Gas Chromatography-olfactometry Research Articles

Oat-based milk alternatives: the influence of physical and chemical properties on the sensory profile.

Oat-based milk alternatives (OMAs) have become increasingly popular, perhaps due to their low allergenicity and preferred sensory attributes when compared to other milk alternatives. They may also provide health benefits from unique compounds; avenanthramides, avenacosides, and the dietary fibre beta-glucan. This has led to a variety of commercial options becoming available. Being a fairly new product, in comparison to other plant-based milk alternatives (PBMAs), means little research has been undertaken on the sensory profile, and how it is influenced by the physical and chemical properties. This study investigated the sensory, physical and chemical profiles of current commercially available OMAs, that varied in fortification, use of stabilisers, and oat content. The volatile compounds and their respective aromas were analysed using solid phase microextraction followed by gas chromatography mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O). Liquid chromatography mass spectrometry (LC-MS) was used for identification of avenanthramides and avenacosides. Particle size and polydispersity index (PDI) were analysed using a Mastersizer and Zetasizer, respectively, with colour analysis carried out using a colourimeter, and viscosity measurements using a rheometer. Descriptive sensory profiling was used to assess the impact on the sensory characteristics of the different samples and the sensory data acquired were correlated with the instrumental data. Samples with smaller particle size appeared whiter-both instrumentally and perceptually. The only clear plastic packaged product differed substantially in volatile profile from all other products, with a higher abundance of many volatile compounds, and high overall perceived aroma. Avenanthramides and avenacosides were present in all samples, but differed significantly in abundance between them. The results suggested smaller particle size leads to whiter colour, whilst differences in processing and packaging may contribute to significant differences in aroma. Astringency did not differ significantly between samples, suggesting that the variation in the concentrations of avenacosides and avenanthramides were below noticeable differences.

Characterization of key aroma compounds in soy sauce flavor baijiu by molecular sensory science combined with aroma active compounds reverse verification method

The distinctive flavor profile of soy sauce flavor baijiu (SAB) is shaped by its unique aroma compounds. The characteristic aroma compounds in Langjiu soy sauce flavor baijiu (LSAB) were explored based on molecular sensory science. A total of 66 aroma active compounds were identified by gas chromatography–olfactometry (GC–O) combined with aroma extract dilution analysis (AEDA), and 6 important unknown sulfur compounds were identified using the aroma active compounds reverse verification method (ACRVW). A total of 39 key aroma compounds were determined to have odor activity values (OAVs) ≥ 1. The aroma contribution of aroma components was verified by aroma recombination and aroma omission experiments. 15 characteristic aroma compounds were identified in LSAB. Meanwhile, a simple and easy-to-understand sensory expression language was described to fully understand the style characteristics of LSAB. Overall, the present paper offers insights into research uncovering the key “sauce flavor” of soy sauce flavor baijiu.

Molecular descriptors of icewine odorants: A first insight into their relationship with metabolism and olfactory perception.

To investigate the differences in physicochemical parameters of compounds that are metabolized from different precursors and contribute to the aroma perception of icewine, odor-active compounds in icewine were identified by gas chromatography-olfactometry (GC-O) analysis combined with comprehensive two-dimensional GC and time-of-flight mass spectrometry (GC × GC-TOFMS) analysis, and the molecular descriptors of these odor-active compounds were calculated by computational chemistry software. The distribution pattern of these odorants classified by their precursors and their olfactory perception was visualized on the basis of their molecular descriptor differences. The results showed that the odorants sourced from different precursors could be clearly separated from each other based on their molecular descriptors, which belonged to blocks such as constitution indices and 2D matrix-based descriptors. The results also showed that honey and cooked potatoe descriptions or peach and smoke descriptions have quite different molecular descriptors. This study should contribute to future research that relates to computational chemistry-based aroma perception and prediction in fermented beverages. PRACTICAL APPLICATION: The results obtained from this study may be useful for the construction of a classification system of various odor-active compounds in a given product and may provide a molecular solution for the determination of different perceptual dimensions of an odor mixture.

Effects of Monascus purpureus on ripe Pu-erh tea in different fermentation methods and identification of characteristic volatile compounds

The present study aimed to explore the key volatile compounds (VCs) that lead to the formation of characteristic flavors in ripe Pu-erh tea (RIPT) fermented by Monascus purpureus (M. purpureus). Headspace solid-phase microextraction coupled with gas chromatography/mass spectrometry (HS-SPME-GC–MS), orthogonal partial least square-discriminant analysis (OPLS-DA) were employed for a comprehensive analysis of the VCs present in RIPT fermented via different methods and were further identified by odor activity value (OAV). The VCs 1,2-dimethoxybenzene, 1,2,3-trimethoxybenzene, (E)-linalool oxide (pyranoid), methyl salicylate, linalool, β-ionone, β-damascenone were the key characteristic VCs of RIPT fermented by M. purpureus. OAV and Gas chromatography–olfactometry (GC-O) further indicated that β-damascenone was the highest contribution VCs to the characteristic flavor of RIPT fermented by M. purpureus. This study reveals the specificities and contributions of VCs present in RIPT under different fermentation methods, thus providing new insights into the influence of microorganisms on RIPT flavor.

Impact of roasting conditions on physicochemical, taste, volatile, and odor-active compound profiles of Coffea arabica L. (cv. Yellow Bourbon) using electronic sensors and GC–MS-O using a multivariate approach

This study investigated the effects of roasting conditions on the physicochemical, taste, and volatile and odor-active compound (OAC) profiles of Coffea arabica L. At 150 ℃, roasting increased chlorogenic acid, total flavonoids, and caffeine concentrations. However, umami and sourness sensor decreased during the roasting process. At 210 ℃ roasting, total flavonoid and caffeine concentrations increased during the roasting process. Aldehydes, ketones, and sulfur-containing compounds dramatically increased during the roasting at 210 ℃ for 20 and 30 min in E-nose analysis. Pyrazines were mainly generated during the roasting at 210 ℃ for 20 and 30 min, and pyrazines showed the highest concentrations among all OACs in GC-olfactometry (GC-O) analysis. E-tongue data showed the separation of beans by roasting temperature. However, the E-nose and GC-O data showed the separation of beans by both roasting temperature and time via multivariate analysis. We identified similar results and patterns in the E-nose and GC-O analyses.

Characterization of Key Odorants in Chinese Texiang Aroma and Flavor Type Baijiu (Chinese Liquor) by Means of a Molecular Sensory Science Approach.

The popularity of texiang aroma type baijiu (liquor), known for its unique production technology and multilayered flavor, has been steadily increasing among consumers. So far, no research has determined its key aroma compounds for characterizing the unique flavor, which is the purpose of this paper. Using gas chromatography-olfactometry (GC-O) coupled with the GC-mass spectrometry (GC-MS) method, 87 aroma-active compounds were identified and screened out with intensity values ≥2.0. 1,1,6-Trimethyl-1,2-dihydronaphthalene (TDN) was first confirmed by GC-O in Chinese liquor. According to a quantitative study and odor activity values (OAVs), 42 odorants were determined as important aroma compounds. These odorants were recombined based on quantitative concentrations, successfully simulating the overall aroma profile. Omission experiments verified ethyl hexanoate, β-damascenone, and 2-furfuryl ethyl ether as the key aroma compounds and revealed that ethyl acetate, furfural, and ethyl 2-phenylacetate were important aroma compounds to the overall flavor of texiang aroma and flavor type liquor.

Characterization of light-induced aroma components in green tea beverages using aroma extract dilution analysis with gas chromatography–olfactometry

Characterization of light-induced aroma components in green tea beverages using aroma extract dilution analysis with gas chromatography–olfactometry

Insights into key aroma of vine tea (Ampelopsis grossedentata) for grade evaluation integrating relative odor activity value, gas chromatography-olfactometry and chemometrics approaches

Insights into key aroma of vine tea (Ampelopsis grossedentata) for grade evaluation integrating relative odor activity value, gas chromatography-olfactometry and chemometrics approaches

Analysis of rice characteristic volatiles and their influence on rice aroma

Rice aroma, one of the most important qualities of rice, was the comprehensive result of volatiles in rice and human sense. In this study, the main volatile compounds in rice were analyzed by using gas chromatography-mass spectrometry and gas chromatography-olfactometry, and their correlations with sensory score were investigated. A total of eighty-five volatiles were found in rice samples. By combining odor activity value and correlation analysis, nine volatiles were considered as potential characteristic volatiles in rice aroma, namely hexanal, 2-pentylfuran, octanal, 2-acetyl-1-pyrroline (2-AP), 1-octen-3-ol, trans-2-octenal, decanal, trans-2-nonenal and trans, trans-2,4-decadienal. It was found that the volatiles negatively correlated with sensory scores were positively correlated with hexanal. It indicated that hexanal might be a representative of the negative volatiles of rice aroma. The effects of the nine potential characteristic volatiles on rice aroma were investigated by using sensory analysis. The results showed that the odor intensity and preference level of 2-AP, hexanal, and 1-octen-3-ol were significantly affected by the content. Furthermore, the aroma of cooked rice was significantly different after adding 2-AP, hexanal or trans, trans-2,4-decadienal. Rice aroma was increased by adding 2-AP and deteriorated by adding hexanal or trans, trans-2,4-decadienal, indicating that 2-AP contributed positively to rice aroma while hexanal and trans, trans-2,4-decadienal contributed negatively to rice aroma. Hexanal, 2-AP, and trans, trans-2,4-decadienal were suggested to be the key characteristic volatiles for future aroma evaluation.

Peracetic acid residues in orange juice can lead to a 5-vinylguaiacol-induced clove-like off-flavor via Baeyer-Villiger oxidation of hesperidin

A balanced flavor is a major quality attribute of orange juice. Formation of 4-vinylguaiacol during storage can lead to an undesirable clove-like off-flavor. However, clove-like off-flavors were occasionally reported despite low 4-vinylguaiacol concentrations, suggesting an alternative molecular background. Application of gas chromatography–olfactometry and aroma extract dilution analysis to an orange juice with a pronounced clove-like off-flavor resulted in the identification of 5-vinylguaiacol. The compound showed the same odor as 4-vinylguaiacol, but was previously unknown in orange juice. In five of six commercial orange juices with clove-like off-flavors, 5-vinylguaiacol was even more odor-active than 4-vinylguaiacol. Spiking and model studies suggested that 5-vinylguaiacol is formed during pasteurization from the natural orange juice component hesperidin and residual peracetic acid used as cleaning agent by a Baeyer-Villiger oxidation. An activity-guided screening approach confirmed the role of hesperidin as 5-vinylguaiacol precursor. In conclusion, peracetic acid should no longer be used in orange juice processing plants.

Comparison of differences in sensory, volatile odour-activity and volatile profile of commercial plant-based meats

Descriptive sensory analysis was paired with temporal check-all-that-apply gas-chromatography olfactometry (TCATA GC-O) to compare differences in perceived flavour and volatile odour activity across a series of commercial plant-based meat analogues (PBMAs) versus conventional beef products. Multiple factor analysis separated PBMAs in two clusters along the first principal axis. The first cluster, rated higher in meaty flavour and odour, also showed higher citation proportions of sulfurous odourants. In contrast, the second cluster, higher in off odour and flavour, had higher citation proportions for fatty / legume odourants. Key odourants correlated with meaty flavour and odour were putatively identified as 2-methyl-3-furanthiol, dimethyl trisulfide, and furfuryl mercaptan while compounds correlated to off flavour and odour were putatively identified as (E,E)-3,5-octadien-2-one, 2-undecanol, and (E,E)-2,4-decadienal. No correspondence was found between PBMA odour-activity and source protein, suggesting that volatile flavour production in PBMAs is derived primarily from exogeneous flavouring materials or precursors rather than the base protein material. Contributions of lipid-protein interactions to overall flavour differences is further suggested by the putative discovery of 5,6-dihydro-2,4,6-trimethyl-4H-1,3,5-dithiazine odour activity in several meat samples profiled.

Exploration of basil (Ocimum basilicum) essential oil profiles using E-nose and GC–MS combined with GC-O and inhalation effects on the human EEG topography and tomography (s-LORETA) and blood pressure

This study aimed to investigate the changes in human EEG activity, Brodmann area, and blood pressure during basil essential oil inhalation. Seven odor-active compounds were detected by GC–MS combined with GC–olfactometry, and three abundant volatile compounds were detected by electronic nose. Linalool was simultaneously regarded as a major volatile compound. The systolic and diastolic blood pressures and pulse levels showed a decreasing trend during BEO inhalation. The relative beta and gamma waves in most brain regions changed during BEO inhalation. The gamma waves decreased, whereas the beta waves increased during BEO inhalation. In particular, the beta waves in the left frontal and right parietal regions and Brodmann area 38 significantly increased during inhalation using sLORETA. Accordingly, these results were highly associated with reduced stress responses by decreased gamma waves, blood pressures, and pulse levels and improved language-related functions by the increased beta wave at Brodmann area 38.

Identification of characteristic aroma compounds in chicken meat and their metabolic mechanisms using gas chromatography–olfactometry, odor activity values, and metabolomics

Aroma has an important influence on the aroma quality of chicken meat. This study aimed to identify the characteristic aroma substances in chicken meat and elucidate their metabolic mechanisms. Using gas chromatography–olfactometry and odor activity values, we identified nonanal, octanal, and dimethyl tetrasulfide as the basic characteristic aroma compounds in chicken meat, present in several breeds. Hexanal, 1-octen-3-ol, (E)-2-nonenal, heptanal, and (E,E)-2,4-decadienal were breed-specific aroma compounds found in native Chinese chickens but not in the meat of white-feathered broilers. Metabolomics analysis showed that L-glutamine was an important metabolic marker of nonanal, hexanal, heptanal, octanal, and 1-octen-3-ol. Exogenous supplementation experiments found that L-glutamine increased the content of D-glucosamine-6-P and induced the degradation of L-proline, L-arginine, and L-lysine to enhance the Maillard reaction and promote the formation of nonanal, hexanal, heptanal, octanal, and 1-octen-3-ol, thus improving the aroma profile of chicken meat.

Sensomics-assisted key aroma molecules decoding of ginger-infused stewed beef

The utilization of ginger (Zingiber officinale Rosc.) is prevalent in beef cuisine for the purpose of flavor modification in China. The key aroma molecules in ginger-infused stewed beef were identified by sensomics methods. GC-MS (gas chromatography-mass spectrometry) identified 54 compounds. Nonanal, citral, β-bisabolene, α-terpineol, geraniol and endo-borneol were responsible for remarkable difference of stewed beef after ginger additions by orthogonal partial least squares-discriminant analysis (OPLS-DA). Seven aroma attributes were chosen for sensory analysis by check-all-that-apply (CATA) and free choice profiling method (FCP). Then, 23 compounds were perceived by gas chromatography-olfactometry (GC-O), and further quantified. Of these, 20 aroma-active compounds presented odor activity values (OAV) ≥ 1. Combined with aroma recombination and omission experiments, 19 compounds, including hexanal, β-myrcene, 2-acetylthiazole et al. were identified to be key contributors to characteristic aroma.

Aromatic profiles and enantiomeric distributions of volatile compounds during the ripening of Dendropanax dentiger honey

Dendropanax dentiger honey (DDH) is a specialty herbal honey from China. Previous research on DDH has mostly focused on its composition and potential chemical markers, no studies have been conducted on the changes in aroma characteristics and chiral odorants during its maturation. Therefore, the present study aims to address the missing parts. The proportions and total concentrations of 185 volatile compounds identified in different classes varied with DDHs ripening. Fourteen common odor-active compounds were identified by odor activity values (OAVs) and GC-olfactometry (GC-O) analysis. The aroma profiles of DDHs were observed to vary at different ripening stages, although the dominant aroma characteristic was “fruity” aroma, which became more pronounced with increasing maturity. The enantiomeric contents and distributions of 7 volatile enantiomers were related to specific physicochemical indicators and the maturity of DDHs, among which the enantiomers of linalool oxide A may be a potential indicator to identify its maturity. Furthermore, precise quantification and OAVs calculation showed that the enantiomer (2S, 5S)-linalool oxide A presented the highest concentration (8.83–27.39 ng/mL) and only the enantiomer R-linalool (OAVs: 5.56–6.14) was an important contributor to the aroma profiles of DDHs at different stages of maturity. These results provided a new research idea for quality control and identification of DDHs at different maturity stages.

Effects of gallic acid on the release of aroma compounds in Moutai Baijiu

Due to the trace concentrations of gallic acid (GA), the interaction mechanism between GA and flavor compounds is limited, and the effects on the aroma compounds of Moutai Baijiu are even more unclear. In this study, the aroma compounds and phenolic compounds in Moutai Baijiu were investigated by stir bar sorptive extraction (SBSE), gas chromatography–olfactometry (GC-O), gas chromatography-mass spectrometry (GC–MS) and liquid chromatography-mass spectrometry (LC-MS). A total of 63 volatiles and 10 phenolic compounds were identified, and 16 esters and 4 alcohols were identified as the important aroma substances (odor activity values ≥1). The effect of GA on the release of aroma compounds was investigated by sensory analysis and partition coefficient. The results showed that GA mainly inhibited the volatilization of alcohols, low concentrations of GA promoted the release of esters, and high concentrations slowed down or even inhibited the release effect affected by the hydrophobicity of aroma compounds. UV spectroscopy and thermodynamic analysis further revealed that the interaction of GA with 1-propanol was attributed mainly to hydrogen bonding and van der Waals forces, and the interaction with other compounds was mainly influenced by hydrophobic effects. These results show that gallic acid can effectively control the release of the aromas of Moutai Baijiu, highlight the important role of GA on the volatiles of baijiu, and provide theoretical support for further healthy improvement of the sensory quality of baijiu.

Characterization of the key odor-active compounds in different aroma types of Fu brick tea using HS-SPME/GC-MSO combined with sensory-directed flavor analysis.

Fu brick tea (FBT) is popular for its unique 'fungal flower' aroma, however, its key odor-active compounds are essentially unknown. In this study, the odor-active compounds of "stale-fungal" aroma (CJX), "fresh-fungal" aroma (QJX), and "fermentation-fungal" aroma (FJX) types FBT were extracted and examined by headspace solid phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS) and gas chromatographyolfactometry (GC-O). A total of 43 volatile and 38 odor-active compounds were identified by these methods. Among them, the content of dihydroactindiolide (4596-13189µg/L), (E)-linalool oxide (2863-6627µg/L), and benzyl alcohol (4992-6859µg/L) were highest. Aroma recombination experiments further verified that these odor-active compounds could be simulated the overall aroma profile of FBT successfully. Furthermore, omission experiments confirmed that 15, 20, and 15 key odor-active compounds in CJX, QJX, and FJX FBT, respectively. This study will provide a theoretical basis for comprehensively understanding the formation of characteristic aromas in FBT.

Effects of pile-fermentation on the aroma quality of dark tea from a single large-leaf tea variety by GC × GC-QTOFMS and electronic nose

Aroma is one of the significant quality factors of dark tea (DT). However, for a single large-leaf tea variety, there are few studies analyzing the effect of pile-fermentation on the aroma quality of DT. The GC × GC-QTOFMS, electronic nose (E-nose) and GC-olfactometry (GC-O) techniques were employed to analysis the difference of tea products before and after pile-fermentation. A total of 149 volatile metabolites (VMs) were identified, with 92 VMs exhibiting differential characteristics. Among these, 31 VMs with OAV > 1.0 were found to be correlated with E-nose results (|r| > 0.8). Additionally, GC-O analysis validated seven major differential metabolites. Notably, naphthalene, 2-methylnaphthalene, and dibenzofuran were found to enhance the woody aroma, while (Z)-4-heptenal, 2-nonenal and 1-hexanol were associated with an increase in mushroom, fatty and sweet odors, respectively. Moreover, 1-octen-3-ol was linked to reducing pungent fishy smell. These findings could provide a certain theoretical basis for understanding the influence of pile-fermentation on the aroma quality of dark tea.

Comparative flavor precursors and volatile compounds of Wenchang chickens fed with copra meal based on GC–O–MS

In the Wenchang chicken (WC) feeding process, copra meal is often added to improve chicken quality. To determine the effect of feeding with copra meal on the flavor formation of WCs, the experimental subjects were fed with 4.5 % and 7.5 % copra meal, and the control group was fed without copra meal. The electronic nose combined with gas chromatography–olfactometry mass spectrometry (GC–O–MS) was used to identify the volatile compounds from the samples. Compared with the control group, the pH of chickens fed copra meal was significantly decreased (P < 0.05) after slaughter. Aldehydes and alcohols were the main volatile compounds in muscle, among which hexanal and 1-octen-3-ol were the highest. Thirty-two and thirty-six compounds were identified in breast muscle and drumstick muscle, respectively. Twelve new volatile compounds were added, including 1-octanol, butanal, 1-heptanol, 3-ethylbenzaldehyde, 2,2-dimethylpentanal, hexanoic acid, 3-heptanone, 2,5-heptanedione, 2-ethylfuran, 2-propylfuran, 2-ethynylpyridine, and 1,2,4,5-tetrazine. The types and contents of volatile compounds in drumstick muscle increased with an increasing proportion of copra meal in the diet. In summary, the addition of copra meal changed the quality of WCs and increased the types and contents of volatile compounds. This study provides a reference for understanding the flavor profile of WC fed copra meal.

Study on the flavor of brown milk fermented by Lactobacillus paracasei K56 in different strain states

A comprehensive investigation of the differences in flavor profiles among different strains of fermented brown milk (FBM) is important to guide the improvement of the flavor quality of FBM. Seven samples were analyzed by dynamic headspace extraction (DHS) and gas chromatography–olfactometry–mass spectrometry (GC–O–MS), and a total of 73 odor compounds were identified. Key odor compounds including 3-methyl-1-butanol, ethyl acetate, linalool, furfuryl alcohol, 2-pentylfuran, hexanal, and 1-octen-3-ol, were screened by multivariate statistical analysis to reveal the flavor differences of FBM from different strains. 3-Methyl-1-butanol and ethyl acetate were found to be the key odor compounds distinguishing FBM by strain K56 from other strains, and the fermentation strains were found to be the key factors affecting the flavor of FBM compared to the fermentation substrate and fermentation process. This study provided a relatively systematic investigation of the flavor of FBM and could be used to monitor changes in odor components and sensory characteristics for product quality control.