Headspace Solid Phase Micro-extraction Combined With Gas Chromatography-mass Spectrometry Research Articles

Identification of the Volatile Compounds and Observation of the Glandular Trichomes in Opisthopappus taihangensis and Four Species of Chrysanthemum.

Opisthopappus taihangensis (Ling) Shih, a wild relative germplasm of chrysanthemum, releases a completely different fragrance from chrysanthemum species. We aimed to identify the volatile compounds of the leaves of O. taihangensis and four other Chrysanthemum species using headspace solid-phase micro-extraction combined with gas chromatography-mass spectrometry (HS-SPME-GC/MS). In total, 70 compounds were detected, and terpenoids accounted for the largest percentage in these five species. Many specific compounds were only emitted from O. taihangensis and not from the other four species. In particular, 1,8-cineole could be responsible for the special leaf fragrance of O. taihangensis as it accounted for the largest proportion of the compounds in O. taihangensis but a small or no proportion at all in other species. The glandular trichomes (GTs) in the leaves are the main organs responsible for the emission of volatiles. To explore the relationship between the emissions and the density of the GTs on the leaf epidermis, the shape and density of the GTs were observed and calculated, respectively. The results showed that the trichomes have two shapes in these leaves: T-shaped non-glandular trichomes and capitate trichomes. Histochemical staining analyses indicated that terpenoids are mainly emitted from capitate glandular trichomes. Correlation analysis showed that the volatile amount of terpenoids is highly related to the density of capitate trichomes. In O. taihangensis, the terpenoids content and density of capitate trichomes are the highest. We identified the diversity of leaf volatiles from O. taihangensis and four other Chrysanthemum species and found a possible relationship between the content of volatile compounds and the density of capitate trichomes, which explained the cause of the fragrance of O. taihangensis leaves.

Effect of bound water on the quality of dried Lentinus edodes during storage.

Water absorption is the dominant factor affecting the quality deterioration of dried Lentinus edodes. We therefore analyzed the effect of moisture content and dynamic water status on physical properties of the mushroom stored at water activity (aw ), 0.33, 0.43, 0.67, 0.76, and 0.84 for 50 days. Moisture mobility and water status were analyzed using low-field nuclear magnetic resonance, while hardness and microstructure were determined as texture characteristics. Meanwhile, an electronic nose and headspace solid-phase micro-extraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) were used to analyze the flavor properties of dried L. edodes. The results showed that bound water was the dominant water status in dried L. edodes. The content and molecular mobility of bound water increased at aw = 0.67, 0.76, and 0.84. This contributed to discoloration, hardness loss, and microstructure sparsity of dried L. edodes. The increasing content and molecular mobility of bound water aggravated the deterioration of characteristic flavor by reducing acid, aldehyde, and ketone content. Unlike immobilized or free water, bound water had a critical influence on the quality deterioration of dried L. edodes during storage. © 2019 Society of Chemical Industry.

Discrimination of Volatiles of Shiitakes (Lentinula edodes) Produced during Drying Process by Electronic Nose

AbstractThis study aimed to investigate the potential of electronic nose (E-nose) to differentiate volatiles of shiitakes produced at different drying stages. Shiitakes at different drying time slots were categorized into four groups (fresh, early, middle and late stage) by sensory evaluation. E-nose was used to analyze the volatiles and compared with headspace solid phase micro-extraction combined with gas chromatography-mass spectrometry (HS/GC-MS). The principal component analysis results showed that shiitakes at each stage could be successfully discriminated by E-nose and HS/GC-MS. The differences in volatile organic compounds produced at each stage were mainly caused by sulfurs and alcohols, leading to apparent changes of sensors sensitive to sulfurs, alcohols and aromatic compounds. The discriminant models were established by partial least squares discriminant analysis and support vector machine classification, with accuracy rates of 91.25 % and 95.83 %, respectively. The results demonstrated the potential use of E-nose in classifying and monitoring shiitakes during drying process.

Comparative studies on flavor substances of leaves and pericarps of <i>Zanthoxylum bungeanum</i> Maxim. at different harvest periods

Purpose: To study the transformation of the aroma components and pungent constituents of Zanthoxylum bungeanum Maxim. (ZBM) leaves and pericarps at different periods, and to provide a basis for selecting an appropriate harvest time for the pericarps and leaves. Methods: Quantitative analysis of the pungent components of ZBM leaves and pericarps was performed by high performance liquid chromatography (HPLC) while their aroma constituents were analyzed by headspace solid phase micro-extraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS). Results: HPLC analysis revealed that hydroxy-α-sanshool was the predominant pungent component in both the leaves and pericarps of different parts of ZBM at different harvest periods, followed by hydroxy- γ-sanshool and hydroxy-β-sanshool. During the growth of ZBM, the contents of pungent substances in the leaves declined gradually, while pungent substances in the pericarps increased. The results of HSSPME- GC-MS analysis showed that linalyl acetate, linalool and limonene were the major aroma components of the leaves and pericarps of ZBM at different harvest periods. During the growth of ZBM, the contents of monoterpenes in the leaves decreased gradually, whereas monoterpenes in the pericarps increased. Conclusion: These results suggest that the pungent and aroma components produced in ZBM at early developmental stages are stored in the leaves, and are gradually transferred to the pericarps at the final developmental stages. Thus, the leaves of ZBM can be used as a new source of food and medicine. Keywords: Zanthoxylum bungeanum Maxim., Pericarp, Pungent components, Aroma components

Analysis of volatile compounds of Tremella aurantialba fermentation via electronic nose and HS‐SPME‐GC‐MS

AbstractTo detect the odor changes of the volatile compounds during the Tremella aurantialba (T. aurantialba) fermentation associated with its degree, electronic nose (E‐nose) technique, and headspace solid phase microextraction combined with gas chromatography‐mass spectrometry (HS‐SPME‐GC‐MS) analyses were performed each day. E‐nose and GC‐MS were used to recognize the comprehensive aroma characterization and volatile compounds of T. aurantialba fermentation, respectively. Principal component analysis (PCA) were used to analyze the data detected by E‐nose technique and GC‐MS. Support vector machine (SVM) was established to analyze E‐nose date for predicting the different stage of the T. aurantialba fermentation. The main volatile compounds were identified by GC‐MS analysis as alcohols, esters, aldehydes, ketones, heterocyclic, and aromatic compounds. The results of PCA by E‐nose were more similar with that of GC‐MS. The discrimination rates of the SVM model were 100 and 97.14% in the training and testing sets. It can be concluded that E‐nose technique coupled with SVM classification tool has high potential to monitor the fermentation process. These may sufficiently demonstrate excellent promise for the E‐nose technique and GC‐MS method to be applied in the liquid state industry.Practical applicationsE‐nose combined with GC‐MS could detect the odor changes of the volatile compounds during the T. aurantialba fermentation. Both analytical techniques showed good performances in the classification of the fermentation degree of T. aurantialba. These may provide a theoretical basis for the design of the portable electronic nose, which would achieve the real‐time smell monitoring of liquid state fermentation of T. aurantialba associated with its degree of fermentation. This equipment can be used to determine the state of fermentation instead of workers. The E‐nose technique and HS‐SPME‐GC‐MS method could be applied in the liquid state fermentation industry in the future.

Interactions between p-Cresol and Ala-Lys-Arg-Ala (AKRA) from Sesame-Flavor-Type Baijiu.

The objective of this study was to investigate the influence of Ala-Lys-Arg-Ala (AKRA), a tetrapeptide newly identified from Chinese Sesame flavor-type Baijiu in our previous work, on its binding ability with aroma compounds. A method using headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC/MS) was employed to determine the corresponding binding ability between different concentrations of AKRA (10 - 1000 μg/L) and aromas in Baijiu. In comparison, the aroma molecules in Baijiu before and after adding AKRA were almost the same; only their volatility was altered, with mostly the esters, alcohols, and phenolic compounds being decreased. Additionally, AKRA slightly changed the whole aroma profile of Baijiu, especially with respect to p-cresol (an off-odor in sesame-flavor-type Baijiu), which was verified by systematic sensory experiments including gas chromatography-olfactometry (GC-O) and odor activity values (OAVs) analysis. The nonvolatile tetrapeptide favored the hydrogen bond interactions with p-cresol, forming the AKRA- p-cresol complex, thus reducing the headspace concentration of phenolic off-flavors as evidenced by HS-SPME-GC/MS, ultraviolet (UV) absorption spectroscopy, and nuclear magnetic resonance spectrum (1H NMR) analysis. Meanwhile, the hydrogen bond interaction was further confirmed with the intermolecular cross-peaks between the carboxyl hydrogen of AKRA and the phenolic hydroxyl of p-cresol by nuclear Overhauser effect spectroscopy (1H-1H NOESY).

Research on Volatile Organic Compounds From Bacillus subtilis CF-3: Biocontrol Effects on Fruit Fungal Pathogens and Dynamic Changes During Fermentation.

The dynamic changes of the levels of volatile organic compounds (VOCs) produced by Bacillus subtilis CF-3 and their biocontrol effects on common fungal pathogens were researched in this study. The results showed that the VOCs in 24-h fermentation liquid (24hFL) of B. subtilis CF-3 inhibited mycelial growth of Botrytis cinerea, Colletotrichum gloeosporioides, Penicillium expansum, Monilinia fructicola, and Alternaria alternata, with a mean inhibition rate of 59.97%. The inhibitory effect on M. fructicola and C. gloeosporioides was the highest; they were therefore selected as target fungal pathogens for further experiments. Based on headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS), 74 potential VOCs were identified during the fermentation: 15 alcohols, 18 ketones, 4 pyrazines, 4 esters, 10 acids, 5 phenols, 3 hydrocarbons, 3 amines, 2 aldehydes, 5 ethers, and 5 other components. At different fermentation times, the type and content of VOCs were different. Most of the potential VOCs (62 VOCs) were identified in the 48hFL. The inhibition rates of all VOCs reached their peaks (73.46% on M. fructicola and 63.63% on C. gloeosporioides) in the 24hFL. Among the identified VOCs, 2,4-di-tert-butylphenol, 1-octanol, and benzothiazole showed significant positive correlations with the rates of M. fructicola and C. gloeosporioides inhibition. Benzoic acid and benzaldehyde showed a significant positive correlation with the rates of M. fructicola inhibition, and anisole and 3-methylbutanal showed a significant positive correlation with the rates of C. gloeosporioides inhibition. In vitro, 2,4-di-tert-butylphenol showed a strong inhibitory effect on both M. fructicola and C. gloeosporioides. In vivo, benzothiazole showed the strongest inhibitory effect on the mycelial extensions of both M. fructicola and C. gloeosporioides, which also led to an increased rate of healthy fruit. The results of the present study clarified that 2,4-di-tert-butylthiophenol and benzothiazole are key inhibitory VOCs produced by B. subtilis CF-3.

Characterization of volatile compounds in pickled and dried mustard (Brassica juncea, Coss.) using optimal HS-SPME-GC-MS

ABSTRACTPickled and dried mustard (PDM; Brassica juncea, Coss) is a traditional fermented vegetable product that is widely consumed as a food ingredient with aromatic flavour in China. Here, we aimed to determine the volatile compounds in PDM by headspace solid-phase micro-extraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that a total of 41 volatile compounds were identified and quantified in PDM by optimized HS-SPME-GC-MS. Approximately 15 compounds were considered to be the dominant volatile compounds in PDM with relatively high concentrations. These findings make the volatile composition characteristics in PDM clear for the first time.

Analysis of volatile compounds in L. edodes blanched by hot water and microwave

AbstractThe comprehensive flavour characterisation and volatile compounds of raw L. edodes, hot water blanching (HB) sample and microwave blanching (MB) sample were comparatively analysed by electronic nose technology and headspace solid‐phase micro‐extraction combined with gas chromatography‐mass spectrometry (HS‐SPME‐GC‐MS). Results indicated that volatile components in L. edodes markedly changed after HB and MB. Volatile compounds of raw L. edodes consisted mainly ketones, sulphide and alcohols, and 3‐octanone, as well as 1‐octen‐3‐one, were the major compounds. The content of ketones and sulphides in blanched samples markedly decreased, while the relative content of aldehydes, hydrocarbons and esters increased, which became the major volatile compounds of treatment samples. In addition, the percentage contents of esters, alcohols and sulphides in MB samples were significantly (P < 0.05) higher than that in HB samples, especially 1‐octen‐3‐ol, which contributes more to mushroom flavour. Therefore, MB is a better pretreatment method of L. edodes processing and cooking according to the results of experiment.

Volatile components of white Hypsizygus marmoreus detected by electronic nose and HS-SPME-GC-MS: Influence of four drying methods

ABSTRACTFour drying methods, viz hot air drying (HD), vacuum drying (VD), microwave-vacuum drying (MVD), and vacuum freeze-drying (FD), were used to dry white Hypsizygus marmoreus (WHM). The volatile and taste components of the dried WHM were comparatively analysed by electronic nose technology (E-nose) and head-space solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GS-MS). Principal component analysis (PCA) showed that E-nose could distinguish fresh WHM and four dried products clearly. Dominant volatile components in fresh WHM were found to be 1-octen-3-ol, 3-octanone, and (E)-2-nonenal. However, it was found that the drying methods caused damage to the 8-carbon compounds (C8), especially to 8-carbon alcohol greatly. For instance, HD produced more ester materials, MVD yielded more aldehyde compounds, FD brought more hydrocarbon products, and VD produced more ketone substances.

Bacterial communities and volatile compounds in Doubanjiang, a Chinese traditional red pepper paste.

To identify core bacterial communities and volatile compounds and to investigate their relationships in Doubanjiang, a Chinese traditional red pepper paste. Two main culture-independent methods, polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and MiSeq sequencing technique, were used to investigate bacterial composition. Headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to isolate and identify volatile organic compounds. Partial least squares (PLS) regression and correlation coefficients analyses were used for elucidating the relationship between core bacterial community and volatile compounds. Lactic acid bacteria (LAB) and Enterobacteriaceae family were identified primarily by the PCR-DGGE fingerprinting. Furthermore, the core microbiome (>1% average relative abundance) were indentified by Miseq sequencing technique, which mainly assigned to Proteobacteria, Cyanobacteria and Firmicutes phyla. For volatile profile, a total of 29 volatile compounds were identified by HP-SPME-GC-MS, mainly alcohols, esters, aldehydes, ketones and phenols. PLS regression and Pearson's correlation coefficients analyses revealed highly covariable relationships between volatile compounds and bacterial taxa. Notably, Pseudomonas most highly significantly associated with 3-methyl butanal, 2-methyl butanal, benzeneacetaldehyde and 2-acetylpyrrole (P<0·001), and significantly correlated with 5-methylfurfural and 5-methyl-2-phenyl-2-hexenal (P<0·01). Core bacterial communities were identified and the relationship between bacterial taxa and flavour compounds was revealed, these results could be beneficial for improving the quality of Doubanjiang.