Varietal and pre-fermentative volatiles during ripening of Vitis vinifera cv Nebbiolo berries from three growing areas

Flavour analysis of grape is a key step in quality evaluation. The Stir Bar Sorptive Extraction technique (SBSE, ‘Twister’®) was used to assess varietal and pre-fermentative volatile accumulation in ‘Nebbiolo’ berries, from véraison to harvest. Grapes were collected in three vineyards, representing different ‘crus’ in the cultivation areas of Barolo, Barbaresco and Roero (North–West Italy). Volatile constituents of grapes were identified and quantified by GC–MS.     

Volatile compounds evolution of three table grapes with different flavour during and after maturation

Volatile compounds of three different flavour table-grapes, ‘Jingxiu’, ‘Bimeijia’ and ‘Jingya’, were investigated during and after maturation using SPME/GC–MS. All the alcohols and carbonyls, along with most of the C₆ compounds and terpenoids, were evident before veraison, while most of the esters were detected at or after veraison. C₆ compounds increased in the early period of maturation, and then decreased. Most alcohols and carbonyls tended to continuously decrease during ripening. Except for geraniol, terpenoids increased until maturation, then decreased. Some esters continued to increase after maturation. Principal component analysis showed that terpenoids and esters were the characteristic volatiles of ripe ‘Bimeijia’ and ‘Jingya’ grapes, respectively. ‘Bimeijia’ had the highest terpenoid content at maturity, while ‘Jingya’ continued to accumulate some esters after maturation. To achieve berries of full-bodied aroma, ‘Bimeijia’ should be harvested at maturity and ‘Jingya’ should have a delayed harvest. For the neutral grape ‘Jingxiu’, delayed harvest is recommended to reduce the ‘green’ odour.     

Electronic nose and GC–MS analysis of volatile compounds in Tuber magnatum Pico: Evaluation of different storage conditions

The characteristic aromatic composition of white truffles (Tuber magnatum Pico) determines its culinary and commercial value. However modifications of truffle organoleptic proprieties occur during preservation. A study of headspace of white truffles by using Electronic nose (E-nose), gas chromatography–mass spectrometry (GC–MS) and sensory analyses was performed. Truffles were stored at different conditions for 7 days: +4 and +8 °C wrapped in blotting paper or covered by rice or none of the above. Headspace E-nose measurements and sensory analyses were performed each day. Statistical multivariate analysis of the data showed the capability of E-nose to predict sensorial analysis scores and to monitor aroma profile changes during storage. Truffle’s volatile molecules were also extracted by headspace solid phase microextraction technique and separated and identified by GC–MS. Partial Components Analysis of data was performed. E-nose and GC–MS results were in agreement and showed that truffle storage in paper at +8 °C seemed to be the best storage condition.     

Volatile characteristics of 50 peaches and nectarines evaluated by HP–SPME with GC–MS

Using HS–SPME–GC–MS, characteristics of the volatiles of 50 peaches and nectarines representing different germplasm origins were investigated. Ten of these peaches and nectarines were studied in two successive years. Eighty-four compounds were identified. Volatile composition was relatively consistent, but the amount of total volatiles and certain individual compounds varied between years. Moreover, the composition of volatiles and their contents depended on genotypic background and germplasm origin. Total volatiles in wild peaches and a Chinese local cultivar ‘Wutao’ were much higher than in the other groups. All the peaches and nectarines could be classified into four groups by principal component analysis of the volatiles (excluding C₆ compounds): ‘Ruipan 14’ and ‘Babygold 7’ with high contents of lactones, Chinese wild peaches and ‘Wutao’ with high contents of terpenoids and esters, seven cultivars with American or European origins with high content of linalool, and others without characteristic composition of volatiles.     

Comparison of two headspace sampling techniques for the analysis of off-flavour volatiles from oat based products

Two different headspace sampling techniques were compared for analysis of aroma volatiles from freshly produced and aged plain oatcakes. Solid phase microextraction (SPME) using a Carboxen–Polydimethylsiloxane (PDMS) fibre and entrainment on Tenax TA within an adsorbent tube were used for collection of volatiles. The effects of variation in the sampling method were also considered using SPME. The data obtained using both techniques were processed by multivariate statistical analysis (PCA). Both techniques showed similar capacities to discriminate between the samples at different ages. Discrimination between fresh and rancid samples could be made on the basis of changes in the relative abundances of 14–15 of the constituents in the volatile profiles. A significant effect on the detection level of volatile compounds was observed when samples were crushed and analysed by SPME–GC–MS, in comparison to undisturbed product. The applicability and cost effectiveness of both methods were considered.     

Monitoring the oxidation of almond oils by HS-SPME–GC–MS and ATR-FTIR: Application of volatile compounds determination to cultivar authenticity

In this study, the oxidative process of Spanish and American almond oils was monitored by using headspace solid-phase microextraction/gas chromatography–mass spectrometry (HS-SPME/GC–MS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Oxidative stability of samples was evaluated after thermal treatment at 100 °C for 1, 3, 5, 7, 10, 15 and 20 days, in order to accelerate the lipid oxidation process. Variations observed in bands of infrared spectra were used to monitor the progress of the oxidation process of almond oils. HS-SPME–GC–MS was used for isolation and determination of volatile compounds in oxidised almond oils. The following aldehydes were identified in all samples: hexanal, (E)-2-heptenal, (E)-2-octenal, nonanal, (E)-2-nonenal, (E,E)-2,4-nonadienal and (E,E)-2,4-decadienal. Determination of volatile compounds resulting from lipid oxidation from three different almond cultivars (Spanish Guara and Marcona and Butte from USA) was performed to obtain a set of parameters for discrimination between Spanish and American cultivars. Successful discrimination was obtained in samples kept under thermal treatment for 7 days, by using HS-SPME/GC–MS combined with multivariate stepwise linear discriminant analysis (LDA).     

The influence of yeast on the aroma of Sauvignon Blanc wine

The main objective of this study was to investigate the effect of different Saccharomyces cerevisiae wine yeast strains on the concentration of aroma-enhancing volatile thiols and fermentation metabolites in Sauvignon Blanc wine. Seven commercial wine yeast strains were selected based on their putative ability to modulate the concentrations of the fruity volatile thiols, 4-mercapto-4-methylpentan-2-one (4MMP), 3-mercapto-hexanol (3MH) and 3-mercapto-hexylacetate (3MHA). Each of these yeasts was used to produce Sauvignon Blanc wines under controlled conditions, in triplicate, in 20-L quantities. The levels of 4MMP, 3MH and 3MHA in these wines were quantified using the p-hydroxymercuribenzoate method. In addition, a total of 24 volatile yeast-derived fermentation aroma compounds were also quantified using headspace solid-phase microextraction coupled with gas chromatography mass spectrometry (HS-SPME–GC–MS). Formal sensory analysis was conducted by 12 trained assessors and, additionally, a panel of 24 experienced wine industry professionals assessed the wines and ranked them in order of preference. The results indicated that the yeast strains varied significantly in terms of their capabilities to (i) produce volatile thiols and fermentation metabolites; and (ii) to modulate the varietal characters of Sauvignon Blanc wine. Yeast strains that produced the highest levels of volatile thiols were responsible for wines with the highest perceived intensity of fruitiness, and these wines were preferred by the tasting panels. While the ‘green’ characters in Sauvignon Blanc wines can be manipulated through vineyard management, the ‘tropical fruity’ characters appear to be largely dependent on the wine yeast strain used during fermentation. Therefore, the choice of yeast strain offers great potential to modulate wine aroma profiles to definable styles and predetermined consumer market specifications.     

Analysis of crab meat volatiles as possible spoilage indicators for blue crab (Callinectes sapidus) meat by gas chromatography–mass spectrometry

Traditionally crab meat spoilage has been evaluated using sensory panels. A method was developed using solid-phase microextraction–gas chromatography–mass spectrometry (SPME–GC–MS) to examine the aroma profile of blue crab (Callinectes sapidus) for chemical indicators of spoilage. The chemicals found to correlate best with spoilage were trimethylamine (TMA), ammonia, and indole over a period of 7 days. In addition, chemicals previously not identified in the aroma profile of blue crab were tentatively detected. Scan mode of the mass spectrometer was used to qualitatively determine compounds extracted from the volatile profile of spoiling blue crab by the SPME fiber. Selected ion monitoring (SIM) mode of the mass spectrometer improved resolution, identified compounds at low concentrations, and allowed spoilage related compounds to be detected in one chromatographic run without sample heating. TMA increased linearly. A significant difference in TMA concentrations were found for day 0 and day 4 samples. Indole concentrations corresponded well with sensory and microbial evaluations, in early, mid, and highly spoiled crab meat samples.     

Characterization of key-aroma compounds of botrytized wines,influence of grape botrytization

Botrytized wines (BW) are famous for their distinctive, complex aromas. To date, only a few studies have analysed the volatile compounds involved in their typical flavours. In this paper, GC–O was applied to BW and dry white wines (DW) made from the same grape varieties to characterize the main odorants responsible for their sensory differences. Surprisingly, only two odorous zones, with grapefruit or curry nuances, were apparently specific to BW. However, GC–AEDA revealed important differences in the FD values between BW and DW, making it possible to screen potent odorants of BW, such as 3-mercaptohexan-1-ol, homofuraneol^®, furaneol^®, sotolon, methional, and phenylacetaldehyde. GC–MS quantification of homofuraneol^®, furaneol^®, norfuraneol^®, phenylacetaldehyde, and methional in 14 BW, mostly at levels above their perception thresholds, confirmed their contribution to the aroma of BW. Increased concentrations of some of these odorants in BW were shown to be associated with grape botrytization, partially through the desiccation process.     

Comparative analysis of clary sage (S. sclarea L.) oil volatiles by GC–FTIR and GC–MS

The comparative analysis of volatiles in essential oil by gas chromatography–Fourier transform infrared spectrometry (GC–FTIR) and gas chromatography–mass spectrometry (GC–MS) are investigated using a DB-wax capillary column. This technique is applied to allelochemicals present in volatiles. The identification analysis of volatile components in four kinds of clary sage (Salvia sclarea L.) oil is described. The GC–FTIR information obtained is complementary to the information obtained from GC–MS. With the IR subtractive spectrum technique, the GC overlap peaks can be resolved without further separate step on the other column of different polarity. Combined with GC–FTIR, GC–MS techniques, and linear retention indices (RI) of the volatile compounds, the reliability of qualitative analysis is greatly enhanced.     

Characterisation of odour active volatile compounds of New Zealand sea urchin (Evechinus chloroticus) roe using gas chromatography–olfactometry–finger span cross modality (GC–O–FSCM) method

Sea urchin roe is a high value product; however, previous attempts to market the roe from the New Zealand sea urchin (Evechinus chloroticus) have been unsuccessful due to its inconsistent sensory quality. The current study investigated the odour active volatile profiles of roe from male and female sea urchins, harvested from two locations in New Zealand, using solvent assisted flavour evaporation (SAFE) extracts and a gas chromatography–olfactometry–finger span cross modality (GC–O–FSCM) method. Panellists detected 81 odour active compounds, 18 of which were identified using GC–mass spectrometry (MS). Generalised procrustes analysis (GPA) of the data revealed that there were differences in the volatile profile that were location and gender specific. These differences may have contributed to the inconsistent sensory properties of sea urchin roe. The differences in volatile profiles between sea urchin populations and genders must be appreciated before developing effective strategies to produce consistent sea urchin roe quality.     

Effect of storage time and heat processing on the volatile profile of Senegalese sole (Solea senegalensis Kaup, 1858) muscle

The effect of heat treatment and the presence or absence of fish skin on the volatile composition of Senegalese sole muscle was studied. The volatile profile of Senegalese sole at different storage periods was also evaluated. All samples were analysed by HS-SPME–GC–IT/MS and subjected to sensory evaluation. As expected, cooking enhanced the production/liberation of volatile compounds. Fish with the skin present, after cooking, had higher levels of sulphur compounds, 2-nonanone, ethyl octanoate and lower contents of hexanol and heptanol than skinned fish; moreover, the samples with the skin had a better overall sensory acceptability. During storage, changes on the volatile composition of Senegalese sole samples were found. The major differences were obtained after 2 weeks of storage. Compounds such as hexanal, heptanal, octanal, decanal, (E)-2-hexenal, (E)-2-decen-1-al, (E,Z)-2,6-nonadienal, benzaldehyde, 4-ethyl-benzaldehyde, 1-penten-3-ol, heptanol and (E)-2-octen-1-ol decreased after 2 weeks of storage, and other compounds, such as 3-methyl-1-butanal, 2-methyl-1-butanal, 2-heptanone, dimethyl trisulphide, dimethyl tetrasulphide and 2-methyltetrahydrothiophen-3-one increased. These differences were confirmed by sensory evaluation. Principal component analysis was applied to the chemical data.     

Changes of volatile compounds in wine vinegars during their elaboration in barrels made from different woods

Changes in the volatile components of red wine vinegars and balsamic vinegars were investigated during 1 year of aging in wood barrels and bottles. Barrels of four different woods (oak, chestnut, acacia and cherry) were used. A total of 57 volatile compounds were analysed by Gas Chromatography–Flame Ionization Detection (GC–FID) and Headspace Sorptive Extraction GC–Mass Spectrometry (HSSE-TD–GC–MS). We observed significant increases in the total content of volatile compounds only for balsamic vinegars. The concentrations of ethyl furoate, ethyl benzoate, benzaldehyde and acetophenone were highest in cherry barrels. These compounds, then, seem to be characteristic of this wood. Oak lactones presented the highest increases for vinegars aged in oak. Eugenol was only present in vinegars aged in chestnut and oak barrels. Oak and cherry seem to be the best type of wood for aging of vinegar due to their distinctive aromatic characteristics.     

Aroma impact components of rabbiteye blueberry (Vaccinium ashei) vinegars

The aroma impact components of the rabbiteye blueberry vinegars made from wine fermented without skin-contact (JV), wine fermented with skin-contact (WV), or blueberries (BV) were evaluated. Headspace volatiles were isolated by solid-phase microextraction (SPME). Headspace volatiles were analysed by gas chromatography–mass spectrometry (GC–MS) and gas chromatography–olfactometry (GCO). The potent odourants were evaluated by the ‘Osme’ method. Acetic acid, 2/3-methyl-butanoic acid, phenethyl acetate, 2-phenylethanol, octanoic acid, eugenol, and phenylacetic acid were the most important aroma-active compounds identified in all three treatments. The contributions of these compounds to each sample were different. There were more aroma-active compounds identified from the BV than from the other two treatments. The type of fermentation impacts the aroma components of rabbiteye blueberry vinegars.     

Analysis of volatile compounds of Antrodia camphorata in submerged culture using headspace solid-phase microextraction

In this work a headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography–mass spectrometry (GC–MS) and GC–olfactometry (GC–O) was developed to evaluate the profile of the volatile compounds that contribute to the aroma of Antrodia camphorata in submerged culture. For this purpose, the HS-SPME sampling method for the volatile compounds of A. camphorata in submerged culture was optimised by a D-optimal design. A HS extraction of the culture broth of A. camphorata followed by incubation on a carboxen/polydimethylsiloxane (CAR/PDMS) fibre during 31.8 min at 54.6 °C gave the most effective and accurate extraction of the volatile compounds. By the optimised method, a total of 49 volatile compounds were identified in culture broth of A. camphorata, while a total of 55 volatile compounds were identified in the mycelia. A series of C₈ aliphatic compounds (mushroom-like odour), several lactones (fruity odour) and l-linalool (citrus-like odour) were the most potent key odourant in both the mycelia and culture broth. This combined technique is fast, simple, sensitive, inexpensive and useful to monitor volatile compounds associated to A. camphorata.     

Climatic factors directly impact the volatile organic compound fingerprint in green Arabica coffee bean as well as coffee beverage quality

Coffee grown at high elevations fetches a better price than that grown in lowland regions. This study was aimed at determining whether climatic conditions during bean development affected sensory perception of the coffee beverage and combinations of volatile compounds in green coffee. Green coffee samples from 16 plots representative of the broad range of climatic variations in Réunion Island were compared by sensory analysis. Volatiles were extracted by solid phase micro-extraction and the volatile compounds were analysed by GC–MS. The results revealed that, among the climatic factors, the mean air temperature during seed development greatly influenced the sensory profile. Positive quality attributes such as acidity, fruity character and flavour quality were correlated and typical of coffees produced at cool climates. Two volatile compounds (ethanal and acetone) were identified as indicators of these cool temperatures. Among detected volatiles, most of the alcohols, aldehydes, hydrocarbons and ketones appeared to be positively linked to elevated temperatures and high solar radiation, while the sensory profiles displayed major defects (i.e. green, earthy flavour). Two alcohols (butan-1,3-diol and butan-2,3-diol) were closely correlated with a reduction in aromatic quality, acidity and an increase in earthy and green flavours. We assumed that high temperatures induce accumulation of these compounds in green coffee, and would be detected as off-flavours, even after roasting. Climate change, which generally involves a substantial increase in average temperatures in mountainous tropical regions, could be expected to have a negative impact on coffee quality.     

Discrimination of oolong tea (Camellia sinensis) varieties based on feature extraction and selection from aromatic profiles analysed by HS-SPME/GC–MS

This study aimed to develop an objective and accurate analytical method to discriminate oolong tea varieties that easily causing adulteration by potential volatile compounds. A total of 75 oolong tea samples of five similar varieties (Tieguanyin, Benshan, Maoxie, Huangjingui and Jinguanyin) were analysed by headspace solid phase microextraction (HS-SPME) coupled with gas chromatography–mass spectrometry (GC–MS). The relative content of 26 major volatile compounds varied significantly according to variety, combined with the results of hierarchical cluster analysis (HCA), indicating that the varietal differences of aromatic profile remain significant for tea cultivars with very close origin. Principal component analysis (PCA) of the aromatic profiles showed that the feature of variety dominated over the other features (like producing region and quality). By stepwise linear discriminant analysis (S-LDA), 18 volatiles with the best discriminating capacity were selected, and 4 discriminant functions (DFs) enabled simultaneously discrimination of the five oolong varieties with 100% correct rate.