Characterisation of aroma active compounds in black truffles (Tuber melanosporum) and summer truffles (Tuber aestivum) by gas chromatography–olfactometry

The aromatic composition of two different species of truffles (black and summer) was evaluated by gas chromatography–olfactometry (GC–O). Volatiles released by the truffles at 25 °C for 7.5 h were collected in a trapping system consisting of 400 mg of LiChrolut EN kept at 0 °C and further eluted with dichloromethane/methanol (95:5). The extract was analysed by two different GC–O strategies: (1) a semiquantitative GC–O study using a panel composed of nine individuals, (three of them truffle experts) and (2) an AEDA (aroma extract dilution analysis) experiment with a small panel of two judges. The results show that the aroma emitted by a typical black truffle is due to at least 17 different aroma molecules, six of which are reported for the first time: 1-hexen-3-one, 2-methyl-3-furanthiol, furaneol, 3-ethylphenol, 3-propylphenol and 5-methyl-2-propylphenol. The most important aroma compounds of black truffle aroma are 2,3-butanedione, dimethyl disulphide (DMDS), ethyl butyrate, dimethyl sulphide (DMS), 3-methyl-1-butanol and 3-ethyl-5-methylphenol. Quantitatively, black truffle emits mostly 3-ethyl-5-methylphenol (more than 50% of the total aroma molecules emitted), 5-methyl-2-propylphenol, β-phenylethanol and 3-ethylphenol. In the case of summer truffle, the most important aroma molecules are DMS, DMDS, methional, 3-methyl-1-butanol, 1-hexen-3-one and 3-ethylphenol. From the quantitative point of view, summer truffle emits mainly β-phenylethanol, DMS and 3-ethylphenol, but the emission is up to 100 times less than that of black truffles.     

Producing headspace extracts for the gas chromatography–olfactometric evaluation of wine aroma

In this work different designs of headspace devices were studied. Using these designs, 23 volatile compounds of wine aroma added to a synthetic wine were purged by an inert gas (nitrogen) and trapped in a solid-phase extraction (SPE) cartridge. Efficiency was measured as the similarity between the odour intensity in a model wine in the glass and the odour intensity recorded in the gas chromatography–olfactometry (GC–O) experiment.     

Comparison on aroma compounds in Chinese soy sauce and strong aroma type liquors by gas chromatography–olfactometry,chemical quantitative and odor activity values analysis

In order to elucidate the differences on aroma compounds in Chinese liquors with different aroma styles and the reasons, aroma compounds of Xijiu in soy sauce aroma and strong aroma type were investigated in the research. By gas chromatography–olfactometry (GC–O), aroma compounds in Chinese liquor were chosen for quantitative and odor activity value (OAV) analysis. Ethyl hexanoate, butanoic acid, 3-methylbutanoic acid, hexanoic acid and dimethyl trisulfide were considered to be the most powerful odorants in both liquor samples (aroma intensity ≥3.5) by GC–O. As important aroma compounds (OAV ≥10) in the liquors, ethyl propanoate, ethyl 2-methylpropanoate and 1-propanol were considered with much higher OAVs in soy sauce aroma type liquor, while OAVs of ethyl pentanoate, ethyl hexanoate, ethyl heptanoate, ethyl octanoate, ethyl lactate, hexyl acetate, butyl hexanoate, hexyl hexanoate and hexanoic acid were far lower in strong aroma type liquor. The OAV of ethyl hexanoate in strong aroma type liquor exceeded 50,000, which explained the reason why strong aroma liquor was considered with prominent fruity aroma. The odor differences between the liquors were mainly caused by the manufacturing practices.     

Characterisation of sugars as the typical taste compounds in soy sauce by silane derivatisation coupled with gas chromatography–mass spectrometry and electronic tongue

A total of 214 taste compounds were identified in soy sauce by silane derivatisation coupled with gas chromatography–mass spectrometry (SD-GC-MS), including 74 kinds of sugars. The proportion of total sugars is highest from 37.24–77.24% among all taste compounds. In particular, rare sugars were detected and identified as the special compounds in soy sauce which come from the sugar metabolism. Rare sugars identified in soy sauce by traditional fermented technology were prominent than Japanese technology. Principal component analysis (PCA) investigation of these results showed that samples can be distinguished by sugars as the first principal component and the general evaluation index (GEI) of samples was consistent with the result of sensory evaluation. Meanwhile, sweetness had the maximum range (from −9.89 to 14.10) in all taste indexes by electronic tongue (E-tongue) analysis.     

Determination of volatile compounds formed in a glucose–selenomethionine model system by gas chromatography–atomic emission detector and gas chromatography–mass spectrometry

In order to gain a better understanding of the formation of organoselenium compounds in food system, the Maillard reaction of selenomethionine and glucose was studied in a model system. The effects of heating time and pH on the volatile compounds formed in a glucose–selenomethionine reaction were also investigated. Nine organoselenium compounds were identified. Pyrazines and dimethyldiselenide are major volatile compounds generated from the glucose–selenomethionine model system. A high pH level favours the formation of pyrazine and dimethyldiselenide. In unbuffered systems, a pH change of three or more pH units may occur, and this may significantly affect the formation of Maillard reaction products.     

Study of the volatile compounds useful for the characterisation of fresh and frozen-thawed cultured gilthead sea bream fish by solid-phase microextraction gas chromatography–mass spectrometry

A simple method, based on solid-phase microextraction gas chromatography–mass spectrometry, was developed for the study of the aromatic profile of cultured gilthead sea bream fish during frozen storage. The method was applied to the study of the volatile profile of fresh and frozen-thawed Italian and Spanish cultured gilthead sea bream fish over 266 days of frozen storage. Variations in the chromatographic responses of a number of volatile compounds during storage were detected and the observed differences evaluated on a biochemical basis. Correlations with oxidation parameters, e.g. peroxide value and thiobarbituric acid-reactive substance indices, indicated 1-octen-3-ol, 1-penten-3-ol, and Z-4-heptenal as markers for the differentiation between fresh and frozen-thawed fish.     

Characterization of the differences in the aroma of cherry wines from different price segments using gas chromatography–mass spectrometry,odor activity values,sensory analysis,and aroma reconstitution

The aroma composition, aroma-active compounds, and sensory attributions of cherry wines from three different price segments were investigated. A total of 48 aroma compounds were identified and quantified using headspace solid-phase microextraction (HS-SPME)/gas chromatography–mass spectrometry (GC–MS), among which 23 aroma compounds were further screened out as important odorants based on their odor activity values (OAVs); then, the previously mentioned 23 volatiles were correlated to sensory attributes using partial least-squares regression (PLSR). The result indicates that the differently priced wines were associated with different compounds and aroma attributions. Finally, aroma reconstitution was performed by mixing odor-active aroma compounds (OAVs>1) on the basis of their measured concentrations in the original sample. The result indicated that the aroma profile of the reconstituted sample was similar to that of the original sample.     

Ultrasound-assisted hydrolysis and gas chromatography–mass spectrometric determination of phenolic compounds in cranberry products

An ultrasound-assisted hydrolysis and gas chromatography–mass spectrometric (GC–MS) method has been developed for determination of phenolics in cranberry products. Prior to GC–MS separation and characterisation, the phenolics in samples were hydrolysed by hydrochloric acid with ultrasound-assistance, extracted with ethyl acetate, and derivatised with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) + 1% trimethylchlorosilane (TMCS) reagents. The application of ultrasonication significantly accelerated the acidic hydrolysation of the conjugated phenolics. A baseline separation of the 20 phenolics and internal standard was achieved in 25 min. Standard calibration curves were linear over the concentration range of 0.0–50 μg/mL and detection limits were 0.06–0.70 μg/mL. Twenty phenolics were identified in cranberry samples and all of them occurred mainly in conjugated forms. Of those, the benzoic acid, quercetin, and myricetin were most abundant phenolics. The total phenolics were 12.4 mg/g in cranberry fruits, 9.1 mg/mL in 100% cranberry juice, and 11.1 mg/g in cranberry sauces, respectively.     

Characterisation of the glycerophospholipid fraction in flaxseed oil using liquid chromatography–mass spectrometry

A high-performance liquid chromatographic method coupled with mass spectrometry was used to characterise the natural phospholipid (PL) classes and molecular species in flaxseed oils. The PL fraction included phosphatidylethanolamine (PE) (27–40%), phosphatidylinositol (PI) (29–32%), phosphatidylcholine (PC) (7–18%), lysophosphatidylcholine (LPC) (8–21%), phosphatidylglycerol (PG) (1–4%) and phosphatidic acid (PA) (1–9%). The distribution of fatty acids was found to differ between phospholipids. Stearic acid was mainly present in the form of PC and LPC. Palmitic acid was present in the most abundant molecular species in PI, PG and PA whereas linoleic acid formed the most abundant molecular species in PE.     

Furanic compounds and furfural in different coffee products by headspace liquid-phase micro-extraction followed by gas chromatography–mass spectrometry: survey and effect of brewing procedures

In this study, the levels of furan, 2-methylfuran, 2,5-dimethylfuran, vinyl furan, 2-methoxymethyl-furan and furfural in different coffee products were evaluated. Simultaneous determination of these six furanic compounds was performed by a head space liquid-phase micro-extraction (HS-LPME) method. A total of 67 coffee powder samples were analysed. The effects of boiling and espresso-making procedures on the levels of furanic compounds were investigated. The results showed that different types of coffee samples contained different concentrations of furanic compounds, due to the various processing conditions such as temperature, degree of roasting and fineness of grind. Among the different coffee samples, the highest level of furan (6320 µg kg^?1) was detected in ground coffee, while coffee-mix samples showed the lowest furan concentration (10 µg kg^?1). Levels in brewed coffees indicated that, except for furfural, brewing by an espresso machine caused significant loss of furanic compounds.     

Analysis of the flavor of aged spirits made from sweet potato and rice by gas chromatography–mass spectrometry

Flavor patterns of sweet potato spirits (SPS) made from sul–deot manufactured by sweet potato showed an increasing tendency for aging from 64 to 128 weeks. When the SPS was blended with spirits made from sul–deot manufactured by rice in a 7:3 ratio, showing an increase for aging from 16 to 60 weeks, using a gas chromatography–mass spectrometry with solid-phase microextration. The main compounds showing increasing tendency of the SPS and blended spirits (BS) were iso-amyl alcohol, n-propanol. Especially, ethyl caprylate, and ethyl acetate increased in SPS. The results were cross-checked by an electronic nose. For the results of SPS in the flavor pattern, a decrease was noted by main ion fragments. For the BS, a decrease was noted. These cross-checked results were useful for controlling quality of aging spirits, especially SPS. Based on these results, it was considered that further experiments are needed to identify key compounds for accurate correlation analysis.     

Characterisation of the mushroom-like flavour of Melittis melissophyllum L. subsp. melissophyllum by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography (GC–FID) and gas chromatography–mass spectrometry (GC–MS)

1-Octen-3-ol is an eight-carbon alcohol responsible for the unique fungal aroma and flavour of edible mushrooms. Among Lamiaceae plants, the highest concentration of this molecule was detected in Melittis melissophyllum subsp. melissophyllum growing in central Italy. On this basis in the present study a HS-SPME coupled with GC–FID and GC–MS was performed to check the influence of several analytical parameters on the amount of 1-octen-3-ol from the plant matrix. Results showed that 1-octen-3-ol is produced in the plant matrix independently from the harvesting time by an enzyme reaction that is enhanced by the optimisation of the extraction conditions (extraction temperature, 40 °C; water addition, 20 μl; extraction time, 30 min; particle size, 1 mm, sample amount, 30 mg). These findings revealed that M. melissophyllum is the first example of a plant, that under appropriate conditions, may be used as a mushroom-like flavouring agent in food products.     

Application of dispersive liquid–liquid microextraction for the determination of selected organochlorine pesticides in honey by gas chromatography–mass spectrometry

Dispersive liquid–liquid microextraction (DLLME) is a rapid and easy technique that consumes minute amounts of organic solvents. In this work, we present chemometric study on optimization of DLLME parameters for the extraction of aldrin, endrin, lindane, α-endosulfan, 4,4′-DDT and its metabolites from honey matrix. Method quantification limits (MQLs) vary between 0.3 ng/g for 2,4′-DDE and 4,4′-DDE to 13.2 ng/g for α-endosulfan and enable determination at levels below EU-established Maximum Residue Limits. The developed method is linear (R ² > 0.994) in the investigated range (MQL—100 ng/g), with preconcentration factors of 13.2–30.5 and good repeatability (CV ≤ 17%). A comparison with other available methods reported in the last decade is provided. The method has been applied to 19 real samples from Poland, and the results show that organochlorine pesticides (OCPs) are present in analysed honeys at levels not posing threat to human health (below 14 ng/g for sum of 4,4′-DDT and metabolites and below 5 ng/g for aldrin, endrin and lindane). To the best of our knowledge, this is the first reported application of DLLME for the determination of OCPs in honey.     

Quantitative analysis of volatiles in transesterified coconut oil by headspace-solid-phase microextraction-gas chromatography–mass spectrometry

A simple and fast headspace-solid-phase microextraction (HS-SPME) method coupled with gas chromatography–mass spectrometry (GC–MS) was developed for the analysis of volatile compounds in transesterified coconut oil by applying solvent dilution. Solvent dilution conditions (solvent type and solvent amount) and HS-SPME sampling parameters (adsorption temperature and time) were optimised through monitoring the adsorption result of the selected volatiles (octanoic acid esters) in transesterified coconut oil samples. The incubation of methanol (800 μl)-diluted oil (200 μl) sample at 60 °C for 30 min led to the best result. The method was further validated by determining the calibration linear range, correlation coefficient (R²), accuracy, precision, limit of detection and limit of quantification through spiking standards into the blank matrix consisting of coconut oil and methanol. This method may also be applicable for detection and determination of volatile compounds in other transesterified oil samples.     

Role of sepiolite in the release of active compounds from gelatin–egg white films

Nanosized material fillers are widely used to enhance certain properties of polymers. Moreover, the use of nanoclays as a delivery host in pharmaceutical fields has gained a great interest. Sepiolite was incorporated to gelatin–egg white films containing clove essential oil. The effect of the incorporation of both sepiolite and clove essential oil on the physical properties of the resultant films was evaluated. Special attention was given to the role of this nanoclay in the release of antioxidant and antimicrobial compounds from the film matrix. Sepiolite showed a reinforcement effect of Young’s modulus and tensile strength, meanwhile the clove essential oil had a certain plasticizing effect by increasing the elongation at break and water vapour permeability (WVP). When both compounds were added together, a noticeable loss of mechanical properties was observed, related to the loss of gelling capacity (G′), protein self-aggregation and α-helix structure decrease (FTIR). However, the WPV increased, probably due to the presence of cavities in the matrix observed by SEM. The incorporation of sepiolite in these films containing clove essential oil increased the release of both protein components and eugenol from the film matrix, leading to a controlled release of the antioxidant activity measured by ferric reducing ability and radical scavenging capacity, as well as a higher antimicrobial effect.     

Characterization of volatile compounds of pu-erh tea using solid-phase microextraction and simultaneous distillation–extraction coupled with gas chromatography–mass spectrometry

Two extraction methods, namely, solid-phase microextraction (SPME) and simultaneous distillation–extraction (SDE) both followed by gas chromatography–mass spectrometry were applied for the determination of a wide range of volatile compounds in pu-erh tea. The conditions of solid-phase microextraction including fiber selections and sampling condition optimization have been previously investigated. By the two methods, 79 volatile compounds belonging to different categories were identified. Among them, 61 volatile compounds were extracted by SDE and 67 by SPME. Qualitative and quantitative differences of pu-erh tea volatile profiles were observed by applying the two aforementioned extraction methods. SDE technique achieved higher percentages of high molecular weight alcohols, acids, and esters of low volatility, whereas SPME technique was found useful for analyzing low molecular weight alcohols, methoxy-phenolic compounds, aldehydes, ketones, and hydrocarbons of high volatility that were closely related to the characteristics of pu-erh tea aroma and its sensory perception. Therefore, SPME technique was a reliable extraction method for controlling pu-erh tea quality flavor.     

Rapid determination of organophosphorous pesticides in leeks by gas chromatography–triple quadrupole mass spectrometry

A rapid multi-residue method was developed for the determination of 20 organophosphorous pesticide residues in leeks by gas chromatography coupled to triple quadrupole mass spectrometry (GC–QqQ-MS/MS). The method was based on the modified QuEChERS sample preparation method. After microwave pre-treatment, leek samples were extracted with acetonitrile containing acetic acid 0.1% and cleaned by dispersive solid phase extraction. The QqQ analyser acquired data in selected reaction monitoring (SRM) mode. Recoveries of 20 organophosphorous pesticides ranged from 81.0% to 109.4% with the relative standard deviations (RSD) below 10.4%. The limits of detection (LODs) were 0.07–1.5 μg/kg. The limits of quantitation (LOQs) ranged from 0.25 to 5 μg/kg. Ten leek samples were analysed for method application.