Search Results (388)

Horse fat is a valuable lipid source for traditional meat products, but its flavor quality is remains unclear during processing conditions. To investigate the effect of dry fractionation on the volatile profile of refined horse fat, samples obtained at different temperature were analyzed using an E-nose, HS/GC-IMS, and SPME/GC-MS. The E-nose results showed that the volatile profiles of the samples differed markedly, with the solid fractions obtained at 25 and 15 °C (S25 and S15) exhibiting stronger sensor responses and clustering together, whereas the liquid fraction at 5 °C (L5) showed the weakest overall signals. HS/GC-IMS identified total 55 volatile compounds, mainly aldehydes, alkenes, esters, alcohols, ketones, and nitrogen-containing compounds. Compared with refined horse fat, S25 and S15 were enriched in ketones, sulfur-containing compounds, and nitrogen-containing compounds, while L5 was dominated by alcohols and aldehydes. SPME/GC-MS identified 53 volatile compounds, with aldehydes as the main class in all samples. S5 showed the highest number of volatile species and the richest aroma profile, whereas S25 and S15 showed the lowest complexity. The total volatile content ranked as refined horse fat > S5 > L5 > S15 > S25, and ester content followed the order S5 > L5 > refined horse fat > S25 > S15. Overall, dry fractionation temperature significantly regulated the distribution of volatile compounds in horse fat. These findings may provide a theoretical basis for the potential application of horse fat in food processing and product development. Full article

Sulfur dioxide (SO₂) is a preservative used in the production of fermented beverages for its antimicrobial and reducing properties. However, its effect on the oxidation–reduction potential (ORP, redox potential) during alcoholic fermentation of apple cider has never been recorded. In this study, freshly pressed apple juice was fermented with a 30 mg/L free SO₂ addition (RED) and without an SO₂ addition (CON) prior to alcoholic fermentation. Fermentation kinetics, ORP, basic chemistry, organic acids, nitrogenous compounds, free and total SO₂, glutathione (GSH), phenolics, and volatiles were monitored during alcoholic fermentation and at racking. Additionally, sensory analysis was conducted after bottling. Sulfur dioxide had no effect on fermentation kinetics, nitrogen utilization, ethanol yield, or the volatile composition of the apple ciders at racking. The ORP (vs. Ag/AgCl reference electrode) reached maximum values of 310 mV in CON and 218 mV in RED before alcoholic fermentation, and minimum values of −94 mV and −136 mV, respectively, near peak alcoholic fermentation. Mean ORP values during alcoholic fermentation were −29 mV in CON and −47 mV in RED. No statistical differences were found between the ORP of CON and RED using net area under the curve (AUC) of the ORP relative to Y = 0 mV, nor in the GSH chemistry of the ciders. The addition of SO₂ inhibited malolactic fermentation (MLF) during alcoholic fermentation. As a result, higher concentrations of malic acid and lower concentrations of lactic acid were observed in RED than in CON at racking. Sulfur dioxide additions preserved monomeric, dimeric, and increased the pool of sulfonated flavan-3-ols, likely due to PPO inhibition during the prefermentative phase and reactive oxygen species (ROS) quenching. The sensory composition of the ciders was affected whereby CON showed higher banana aroma and RED trended towards reduction aromas. Overall, SO₂ additions before alcoholic fermentation of apple cider preserved phenolics, inhibited MLF, and increased reduction aroma with no clear effect on fermentation kinetics and ORP, highlighting trade-offs between the impact of SO₂ additions on the chemical and sensory attributes of apple cider. Full article

Over the past decade, stringent emission control policies have been implemented in the North China Plain, fundamentally altering regional air pollution profiles. This study investigates the long-term temporal evolution (2015–2025) and chemical reconstruction of air pollutants in Jinan, China. Benefiting from rigorous emission controls, annual median concentrations of PM_2.5, SO₂, and CO decreased significantly by 64%, 81%, and 54%, respectively. Conversely, NO₂ exhibited a slower decline (47%), and the maximum 8-h daily average (MDA8) ozone (O₃) increased by 23%. Generalized additive model (GAM) analysis identified solar radiation, temperature, relative humidity, and NO₂ as the primary factors strongly associated with O₃ variations. The amplified atmospheric oxidation capacity driven by O₃ has triggered a profound chemical reconstruction of secondary inorganic aerosols (i.e., SO₄²⁻, NO₃⁻, and NH₄⁺), with a significant increase in sulfur and nitrogen oxidation ratios (SOR and NOR), which may continue to intensify the combined pollution trend of ozone and PM_2.5. These findings emphasize that coordinated reductions in nitrogen oxides and volatile organic compounds must be achieved in future air quality management while also taking into account the promoting effect of climate warming on ozone generation. Full article

Huangshui (HS), fermented grains (FG), and pit mud (PM) are closely connected during the fermentation of Nongxiangxing baijiu (NXB); however, the contribution of HS to the differences in flavor profiles across PM, FG, and distilled baijiu has not been fully elucidated. Herein, instrumental techniques of electronic nose (E-nose), headspace gas chromatography–ion mobility spectrometry (HS-GC-IMS), and headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME-GC-MS) were used to compare the volatile profiles of HS, FG, PM, and two quality grades of NXB. E-nose analysis revealed that PM exhibited stronger signals related to sulfur-containing, organic, and terpene-associated compounds. Gas chromatography indicated that special-grade baijiu had a more favorable ethyl caproate/ethyl lactate ratio than superior-grade baijiu. Furthermore, HS-GC-IMS revealed different volatile profiles of the samples. Up to 183 volatile organic compounds (VOCs) were identified via HS-SPME-GC-MS, with esters and acids being the dominant classes. Multivariate analysis showed close relationships among HS, FG, and PM, and 35 VOCs were identified as important discriminatory compounds. These results suggest the differences and similarities in VOCs among the HS, FG, PM, and NXB samples, indicating that HS is chemically associated with both FG and PM. This study provides useful insights into HS utilization and quality regulation of NXB through the effective management of HS. Full article

Originating from Hunan Province, China, Huangjin green tea (HJGT) is known for its diverse aromas, including green, floral, and chestnut-like, but their characteristic volatile components remain unclear. In this study, 111 volatiles were identified from 26 HJGT samples using HS-SPME-GC-MS. Floral HJGT showed the highest relative content of ester, chestnut-like HJGT was richest in sulfur-containing compounds, and green HJGT was dominated by alcohols. Partial least-squares discriminant analysis identified 61 differential volatiles (VIP > 1), whose distribution patterns across aroma types fell into four categories. Based on relative odor activity value (≥1) and ANOVA (p < 0.05), 26 key aroma-active compounds were further screened. Ten characteristic compounds, such as linalool, indole, and dimethyl sulfide contributed floral, fresh, green, cabbage, and violet-like notes to floral HJGT. Seven compounds, including heptanal, nonanal, and 2-pentylfuran, imparted nutty, waxy, pungent, and beany notes to chestnut-like HJGT. Nine compounds, including geraniol, hexanal, and phenylethyl alcohol, contributed green, floral, fragrant, and minty notes to green HJGT. These findings elucidate the chemical basis of HJGT aroma and provide a theoretical foundation for the targeted regulation of its aroma types in production. Full article

The adsorption behavior of selected volatile sulfur compounds on graphene was examined using density functional theory. The analytes of interest are hydrogen sulfide, methyl mercaptan and dimethyl sulfide, which are found in the exhaled breath of halitosis patients. The human breath contains several volatile compounds that act as chemical fingerprints of what is happening inside the body. This study employs first-principles calculations to investigate the structural, electronic, and adsorption properties of pristine and transition-metal-doped graphene (Fe, Ru, and Os) for the detection of key volatile sulfur compounds relevant to breath analysis and halitosis screening. According to our findings, when a single carbon atom is substituted with an iron, ruthenium or osmium atom in the optimized graphene sheet, which is equivalent to a dopant concentration of 2 mol% in experiments, the adsorption behavior of the system is altered significantly. Based on the resultant adsorption behavior and electronic structure alterations, important sensor properties were examined. This work presents a non-invasive approach for halitosis detection, therapeutic monitoring, and metabolic status observation by analyzing the volatile sulfur compounds present in exhaled breath. Additionally, this study demonstrates how computational modeling can be used as a decision support tool. Full article

Maritime transport emits a range of atmospheric pollutants, including sulfur oxides (SO_x), nitrogen oxides (NO_x), particulate matter (PM), and volatile organic compounds (VOCs), which contribute to air pollution and are associated with adverse environmental and public health impacts. To mitigate these impacts, the International Maritime Organization (IMO), London, UK introduced the global sulfur cap (IMO 2020), which entered into force on 1 January 2020, limiting the sulfur content of marine fuels to 0.50% m/m. This study systematically reviews the environmental and public health impacts of shipping emissions following the implementation of IMO 2020. A systematic literature review was conducted in accordance with PRISMA 2020 guidelines using Scopus, Web of Science, PubMed, and supplementary sources. Following a structured screening process, 67 studies published between 2020 and 2025 were included and analyzed through descriptive, bibliometric, and thematic synthesis approaches. The reviewed studies consistently reported substantial reductions in sulfur dioxide (SO₂) emissions, sulfate aerosols, and shipping-related particulate matter following IMO 2020. These reductions were associated with improved air quality in major maritime and port regions and reduced population exposure to harmful pollutants. However, the reviewed evidence also identified ongoing challenges, including emissions of ultrafine particles and volatile organic compounds, secondary pollutant formation, contamination associated with scrubber washwater discharge, and reduced sulfate aerosols contributing to positive radiative forcing. Overall, the reviewed evidence suggests that sulfur-related air pollution generally declined following the entry into force of IMO 2020, although these observations should be interpreted alongside other concurrent developments that influenced global shipping activities during the study period. This review synthesizes current evidence on the environmental and public health impacts of IMO 2020, identifies emerging knowledge gaps, and provides an evidence base to support future shipping emission policies and research. Full article

Volatile sulfur compounds (VSCs) are a subgroup of plant volatile organic compounds (VOCs) that are chemically reactive and sensory-active. In tomato (Solanum lycopersicum), sulfur-containing volatiles such as methanethiol, dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide, volatile thiols, and heterocyclic sulfur compounds are of particular relevance due to their extremely low odor thresholds and strong influence on aroma perception. Beyond their sensory importance, VSCs have been shown to be involved in plant defense mechanisms, stress responses, redox homeostasis, and multitrophic interactions with microorganisms, herbivores, and neighboring plants. The formation of these structures is governed by complex interactions between sulfur assimilation pathways, lipid peroxidation processes, environmental factors, and both enzymatic and non-enzymatic reactions. The accurate characterization of VSCs remains challenging due to the following factors: their high reactivity; their low abundance; their chemical instability; and their susceptibility to oxidation. Despite the significant enhancement in detection of VSC capabilities brought about by modern analytical approaches, such as gas chromatography coupled with sulfur-selective detection and high-resolution mass spectrometry, significant methodological limitations remain. This review summarizes the current state of knowledge on the analytical challenges of VSCs in tomato plants, their biosynthesis and biological functions, mainly in the context of plant defense. Full article

Malodorous gases such as ammonia (NH₃) and hydrogen sulfide (H₂S) emitted from pig intestines and excrement have become critical environmental bottlenecks restricting the green transformation of the swine industry. Therefore, identifying sustainable protein feed alternatives with odor-reducing potential has become increasingly important. This study evaluated the effects of replacing soybean meal with four distiller’s grains-derived protein raw materials (DGPRMs), including Baijiu DDGS, Sorghum DDGS, Corn DDGS, and Cassava DDGS, using an in vitro fermentation system simulating the intestinal environment of six fattening pigs. After 24 h of fermentation, odor-related gas production, short-chain fatty acid (SCFA) concentrations, and microbial community composition were analyzed to assess the odor-mitigation potential of these alternative protein sources. Results demonstrated that Baijiu distiller’s grains, sorghum distiller’s grains, and corn distiller’s grains significantly reduced the yields of NH₃ and H₂S under the in vitro fermentation system (p < 0.05). Meanwhile, they reshaped the intestinal microbial community structure by inhibiting the growth and reproduction of odor-producing genera (e.g., Ligilactobacillus) and promoting the enrichment of beneficial genera (e.g., Limosilactobacillus) that were significantly negatively correlated with malodor indicators. Notably, among all tested DGPRMs, Baijiu DDGS exhibited the strongest odor-reducing effect, markedly decreasing NH₃, H₂S, and volatile sulfur compounds while enriching beneficial bacterial taxa associated with reduced odor generation. These findings suggest that selected DGPRMs, particularly Baijiu DDGS, may serve as promising alternative protein ingredients for mitigating odor emissions in pig production systems. Full article

Catfish (Clarias macrocephalus × C. gariepinus) is economically important but perishable, and hot-air drying yields shelf-stable catfish powder (CFP); however, its quality response to high-temperature drying (>100 °C) remains poorly understood. The present study aimed to examine the effects of five drying temperatures (60–180 °C) on the physicochemical, nutritional, functional, structural, volatile, oxidative, and microbiological properties of CFP. Drying exerted parameter-specific effects. Moisture and water activity fell from 6.24% to 4.75% and 0.42 to 0.23, with microbial counts reduced at ≥120 °C. Browning raised lightness, redness, and yellowness from 49.53 to 57.64, 1.94 to 2.97, and 13.95 to 18.14, respectively. Protein concentrated from 57.63% to 62.24%, whereas oxidation lowered fat from 22.49% to 17.17%. Minerals rose marginally, although iron and zinc declined. Amino acids were largely preserved, though methionine (2.71 to 2.21 g/100 g protein) and cysteine declined and glycine and proline increased. DHA declined most, from 4.61% to 3.20%, followed by EPA and AA. Water holding, oil holding, wettability, dispersibility, and colloidal stability decreased, whereas emulsion stability decreased from 57.14% at 60 °C to 42.10% at 180 °C. Zeta potential became less negative (−35.82 to −20.74 mV), with larger particle size and polydispersity. Among 72 volatiles across 11 classes, 60–90 °C favored fishy aldehydes and 2-pentyl furan and ≥150 °C generated Maillard and sulfur compounds, whereas 120 °C produced the most balanced volatile profile, with lower relative abundance of fishy aldehydes than at 60–90 °C, consistent with the intermediate TBARS values and comparatively better retention of unsaturated fatty acids at this temperature, and limited accumulation of Maillard-derived and sulfur compounds relative to 150–180 °C. FTIR, XRD, TGA, and SEM confirmed preserved structure. Overall, the results showed that 120 °C provided the best balance of dehydration, nutrient and functional retention, flavor, and microbial safety. Full article

Volatile composition is a core trait that determines the ornamental and application value of Rosa flowers. In the current study, the volatile profiles of freeze-dried Rosa gallica flowers were comprehensively characterized via gas chromatography-mass spectrometry (GC-MS), coupled with heatmap clustering, principal component analysis (PCA), and relative odor activity value (rOAV) determination. A total of 181 volatile compounds were identified, and distinct volatile profiles were observed between flower samples treated with headspace extraction (RG-HS) and solid-phase microextraction (RG-SPME). Alcohols were the dominant volatile class in RG-SPME, whereas aldehydes were abundant in the RG-HS group. In terms of aroma characteristics, RG-SPME presented stronger green, floral, citrus, and fatty odors, while RG-HS exhibited a more pronounced fruity note. Moreover, sulfurous and dairy notes were unique to RG-SPME and RG-HS, respectively. Additionally, 27 volatiles showed rOAV above one, with 2,3-butanedione and trans-citral having the greatest rOAV value of 100, were identified as the potential aroma-active contributors to butter-like and citrus odors in RG-HS and RG-SPME, respectively. These results provide a methodological reference for volatile profiling of R. gallica flowers, and support the selection of appropriate extraction methods for future research and resource utilization. Full article

Artisanal raw-milk cheese represents a complex biochemical ecosystem where the indigenous microbiota acts as the primary driver of the volatile profile. This study utilizes an innovative synchronized biological relay model to decipher the mechanistic interplay between the successional dynamics of indigenous lactic acid bacteria (LAB) and the temporal evolution of the volatile metabolome over a 10-week maturation period of an artisanal cow-milk cheese. Utilizing a culture-dependent approach focused on the quantitative enumeration of broad morpho-physiological groups—without species-level identification—integrated with HS-SPME/GC-MS, we characterized the precise shifts from early-stage lactic cocci to dominant rod-shaped lactobacilli. Initial populations at Week 0 consisted of 8.2 log CFU/g of cocci and 4.1 log CFU/g of rod-shaped LAB. Lactic cocci peaked at Week 2 (8.5 log CFU/g) before undergoing mass autolysis down to 7.1 log CFU/g by Week 4, releasing intracellular enzymes that catalyzed a 900% surge in total esters and a 215% increase in volatile alcohols. Concurrently, rod-shaped LAB proliferated to a maximum of 8.6 log CFU/g at Week 6, directly correlating with a 125% increase in total carboxylic acids, prominently driven by a 750% accumulation of hexanoic acid. The late-phase maturation (Weeks 8–10) established a technological equilibrium: volatile sulfur compounds collapsed by over 90% within the first two weeks, initial transient lactones were replaced by a 1200% late-stage increase in dodecalactone, and matrix-sequestered dietary terpenes were liberated via an 8-fold (700%) increase at Week 8. This study introduces an innovative, statistically validated volatilomic framework that equips the dairy sector with an advanced metabolomic tool for rigorous product authentication and targeted flavor optimization, thereby establishing a scientific baseline for the reproducible production of premium, organoleptically superior artisanal cheeses. Full article

Pixian Doubanjiang (PXDB) is a traditional Chinese fermented condiment whose characteristic aroma and taste are strongly influenced by fermentation conditions. This study aimed to systematically compare the flavor profiles of PXDB produced via traditional open fermentation (TOF) and industrial closed fermentation (ICF), aiming to elucidate the chemical basis of sensory divergence and provide scientific support for industrial process optimization. In this study, PXDB samples were evaluated using sensory evaluation, GC-IMS, ¹H-NMR metabolomics, and multivariate statistical analysis. Sensory evaluation revealed that ICF exhibited a stronger soy sauce-like aroma, alcohol note, and umami intensity, whereas TOF and ICF showed comparable sweetness, sourness, chili-like aroma, and roasted aroma. GC-IMS putatively identified 126 volatile compounds, and multivariate analyses demonstrated a clear separation between the two fermentation modes. Based on combined criteria of VIP > 1, FDR-adjusted p < 0.05, and |fold change| > 2, 35 differential volatile compounds were identified. ICF was characterized by higher levels of esters, particularly ethyl esters, and selected ketones, while TOF showed enrichment of higher alcohols, terpenes, and sulfur compounds. ¹H-NMR analysis identified 54 non-volatile metabolites, of which 16 differed significantly between TOF and ICF, mainly involving amino acids, organic acids, and carbohydrates. Pathway analysis highlighted branched-chain amino acid and glutamate-related metabolism as key contributors to flavor divergence. Correlation analysis further revealed that soy sauce-like aroma and umami perception were strongly associated with amino acid-derived metabolites, esters, sulfur-containing compounds, and branched-chain aldehydes, highlighting the coordinated contribution of volatile and non-volatile compounds to flavor differentiation. Overall, fermentation mode was found to reshape PXDB flavor through coordinated modulation of volatile and non-volatile metabolism, providing experimental insight for improving industrial fermentation quality. Full article

Volatile sulfur compounds (VSCs) are important contributors to mango volatile profiles but are challenging to analyze due to their trace concentrations, susceptibility to transformation, and interference from the complex fruit matrix. This study investigated how key extraction parameters—material chemistry, surface area-to-volume ratio, sorbent volume, temperature, and time—affect VSC extraction using mango as a complex botanical model. Three sorptive extraction configurations were evaluated: HiSorb (PDMS and DVB/CWR/PDMS) and a high-capacity combined headspace thin-film solid-phase microextraction and stir bar sorptive extraction (HS-TFSPME-SBSE) system. The optimized HS-TFSPME-SBSE configuration (40 °C, 150 min) provided the broadest VSC coverage, achieving limits of detection of 0.1–0.6 μg/kg and good linearity (R² > 0.9927). In spiked mango puree (10 μg/kg), HS-TFSPME-SBSE detected methyl mercaptan and diallyl trisulfide, which were not recovered using HiSorb (PDMS). Application to three mango cultivars (Golden Honey, Sindhura, and Palmer) revealed broader VSC profiles and enabled differentiation of cultivars and tissues (flesh and peel) through principal component analysis (PCA). Distinct cultivar-associated VSC patterns were observed, including elevated dimethyl disulfide in Golden Honey and ethyl 3-(methylthio)-cis-2-propenoate in Sindhura. These findings demonstrate the suitability of HS-TFSPME-SBSE for sensitive profiling of trace VSCs in complex fruit matrices. Full article

The effects of ambient storage (A), cold storage (C), and frozen storage (F) on the quality, metabolomic characteristics, and sulfur-related aroma of red onion ‘Kewei Red 10’ (R10) and yellow onion ‘Kewei Yellow 14’ (Y14) were investigated using integrated non-targeted and volatile metabolomics. Ambient storage accelerated shrinkage, firmness loss, and sensory deterioration in both cultivars, whereas low-temperature storage effectively delayed quality decline. R10 exhibited better tolerance to frozen storage, while Y14 performed better under cold storage. Metabolomic analysis revealed that amino acids and lipid-related metabolites were closely associated with onion senescence in both cultivars. In contrast, flavonoids were enriched in preservation-associated subclasses in R10, whereas organic acids and their derivatives were more strongly associated with delayed senescence in Y14. Volatile metabolomic analysis identified sulfur compounds and heterocyclic sulfur compounds as the major contributors to onion aroma. Sulfur-related volatiles showed distinct cultivar-dependent accumulation patterns, with many sulfur compounds accumulating prominently in ambient-stored R10-A, whereas cold-stored Y14-C maintained relatively higher levels of characteristic onion-like aroma compounds. These findings demonstrate distinct metabolic adaptation strategies between red and yellow onions during storage and suggest that cultivar-specific storage conditions are required to optimize both shelf life and flavor quality. Full article