Characterization of the volatile profile of thistle honey using headspace solid-phase microextraction and gas chromatography–mass spectrometry

In this study, a headspace solid-phase microextraction method was developed for the characterization of the volatile fraction of thistle honey and compared with a dynamic headspace extraction method. A DVB/CAR/PDMS fibre was used. The effects of extraction time, equilibration time and salt addition on extraction yield were evaluated. The volatile fraction of seven Italian thistle honey samples was extracted under the optimized conditions and analyzed by gas chromatography–mass spectrometry. Characterization of the volatile profile was performed in terms of nature and relative amount of the extracted compounds. A total of 40 compounds, belonging to different chemical classes, were identified. The relative amounts of 16 compounds found in all the analyzed thistle honeys, i.e. nonanal, furfural, decanal, 3,6-dimethyl-2,3,3a,4,5,7a-hexahydrobenzofuran, benzaldehyde, α-linalool, lilac aldehyde (isomer IV), hotrienol, phenylacetaldehyde, 4-oxoisophorone, benzyl alcohol, 2-phenylethanol, a not identified compound, octanoic acid, nonanoic acid and methyl anthranilate, were calculated and submitted to statistical analysis, in order to define for each compound a typical range. On the basis of the obtained data, a characteristic set of values was defined for thistle honey volatile fingerprint. The developed model proved to be effective in recognizing the botanical origin of thistle honey.     

Detection of volatile spoilage metabolites in fermented cucumbers using nontargeted, comprehensive 2-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS)

A nontargeted, comprehensive 2-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS) method was developed for the analysis of fermented cucumber volatiles before and after anaerobic spoilage. Volatile compounds extracted by solid-phase microextraction were separated on a polyethylene glycol 1st-dimension column and 14% cyanopropylphenyl 2nd-dimension column. Among 314 components detected in fermented cucumber brine, 199 had peak areas with coefficients of variation below 30%. Peak identifications established by mass spectral library matching were 92% accurate based on 63 authentic standards. Analysis of variance of analytes' log peak areas revealed 33 metabolites changed in concentration after spoilage (P < 0.05), including increases in acetic, propanoic, and butyric acids, n-propyl acetate, several alcohols, and a decrease in furfural. GC×GC-TOFMS with a nontargeted, semi-automated approach to data analysis made possible the separation, identification, and determination of differences in polar volatile components, facilitating the discovery of several metabolites related to fermented cucumber spoilage. Practical Application: An optimized method for the chemical analysis of volatile food components is described and applied to the profiling of volatile compounds in fermented cucumbers, resulting in the identification of 137 components, many of which are being reported for the first time in fermented cucumbers. This nontargeted GC×GC-TOFMS method and inclusive data analysis platform facilitated the discovery of several metabolites that were formed or utilized during anaerobic spoilage of fermented cucumbers. Further study of these metabolites will enhance our ability to understand and potentially control the metabolism of spoilage bacteria that can degrade lactic acid under the restrictive environmental conditions present in fermented cucumbers.     

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.     

Microwave distillation followed by headspace single drop microextraction coupled to gas chromatography-mass spectrometry (GC–MS) for fast analysis of volatile components of Echinophora platyloba DC

To avoid the traditional and time consuming hydrodistillation, the analyses of volatile components in aerial parts of Echinophora platyloba DC was carried out by a simple microwave distillation followed by headspace single drop microextraction (MD–HS–SDME) coupled to gas chromatography–mass spectrometry (GC–MS). The headspace volatile compounds were collected after irradiation using a single drop of n-heptadecan. The extraction conditions were optimised using the relative peak areas as index. The chemical composition of the MD–HS–SDME extracts was confirmed according to their retention indexes and mass spectra. Fifty-three components were extracted and identified by using the MD–HS–SDME method. E-β-ocimene (53.81%), R-d-decalactone (12.75%), α-pinene (6.43%), n-heptanol (6.27%), β-phellanderne (2.70%) and linalool (1.89%) were the major constituents.     

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.     

Determination of phthalate esters in wine using solid-phase extraction and gas chromatography–mass spectrometry

A method for the determination of six phthalate esters in wine samples has been developed. The phthalates were extracted from wine samples with an optimised solid-phase extraction method on C18 column and quantification was achieved via gas chromatography coupled with a mass spectrometer. The method was linear between 0.015 and 5.000 μg mL⁻¹ for DMP, DEP and DEHP and between 0.018 and 5.000 μg mL⁻¹ for iBP, DBP and BBP. The LOQs of DMP, DEP and DEH were 0.024 μg mL⁻¹ while those of iBP, DBP and BBP were 0.029 μg mL⁻¹. The intra-day method repeatability was between 10% and 15% RSD, whereas the inter-day method repeatability was between 13% and 21% RSD. A survey was performed on white and red wines (n = 62) from the market, winemakers and an experimental pilot plant. All the analysed samples were phthalate contaminated. Commercial wine showed higher detection frequency and level of total phthalate, DBP and BBP than those produced in a pilot plant. iBP and DEHP concentrations were similar in all the groups of samples. iBP concentration was higher in red wines than in white ones.     

Research on degradation of penicillins in milk by β-lactamase using ultra-performance liquid chromatography coupled with time-of-flight mass spectrometry

The degradation of penicillin G, penicillin V, and ampicillin in milk in the presence of β-lactamase was investigated by ultra-performance liquid chromatography coupled with electrospray ionization-time-of-flight mass spectrometry. Degradation products of the 3 penicillins in milk were identified based on the fact that the metabolites or degradation products contain a substructure of penicillin, and their degradation pathways in acidic milk in presence of β-lactamase were developed. The influence of factors on the degradation was investigated, including β-lactamase dosage, temperature, time, and acidity. The ratio of the 2 degradation products (penicilloic acid and penilloic acid) is different at different temperatures and pH. Penicilloic acid was the dominant species obtained at pH 6 under 40°C, but, being unstable, it could not be used as a standard for accurate analysis of penicilloic acid, and also could not be used as target for detection of penicillins in milk. Penilloic acid was the dominant species obtained at pH 2 above 40°C; it was stable and could be used as a standard for quantitative analysis and as target for detecting whether penicillins were used in milk.     

Determination of volatile compounds in New Zealand Greenshell™ mussels (Perna canaliculus) during chilled storage using solid phase microextraction gas chromatography–mass spectrometry

Greenshell™ mussels (Perna canaliculus) were dry-stored at 6.44 ± 0.54 °C for 8 days during which time volatile organic compounds (VOCs) were monitored using SPME GC–MS. Thirty-four VOCs were identified in homogenised mussel meat and 29 in the mussel liquor (i.e. the seawater enclosed in the mantle cavity). Of the 34 VOCs identified 20 were reliably identified throughout the storage treatment and 9 were found to change in relative concentration in homogenised mussel meat. Dimethyl sulphide, 1-penten-3-ol, 1-hexen-3-ol and 1-octen-3-ol increased during storage, whereas pentanal, hexanal, heptanal, octanal and 3-undecen-2-one decreased. In the mussel liquor, dimethyl sulphide was undetectable pre-storage, becoming detectable after 2 days, and a large increase was noted after 6 days. SPME GC–MS was a useful tool for monitoring VOC profiles of Greenshell™ mussels and could aid in the development of technologies that monitor and improve product quality and consistency.     

Establishment of Monstera deliciosa fruit volatile metabolomic profile at different ripening stages using solid-phase microextraction combined with gas chromatography–mass spectrometry

The volatile metabolomic profile of Monstera deliciosa fruits (M. deliciosa, ceriman) at three ripening stages, ripe, half-ripe and unripe, was established using headspace solid-phase microextraction (HS-SPME) combined with gas chromatography–quadrupole mass spectrometry detection (GC–qMS). To obtain the optimal HS-SPME conditions, the main experimental parameters that influence the extraction efficiency and experimental response were analyzed. The highest extraction efficiency was achieved with 1 g of ceriman sample, using a polydimethylsiloxane/divinylbenzene (PDMS/DVB) fiber for 60 min at 40 °C with 15% NaCl (w/w). After optimization, all ceriman samples were analyzed with the best extraction conditions that allowed to identify 80 volatile metabolites (VOMs), belonging to different chemical groups namely ethyl esters (88.61–77.94%), terpenoids (18.08–9.83%), carbonyl compounds (3.41–1.05%), higher alcohols (1.41–0.51%) and lactones (0.14–0.03%). Thirty-eight of the identified volatile metabolites (47.50%) have not been reported in M. deliciosa, so far, providing a more complete characterization of its volatile composition. The predominant VOMs identified in M. deliciosa fruits were ethyl butanoate, linalool, ethyl hexanoate, ethyl 2-methyl butanoate, butanoic acid, ethyl benzoate and propyl butanoate. Remarkable differences were found in both the quantitative and qualitative composition of M. deliciosa fruits at different ripening stages.Principal component analysis (PCA) provided a suitable tool to differentiate the volatile profile of target fruits among three ripening stages.     

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 polyphenol components of Korean Scutellaria baicalensis Georgi using liquid chromatography–tandem mass spectrometry: Contribution to overall antioxidant activity

In order to explore the possibility to process Korean Scutellaria baicalensis Georgi (Hwang Gum) to produce a high quality functional food, biologically active substances were analyzed. Four different mixtures of polyphenol components were isolated from the flower, leaf, stem, and root of S. baicalensis Georgi via methanol extraction followed by silica gel column chromatography. The polyphenol components of these mixtures were determined using high-performance liquid chromatography–tandem mass spectrometry (HPLC–MS/MS) and compared with reported data. Among the 46 characterized components, seven constituents were identified for the first time. The compounds were validated and quantified based on a representative standard from the same group. The antioxidant activity of the polyphenol mixtures of the four tissues was determined. The antioxidant activity of the root was the highest, followed by the leaf, stem and flower.     

Determination of biogenic diamines with a vaporisation derivatisation approach using solid-phase microextraction gas chromatography–mass spectrometry

A gas-phase on-fibre derivatisation method for the determination of putrescine and cadaverine by gas chromatography/mass spectrometry using trifluoroacetylacetone (TFAA) has been studied and optimised. Small amounts (2 μl) of putrescine, cadaverine and TFAA standards were vaporised at high temperature in a 20 cm³ closed SPME vial. The subsequent derivatives were recovered from the headspace of the vial using a PDMS/DVB fibre. The optimised mole ratio for [TFAA]/[Putrescine + Cadaverine] reaction was 22.3/1 with a derivatisation and extraction temperature of 120 ^oC and an extraction time of 20 min. The retention times for the derivatised putrescine and cadaverine were 20.5 and 22.2 min, respectively on a capillary column, CP-Sil 8CB; 30 m length × 0.25 mm i.d. × 0.25 μm film thickness. The correlation coefficients (R²) of calibration curves for putrescine and cadaverine were 0.999 and 0.997, respectively over a range of sample masses of 20–350 ng, using nonadecane as an internal standard. Putrescine and cadaverine recoveries were determined to be 93.9% and 103.3%, respectively. The method was found to be a straightforward single step procedure that was unaffected by complex sample matrices and was successfully tested on samples of meat, vegetables and cheese.     

Comprehensive authenticity assessment of lavender oils using multielement/multicomponent isotope ratio mass spectrometry analysis and enantioselective multidimensional gas chromatography–mass spectrometry

¹³C_V-PDB, ²H_V-SMOW and ¹⁸O_V-SMOW multielement isotope ratio mass spectrometry analysis of linalool and linalyl acetate, the main components of lavender oils, is reported. Self-prepared and commercially available lavender oils, as well as samples of linalool and linalyl acetate labelled as synthetic and natural products respectively, were investigated. Multielement/multicomponent isotope ratio mass spectrometry analysis and—as far as possible—in conjunction with enantioselective analysis is judged to be the most comprehensive basis of authenticity assessment in flavour and essential oil analysis.     

Characterization of Arabica and Robusta volatile coffees composition by reverse carrier gas headspace gas chromatography–mass spectrometry based on a statistical approach

Food Science and Biotechnology - Nineteen samples of Arabica and 14 of Robusta coming from various plantation were analysed by dynamic headspace capillary gas chromatography–mass spectrometry...     

Determination of 3-MCPD in grilled meat using pressurized liquid extraction and gas chromatography–high resolution mass spectrometry

An analytical method for the determination of free 3-monochloropropane-1,2-diol (3-MCPD) in grilled meat using pressurized liquid extraction, derivatisation using phenylboronic acid, and gas chromatography/high resolution mass spectrometry was developed. The limit of quantification was 1???g/kg. Using this method, the contents of 3-MCPD in grilled steaks (collar) were analysed for different grilling conditions. Charcoal, an electric grill, and a gas grill were used for grilling collars. Further parameters investigated were the pre-treatment of meat (untreated, salted, marinated with oil or emulsion marinade), the use of aluminium grill trays, and a lid. For grilled steaks, contents of 3-MCPD in the range of <1 to 365???g/kg (median 16???g/kg) were detected. The highest contamination was found for a steak pre-treated with an oily marinade grilled on a charcoal grill with a closed lid. Consuming such a steak will exhaust the tolerable daily intake of 2???g/kg body weight for 3-MCPD to about 26?%.     

Headspace solid-phase microextraction gas chromatography–mass spectrometry (HS-SPME-GC–MS) determination of volatile compounds in roasted plantains (French sombre and Dwarf Kalapua)

Volatile compounds from roasted plantains (French sombre, AAB) and (Dwarf Kalapua, ABB) at different stages of ripening were evaluated by a gas chromatography–mass spectrometry (GC–MS) with headspace solid-phase microextraction (HS-SPME). A total of 42 volatile compounds were identified in the roasted plantain cultivars. Some of the volatile compounds with high concentration were 2,3-dimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine, (E)-2-hexenal, 2,5-dimethylpyrazine and 2,3-dihydro-5-hydroxyl-6-methyl-(4H)-pyran-4-on respectively. Principal component analysis (PCA) based on the relationships between ripening/quality of volatiles showed that 2-methyl propanol, furfural, 2,5-dimethyl pyrazine, 2,3-butanedione, guaiacol, 2-ethyl-3-methyl pyrazine, 5-, ethyl acetate, 2-pentanol, 3-isobutyl-2-methoxy pyrazine and 7,8-dihydro-β-ionol were considered to contribute significantly to the overall aroma quality of fairly riped (stages 4 & 5) and roasted plantains.     

Changes in flavour compound profiles of precooked pork after reheating (warmed-over flavour) using gas chromatography–olfactometry–mass spectrometry with chromatographic feature extraction

The unclear components and complex evaluation indicators affect the effectiveness of inhibition methods for warmed-over flavour (WOF). To evaluate the main components of WOF, the changes in flavour compound profiles of precooked pork after reheating were investigated quantitatively by using gas chromatography–olfactometry–mass spectrometry with chromatographic feature extraction. A total of 49 volatile compounds were identified, including 22 aroma-active compounds that were primarily derived from lipid oxidation. Fifteen key volatile compounds were obtained that represented principal components of the changes in flavour compound profiles, of which 1-octen-3-ol, (Z)-2-octenal and (E,E)-2,4-decadienal made the greatest contribution to the principal components and achieved odour activity value (OAVs) >1.0 after reheating. The results showed that the three compounds are the dominant volatile compounds and potential evaluation indicators of WOF. This study provides a further understanding of the components of WOF in precooked pork and an effective analysis method of gas chromatography.