Volatile Compound Profiles Research Articles

Metabolomics of Vitis davidii Foëx. grapes from southern China: Flavonoids and volatiles reveal the flavor profiles of five spine grape varieties

The spine grapes (Vitis davidii Foëx.) are wild grape species that grow in southern China, and can be used for table grapes, juicing and winemaking. To systematically investigate the flavor profiles of spine grapes, flavonoids and volatile compounds were detected in five spine grape varieties (Seputao, Ziqiu, Miputao, Tianputao and Baiputao) using HPLC-QqQ-MS/MS and GC–MS. The content of flavonoids highly depended on the variety, such as the total concentrations of anthocyanins (91.43–328.85 mg/kg FW) and flavonols (33.90 to 83.16 mg/kg FW). The volatile compounds with higher odor active value were selected to describe the aroma of spine grapes. Hexanal, (E)-2-hexenal and (E, Z)-2,6-nonadienal contributed to the higher herbaceous flavor to Baiputao and Ziqiu. β-Damascenone and (E)-2-nonenal gave Baiputao a flavor with more floral, fruity and earthy. Their characteristic flavor compounds were subsequently revealed using multivariate statistical analysis. The results helped producers to further develop and utilize the spine grapes.

Exhaled breath analysis in adult patients with cystic fibrosis by real-time proton mass spectrometry

BackgroundProton-transfer reaction time-of-flight mass spectrometry (PTR-TOF-MS) is a promising tool for a rapid online determination of exhaled volatile organic compounds (eVOCs) profiles in patients with cystic fibrosis (CF). ObjectiveTo detect VOC breath signatures specific to adult patients with CF compared with controls using PTR-TOF-MS. Methods102 CF patients (54 M/48, mean age 25.6 ± 7.8 yrs) and 97 healthy controls (56 M/41F, mean age 25.8 ± 6.0 yrs) were examined. Samples from normal quiet breathing and forced expiratory maneuvers were analyzed with PTR-TOF-MS (Ionicon, Austria) to obtain VOC profiles listed as ions at various mass-to-charge ratios (m/z). ResultsPTR-TOF-MS analysis was able to detect 167 features in exhaled breath from CF patients and healthy controls. According to cluster analysis and LASSO regression, patients with CF and controls were separated. The most significant VOCs for CF were indole, phenol, dimethyl sulfide, and not indicated: m/z = 297.0720 ([C12H13N2O7 and C17H13O5]H + ), m/z = 281.0534 ([C19H7NO2, C12H11NO7 and C16H9O5]H + ) during five-fold cross-validation both in forced expiratory maneuver and in normal quiet breathing. ConclusionPTR-TOF-MS is a promising method for determining the molecular composition of exhaled air specific to CF.

Defects of Coffee Beans with Different Postharvest Processes and Roasting Temperatures on Volatile Compounds of Coffee Beans from Coffee Small-Scale Industries of West Lampung Indonesia

Specialty coffee is processed by performing high standards nationally (SNI) and internationally (SCAA). Good handling in the small coffee industry is essential to producing coffee raw materials as a refreshing drink. The aroma released from the best coffee beans gives an emotional flavor to the drinker - the aroma produced from the best coffee beans with different post-harvest methods. This study analyzed the physical quality of moisture content, coffee bean defects from dry processing post-harvest handling (natural and honey), and different roasting temperature differences to produce volatile compound profiles from three small-scale coffee industries. Six samples of raw materials from 3 small-scale coffee industries were selected by purposive sampling with the criteria that the processing farmer had performed SNI standards. Six coffee samples from the September harvest in 2022. Observations were made in the laboratory for analysis of moisture content and quality defects of coffee beans, then roasted by the industry and analyzed descriptively and multivariate analysis for volatile compounds. The moisture content of coffee beans from all coffee industries has met the requirements following SNI 01-2907-2008, that the moisture content is not more than 12.5 %. All coffee beans produced have 50 % potential as fine robusta coffee beans because they have no primary defects. Increasing the roasting temperature on all coffee beans increases volatile compounds. Coffee beans processed with honey produced more volatile compounds than the natural post-harvest method. The caffeine content in all post-harvest processing processes in the three industries has a difference in concentration due to differences in roasting temperature and time. The study that in the three-ground coffee small-scale industries processed by the natural post-harvest method, carbamic acid compounds were suspected to be from carbamate class insect pesticides (carbofuran) and the fungicide pyraclostrobin. Considering that pesticide residues harm human health, it is essential to implement measures to educate farmers to use organic fertilizers and ensure consumer safety. HIGHLIGHTS Kopi merupakan komoditas unggulan Provinsi Lampung Indonesia Kopi cacat mempengaruhi Kualitas mutu biji kopi Kopi yang dihasilkan IKM merupakan Kopi robusta petik buah merah Terdapat temuan kontaminasi dari senyawa kimia carbamate acid dari pemakaian herbisida/insektisida yang digunakan petani GRAPHICAL ABSTRACT

Comparative profiling of microbial communities and volatile organic compounds in fermented wrapper, binder, and filler cigar tobaccos

BackgroundEconomic benefits for tobacco growers are closely linked to the quality of fermented cigar tobacco leaves (CTLs). This research focused on an in-depth examination of the microbial community and flavor compounds within CTLs, specifically analyzing the wrapper, binder, and filler components of a cigar. The primary objective was to unravel the complex relationship between the microbial composition and the resultant flavor profiles, thereby providing insights that could enhance the economic value of CTLs.ResultsThe study revealed distinct variations in flavor chemicals and microbiota across different sections of CTLs. Prominent species identified in the fermented CTLs included Corynebacterium, Pseudomonas, Staphylococcus, Aspergillus, and Cladosporium. Bidirectional orthogonal partial least squares (O2PLS) analysis pinpointed five bacterial and four fungal species as key contributors to flavor compound formation. Additionally, an analysis considering Within-module and Among-module connectivity highlighted two bacterial and thirteen fungal genera as keystone species. The insights from Partial Least Squares Structural Equation Modeling (PLS-SEM) further underscored the influential role of fungal microorganisms in defining CTLs' flavor profile.ConclusionsThe research findings illuminate the intricate interplay between flavor chemicals and microbes in the traditional fermentation process of CTLs.Graphical

Plant In Vitro Cultures of Coleus scutellarioides (L.) Benth. "Electric Lime" and Possibilities of Modification in the Biosynthesis of Volatile Compounds.

Coleus scutellarioides (L.) Benth. is a globally spread species, known for its characteristic spectacularly colorful leaves of decorative value. Thanks to its rich chemical composition, the plant is used in ethnopharmacology, and it is also regarded as having high medicinal potential. The application of in vitro cultures enables the acquisition of homogeneous certified material of high quality. Additionally, excluding the effect of biotic and abiotic factors on the plants is a way to fully recognize the influence of phytohormones on the plant morphology and the biosynthetic pathways of compound production. The best way to grow C. scutellarioides "Electric Lime" under in vitro conditions is to use the basic MS medium (Murashige and Skoog medium), enriched with naphthyl-1-acetic acid at a concentration of 0.5 mg dm-3. The analysis of volatile compounds demonstrated that the content of volatile compounds in the plants cultivated under in vivo conditions was expressed at a level of 2848.59 µg g-1, whereas in the plants bred in vitro without supplementation with phytohormones, the level was 8191.47 µg g-1. The highest content was noted for copaene, α-pinene, 1-octene-3-ol, α-selinene, sabinen, γ- and δ-cadinene, 3-octanol, and β-pinene. Aroma profiling revealed a lack of boranyl acetate, 2-hexenal, and 2-hexen-1-ol in the plants cultivated under in vivo conditions. Differences were found in the volatile composition between plants bred in vivo and in vitro, with the most significant recorded for the contents of 1-octen-3-ol and 3-octanol. The addition of plant growth regulators into the basic medium under in vitro conditions affected the percentage ratio and contents of specific compounds in plant tissues. The most intense biosynthesis of volatile compounds took place in the plants cultivated on the medium enriched with NAA at 10,579.11 µg g-1, whereas the least intense was noted for plants cultivated on the medium supplemented with BA, where it was recorded at the level of 5610.02 µg g-1. So far, there has been no research published which would pertain to the profiling of volatile compounds performed using the SPME (solid-phase microextraction) technique. Moreover, the very few studies conducted on the chemical composition of these compounds do not mention the specific variety of C. scutellarioides under analysis.

Effects of prebiotics on the fermentation of traditional suancai of Northeast China

Suancai is a traditional fermented vegetable widely consumed in Northeast China. In this study, different prebiotics were used to improve the quality of suancai. Four prebiotics (inulin (INU), xylooligosaccharide (XOS), galactooligosaccharide (GOS), and stachyose (STA)) were shown to reduce the pH value and increase the content of total titratable acidity (TTA) in suancai, while the contents of most organic acids were also increased. The addition of prebiotics had significant effects on the bacterial microbiota during the suancai fermentation process. All prebiotics were shown to contribute to the growth of Lactobacillus. The suancai sample with fructooligosaccharides (FOS) had the highest relative abundance of Lactobacillus. Besides, INU and XOS could increase the abundance of Weissella. To evaluate the quality of suancai fermented with prebiotics, profiles of volatile flavor compounds (VOCs) and free amino acids (FAA) were analyzed. The prebiotics affected the VOCs and FAA profiles via transforming the bacterial microbiota. In addition, the addition of prebiotics also changed the taste profiles of the suancai samples. This study is among the first attempts to reveal the effects of different prebiotics on suancai fermentation, and the findings provide a foundation to develop new ways for improving the quality of suancai.

Monitoring the Dough Properties, Quality Characteristics and Volatile Compounds of Whole Wheat Bread Made by Different Sourdough Types during Frozen Storage.

There is a need to increase the consumption of whole wheat bread (WWB) due to its health benefits by overcoming its poor technological quality and improving its sensory characteristics. In this study, sourdough bread-making and frozen dough technology were combined to provide fresh WWB at any time with better quality. Also, it was aimed to investigate the effects of three types of sourdough (type I, II, and IV) on the final quality of WWB during frozen storage (-30 °C, 14 and 28 days). The tan δ of WWB with type I sourdough was highest at the end of the frozen storage. Freezable water content was lower on day 0 for WWB with type II and IV sourdough than other bread types. No significant effect of frozen storage was observed in bread types in terms of an α helix structure, except for WWB with type I sourdough. A lower hardness increment was shown in WWB with baker's yeast and WWB with type II sourdough over 14 days of frozen storage when compared to other bread types. WWB with type I sourdough and WWB with type IV sourdough were differentiated from other bread samples in volatile compound (VC) analysis on frozen storage days 28 and 0, respectively. The frozen storage of WWB with baker's yeast and WWB with type II sourdough caused no notable changes in the VCs profile. These results suggest that a less detrimental effect of frozen storage was observed in WWB with type II sourdough, indicating a more favorable choice for producing WWB with sourdough.

Characterization of lipids and volatile compounds in boiled donkey meat by lipidomics and volatilomics.

Lipids are crucial substances for the formation and retention of volatile compounds (VOCs). The lipid and VOC profiles of boiled donkey meat were investigated by lipidomics and volatilomics. In total, 4277 lipids belonging to 39 subclasses were identified, comprising 26.93% triglycerides (TGs), 15.74% phosphatidylcholins (PCs), and 9.40% phosphatidylethanolamines. The relative percentage of TG in the meat significantly decreases (p<0.001) from 0 to 40min, after which there is no significant change, whereas PCs, sphingomyelins, and methyl phosphatidylcholines (MePCs) show the opposite trend. TG(16:1_18:1_18:2) and TG(16:0_16:1_18:2) appear to be key lipids for retaining VOCs in boiled donkey meat. Furthermore, PC(18:3e_16:0) and MePC(31:0e) were found to be potential markers for discriminating donkey meat. A total of 83 VOCs were detected, including 25.30% aldehydes, 18.07% hydrocarbons, 14.46% ketones, and 13.25% alcohols. Eleven characteristic VOCs with relative odor activity values >1 were identified as the predominant flavor compounds in boiled donkey meat, mainly hexanal and 1-octen-3-ol. Of the 258 differential lipids, 72 of them, especially polyunsaturated-fatty acid-rich lipids, are the main contributors to the formation of VOCs. Together, the key lipids for retention and formation of VOCs in donkey meat were revealed, providing a theoretical basis for VOC regulation.

Markers of sensory dynamics in phenols-rich virgin olive oils under optimal storage conditions

Early changes in sensory quality of phenols-rich virgin olive oil (VOO) and their relationship with the chemical changes are less studied in the literature. Therefore, the objective of this study was to propose a predictive model of dynamics of sensory changes based on specific chemical markers. The evolution of the sensory quality of phenol-rich VOOs from Tuscan cultivars stored under optimal storage conditions (i.e., absence of light, no O2 exposure, low temperature) was investigated using a multi-step methodological approach combining sensory (official sensory analysis (so-called Panel Test), Descriptive Analysis and Temporal Dominance of Sensation) and chemical measurements. The sensory map from descriptive data was related to the phenolic and volatile profiles, measured using HPLC-DAD and HS-SPME-GC–MS, respectively. A predictive model of the sensory changes over storage based on chemical compounds was developed. Results showed that very early changes involving phenolic and volatile compounds profiles occur in VOOs stored under optimal storage conditions, which turn in changes in sensory properties evaluated by the official panel test, the descriptive analysis and the temporal dominance of sensation. Furthermore, a chemical marker of sensory dynamics of oils during storage was identified as the ratio between two groups of secoiridoids. The proposed model, supported by the mentioned chemical marker, has the potential of improving the control of sensory changes in phenols-rich virgin olive oils during storage in optimal conditions.

Identification of exhaled volatile organic compounds that characterize asthma phenotypes: A J-VOCSA study

BackgroundAsthma is characterized by phenotypes of different clinical, demographic, and pathological characteristics. Identifying the profile of exhaled volatile organic compounds (VOCs) in asthma phenotypes may facilitate establishing biomarkers and understanding asthma background pathogenesis. This study aimed to identify exhaled VOCs that characterize severe asthma phenotypes among patients with asthma. MethodsThis was a multicenter cross-sectional study of patients with severe asthma in Japan. Clinical data were obtained from medical records, and questionnaires were collected. Exhaled breath was sampled and subjected to thermal desorption gas chromatography-mass spectrometry (GC/MS). ResultsUsing the decision tree established in the previous nationwide asthma cohort study, 245 patients with asthma were divided into five phenotypes and subjected to exhaled VOC analysis with 50 healthy controls (HCs). GC/MS detected 243 VOCs in exhaled breath samples, and 142 frequently detected VOCs (50% of all samples) were used for statistical analyses. Cluster analysis assigning the groups with similar VOC profile patterns showed the highest similarities between phenotypes 3 and 4 (early-onset asthma phenotypes), followed by the similarities between phenotypes 1 and 2 (late-onset asthma phenotypes). Comparisons between phenotypes 1–5 and HC revealed 19 VOCs, in which only methanesulfonic anhydride showed p < 0.05 adjusted by false discovery rate (FDR). Comparison of these phenotypes yielded several VOCs showing different trends (p < 0.05); however, no VOCs showed p < 0.05 adjusted by FDR. ConclusionsExhaled VOC profiles may be useful for distinguishing asthma and asthma phenotypes; however, these findings need to be validated, and their pathological roles should be clarified.

Characterization of flavor-related compounds and sensory profiles of four fermented fish products prepared from silver rasbora (Rasbora argyrotaenia) and anchovy (Stolephorus sp.)

Fermented fish products are grouped into salt and salt-carbohydrate types based on the fermentation substrate. A series of biochemical reactions on the substrate affects the flavor characteristics of the resulting products. This study compared the amino acids, fatty acids, and volatile compound profiles of four fermented fish products: bekasam, rusip, fish paste, and fish sauce made from silver rasbora and anchovy. The quantitative descriptive analysis (QDA) was carried out to determine the sensory profiles of those products. The results indicated that rusip and bekasam, which belong to salt-carbohydrate fermented fish, were characterized as high in arginine, stearic, capric, and oleic acid, with ketones, lactones, and fatty acid derivative compounds dominating their flavor profiles. The flavor profile of fish paste was characterized by high concentrations of aldehydes such as 3- methylbutanal and hexanal, whereas that of fish sauce was characterized by large concentrations of pyrazine and aromatic compounds. Based on the findings of the QDA, no significant difference was observed within the sensory variables of fish sauce and fish paste prepared from anchovy and silver rasbora, indicating that both fish are equally usable as raw materials. Whereas different saltiness was identified in both rusip and bekasam prepared from anchovy and rasbora. The results of PCA on QDA data separated fermented fish type 1 from the type 2. Fermented fish type 1 was more correlated with umami and sweet taste, while type 2 was correlated with fishy, salty, sour, and astringent taste. The result is useful as a basis for further product development and quality control.

Mechanical recycling of printed flexible plastic packaging: The role of binders and pigments

Low-density polyethylene (LDPE), extensively employed in flexible plastic packaging, often undergoes printing with inks. However, during the mechanical recycling of post-consumer waste, these inks act as contaminants, subsequently compromising the quality and usability of recycled material. To understand better exactly which ink components cause which effects, this study comprehensively assesses the thermal behavior of three organic pigments and two commonly utilised binders, correlated with the impact on the mechanical recycling of LDPE-based flexible plastic packaging. In this regard, the study focuses on four pivotal factors: processability, mechanical properties, aesthetic attributes, and volatile organic compound profiles. The results indicate that nitrocellulose, used as a binder, degrades during reprocessing, resulting in film discoloration and the emission of potentially odorous compounds. Conversely, pigments are found to be dispersed within droplets of polyurethane binder in LDPE recyclates, whilst reprocessing printed samples detrimentally affects film properties, notably dart drop impact resistance, strain at break, and the number of inclusions. Additionally, it is shown that both inks comprise components that emit volatile compounds during reprocessing: non-thermally stable components, nitrocellulose and pigment yellow PY13, as well as low-molecular weight molecules from polyurethane and by-products from wax, plasticisers, and additives.

Changes in Chemical Composition of Lentils, Including Gamma-Aminobutyric Acid and Volatile Compound Formation during Submerged and Solid-State Fermentation with Pediococcus acidilactici.

The aim of this study was to evaluate and compare the characteristics of non-treated and fermented [via submerged (SMF) and solid-state (SSF) fermentation using Pediococcus acidilactici] lentils (Lens culinaris) grown either in pure stands (L) or relay intercropped with winter rye (LR). It was observed that the lentils were suitable substrate for lacto-fermentation. Most of the free amino acid concentrations increased in lentils after both fermentations. The highest concentration of γ-aminobutyric acid was found in SSF LR samples. However, fermentation led to higher biogenic amines (BA) content in lentils. The most abundant fatty acid in lentils was C18:2. SSF lentils showed more complex volatile compound (VC) profiles (with between nine and seventeen new VCs formed), whereas, in SMF samples, between two and five newly VCs were formed. When comparing lentil grown types, L contained significantly higher concentrations of Na, K, Ca, P, Mn, and Se, while LR contained significantly higher concentrations of Fe and Ni. To sum up, fermentation with lactic acid bacteria (LAB) contributed to the improved biological value of lentils; still, the quantity of BA needs to be considered. Further investigations into the P. acidilactici metabolism of certain compounds (such as phenolic and antinutritional compounds) in lentils during fermentation ought to be carried out.

The dynamic changes in volatile metabolites provide a new understanding for the special flavor formation in z. Mioga flower buds during the growth stages

Although Z. mioga flower buds are popular among consumers for its unique spicy flavor, high nutritional and medicinal value, there are few reports on the formation and changes of the flavor during its growth and maturation process. The understanding of the profile of volatile compounds would help to unravel the flavor formation for Z. mioga flower buds during growth. The volatile changes in Z. mioga flower buds were analyzed by GC–MS and a total of 182 volatile compounds identified, and the terpenoids accounted for the most abundant volatile substances. Almost all the identified volatiles presented an intuitive upward trend throughout the growth period and reached the maximum at the later stage of development (DS3 or DS4). Regarding the PCA and HCA results, there were significant differences found among the four stages, and the DS3 was the critical node. The top 50 differential volatiles screened by OPLS-DA and PLS-DA were all up-regulated, and the correlation analysis indicated that terpenoids might synergize with other chemical types of volatiles to jointly affect the flavor formation of Z. mioga flower buds during growth. The association network for flavor omics revealed that the most important sensory flavor for Z. mioga flower buds were woody and sweet, and the main contribution compounds for the unique flavor contained β-guaiene, β-farnesene, δ-cadinene and citronellyl isobutanoate. Taken together, the results of this study provided a reference for flavor quality evaluation of flower buds and determination of the best harvest period.

Unveiling the hidden impact: How biodegradable microplastics influence CO2 and CH4 emissions and Volatile Organic Compounds (VOCs) profiles in soil ecosystems

Biodegradable plastics promise eco-friendliness, yet their transformation into microplastics (bio-MPs) raises environmental alarms. However, how those bio-MPs affect the greenhouse gases (GHGs) and volatile organic compounds (VOCs) in soil ecosystems remains largely unexplored. Here, we investigated the effects of diverse bio-MPs (PBAT, PBS, and PLA) on GHGs and VOCs emission in typical paddy or upland soils. We monitored the carbon dioxide (CO2) and methane (CH4) fluxes in-situ using the self-developed portable optical gas sensor and analyzed VOC profiles using a proton-transfer reaction mass spectrometer (PTR-MS). Our study has revealed that, despite their biodegradable nature, bio-MPs do not always promote soil GHG emissions as previously thought. Specifically, PBAT and PLA significantly increased CO2 and CH4 emissions up to 1.9–7.5 and 115.9–178.5 fold, respectively, compared to the control group. While PBS exhibited the opposite trend, causing a decrease of up to 39.9% for CO2 and up to 39.9% for CH4. In addition, different types of bio-MPs triggered distinct soil VOC emission patterns. According to the Mann-Whitney U-test and Partial Least Squares Discriminant Analysis (PLS-DA), a recognizable VOC pattern associated with different bio-MPs was revealed. This study claims the necessity of considering polymer-specific responses when assessing the environmental impact of Bio-MPs, and providing insights into their implications for climate change.

Storage Conditions for ‘Barton’ Pecan: Impact of Moisture Content and Temperature on Quality Maintenance and Volatile Compounds Profile

Storage Conditions for ‘Barton’ Pecan: Impact of Moisture Content and Temperature on Quality Maintenance and Volatile Compounds Profile

Preliminary Investigation towards the Use of Infrared Technology for Raw Milk Treatment.

Infrared (IR) technology offers a promising solution for reducing microbiological loads in various food types while preserving their quality traits, such as flavour. However, research on IR's application in complex matrices is limited. Therefore, our preliminary study aimed to evaluate its effectiveness in sanitizing bovine raw milk. We assessed the bacterial count before and after IR treatment by comparing volatile organic compound profiles via headspace extraction and GC/MS analysis. Our findings showed that higher energy levels led to a greater bacterial reduction. IR85 was the most effective in reducing Coliforms and Enterobacteriaceae in non-homogenised samples, with a reduction ranging from -1.01 to >-2.99 and from -1.66 to -3.09 Log CFU/mL, respectively. IR60 and 70 showed no efficacy, while IR80 had intermediate but still satisfactory effect. IR85 notably affected volatile compounds, particularly increasing hexanal (from 0.08 to 4.21 ng g-1) and dimethyl sulphone (from 10.76 to 26.40 ng g-1), while IR80 better preserved the aroma profile. As a result, only IR80 was tested with homogenised raw milk, demonstrating significant bacterial reduction (from >2.39 to 3.06 Log CFU/mL for Coliforms and from 1.90 to >2.45 Log CFU/mL for Enterobacteriaceae) and maintaining the aroma profile quality.

Conjugated linoleic acid‐enriched yoghurts development through homogenization: Study of fatty acids, volatile compounds profiles and physicochemical, rheological and sensory properties

Conjugated linoleic acid (CLA) is recognised for its health benefits: anticancer, antiinflamatory and antiatherogenic effects have been reported. CLA enriched yoghurts were developed through homogenization at two levels (H1 and H2 with 40 and 80 mg CLA/100 g of yoghurt, respectively) with a view to creating functional foods. CLA modified the volatile profile in a positive way: higher levels of diacetyl and ethyl butanoate and lower values of 2‐hexanone and 2‐heptanone, ethanol and certain acids were recorded. Yoghurts presented similar microstructure, but H1 showed higher consistency and lower pseudoplastic behaviour; meanwhile H2 presented less syneresis. All products had high acceptability.

Modulating peppermint oil flavor release properties of emulsion-filled protein gels: Impact of cross-linking method and matrix composition

For some food applications, it is desirable to control the flavor release profiles of volatile flavor compounds. In this study, the effects of crosslinking method and protein composition on the flavor release properties of emulsion-filled protein hydrogels were explored, using peppermint essential oil as a model volatile compound. Emulsion-filled protein gels with different properties were prepared using different crosslinking methods and gelatin concentrations. Flavor release from the emulsion gels was then monitored using an electronic nose, gas chromatography-mass spectrometry (GC–MS), and sensory evaluation. Enzyme-crosslinked gels had greater hardness and storage modulus than heat-crosslinked ones. The hardness and storage modulus of the gels increased with increasing gelatin concentration. For similar gel compositions, flavor release and sensory perception were faster from the heat-crosslinked gels than the enzyme-crosslinked ones. For the same crosslinking method, flavor release and perception decreased with increasing gelatin concentration, which was attributed to retardation of flavor diffusion through the hydrogel matrix. Overall, this study shows that the release of hydrophobic aromatic substances can be modulated by controlling the composition and crosslinking of protein hydrogels, which may be useful for certain food applications.

Emission factors and source profiles of volatile organic compounds from the automobile manufacturing industry

Controlling volatile organic compounds (VOCs) emitted from the automobile manufacturing industry requires establishing VOCs emission factors (EFs) and source profiles refinedly. In this study, 41 samples involved 32 VOCs discharge links were collected from three factories. The EFs and VOCs source profiles were estimated by the material balance method and weighted average method, respectively. The ozone formation potential (OFP) of the 110 VOCs species were calculated by the maximum incremental reactivity (MIR). According to estimations, the ranges of EFs were 0.23–1.66 kg VOCs/SUV car and 2.14–14.86 g VOCs/m2 painted area. EFs of six materials were firstly estimated, which are electrophoretic primer (152.31 ± 97.39 g VOCs/SUV car, 0.97 ± 0.38 g VOCs/m2 painted area), sealant (48.39 ± 26.20 g VOCs/SUV car, 0.46 ± 0.25 g VOCs/m2 painted area), floating coat (87.40 ± 75.63 g VOCs/SUV car, 0.86 ± 0.74 g VOCs/m2 painted area), colored paint (127.24 ± 168.24 g VOCs/SUV car, 1.25 ± 1.66 g VOCs/m2 painted area), varnish (205.46 ± 218.14 g VOCs/SUV car, 2.01 ± 2.15 g VOCs/m2 painted area), and cleaning solvent (328.54 ± 404.94 g VOCs/SUV car, 3.23 ± 3.98 g VOCs/m2 painted area). OVOCs (37.40–51.60 %) and aromatics (36.40–37.00 %) were the dominant components. n-Butyl acetate, 1,2,4-trimethylbenzene, undecane, n-hexanal, acetone, 1,2,3-trimethylbenzene, 1,3,5 -trimethylbenzene, m/p/o-xylene, 3-ethylbenzene, and 4-ethylbenzene were the major VOCs species, accounting for 68 % of total VOCs in the automobile manufacturing industry. Considering the OFP values of species, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, 1,2,3-trimethylbenzene, m/p-xylene, acetaldehyde, methyl ethyl ketone are the key active species that should be prioritized for control.