Gas Chromatography-ion Mobility Spectrometry Research Articles

Characterization of the key flavor compounds in cream cheese by GC-MS, GC-IMS, sensory analysis and multivariable statistics

The aroma types of cream cheese affect its commercial value and consumer acceptability. However, the types of volatile substances and sensory characteristics of cream cheese at different fermentation stages are still unclear. Therefore, in this study, headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) were used to analyze the volatile substances in cream cheese fermentation. Orthogonal partial least squares discriminant analysis (OPLS-DA), odor activity value (OAV), relative odor activity value (ROAV) and variable projection importance (VIP) were used to identify the characteristic flavor substances in cream cheese fermentation. Finally, the relationship between key flavor substances and sensory characteristics was determined by partial least squares (PLS) analysis. A total of 34 and 36 volatile organic compounds were identified by HS-SPME-GC-MS and HS-GC-MS, respectively, and 14 characteristic flavor substances were found, based on VIP, ROAV and OAV models. Combined with sensory analysis and flavor substance changes, it was found that the cream cheese fermented for 15 d had the best flavor and taste. This study reveals the characteristics and contribution of volatile substances in cream cheese at different fermentation stages, which provides new insights into improving flavor and quality control.

HS-GC-IMS and HS-SPME/GC-MS coupled with E-nose and E-tongue reveal the flavors of raw milk from different regions of China

Milk authentication requires identification of the origin and assessment of the aroma characteristics. In this study, we analyzed 24 raw milk samples from different regions of China by profiling volatile flavors using headspace solid phase microextraction-gas chromatography-mass spectrometry, headspace gas chromatography-ion mobility spectrometry, and intelligent sensory technology (E-tongue and E-nose). The flavor of raw milk in Southern and Northern China had evident differences based on the intelligent sensory technology. However, the differences among the samples from the northeast, northwest, and central regions were not significant. Correlations between milk origin and volatile compounds based on variable importance prediction > 1 and principal component analysis results revealed differential compounds including pyridine, nonanal, dodecane, furfural, 1-decene, octanoic acid, and 1,3,5,7-cyclooctatetraene. Our study findings provided a deeper understanding of the geographical differences in raw milk volatile compounds in China.

Non-volatile and volatile compound changes in blueberry juice inoculated with different lactic acid bacteria strains.

Lactic acid bacteria (LABs) are widely present in foods and affect the flavour of fermented cultures. This study investigates the effects of fermentation with Lactobacillus acidophilus JYLA-16 (La), Lactobacillus plantarum JYLP-375 (Lp), and Lactobacillus rhamnosus JYLR-005 (Lr) on the flavour profile of blueberry juice. This study showed that all LABs strains preferentially used glucose rather than fructose as the carbon source during fermentation. Lactic acid was the main fermentation product, reaching 7.76 g L-1 in La-fermented blueberry juice, 5.86 g L-1 in Lp-fermented blueberry juice, and 6.41 g L-1 in Lr-fermented blueberry juice. These strains extensively metabolized quinic acid, whereas oxalic acid metabolism was almost unaffected. Sixty-four volatile compounds were identified using gas chromatography-ion mobility spectrometry (GC-IMS). All fermented blueberry juices exhibited decreased aldehyde levels. Furthermore, fermentation with La was dominated by alcohols, Lp was dominated by esters, and Lr was dominated by ketones. Linear discriminant analysis of the electronic nose and principal component analysis of the GC-IMS data effectively differentiated between unfermented and fermented blueberry juices. This study informs LABs selection for producing desirable flavours in fermented blueberry juice and provides a theoretical framework for flavour detection. © 2023 Society of Chemical Industry.

GC-IMS determination of volatile organic compounds as potential indicators of wheat germination rate

The objective of this research was to investigate the correlation between volatile organic compounds (VOCs) and the germination rate of stored wheat, as well as to identify the potential markers for predicting the germination rate. The findings of this study are expected to contribute to the advancement of a non-destructive and rapid method for evaluating the quality of wheat storage, thereby establishing a theoretical foundation for further research in this area. Gas chromatography-ion mobility spectrometry (GC-IMS) was utilized to analyze the VOCs of wheat samples subjected to accelerated storage condition at 40 °C, RH 65%, as well as natural storage condition at room temperature. A total of 68 and 79 VOCs were detected under accelerated and natural storage conditions, respectively. The germination rate of wheat was found to decreased significantly with prolonged storage time under both storage conditions. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were utilized to differentiate wheat samples stored for varying durations. Furthermore, correlation analysis revealed that 31 VOCs exhibited a significant correlation (p < 0.05) with the germination rate. Through multiple linear stepwise regression analysis, four VOCs—namely isoamyl butyrate, (Z)-3-nonen-1-ol, 1-propanol, and Propanal—were identified as potential markers. Subsequently, a prediction model was constructed using these markers. The results of this study demonstrate that these VOCs can serve as indicators for predicting the germination rate, thus facilitating the evaluation of the germination ability and quality of stored wheat. This research holds implications for enhancing the efficiency of wheat storage management and ensuring food security.

Temporal dynamics of aroma compounds and precursors in dry‐fried shredded beef during culinary processing

SummaryThis study aimed to investigate aroma compound transformation and precursor relation in dry‐shredded beef using gas chromatography–ion mobility spectrometry, gas chromatography–mass spectrometry, high‐performance liquid chromatography, and electronic nose technologies. Forty‐eight aroma compounds were identified, of which twelve (pentanal, hexanal, heptanal, 3‐methylbutanal, nonanal, phenylacetaldehyde, trans‐2‐decenal, acetoin, 3‐octenol, 3‐octanol, ethyl hexanoate, and 2‐acetylthiazol) exhibited odour activity values (OAVs) &gt;1. The concentration of fatty acids (FAs) decreased progressively, while that of 19 free amino acids (FAAs) increased with prolonged cooking. Pearson's correlation analysis revealed correlations between aroma components (OAV &gt;1), FAAs, and FAs. Specifically, 2‐acetylthiazol, acetoin, heptanal, 3‐methylbutanal, and hexanal exhibited positive correlations, while phenylacetaldehyde and trans‐2‐decenal showed inverse correlations with most FAAs. Notably, phenylacetaldehyde positively correlated with C16:0, C18:1, n9c, and C18:2, n6c. This research presents a practical framework for the application of analytical and computational techniques in the commercial production of cooked beef and meat products.

Effect of different thermal processing methods on flavor characteristics of Penaeus vannamei

This study explored the effect of three thermal processing methods, namely drying, steaming and microwaving on non-volatile and volatile flavor compounds of Penaeus vannamei; electronic tongue, electronic nose and gas chromatography-ion mobility spectrometry (GC-IMS) were used in combination with multiple statistical methods. Correlation analysis of the results showed that these processing methods resulted differences in flavor composition; the non-volatile flavor compounds, such as sweet free amino acids, 5′-nucleotides, and organic acids were higher in thermal processed samples. Aspartic acid, glutamic acid, succinic acid, guanine nucleotide, and hypoxanthine nucleotide were main flavor active components. Additionally, the volatile flavor compounds determined were 38 compounds via GC-IMS analysis, which mainly included 9 alcohols, 8 esters, 6 aldehydes, 4 ketones, 4 acids, 1 ether, 1 pyrazine, 1 furan, 1 thiazole, and 3 others. Based on these flavor profiles, the principal component analysis of E-tongue and E-nose data showed a distinct difference among the different thermally processed samples. Overall, the diversity and content of flavor compounds were higher in dried and microwaved samples than in steamed ones, indicating the former two processing as better methods. This study is expected to provide knowledge for consumers to choose thermal processing method while purchasing Penaeus vannamei products.

Variations of volatile flavors and microbial communities in Chinese Chaozhou pickle during natural fermentation revealed by GC-IMS and high-throughput sequencing

Chaozhou pickle, a traditional Chinese fermented vegetable product, is highly regarded among consumers due to its unique flavor. This work monitored the flavor substances and microbial communities of Chaozhou pickles during fermentation by gas chromatography-ion mobility spectrometry (GC-IMS) and high-throughput sequencing. A total of 70 volatile compounds were identified from Chaozhou pickles. In addition to fruit aroma esters, the pickles also contain aldehydes, ketones, alcohols, acids, and heterocyclic compounds. The four pickles exhibited a prevalence of Cyanobacteria, Proteobacteria, and Firmicutes as the leading bacterial phyla, while Weissella, Leuconostoc, and Lactobacillus were identified as the predominant bacterial genera. Physiochemical quality and acid properties of Chaozhou pickle were also investigated. Results revealed a significant reduction in hardness, chewiness and pH during fermentation, as well as a notable increase in free amino acids, and organic acid levels. These results could contribute to a greater comprehension of the role of microorganisms in flavor formation during fermentation and provide a scientific foundation for the industrialization of Chaozhou pickle.

Gas chromatography ion mobility spectroscopy: A rapid and effective tool for monitoring oil oxidation

Oil autoxidation is an early process of food deterioration, monitoring oil oxidation is therefore of great significance to ensure food quality and safety. In this study, a detection method of the primary and secondary oxidative products was developed by gas chromatography ion mobility spectrometry (GC-IMS).The secondary oxidative products was analyzed by GC-IMS. Then, the relationships between peroxide values and the contents of secondary oxidative products were investigated by constructing a prediction model of peroxide value of rapeseed oil with the help of secondary oxidative products and chemometrics. The coefficient of determination Q2 of the model validation set is 0.96, and the RMSECV is 0.1570 g/100 g. These validation results indicated that secondary oxidative products could also reflect the content of the primary oxidative products. Moreover, 10 characteristic markers related to oxidative rancidity were identified for monitoring edible oil rancidity and oxidative stability.

Characterization of honey-like characteristic aroma compounds in Zunyi black tea and their molecular mechanisms of interaction with olfactory receptors using molecular docking

The important characteristics of honey-like aroma compounds in six Zunyi black tea were determined by gas chromatography-mass spectrometry-olfactometry (GC-MS-O), odor activity value (OAV), gas chromatography-ion mobility spectrometry (GC-IMS) and partial least squares-discriminant analysis (PLS-DA) methods, including geraniol, 2-phenylethyl alcohol, 2-phenyl-2-butenal, furaneol, cinnamaldehyde, ethyl cinnamate, benzoic acid, ethyl pentanoate-M. Furthermore, the molecular docking was used to study the region, site, binding energy, and force of the interaction between the honey-like aroma compounds (geraniol, 2-phenylethyl alcohol, furanol, cinnamaldehyde, and ethyl cinnamate) and olfactory receptors (OR1A1, OR1G1, OR2W1, OR1D2, and OR5M3). The average binding energies of these compounds on the five receptors were −4.34 kcal/mol, −4.14 kcal/mol, −4.24 kcal/mol, −5.08 kcal/mol, and −5.33 kcal/mol, respectively. The experiment indicated the interaction sites of five characteristic compounds and key residues of ORs, such as geraniol and Tyr252 (OR1D2), 2-phenylethyl alcohol and Thr219 (OR1G1), furaneol and Asn155/Ser109 (OR2W1), furaneol and Phe166/Leu164/Val7 (OR5M3), and ethyl cinnamate and Asn155/Asn109 (OR1A1). Further research has found that hydrogen bonding and hydrophobic interactions are important driving forces for the binding of aroma compounds to ORs. By systematically studying the material basis, formation mechanism of honey-like aroma, theoretical guidance can be provided for the regulation of honey-like aroma in Zunyi black tea.

Investigation of volatiles and quality attributes of indica-japonica hybrid paddy by radio frequency combined hot air drying

The study was aimed at investigating the effects of radiofrequency combined hot air drying (RF-HAD) on volatiles and quality attributes of indica-japonica hybrid paddy. The results indicated that RF-HAD reduced the drying time by 40% compared to hot air drying (HAD). In addition, HA-RF-dried samples showed significantly higher color, vigor, and taste value but less fatty acid value than HA dried-ones. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that RF-HAD did not affect the protein profile of rice protein. Gas chromatography-ion mobility spectrometry characterized changes in volatile components of paddy before and after drying, results showed that the content of aldehyde and ester aromatic compounds increased after drying and the content of most volatile components in RF-HA-dried paddy was higher than in HA-dried samples. Thus, the inference was that RF-HAD technology may be an innovative alternative to existing drying methods such as microwave, HA, and other drying technologies.

Analysis of roasted peanuts based on GC-MS combined with GC-IMS.

The present study used gas chromatography-mass spectrometry (GC-MS) and gas chromatography-ion mobility spectrometry (GC-IMS) to separate and identify the characteristic volatile flavor substances in 30 roasted peanut samples. GC-MS identified 59 volatile compounds, and GC-IMS detected 61 volatile flavor substances. The 30 peanut varieties were then divided into four groups on the basis of their volatile flavor substances using principal component analysis (PCA), and a fingerprint profile of the varieties' volatile characteristics was established from information peaks identified in the spectra. Descriptive sensory analysis (DSA) was performed to distinguish differences in flavor attributes between roasted peanut varieties. Partial least squares regression (PLSR) was performed with the volatile flavor content of roasted peanuts as the independent variable and the flavor attribute score as the dependent variable. These findings provide a basis for predicting the appeal of roasted peanuts based on their composition and demonstrate a potential avenue for improving food flavor quality.

Monitoring of Volatile Compounds of Ready-to-Eat Kiwifruit Using GC-IMS.

Ready-to-eat kiwifruit has gained significant market value in recent years due to its convenience and the increasing consumer demand for healthy ready-to-eat snacks. The volatile compound content (VOC) in ready-to-eat kiwifruit is a crucial factor determining its flavor and aroma. VOC is an important characteristic that positively affects the overall evaluation of ready-to-eat kiwifruit. In this study, we utilized gas chromatography-ion mobility spectrometry (GC-IMS) to investigate changes in the composition of VOCs in ready-to-eat kiwifruit during different storage periods (every 12 h). Our results revealed the presence of 55 VOCs in ready-to-eat kiwifruit, with alcohols, esters, and ketones being the dominant compounds responsible for the aromatic flavor. Among these compounds, methyl caproate, ethyl butyrate, and ethyl propionate provided specific fruit flavors to ready-to-eat kiwifruit, whereas esters played a secondary role. Furthermore, varying trends were observed for different compound types as the storage period increased: alcohols exhibited a decreasing trend, whereas ester products and some sulfur-containing compounds showed an increase. Additionally, fingerprint profiles of volatile compounds were established for each storage period, enabling the identification of characteristic substances. This comprehensive analysis of volatile flavor substances during the ripening of ready-to-eat kiwifruit will greatly contribute to enhancing its sensory quality, consumer appeal, and overall marketability.

Exhaled VOC Biomarkers from Rats Injected with PMs from Thirty-One Major Cities in China.

Particulate matter (PMs) of different origins can cause diverse health effects. Here, a homemade box was used to facilitate real-time measurements of breath-borne volatile organic compounds (VOCs) by gas chromatography-ion mobility spectrometry. We have tracked exhaled VOC changes in 228 Wistar rats that were injected with water-soluble PM suspension filtrates (after 0.45 μm) from 31 China cities for 1 h to up to 1-6 days during the experiments. Rats exposed to the filtrates exhibited significant changes in breath-borne VOCs within hours, featuring dynamic fluctuations in the levels of acetone, butan-2-one, heptan-2-one-M, acetic acid-M, and ethanol. Subsequently, on the fifth to sixth day after the injection, there was a notable increase in the proportion of aldehydes (including hexanal-M, hexanal-D, pentanal, heptanal-M, and (E)-2-hexenal). The 10 dynamic VOC fingerprint patterns mentioned earlier showcased the capability to indirectly differentiate urban PM toxicity and categorize the 31 cities into four distinct groups based on their health effects. This study provides valuable insights into the mechanisms of exhaled VOCs and underscores their critical role as biomarkers for differentiating the toxicity of different PMs and detecting the early signs of potential diseases. The results from this work also provide a scientific basis for city-specific air pollution control and policy development.

Dynamic evolution of volatile organic compounds in infant formula during storage: Insights from gas chromatography-ion mobility spectrometry

The flavor profile of infant formula (IF) determines its overall acceptability and palatability, significantly impacting its desirability for infants, while the presence of off-flavors challenges the feeding experience and IF quality, even may lead to the rejection by infants. In this study, the dynamic changes in volatile organic compounds (VOCs) during 12 weeks of IF storage at 4 °C–60 °C were monitored by Gas chromatography-ion mobility spectrometry (GC-IMS) for capturing the fingerprints of VOCs. The GC-IMS revealed that a total of 44 VOCs, including acids, alcohols, aldehydes, esters, ketones, and furans. The alternative principal component analysis (PCA) and Sankey diagram in this study offered a comprehensive tracing of the dynamic changes in VOCs, providing valuable implications for the optimization of IF quality control, assessment for validity period and origin tracking in the food industrial.

Explorative study for the rapid detection of adulterated surimi using gas chromatography-ion mobility spectrometry

Driven by economic interests, surimi adulteration has become a high-frequency issue. This study aims to assess the feasibility of gas chromatography-ion mobility spectrometry (GC-IMS) in detecting surimi adulteration. In this work, three common adulterated surimi models were established by mixing with different fish species and ratios. The fingerprints enabled a clear discrimination among different tuna surimi, and other two surimi models with different mixing ratios also showed VOCs (volatile organic compounds) differences. Results of unsupervised principal component analysis (PCA) and supervised partial least-squares discrimination analysis (PLS-DA) revealed that different types of adulterated surimi models can be well separated from each other. A total of 12, 16, and 9 VOCs were selected as the potential markers in three simulated models by PLS-DA method, respectively. Therefore, GC-IMS coupled with certain chemometrics is expected to serve as an alternative analytical tool to directly and visually detect adulterated surimi.

Towards the identification of the volatile organic compounds emitted by the coatings used in a car factory painting line

AbstractOne of the main reasons for the degradation of working conditions is the lack of air quality. It is known that indoor air contaminants pose a risk to both the human organism and the environment, which constitutes a challenge for employers and major industries. A car factory painting line is an evident example of a work location in which the employers must be especially aware and concerned with the employees' health. Since the coatings are the main VOCs-emitting source, this work studied the analytes emitted by four primers, 17 basecoats and one varnish used in a car factory of a world-renowned automotive brand, with gas chromatography-ion mobility spectrometry (GC-IMS), as a way of identifying all the coating-borne VOCs that can be emitted to the indoor air. The variability of the collected data was assessed, and the repeatability of the results proved the suitability of GC-IMS for this type of study. Among primers, inks and varnish, 45 VOCs were accurately identified using an exclusively developed database of compounds. The presence of the identified analytes in the composition of the coatings represents the potentiality of being emitted to the indoor air of the factory and, consequently, denotes their eventual toxicity for the employees of the painting line. These results represent a step forward in the assessment of the panting line work conditions, so eventual consequences to the employees’ health are theoretically discussed; nonetheless, further studies aim to examine air samples of the factory and evaluate the work conditions and actual consequences to the employees that must be developed.

Characterization of key aroma compounds in Rice flavor baijiu from different rice raw materials by gas chromatography-ion mobility spectrometry and gas chromatography-olfactometry-quadrupole time of flight mass spectrometry

Rice flavor baijiu is one of the four traditional Chinese liquors, but the flavor difference caused by rice raw materials has received little attention. In this study, gas chromatography-ion mobility spectrometry (GC-IMS) combined with gas chromatography-olfactometry-quadrupole time of flight mass spectrometry (GC-O-QTOF/MS) were used to analyze five Rice flavor baijiu brewed from different rice raw materials. The results showed that there was a significant difference in the number and content of aroma compounds between the baijiu made from japonica rice and indica rice, and a total of 34 volatiles were characterized by the GC-IMS technique, which effectively constructed the fingerprint profile of the flavor differences of Rice flavor baijiu. GC-O-QTOF combined with aromatic extract dilution analysis (AEDA) tests identified 42 characteristic aroma active regions, 34 of which could be identified and quantified by the internal standard method. Sixteen aroma-active compounds in five baijiu samples showed high odor activity values (OAV). In addition, multivariate statistical analyses such as principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA) effectively revealed the distribution patterns of the samples and their separation of relevant aroma activity markers. Six key aroma compounds, including isopentyl acetate, ethyl hexanoate, benzeneacetaldehyde, phenethyl acetate, undecane-2-one, and ethyl decanoate, were screened to have a greater effect on the flavor of Rice flavor baijiu.

Effect of raw material frozen storage on physicochemical properties and flavor compounds of fermented mandarin fish (Siniperca chuatsi)

Frozen mandarin fish (MF) is utilized for preparation fermented MF. However, how raw material (RM) affects the quality and flavor of fermented MF is unclear. This study investigated the impact and mechanism of RM frozen storage on the microstructure, texture, water distribution, and flavor of fermented MF by light microscopy, texture profile analysis, low-field nuclear magnetic resonance, gas chromatography-ion mobility spectrometry, and multivariate analysis. With increasing RM frozen storage time, both frozen MF and frozen-based fermented MF decreased in muscle fiber density while increased in muscle fiber diameter. Additionally, RM frozen storage exhibited a significant impact on the water distribution of frozen MF, while no obvious effect on that of frozen-based fermented MF. Seven odorant (2-methyl-1-propanol, 3-hydroxy-2-butanone, 2,3-butanedione, hexanal-D, ethyl acetate-D, 3-pentanone, and acetone) were shown as potential markers to distinguish fermented MF. This study could provide a theoretical basis for the production of high-quality frozen-based fermented MF.

Discrimination of pharmacodynamic components and volatile compounds of Poria cocos cultivated with five different materials based on GC-IMS analysis

Abstract Objectives The chemical constituents of Poria cocos grown with different substrates vary significantly; thus, identifying and comparing their biomarkers are important. Materials and Methods Herein, the chemical constituents of Poria cocos obtained with five different substrates were assessed using gas chromatography–ion mobility spectrometry (GC-IMS), high-performance liquid chromatography and multivariate statistical analysis. Results The content of moisture, ash, alcohol-soluble matter, and heavy metals, except for those of the miscellaneous wood Poria cocos, conform to the specifications defined in the Chinese Pharmacopoeia (Edition 2020), and the polysaccharide contents are all greater than 57%. Conclusions Based on GC-IMS and the established fingerprints, 87 compounds were detected, 70 of which were identified in each group. Multivariate statistical analysis revealed seven compounds (two esters, three alcohols, and two aldehydes), which could be considered as potential marker compounds for discrimination.

Influence of ionization volume and sample gas flow rate on separation power in gas chromatography-ion mobility spectrometry

In this work, the influence of the sample gas flow rate and the ionization region volume of an ion mobility spectrometer (IMS) used as a detector in gas chromatography (GC) on GC-IMS peak shape has been investigated. Therefore, a drift tube IMS with a field-switching ion shutter, a defined ionization region volume and an ultra-violet radiation source was used. To identify the influence of the sample gas flow rate entering the ionization region (equals the GC carrier gas flow rate if no further make-up gas is used) and the ionization region volume on peak broadening and signal intensity, different sample volumes as they would elute from a GC were tested at a variety of sample gas flow rates at a given ionization region volume. The results clearly show that for low sample gas flow rates a depletion of sample molecules in the ionization region leads to a significant decrease in effective detector volume but also to reduced signal intensities. Therefore, for optimal performance of a GC-IMS, the optimal operating point of the GC should match the flow range, where the IMS provides the best compromise between signal-to-noise ratio and peak broadening.