Search Results (870)

Sauce-aroma Baijiu is produced through a one-year cyclic process involving multiple fermentations and distillations. However, the dynamic changes and correlations among fermented grains (FG), distilled fermented grains (DG), heart liquor (HL) and tail liquor (TL) remain unclear. In this study, the physicochemical indicators and volatile compounds (VCs) from the 3rd to 6th distillation rounds were systematically analyzed. Across successive rounds, FG and DG exhibited similar trends in key physicochemical indicators, as did HL and TL. Headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME/GC-MS) identified 76, 73, 80 and 93 VCs in FG, DG, HL and TL, respectively. Multivariate statistical analyses revealed significant inter-round differences in volatile profiles, and further indicated that total acids and water contents in FG were positively correlated with the majority of VCs in liquor. These results clarify the dynamic change of physicochemical and flavor components during Baijiu production and provide a basis for quality evaluation. Full article

Polishing enhances the appearance and market competitiveness of rice. To better understand the effect of polishing on rice flavor, volatile flavor compounds in polished rice (PR), unpolished rice (UR), cooked polished rice (CPR), and cooked unpolished rice (CUR) were examined using headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME-GC-MS). The results revealed fourteen volatile flavor compounds displayed significant differences in abundance, with eight of these compounds potentially contributing to the overall flavor profile based on their volatility and reported odor characteristics. Among these compounds, only eicosane and hexanal were detected in uncooked rice, whereas acetophenone, hexadecanol, dodecane, and octadecane were unique to CUR. Four compounds were associated with aroma notes reminiscent of flowers, wax, and almond, among others. However, nonanal and nerol were common in both cooked rice samples, and they may contribute to a sweet-like aroma in cooked rice. These findings illuminate the changes in volatile composition, offer insights to prevent over-polishing, and inspire further research toward producing rice with potentially improved aroma profiles. Full article

Crackers and cookies have become the most widely consumed snacks due to their low production costs, long shelf life, and ability to deliver essential nutrients. Increasing consumer health consciousness has shifted preferences toward foods perceived as natural and beneficial. This shift elevates demand for cracker formulations with novel, health-promoting natural ingredients. This study examined the effects of incorporating freeze-dried olive leaf powder (FDOLP) into crackers on their physicochemical properties, phenolic and volatile compound profiles, antioxidant capacity, and sensory acceptability. Total polyphenol content of crackers was determined using the Folin–Ciocalteu method, while antioxidant capacity was evaluated by FRAP and DPPH assays. The UHPLC-ESI-HRMS analysis evaluated olive-derived compounds, including tyrosol, oleuropein derivatives, and pinoresinol 4-O-glucoside, present in olive leaf-enriched crackers. The characterisation of volatile compounds in crackers was performed using headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME/GC-MS). A darker colour was observed in the enriched crackers compared to the control samples. Results demonstrated that increasing the proportion of FDOLP led to enhanced phenolic composition and antioxidant activity, as well as changes in the volatile profile of the crackers. Sensory analyses indicated that crackers enriched with moderate levels of FDOLP maintained acceptable overall sensory scores, suggesting a potential for the development of functional snacks. These findings demonstrate that olive leaves can be effectively utilised as a natural functional ingredient in cracker formulations to enhance their nutritional value and bioactive properties. Full article

Seasonal variation in aroma quality is critical for commercial grading of Xinyang Maojian (XYMJ) green tea, and how seasonal changes shape its volatile composition and aroma profile remains unclear. This study investigated the volatile profiles of XYMJ harvested in spring, summer, and autumn using headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and odor activity value (OAV) analysis. A total of 93 volatile compounds were identified, with alkenes, alcohols, and esters being the most numerous chemical classes. Total volatile content decreased significantly seasonally (p < 0.05), being highest in spring (1716.68 μg/kg), followed by summer (1566.72 μg/kg) and autumn (1378.21 μg/kg). PCA and PLS-DA clearly distinguished seasons. Using a dual-filtering strategy (variable importance in the projection > 1.0 and p < 0.01), 14 differential volatile metabolites were identified as core seasonal markers. Geraniol, cis-jasmone, and indole were identified as key drivers of the premium floral fragrance in spring XYMJ, while cis-3-hexenyl hexanoate and linalool peaked in the summer harvest. OAV results and cross-modal sensory interaction principles suggest that the superior flavor of spring XYMJ arises from both higher aromatic intensity and an optimized aroma-taste balance. These findings provide useful insights into the seasonal variations in the metabolic and chemical profiles of XYMJ, enhancing our understanding of the biochemical markers associated with its production timeline. Full article

While withering is a critical processing step influencing the flavor profile of white teas, the effects of temperature-changing withering remain elusive. This study systematically investigated the variations in two withering methods (natural withering, temperature-changing withering) in volatile compounds of white teas made from four cultivars. The quality of white teas produced from ‘Mingshan No. 131’ (MS131), ‘Fuxuan No. 9’ (FX9), ‘Ziyan’ (ZY), and ‘Fudingdabai’ (FDDB) was evaluated using quantitative descriptive analysis (QDA), headspace solid-phase microextraction coupled with gas chromatography–mass spectrometry (HS-SPME-GC-MS), and odor activity value (OAV) analysis. The sensory evaluation results indicated that temperature-changing withering enhanced the development of sweet and fruity aromas while suppressing grassy notes. A total of 176 volatile compounds were identified, and temperature-changing withering induced significant alterations in the aroma profile, notably increasing the levels of ketones, esters, and alkenes (p < 0.05). Based on the criteria of OAV > 1, p < 0.05, and a fold change ≥ 1.5 (for upregulated compounds) or ≤0.67 (for down-regulated compounds), key volatile compounds in white teas from the four cultivars were identified. The common upregulated volatile compounds, namely 1-octen-3-one, cedrol, (E,E)-2,4-heptadienal, and (E)-2-hexenal, promoted the fresh flavor profile of white teas. These findings demonstrate that temperature-changing withering optimizes flavor-related metabolites, thereby providing a theoretical foundation for improving white tea processing. Full article

Insects secrete volatile organic compounds (VOCs) for various reasons, such as intra- or inter-species communication, attracting mates, or repelling predators. The volatiles from indoor insect pests, e.g., phenolic secretions, can impact inhabitants in various ways, causing allergies, skin and eye irritations, etc. The Mupli beetle (Luprops tristis Fabricius, 1801) is one such nuisance pest that aggregates in great numbers in indoor spaces, especially near rubber plantations in tropical African and Asian countries. This study aimed to understand the whole-body volatilome of L. tristis, comprising the first detailed study of volatiles in this insect, particularly under aggregation and laboratory conditions. Whole-body VOCs were collected from sets of 500 and 1000 beetles at different time intervals and analysed by solvent-assisted desorption followed by gas chromatography–mass spectrometry (GC-MS). Compounds released by the Mupli beetle, such as 1-Octadecanesulphonyl chloride, Decane-1,1′-oxybis-, n-Nonadecanol-1 and n-Heptadecanol-1, are reported in the literature to be allergens that cause allergic reactions such as skin and eye irritations in humans. This understanding may indicate the possible reasons for the allergic reactions in people living in these insect-inhabited indoor spaces. We also report and describe the design and development of an economically feasible glass chamber for the dynamic headspace collection of volatiles released by these beetles. Full article

With the growing interest in the microbiome, short-chain fatty acids (SCFAs) have emerged as key metabolites due to their critical roles in host physiology, including immune regulation, energy homeostasis, and inflammatory control. As a result, the accurate quantification of SCFAs in various biological samples has become increasingly important. However, reliable and standardized methods for measuring SCFAs across different sample types remain underdeveloped, highlighting the need for methodological refinement. To address this need, we optimized two analytical methods, headspace GC-MS and GC-MS/MS, for SCFA quantification. These techniques were applied to a range of biological matrices, including pure microbial cultures, low-abundance animal liver, animal feces, and standardized simulated human fecal samples. The headspace GC-MS approach enables direct analysis with minimal sample preparation, thereby enhancing throughput and ease of use. In contrast, the GC-MS/MS method, involving methanol extraction, alkaline treatment, and derivatization with MTBSTFA, offers superior sensitivity and precision, making it particularly suitable for small-volume and low-abundance samples. Together, these optimized protocols provide robust, sensitive platforms for profiling SCFAs across diverse biological matrices, facilitating a deeper understanding of microbiome–host interactions and supporting future translational applications. Full article

Musalais is a traditional fermented beverage of the Uyghur people in Xinjiang, China. Its production involves boiling grape juice at high temperatures to concentrate it and enhance its sugar content, followed by natural fermentation. However, this high-temperature concentration process leads to a significant loss of bioactive and flavor compounds, adversely affecting the quality of the final product. Adding composite ingredients may help mitigate this quality decline. This study compares Musalais new product with traditional Musalais. Phenolic analysis showed that total monomeric phenols were 182.36 mg·L⁻¹ in the new product versus 14.76 mg·L⁻¹ in traditional Musalais. Headspace solid-phase microextraction/gas chromatography–mass spectrometry (HS-SPME/GC-MS) identified 72 volatile compounds in the new product (total content of 569,848.88 μg·L⁻¹) compared to 58 compounds (total content of 362,774.17 μg·L⁻¹) in traditional Musalais. Compared to traditional Musalais, the new product exhibits a 24.14% increase in volatile compound variety and a 57.09% increase in total concentration, with more pronounced floral, fruity, and vinous aromas, as well as higher sensory scores. Non-targeted metabolomics suggests that the new product may have superior phenolic and volatile profiles. Full article

To investigate how spreading conditions affect green tea taste and aroma and to develop a generalizable prediction model from small data for process optimization, this study integrated SEM, non-targeted dual-omics, and TabPFN to systematically analyze Echa No. 10 spreading. A central composite design was used. Dehydration-induced mechanical stress altered cell membrane permeability, driving non-volatile taste compound transformation and volatile aroma release. Two chemical-sensory proxies, relative polyphenol-to-amino acid ratio (R-PAR) and floral intensity index (FII), were established using ultra-high performance liquid chromatography–high-resolution mass spectrometry (UHPLC-HRMS) and headspace solid-phase microextraction–gas chromatography–mass spectrometry (HS-SPME-GC-MS). A prediction model was built with these indicators and TabPFN. Multi-objective optimization yielded optimum conditions: initial moisture 76.8%, temperature 26.2 °C, relative humidity 61.5%, air speed 0.85 m/s, achieving R-PAR 0.465 and FII 125.70. Compared with response surface methodology (RSM), partial least squares regression (PLSR), and support vector regression (SVR), TabPFN showed prediction R² of 0.81 and 0.77, showing favorable applicability and predictive capability on small-sample data. This study validates TabPFN’s suitability for small-sample tea processing modeling, quantifies the mapping between spreading and key taste/aroma metabolism, and provides a methodological foundation for digital precision and intelligent optimization in green tea production. Full article

Storage duration critically shapes the characteristic sweet and mellow quality of ripened pu-erh tea (RPT), yet the underlying chemical mechanisms remain poorly understood. This study investigated the sensory and chemical evolution of a representative commercial RPT product across a nine-year storage gradient (1, 3, 5, 7, and 9 years) by integrating Quantitative Descriptive Analysis (QDA), chromaticity measurement, targeted quantification of 42 non-volatile components, and Headspace Gas Chromatography–Mass Spectrometry (HS-GC-MS) volatilomics with multivariate statistical modeling. Prolonged storage drove systematic sensory maturation: the stale aroma gradually purified, and the taste profile transitioned significantly from heavy and mellow to sweet and mellow (p < 0.05), accompanied by a deepening infusion color with increased redness and yellowness indices. Targeted chemical profiling revealed significant decreases in total polyphenols and astringent esterified catechins, particularly epicatechin gallate (ECG) and epigallocatechin gallate (EGCG) (p < 0.05), while theabrownins remained stable and soluble sugars peaked at intermediate storage stages. Pearson correlation analysis linked these chemical shifts to sensory perception, with enhanced sweetness, mouthfeel thickness strongly associated with reduced monomeric catechins and free amino acids (p < 0.001). Volatilomics combined with K-means clustering and relative odor activity value (ROAV) analysis revealed a dual mechanism of flavor refinement: progressive accumulation and increasing odor activity of aged aroma markers (1,2,3-trimethoxybenzene, β-ionone) coupled with systematic attenuation of pungent acids and grassy aldehydes. These findings, based on a single, standardized commercial product, elucidate the chemical-sensory foundation of the sweet and mellow profile in aged RPT and provide candidate markers and a transferable analytical framework for quality assessment of stored teas. Full article

This study presents a novel analytical approach combining headspace solid-phase microextraction (HS-SPME) with gas chromatography–mass spectrometry (GC–MS) and advanced chemometric techniques to detect adulteration in coriander honey. A total of 34 volatile compounds were identified and quantified, revealing a progressive decrease in both profile complexity and compound abundance with increasing levels of invert sugar and high-fructose corn syrup (HFCS) adulteration. Chromatographic and chemometric analyses effectively distinguished authentic from adulterated samples, with the Extreme Gradient Boosting (XGBoost) model achieving a high classification performance of 95.83% accuracy. The study highlights the critical impact of adulteration on honey’s chemical composition and confirms the efficacy of integrating modern analytical and machine learning tools for rapid, sensitive, and reliable honey authenticity assessment. This methodology offers a valuable framework for food quality control and fraud prevention, addressing current challenges in the honey market and protecting consumer interests. Full article

Chemical recycling of mixed plastic waste can recover hydrocarbon products, but additive-derived non-intentionally added substances (NIASs) and other volatile or extractable residues may affect product quality and safety. In this study, six polyolefin-rich waste streams (P1–P6) were analyzed by analytical pyrolysis coupled with comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (Py–GC×GC–TOF–MS), while three additional consumer-grade plastics (P7–P9) were examined by headspace/solvent-extraction GC–MS and aqueous migration testing to profile volatile organic compounds (VOCs), semi-volatile organic compounds (SVOCs), and water migrants. Under rapid pyrolysis at 650 °C, the condensable products were dominated by C5–C30 aliphatic hydrocarbons. Polyethylene (PE)-rich feeds produced mainly n-paraffins and α-olefins, whereas polypropylene (PP)-rich feeds produced more branched olefins and modest mono-aromatics. Oxygenated compounds were negligible in non-oxidized feeds, but persisted at low levels in weathered high-density polyethylene (HDPE), consistent with pre-existing oxidation. Antioxidant-derived NIASs, including 2,4-di-tert-butylphenol and an Irganox 1010-related spiro-dione, were detected at trace to low area-fraction levels. VOC/SVOC and migration analyses revealed mainly low-intensity hydrocarbons, esters, antioxidant-related degradation products, caprolactam, and selected plasticizer-related compounds. These results show that relatively clean polyolefin streams can yield hydrocarbon-rich pyrolysates, but oxidized PE and additive-derived NIASs remain important quality-control targets. The GC-based methods used here characterize the volatile, condensable, and readily extractable fraction and do not represent the total contaminant load of the source waste. Full article

The chemical composition and sensory profile of coffee are influenced by brewing method, namely extraction pressure, temperature, contact time, and equipment. This study compared coffee prepared with a traditional moka pot, a conventional espresso machine, and a novel Italian device (Kamira). Volatile compounds were analyzed by headspace solid-phase microextraction (HS-SPME) coupled with gas chromatography–mass spectrometry (GC–MS), leading to the determination of furan (34–42%), pyrrole (4–10%), and pyrazine (13–14%) derivatives. The most abundant fatty acids were palmitic (36–37%), linoleic (40%), and oleic (11%) acids. Physicochemical parameters (total solids, pH, and refractive index) were also measured. Caffeine and chlorogenic acids were quantified by liquid chromatography (HPLC). Differences in chlorogenic acids and volatile compounds were associated with variations in bitterness, acidity, astringency, and aroma intensity. Finally, a trained panel performed sensory evaluation to evaluate the olfactory and flavor attributes of the three types of coffee brews. Significant differences emerged among brewing systems. Espresso showed the highest caffeine content (55.3 ± 4.1 mg/100 g) and total solids (2.61 ± 0.11 g/100 g), together with a stable crema and intense sensory attributes. Moka coffee exhibited a rich aromatic profile but limited crema. The Kamira device produced an abundant crema and a chemical profile partially comparable to espresso. These findings confirm that brewing technology markedly affects coffee composition and sensory perception. Full article

Foeniculum vulgare Mill. (fennel) is an edible and medicinal plant cultivated worldwide. Owing to its distinctive aroma and diverse biological activities, its essential oils (EOs) have been widely investigated. However, available data predominantly focus on cultivated fennel or commercial EOs, while comprehensive investigations of wild-growing Mediterranean populations—particularly comparisons among different plant parts—remain scarce. In this study, EOs obtained by hydrodistillation from stems, leaves, flowers, and fruits of native Croatian fennel, were chemically characterised using gas chromatography-mass spectrometry (GC-MS), while antimicrobial activity was evaluated using the disc diffusion method against four bacterial strains. Additionally, the volatile profiles of fennel hydrolates were determined by headspace solid-phase microextraction (HS-SPME) and GC-MS analysis. Fennel flowers gave the highest EO yield (1.95%), followed by mature fruits (1.43%), whereas significantly lower yields were obtained from leaves (0.69%) and stems (0.58%). Trans-anethole was identified as the dominant constituent (from 40.96% in stems to 80.71% in fruits), while α-phellandrene predominated in stem EO (42.77%). Hydrolate volatile profiles were more complex—particularly leaf hydrolate, where 29 compounds were identified. The principal constituents were trans-anethole (39.58–57.40%) and fenchone (16.01–28.80%), while the highest content of estragole was observed in fruit hydrolate (6.56%). The EOs demonstrated moderate antimicrobial activity, showing effectiveness exclusively against Escherichia coli, likely attributable to high phenylpropanoid (primarily trans-anethole) and fenchone contents. Full article

The fermentation cycle critically influences flavor formation in Laobaigan Baijiu, but its effect on the bacterial community–flavor compound correlation remains unclear. This study investigated the co-variation between bacterial community turnover and flavor changes across distinct fermentation rounds of Hengshui Laobaigan Baijiu. Bacterial community structure was characterized via high-throughput sequencing (HTS), while volatile flavor compounds were profiled using headspace solid-phase microextraction combined with gas chromatography–mass spectrometry (HS-SPME–GC–MS). Partial least squares regression (PLSR) revealed their correlation. The analysis revealed 45 volatile compounds in total, with the D-2–D-3 stages serving as the peak production period and stages E-5–E-6 as the key formation period for esters. Lactobacillus dominated the early Dacha (first batch) fermentation, whereas Pseudomonas, Chryseobacterium, and Delftia became dominant after Jiuqu addition in Ercha (second batch). Sphingomonas and Pseudomonas were the major flavor contributors, showing very strong correlations with 9 and 6 compounds, respectively. Sphingomonas was positively correlated with nine compounds (e.g., isoamyl acetate, ethyl pentanoate, acids, benzaldehyde), while Pseudomonas was positively correlated with six esters (e.g., ethyl acetate, ethyl butyrate). Delftia, Pantoea, and Lactobacillus also played important roles in volatile formation. This study establishes a correlation network between bacterial communities and flavor compounds in a multi-round solid-state fermentation system, offering a methodological reference for flavor regulation not only in Laobaigan Baijiu but potentially in other traditional fermented foods with similar batch fermentation processes. This study provides theoretical support for the optimization of Laobaigan Baijiu fermentation and the enhancement of final Baijiu quality. Full article