Identification of pyrazine derivatives in a typical maple syrup using headspace solid-phase microextraction with gas chromatography–mass spectrometry

Headspace solid-phase microextraction combined with gas chromatography–mass spectrometry was applied to identify pyrazines in a typical maple syrup characterised by plant ligneous or sawdust flavour. Carboxen/polydimethylsiloxane (85 μm) fibre and Supelcowax 10 column were selected instead of Carbowax/divinylbenzene (65 μm) fibre and VF-5ms column, respectively, because of their high capacity to extract and separate pyrazines. A total of 27 pyrazines were identified. To our knowledge, about half of these compounds had not previously been detected in maple syrup and 15 pyrazines were flavour components.     

Analysis of odour‐active compounds of black mangrove (Avicennia germinans L.) honey by solid‐phase microextraction combined with gas chromatography–mass spectrometry and gas chromatography–olfactometry

The volatile compounds of Cuban black mangrove (Avicennia germinans L.) honey were analysed by solid‐phase microextraction (SPME) followed by gas chromatography–mass spectrometry and gas chromatography–olfactometry. A total of 66 compounds were positively identified in this product for the first time. Application of the aroma extract dilution analysis in a novel approach, which consisted of carrying out successively dilutions of the honey sample with a synthetic honey before the SPME, revealed 17 odour‐active areas in the flavour dilution factor range of 32–1024. On the basis of the quantitative data and odour thresholds, odour activity values (OAV; ratio of concentration to odour threshold) were calculated. Sixteen compounds showed OAVs >1, among which dimethyl sulphide, 3‐methyl butanal, 2‐methylbutanal, heptanal, octanal, phenylacetaldehyde, (Z)‐linalool oxide, (E)‐linalool oxide, nonanal, hotrienol, isophorone, lilac aldehyde A, 1‐nonanol, decanal, 4‐vinyl‐2‐methoxyphenol and (E)‐β‐damascenone showed the highest values and should be considered as the most odour‐active compounds, particularly (E)‐β‐damascenone, nonanal and decanal.     

Headspace volatile components of smoked swordfish (Xiphias gladius) and cod (Gadus morhua) detected by means of solid phase microextraction and gas chromatography–mass spectrometry

A study of the headspace of smoked swordfish and cod was carried out by means of Solid Phase Microextraction followed by gas chromatography–mass spectrometry. The headspace of both smoked fish species contains ketones, aldehydes, alcohols, acids, esters, hydrocarbons, ethers, nitrogen derivatives, phenol, guaiacol, and syringol derivatives, as well as some chlorinated contaminants. The differences found between the headspace of both smoked fish are basically due both to a higher proportion of smoke components in cod than in swordfish, and to specific fish components being present or absent in each fish sample. The high proportion of syringol in both fish samples indicates that smoking was carried out using hardwood. Some smoke components were not detected in the headspace of these smoked fish samples.     

Optimization of equilibrium headspace analysis of volatile flavor compounds of malaysian soursop (Annona muricata): Comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS)

Headspace solid-phase microextraction (HS-SPME) coupled to comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) was applied for equilibrium headspace analysis of Malaysian soursop (Annona muricata) volatile flavor compounds. A two-level fractional factorial design (2^5-1) was used to determine the effect of SPME variables, namely, SPME fibers, adsorption temperature, extraction time, amount of salt, sample amount and sample concentration on the extraction efficiency of volatile flavor compounds. A total of 37 volatile compounds were identified, comprising 21 esters, 6 alcohols, 3 terpenes, 2 acids, 2 ketones, 2 aldehydes and an aromatic with different hydrophobicities (log P) ranging between −0.14 and 4.83. Extraction using 10 g of diluted (5% w/w) blended soursop pulp with CAR/PDMS fiber at 25 °C for 30 min and 30% (w/w) of NaCl under stirring mode resulted in the highest extraction efficiency of volatile flavor compounds. The principal component analysis score discriminated the influence of SPME variables on the equilibrium headspace concentration of target volatile compounds.     

Characterization of volatile compounds in fermented milk using solid-phase microextraction methods coupled with gas chromatography-mass spectrometry

Lactic acid bacteria (LAB) are industrially important bacteria that are widely used in the fermented food industry, especially in the manufacture of yogurt. Characteristic flavors are produced by LAB during fermentation and storage that affect the quality and acceptability of fermented milk products. In this study, the volatile compounds in milk fermented by Streptococcus thermophilus IMAU80842 alone, Lactobacillus delbrueckii ssp. bulgaricus IMAU20401 alone, or both species together were identified using solid-phase microextraction methods coupled with gas chromatography-mass spectrometry. A total of 53, 43, and 32 volatile compounds were identified in milk fermented by S. thermophilus alone, L. delbrueckii ssp. bulgaricus alone, or both species together, respectively. The presence of some important flavor compounds was confirmed: acetic acid, acetaldehyde, acetoin, 2,3-butanedione, ethanol, and 1-heptanol. Our results demonstrate that the composition of the volatile compounds in fermented milk depends on the species of LAB used and whether they are used alone or in combination. This is important for the selection of appropriate starter cultures for the production of different types of fermented milk product with particular flavors.     

Variety‐based discrimination of apple juices by an electronic nose and gas chromatography–mass spectrometry

The variety of raw material plays a crucial role in the quality and authenticity of fruit juices and juice products. To characterise and classify apple juices according to variety on the basis of their volatile compounds, electronic nose (EN) and gas chromatography–mass spectrometry (GC‐MS) were applied to detect the apple juices prepared by eight different varieties. The EN was used to analyse the mixture of volatile compounds as a whole and enabled rapid classification of juice samples when coupled with linear discriminant analysis (LDA). LDA showed a perfect discrimination of apple juices based on varieties. GC‐MS was utilised to illustrate the differences of volatile compounds among juice samples. Identification of volatile compositions and their contents provides useful access to differentiate juices from different varieties.     

Profiling volatile compounds from Mucuna beans by solid phase microextraction and gas chromatography-high resolution time of flight mass spectrometry

Four solid phase microextraction (SPME) fibres, polydimethylsiloxane (PDMS), polydimethylsiloxane/divinylbenzene (PDMS/DVB), polyacrylate (PA), and carboxen/polydimethylsiloxane (CAR/PDMS), were evaluated for profiling of volatile compounds during cooking of Mucuna pruriens beans. A gas chromatograph coupled to a high resolution time of flight mass spectrometer system was employed for separation, detection and identification of the volatile compounds. For the first time we report a total of 26 compounds, mostly alkyl benzenes and polycyclic compounds, identified in black, white, black–white, and yellow green Mucuna beans during head space sampling employing a CAR/PDMS fibre with subsequent detection with high resolution mass spectrometry. The number of volatile compounds sampled, most notably alkylbenzenes, decreased with each hour of boiling and discarding of water extracts. As the beans approached being fully cooked, benzoic acid 2-hydroxy methyl ester was the most dominant compound in all the four types of beans. These results are a first step towards addressing some of the occupational exposure associated with cooking Mucuna beans by rural communities.     

Simultaneous determination of 22 residual steroid hormones in milk by liquid chromatography–tandem mass spectrometry

Food safety and consumers’ health are paramount; therefore, it is essential to establish a novel method to determine hormone content in milk. Herein, a novel method was developed that can simultaneously determine 22 residual steroid hormones in milk. To obtain the maximum detection sensitivity, the preparation method of sample, mass spectrometer parameters and liquid chromatography conditions were optimised. The samples were concentrated using Oasis HLB solid‐phase extraction cartridge, followed by quantification via liquid chromatography (C18 column)–tandem mass spectrometer (LC‐MS). Determination of oestrogens and glucocorticoids was conducted in negative mode, whereas androgens and progesterone were in positive multiple reaction monitoring mode. The limit of detection (LOD) and limit of quantification (LOQ) of the target compounds were 0.10–1.20 μg/kg and 0.33–3.96 μg/kg, respectively. The average extraction recoveries of 22 steroid hormones were generally high (82.6–95.3%). The proposed method can be an effective alternative to measure hormonal compounds in milk.     

HS-SPME-GC-MS分析发芽糙米储藏过程中挥发性成分的变化

以水分含量为(14±0.5)％的发芽糙米为原料,取1 kg装入聚乙烯(PE)袋(15 cm×20 cm)密封后分别在湿度(65±3)％的4℃和35℃条件下储藏6个月.采用顶空固相微萃取(HS-SPME)和气相色谱-质谱联用(GC-MS)对4℃和35℃储藏及新鲜的发芽糙米中的挥发性物质进行提取、鉴定与分析.结果表明:发芽糙米挥发性成分主要有烃类、醛类和酯类,其次是醇类和酸类;随着储藏时间的延长,发芽糙米挥发性成分发生明显变化;4℃与35℃储藏下的发芽糙米挥发性成分种类、含量有差异性;在35℃下储藏的发芽糙米中的挥发性成分种类含量较4℃下有显著性增加.储藏6个月之后,变化较明显的挥发性成分有十六烷、十八烷、己醛、n-十六酸、2-乙基-1-己醇、乙酸乙酯.     

Determination of volatile compounds to characterize fish spoilage using headspace/mass spectrometry and solid‐phase microextraction/gas chromatography/mass spectrometry

Changes in volatile compounds were monitored in whiting (Merlangius merlangus), cod (Gadus morhua) and mackerel (Scomber scombrus) and related to spoilage. Data are presented from headspace/mass spectrometric (HS/MS) analysis and solid‐phase microextraction/gas chromatographic/mass spectrometric (SPME/GC/MS) analysis at two time points (day 0 and day 10) during storage at 4 °C. HS/MS revealed 24 ions that could be used as markers of spoilage. SPME/GC/MS identified 86 compounds, 20 of which could perhaps be used to characterize freshness: principally alcohols, ketones, aldehydes and C₂–C₁₁ esters. Compounds common to the three species studied appear to be generated by microbial degradation. Copyright © 2005 Society of Chemical Industry     

Development of volatile compounds of cava (Spanish sparkling wine) during long ageing time in contact with lees

In order to study the evolution of volatile compounds during long ageing times in contact with lees (more than 2 years), Headspace–solid phase microextraction (HS/SPME) method was applied to different cavas (Spanish Sparkling wine). Two different fiber coatings were used: PDMS which extracts the analytes by partitioning and DVB–CAR–PDMS which extracts either by partitioning or physically trapped the target compounds. Even though the volatile profile obtained by gas chromatography/mass spectrometry (GC/MS) was similar, the triple phase seems to be more suitable to follow the development of the volatile profile during its ageing time. Hexyl, 2-phenylethyl and isoamyl acetates significantly decrease over time, while 1,2-dihydro-1,1,6-trimethylnaphthalene (TDN), vitispirane and diethyl succinate significantly increase during ageing in contact with lees.     

Liquid-phase microextraction combined with gas chromatography mass spectrometry for rapid determination of nicotine in one-drop of nightshades vegetables and commercial food products

A simple, rapid and sensitive ultrasound-assisted hollow fibre liquid-phase microextraction (UA-HF-LPME) is evaluated for the determination of nicotine in one-drop of nightshade vegetables and some of the commercial food products. The optimum extraction of nicotine was obtained by using 1.5 μL as an extracting solvent in 1.0 cm of hollow fibre for 10 min extraction time with addition of salt. The calculated calibration curves showed a high level of linearity in the range 2–100 ng g⁻¹ with correlation coefficients >0.998. The limit of detection (LOD) for the target analyte was found to be in the range of 0.2–0.5 ng g⁻¹ and the relative standard deviations (RSD) of 2.3–4.5% were obtained. The results showed that under the optimised experimental conditions, the method showed good sensitivity and relative recoveries, as well as advantages such as linearity, simplicity, low cost and high feasibility. The extraction performance of present method to the target compound was also compared with drop-to-drop solvent microextraction (DDSME) and we found that the present approach showed better extraction efficiency of target molecule from sample solution. Finally, the proposed method was successfully applied for the determination of nicotine in nightshade vegetables (potatoes, tomatoes, peppers and eggplants) and commercial food products (tomato sauce, tomato juice, and pepper sauce).     

Optimization of solid‐phase microextraction methods for GC‐MS determination of terpenes in wine

Solid‐phase microextraction using a 100 µm poly(dimethylsiloxane) fiber, followed by gas chromatography–mass spectrometry determination, has been optimized for the analysis of some terpenes in wine samples. The best results were obtained by direct immersion of the fiber using a sampling period of 15 min with constant magnetic stirring (1100 rpm) and an extraction temperature of 20 °C. The sample volume was 7 ml with 25% NaCl, in a 15 ml capped vial. Desorption was performed directly in the gas chromatograph injector port over 5 min at 250 °C using the splitless mode. The method is sensitive, with detection limits between 11 and 25 µg l^?1, precise, with variation coefficients in the range 1.28–3.71%, and linear over more than one order of magnitude. The related conditions were used for wine sample analyses with recoveries between 71.8 and 90.9%. Solid‐phase microextraction remains an attractive alternative technique due to its rapidity and because it is a solvent‐free extraction. Copyright © 2005 Society of Chemical Industry     

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.     

顶空固相微萃取气相色谱/质谱法测定 "米邦塔"仙人掌挥发性成分

用顶空固相微萃取方法收集仙人掌的挥发性成分。所得到的仙人掌挥发性成分用气相色谱-质谱(GC-MS)法分离并分析鉴定其成分及质量分数,共鉴定出47个化合物,主要为酸、醛、脂类和酮类物质,其中酸类物质41.99%;醛类物质20.15%;醇类物质19.92%;酯类物质4.25%;酮类物质3.43%。此外还鉴定出4种胺类物质(2.22%),1种酚类物质(0.80%),1种呋喃类物质和2种硫化物(1.46%)。     

Changes in volatile aroma compounds of pineapple (Ananas comosus) during freezing and thawing

Changes in the volatile aroma compounds of pineapple (Ananas comosus) during freezing and thawing were compared against fresh samples to determine the effect of freezing on pineapple flavour. An HS‐SPME–GC–MS analysis showed that the Smooth Cayenne pineapple variety had nineteen volatile compounds, in four classes of compounds including fourteen esters, two hydrocarbons, two sulphur‐containing compounds and one lactone. The main characteristic volatile compounds of the fresh pineapple were methyl hexanoate, ethyl hexanoate, ethyl 3‐methylthiopropanoate and 1‐(E,Z)‐3,5‐undecatriene. Freeze–thaw cycles were associated with the loss of some volatile aroma compounds, particularly the esters which were found to be the main characteristic of fresh pineapples. The freezing and thawing process was found to cause damage to the pineapple tissues due to ice recrystallisation and dehydration which lead to the reduction of volatile aroma compounds.