Wine Flavor and Quality Based on Multidimensional Analysis Technology

Triazole pesticides are widely used to control grapevine diseases. In this study, we investigated the impact of three triazole pesticides—triadimefon, tebuconazole, and paclobutrazol—on the concentrations of wine aroma compounds. All three triazole pesticides significantly affected the ester and acid aroma components. Among them, paclobutrazol exhibited the greatest negative influence on the wine aroma quality through its effect on the ester and acid aroma substances, followed by tebuconazole and triadimefon. Qualitative and quantitative analysis by solid-phase micro-extraction gas chromatography coupled with mass spectrometry revealed that the triazole pesticides also changed the flower and fruit flavor component contents of the wines. This was attributed to changes in the yeast fermentation activity caused by the pesticide residues. The study reveals that triazole pesticides negatively impact on the volatile composition of wines with a potential undesirable effect on wine quality, underlining the desirability of stricter control by the food industry over pesticide residues in winemaking.     

Effect of maturation in small oak casks on the volatility of red wine aroma compounds

Wood maturation of red wine produces complex interactions between oak extracted compounds and pre-existing components in wine. Wood contributes with some aroma volatiles; but the whole volatile fraction, including the volatiles extracted from grape or produced during fermentation, could be involved in interactions with the non-volatile fraction. Samples of red wine with increasing time of wood contact, matured in 25 l casks of new American oak, were analysed on their volatile composition both in solution and headspace, and phenolic components. There was an increase of acetic acid and acetate esters as the time of wood contact increased. On the other hand, ethyl esters decreased as the time in wood increased. Some volatiles showed different behaviour when comparing their relationship between headspace and solution from two different casks, even though they were treated as replicates. This different evolution among casks was also consistent with different evolution of phenolic compounds, suggesting that there was an interaction among the volatile fraction and phenolic components.     

Contribution of non-volatile and aroma fractions to in-mouth sensory properties of red wines: Wine reconstitution strategies and sensory sorting task

This work explores to what extent the aroma or the non-volatile fractions of red wines are responsible for the overall flavor differences perceived in-mouth. For this purpose, 14 samples (4 commercial and 10 reconstituted wines), were sorted by a panel of 30 trained assessors according to their sensory in-mouth similarities. Reconstituted wines were prepared by adding the same volatile fraction (coming from a red wine) to the non-volatile fraction of 10 different red wines showing large differences in perceived astringency. Sorting was performed under three different conditions: (a) no aroma perception: nose-close condition (NA), (b) retronasal aroma perception only (RA), and (c) allowing retro- and involuntary orthonasal aroma perception (ROA). Similarity estimates were derived from the sorting and submitted to multidimensional scaling (MDS) followed by hierarchical cluster analysis (HCA). Results have clearly shown that, globally, aroma perception is not the major driver of the in-mouth sensory perception of red wine, which is undoubtedly primarily driven by the perception of astringency and by the chemical compounds causing it, particularly protein precipitable proanthocyanidins (PAs). However, aroma perception plays a significant role on the perception of sweetness and bitterness. The impact of aroma seems to be more important whenever astringency, total polyphenols and protein precipitable PAs levels are smaller. Results also indicate that when a red-black fruit odor nuance is clearly perceived in conditions in which orthonasal odor perception is allowed, a strong reduction in astringency takes place. Such red-black fruit odor nuance seems to be the result of a specific aroma release pattern as a consequence of the interaction between aroma compounds and the non-volatile matrix.     

Headspace solid-phase microextraction–gas chromatography–mass spectrometry for profiling free volatile compounds in Cabernet Sauvignon grapes and wines

The complex aroma of wine is derived from many sources, with grape-derived components being responsible for the varietal character. The ability to monitor grape aroma compounds would allow for better understanding of how vineyard practices and winemaking processes influence the final volatile composition of the wine. Here, we describe a procedure using GC–MS combined with headspace solid-phase microextraction (HS-SPME) for profiling the free volatile compounds in Cabernet Sauvignon grapes. Different sample preparation (SPME fiber type, extraction time, extraction temperature and dilution solvent) and GC–MS conditions were evaluated to optimize the method. For the final method, grape skins were homogenized with water and 8 ml of sample were placed in a 20 ml headspace vial with addition of NaCl; a polydimethylsiloxane SPME fiber was used for extraction at 40 °C for 30 min with continuous stirring. Using this method, 27 flavor compounds were monitored and used to profile the free volatile components in Cabernet Sauvignon grapes at different maturity levels. Ten compounds from the grapes, including 2-phenylethanol and β-damascenone, were also identified in the corresponding wines. Using this procedure it is possible to follow selected volatiles through the winemaking process.     

Characterization of odorant compounds of mussels (Mytilus edulis) according to their origin using gas chromatography-olfactometry and gas chromatography-mass spectrometry

Gas chromatography-olfactometry consists of sniffing the effluent of a gas chromatograph and leads to the direct determination of potent odorants in food. GC-olfactometry and GC-MS were applied in order to identify volatile compounds, and to characterize potent odorants of cooked wild mussels and bouchot mussels. Eighty-five volatiles were identified by GC-MS, among those the majority were identified for the first time in mussels. Using GC-olfactometry, the main contributors of cooked mussels aroma were characterized. Of the 85 volatiles identified in the flavor, only 33 were odor-active and contribute to the overall aroma of mussels. Dimethyl disulfide (sulfury odor) was the odorant the most differently perceived between the two extracts and seems to be characteristic of wild mussels. Combined GC-MS and GC-olfactometry made it possible to point out odorants which actually contribute to the aroma of cooked mussels and those which showed typical dependence on the origin of mussels.     

Screening of key odorants and anthocyanin compounds of cv. Okuzgozu (Vitis vinifera L.) red wines with a free run and pressed pomace using GC‐MS‐Olfactometry and LC‐MS‐MS

The principal purpose of the present work is to characterize the aroma, aroma‐active, and anthocyanin profiles of Okuzgozu wines and to observe the effect of the pomace pressing technique on these parameters. A total of 58 and 59 volatile compounds were identified and quantified in free‐run juice wine (FRW) and pressed pomace wine (PW). Alcohols were found as the most dominant group among aroma compounds followed by esters and acids. However, among all these compounds, only 11 and 13 of them could be considered as key odorants in aromatic extracts of FRW and PW, respectively. According to GC‐MS‐O analysis, ethyl octanoate (fruity), phenyl ethyl acetate (fruity), and 2‐phenyl ethanol (flowery) were found as the main contributors to the overall scent of both wines. Beyond the aroma profiles, anthocyanin contents of both types of wines were also investigated, and total 14 and 15 anthocyanins were identified and quantified in FRW and PW. Malvidin‐3‐glycoside and its acetyl and coumaroyl forms were identified as the dominant anthocyanins in both wines. It is worth noting the pressing application (2.0 atm) led to an increase of some unpleasant notes in the aroma providing chemical, pharmacy, and fermented aromas in wine. On the other hand, the wines produced with pressed pomace presented higher amounts of anthocyanins.     

Optimization of HS-SPME for GC-MS Analysis and Its Application in Characterization of Volatile Compounds in Sweet Potato

Volatile compounds are the main chemical species determining the characteristic aroma of food. A procedure based on headspace solid-phase microextraction (HP-SPME) coupled to gas chromatography-mass spectrometry (GC-MS) was developed to investigate the volatile compounds of sweet potato. The experimental conditions (fiber coating, incubation temperature and time, extraction time) were optimized for the extraction of volatile compounds from sweet potato. The samples incubated at 80 °C for 30 min and extracted at 80 °C by the fiber with a divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) coating for 30 min gave the most effective extraction of the analytes. The optimized method was applied to study the volatile profile of four sweet potato cultivars (Anna, Jieshu95-16, Ayamursaki, and Shuangzai) with different aroma. In total, 68 compounds were identified and the dominants were aldehydes, followed by alcohols, ketones, and terpenes. Significant differences were observed among the volatile profile of four cultivars. Furthermore, each cultivar was characterized by different compounds with typical flavor. The results substantiated that the optimized HS-SPME GC-MS method could provide an efficient and convenient approach to study the flavor characteristics of sweet potato. This is the basis for studying the key aroma-active compounds and selecting odor-rich accessions, which will help in the targeted improvement of sweet potato flavor in breeding.     

Analysis of Wine Bouquet Components Using Headspace Solid-Phase Microextraction-Capillary Gas Chromatography

Headspace solid-phase microextraction (HS/SPME) was studied and optimized for the capillary gas chromatographic (CGC) analysis of wine aroma compounds. The results were compared with those obtained using the direct sampling mode (DI/SPME) and using liquid/liquid extraction with Kaltron. The aromatic patterns obtained by HS/SPME-CGC were applied to the chemometric classification of wine varieties. The HS/SPME-CGC standard additional method is an appropriate technique for the quantitative analysis of volatile wine aroma compounds.     

Aroma Profile and Chemical Composition of Reverse Osmosis and Nanofiltration Concentrates of Red Wine Cabernet Sauvignon

Wine aroma represents one of the main properties that determines the consumer acceptance of the wine. It is different for each wine variety and depends on a large number of various chemical compounds. The aim of this study was to prepare red wine concentrates with enriched aroma compounds and chemical composition. For that purpose, Cabernet Sauvignon red wine variety was concentrated by reverse osmosis (RO) and nanofiltration (NF) processes under different operating conditions. Different pressures (2.5, 3.5, 4.5 and 5.5 MPa) and temperature regimes (with and without cooling) were applied on Alfa Laval LabUnit M20 equipped with six composite polyamide RO98pHt M20 or NF M20 membranes. Higher pressure increased the retention of sugars, SO₂, total and volatile acids and ethanol, but the temperature increment had opposite effect. Both membranes were permeable for water, ethanol, acetic acid, 4-ethylphenol and 4-ethylguaiacol and their concentration decreased after wine filtration. RO98pHt membranes retained higher concentrations of total aroma compounds than NF membranes, but both processes, reverse osmosis and nanofiltration, resulted in retentates with different aroma profiles comparing to the initial wine. The retention of individual compounds depended on several factors (chemical structure, stability, polarity, applied processing parameters, etc.).     

Changes in the Volatile Profile of Wheat Sourdough Produced with the Addition of Cava Lees

The volatile fraction is of great importance for the organoleptic quality and consumer acceptance of bread. The use of sourdough improves the sensory profile of bread, as well as the addition of new ingredients to the fermentation. Cava lees are a sparkling wine by-product formed of dead microorganisms, tartaric acid, and other inorganic compounds, rich in antioxidant compounds as well as β-glucans and mannoproteins. The aim of this study was to evaluate the effect of different concentrations of Cava lees (0–2% w/w) on sourdough volatile compounds to re-valorize this by-product of the wine industry. Headspace solid-phase microextraction (HS-SPME) was optimized to study the volatile fractions of sourdoughs. The parameters selected were 60 °C, 15 min of equilibrium, and 30 min of extraction. It was found that the addition of Cava lees resulted in higher concentrations of volatile compounds (alcohols, acids, aldehydes, ketones and esters), with the highest values being reached with the 2% Cava lees. Moreover, Cava lees contributed to aroma due to the compounds usually found in sparkling wine, such as 1-butanol, octanoic acid, benzaldehyde and ethyl hexanoate.     

Multivariate optimization and HS-SPME/GC-MS analysis of VOCs in red, yellow and purple varieties of Capsicum chinense sp. peppers

Peppers are used not only in cookery, but also in many other applications, like cosmetic, pharmaceutical and nourishing industry. The chemical composition of peppers is quite complex and several volatile and non-volatile substances contribute to their flavor, which is an important sensorial propriety. In this work a headspace/solid phase microextraction/gas chromatography coupled to mass spectrometry method was developed to evaluate the profiles of volatile compounds that contribute to the aroma of red, yellow and purple varieties of Capsicum chinense sp. peppers. The optimization of the extraction conditions was carried out using multivariate strategies such as factorial design and response surface methodology. The GC-MS analysis allowed the tentative identification of 34 compounds, with similarities higher than 85%, in accordance with the NIST mass spectral library. The data obtained by the analysis of volatile compounds, according to the proposed method, were treated with PCA chemometrics tool in order to group different varieties of C. chinense sp. peppers with similar VOC profiles. Amongst the most abundant VOCs, hexyl ester of pentanoic acid, dimethylcyclohexanols, humulene and esters of butanoic acid were found. Principal component analysis turned possible to visualize the grouping tendencies of the studied varieties of pepper, as well as the identification of the volatile compounds responsible for discriminating the three groups. Considering the fact that many species of peppers are used as human food, the significance of this work is further emphasized by its applicability to the study of food quality indicators, and as a tool for investigations on the composition of the pepper sources.     

Stable isotope dilution analysis of wine fermentation products by HS-SPME-GC-MS

The aim of this study was to quantify, in a single analysis, 31 volatile fermentation-derived products that contribute to the aroma of red and white wine. We developed a multi-component method based on headspace solid-phase microextraction coupled with gas chromatography mass spectrometry (HS-SPME-GC-MS). The 31 volatile compounds analysed include ethyl esters, acetates, acids and alcohols. Although these compounds have a range of functional groups, chemical properties, volatilities, affinities for the SPME fibre, and are found in wine at various concentrations, the accuracy of the analysis was achieved with the use of polydeuterated internal standards for stable isotope dilution analyses (SIDA). Nine of the labelled standards were commercially available, while 22 were synthesised. The method was validated by a series of duplicate spiked standard additions to model, white and red wine matrices over the concentration range relevant for each compound in wine. This demonstrated that the appropriate use of SIDA helped to account for matrix effects, for instance potential sources of variation such as the relative response to the MS detector, ionic strength, ethanol content and pH of different wine matrices. The resultant calibration functions had correlation coefficients (R²) ranging from 0.995 to 1.000. Each compound could be quantified at levels below its aroma threshold in wine. Relative standard deviations were all <5%. The method was optimised for the best compromise (over the 31 compounds) of wine dilution factor, level of sodium chloride addition, SPME fibre, SPME temperature, SPME time, GC column and MS conditions. Confirmation of identity was achieved by retention time and peak shape, and measurement of at least three ions for each analyte and internal standard with the MS operating in selected ion monitoring mode to facilitate more precise quantitation with a high sampling rate. The method is a valuable research tool with many relevant applications. A novel method for the combined chiral separation and SIDA quantification of 2- and 3-methylbutanoic acid is also demonstrated.     

Characterization of Aroma Compounds in Cooked Sorghum Using Comprehensive Two-Dimensional Gas Chromatography-Time-of-Flight Mass Spectrometry and Gas Chromatography-Olfactometry-Mass Spectrometry

Sorghum is the major raw material for the production of Chinese Baijiu (Chinese liquor) and has a great effect on the flavor of Baijiu. Volatiles in cooked glutinous and non-glutinous sorghum samples were extracted using solid-phase microextraction (SPME) and analyzed via comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS) and gas chromatography-olfactometry/mass spectrometry (GC-O/MS). A total of 145 volatile compounds and 52 potent odorant compounds were identified from both sorghum types according to the retention index, MS, aroma, and standards. Based on their aroma features, the compounds were grouped into eight general categories, and the intensities of each aroma group were summed. Moreover, most of the compounds detected in the cooked sorghums were also detected in commercial Chinese Baijiu, indicating that the aroma compounds produced during the sorghum cooking process have a direct and significant influence on the final flavor quality of Baijiu.     

Wein — Qualität entscheidet sich in Nanogramm: Zur Biochemie des sortentypischen Weinaromas

The varietal aroma of most wines is determined by a relatively small number of odor-active compounds, that are generated in ripening berries. These trace compounds occur in the ppb-to ppt-range and are mainly monoterpenes, C₁₃-norisoprenoids, thiols and pyrazines. Identification and elucidation of their biosynthetical pathways are important to unlocking the secrets of wine flavor.     

Quantitative solid phase microextraction – Gas chromatography mass spectrometry analysis of five megastigmatrienone isomers in aged wine

Megastigmatrienone is a key flavor compound in tobacco. It has also been detected in wine, where it may contribute to a tobacco/incense aroma, but its importance and concentration in wines had never previously been evaluated.