Search Results (943)

Packing density regulates the microenvironment of tobacco (Nicotiana tabacum L.) fermentation and may thereby influence microbial activity and product quality. However, its effects on microbial community assembly and quality formation remain poorly understood. This study aimed to clarify how packing density affects flue-cured tobacco quality by shaping microbial communities, functional potential, and ecological interactions. Here, we investigated the effects of three packing densities (60%, 70%, and 80%) on chemical components, aroma compounds, microbial community structure, functional potential, co-occurrence networks, and assembly mechanisms of flue-cured tobacco (cv. Piaohe No. 2) after 10 days of fermentation. Moderate density (70%) achieved the most balanced chemical profile, with appropriate nicotine retention, potassium/chlorine ratio, and sugar/nicotine balance. T70 also exhibited the highest levels of total esters, total ketones, and β-ionone, key contributors to fruity, floral, and woody aromas. Microbial analysis revealed that T70 supported the highest diversity and was characterized by the enrichment of aroma-related bacterial taxa, including Bacillus and lactic acid bacteria, as well as the fungal genus Pichia. In contrast, T60 favored aerobic nicotine degraders, whereas T80 selected for obligate anaerobes associated with off-odor production. Functional predictions and network analysis showed that T70 upregulated fatty acid and carotenoid biosynthesis pathways and exhibited the highest modularity, indicating a compartmentalized, functionally complementary community. Neutral model fitting revealed increasing stochasticity with density, with T70 displaying a mixed assembly regime. Collectively, our findings show that packing density influences tobacco quality by regulating microbial community composition, functional potential, network interactions, and assembly processes. These results provide a scientific basis for optimizing packing density in tobacco processing. Full article

Sea buckthorn is rich in functional components but features high acidity and susceptibility to oxidative deterioration, leading to flavor defects such as sour–astringent taste and rancidity in single-fruit wine. Co-fermentation is an effective strategy for flavor and nutrition complementarity, but the dynamic evolution of volatile aroma during yeast–lactic acid bacteria combined fermentation of such wine remains unclear. This study employed ‘Zhuangyuan Huang’ sea buckthorn and ‘Marselan’ grape to produce the composite fruit wine via sequential co-fermentation, and systematically investigated dynamic aroma changes using HS-SPME-GC-MS, orthogonal partial least squares discriminant analysis (OPLS-DA), and relative odor activity value (ROAV) analysis. Results revealed that post-fermentation, total detected volatile compounds increased from 90 to 118, with esters and alcohols rising by 24 and 11 respectively, serving as core contributors to enhanced aroma richness. ROAV analysis demonstrated this process significantly reduced the contribution of off-flavor acids, boosted the importance of floral, fruity, and sweet compounds, and elevated the sensory score from 26.8 to 84.1. OPLS-DA further confirmed significant inter-stage aroma differences with excellent intergroup discrimination. These findings confirm that this sequential fermentation breaks processing bottlenecks of high-acid fruits, reveals the synergistic flavor-modulating effects of multi-microbial sequential fermentation, and provides theoretical support for process optimization and high-value processing of composite fruit wine. Full article

The increasing demand for low-alcohol wine products calls for effective vineyard strategies to reduce grape sugar concentration, while climate change is exacerbating sugar accumulation through warmer growing conditions. In this context, severe shoot trimming applied at specific phenological stages may represent a promising approach to induce sustained source limitation. A field experiment was conducted in 2025 on Vitis vinifera L. cv. Ortrugo to evaluate severe shoot trimming performed at the onset of berry softening. Vine growth, yield components, grape composition, and seasonal total soluble solids (TSSs) were monitored. Vine carbon reserves and shoot fruitfulness were assessed to evaluate carry-over effects. Experimental wines were produced to determine alcohol and fermentative aroma. Severe trimming markedly reduced leaf area and vine balance, leading to a sustained reduction in sugar accumulation. At harvest, grape TSSs decreased by 4.1 °Brix (17.6 vs. 21.7 °Brix) and the final wine alcohol concentration was lower by 3.4% (v/v). Yield was unaffected and no substantial negative effects on wine fermentative aroma were observed, while titratable acidity slightly increased. Even if trimming reduced winter starch concentration in roots, no reduction in shoot fruitfulness was observed in the subsequent spring. Severe trimming successfully reduced grape sugar and wine ethanol without compromising yield, aroma, or vine performance, supporting its potential for low-alcohol wine production and reduced-impact dealcoholization. Full article

Olfactory detection of essential oils (EOs), natural plant-derived mixtures of odorous volatile compounds, stimulates neural pathways involved in emotion, cognitive function, and memory in humans and significantly influences insect behavior (inducing attractiveness or repellency). In this study, the olfactory perception of rose (EO 1, a synthetic mixture with rose aroma), eucalyptus (EO 2), lemon (EO 3), clove (EO 4), rosemary (EO 5), and caraway (EO 6) EOs in untrained human participants was compared to the behavioral responses induced in Tenebrio molitor (adult insects) by EO exposure. Significant differences emerged in the perception of EO odor dimensions (pleasantness, intensity, and familiarity) using a Likert-type scale in untrained participants. The tested EOs elicited different behavioral responses in T. molitor insects, as assessed by repellency, escape, and choice tests. A positive correlation (r = 0.7861, p < 0.05) emerged between EO odor intensity perceived by participants and escape induction in T. molitor adults. GC–MS analysis revealed citronellol, 1,8-cineole, limonene, eugenol, α-pinene, and carvone as the most abundant volatile compounds in EO 1, EO 2, EO 3, EO 4, EO 5, and EO 6, respectively. The EO odor dimensions in participants and insect behavioral responses were also related to the in silico physicochemical/pharmacokinetic properties of the main EO components. Our results provide new insights into the chemical basis of olfactory preferences both in T. molitor adults and humans. Full article

Pineapple glutinous rice wine is a popular fermented beverage, yet its flavor and quality remain highly affected by yeast strains. This study aimed to explore the effects of four commercial yeasts, namely La Raffinée (Ra), La Bayanus (Ba), La Délicieuse (De), and Angel wine yeast (AWY), on the quality of pineapple glutinous rice wine. Fermentation indices including Brix and alcohol content were dynamically monitored, while final wine samples were analyzed for color difference, sensory quality and aroma components by gas chromatography–ion mobility spectrometry (GC-IMS). Results showed that all yeasts had optimal fermentation efficiency, sugar-to-alcohol conversion, physicochemical properties and sensory quality at an addition level of 0.2 g/L. The 0.2 g/L De group achieved the optimal overall quality with an alcohol content of 10.01% vol, the highest ester content (22.55%) and the lowest acid content (12.18%), presenting a balanced flavor, prominent pineapple aroma and refreshing taste. In contrast, Ba led to higher acidity and Angel wine yeast contributed to greater sweetness. Overall, 0.2 g/L De yeast effectively coordinated pineapple aroma and glutinous rice wine characteristics, providing a practical reference for optimizing the production and quality improvement of pineapple glutinous rice wine. Full article

Honeybee brood is a nutrient-rich food source containing natural umami-active compounds, such as glutamic acid, aspartic acid, and 5′-nucleotides, which are responsible for its characteristic umami taste. This study aimed to optimize drying conditions to enhance the umami composition and sensory properties of honeybee brood umami powder (HBb-UP). A factorial design was employed to evaluate the effects of drying temperature and time on umami-related amino acids, 5′-nucleotides, and equivalent umami concentration (EUC). Drying temperature and time significantly influenced the formation of umami compounds, with the optimized drying condition (65 °C for 3 h) promoting higher umami composition and improved sensory attributes of HBb-UP. Volatile flavor analysis using GC–MS and an electronic nose revealed a diverse range of aroma compounds contributing to the overall flavor profile. Descriptive sensory evaluation and electronic tongue analysis indicated that umami and saltiness were the dominant taste attributes, accompanied by mild seasoning and fishy notes associated with interactions between amino acids and nucleotides. Principal component analysis demonstrated positive correlations among umami-related amino acids, nucleotides, EUC, and sensory attributes, confirming their combined contribution to taste perception. These findings highlight the potential of optimized HBb-UP as a natural flavor enhancer and functional ingredient for use in sustainable food systems. Full article

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

Black tea quality is governed by aroma chemistry: terpene alcohols (linalool, geraniol, nerolidol), methyl salicylate, and short-chain aldehydes whose abundance and release kinetics from the polyphenol-rich leaf matrix shape perceived grade. Grade information lies not only in the average headspace concentration but in the temporal shape of volatile organic compound (VOC) release under controlled heating. Conventional electronic noses obscure this signal: they rely on multi-sensor arrays, compress each response into summary statistics, and report accuracy only at the level of individual measurements. Whether a single low-cost metal–oxide–semiconductor (MOS) gas sensor can recover grade-defining aroma chemistry, and whether waveform-level modeling can exploit it, was therefore investigated. A portable electronic nose built around a Bosch BME688 sensor recorded 90 time series, each comprising four directly measured channels (temperature, humidity, pressure, gas sensor resistance) and a derived indoor-air-quality (IAQ) proxy computed from them by the on-chip BSEC library, from 16 commercial Turkish black teas across three quality grades. Two representations were compared on the same data: a feature-based pipeline reducing 25 statistical descriptors to seven principal components for six classifiers (best F1-macro = 0.624, MLP), and a raw-waveform Multi-Scale 1D-CNN with Squeeze–Excitation and temporal self-attention (MS-CNN-Attention). Under product-grouped cross-validation, the deep model reached F1-macro = 0.811 (+30%) and graded 14 of 16 products correctly by majority vote, against 11 of 16 for the MLP, with the largest gain in the medium grade (F1: 0.52 → 0.79), where summary-statistic compression destroys the release-kinetic signal. The contributions are threefold: one programmable MOS sensor operated as a thermal-desorption profiler rather than a sensor array; a direct comparison of feature-based classical learning against raw-waveform deep learning on the same small, non-normally distributed dataset; and a product-level decision-consistency metric suited to batch screening. Pairing a low-cost MOS sensor with waveform-level modeling offers a rapid, non-destructive route to aroma-chemistry-based tea quality screening. Full article

Blueberry fruit quality is characterized by multi-dimensional traits such as color, sugar-acid flavor, and volatile aroma. However, variations in progeny metabolites during seedling selection need further study. This research used the blueberry variety ‘Baldwin’ (BW) and its seedling offspring (BWSO) to compare fruit appearance, as well as sugar and acid components, anthocyanin monomers, and volatile metabolites. High-performance liquid chromatography was used to analyze anthocyanins, sugars, and acids, and gas chromatography–mass spectrometry was used to analyze volatile compounds. The results showed that, compared with BW, BWSO had a blacker skin and a lower L* value. Its total anthocyanin content increased by 35.90%, with delphinidin increasing the most (52.70%); component ratios were reconstructed. The main organic acids in BWSO decreased; titratable acid dropped by 29.82%, and the total soluble solids–acid ratio rose by 37.49%, indicating a good low-acid, high-sugar flavor. Forty-three differential volatile metabolites were found, and BWSO differed from BW in its green, fruity, and floral flavors. Notably, BWSO’s vitamin C (Vc) content decreased by 70.45% compared to BW, and Vc was negatively correlated with anthocyanin components. In conclusion, BWSO exhibits a black phenotype due to elevated total anthocyanins and restructured component ratios. Its low-acid trait yields better taste, but the antagonism between anthocyanin and Vc means balanced nutritional quality selection is crucial in dark-blueberry breeding. These findings offer new insights into the mechanism of color variation and provide a reference for balanced quality trait selection in seedling selection. Full article

Distillation is widely used for essential oils extraction, and distillation time (DT) influences the quality and quantity of oils. This study presents the effects of 14 DTs (1, 3, 5, 10, 20, 40, 80, 120, 160, 200, 240, 280, 360, and 480 min) on leaf oils from Thuja occidentalis L., aiming to maximise the yield and modulate chemical profiles. Also, a safety assessment of T. occidentalis oils obtained at different DTs was conducted based on thujone levels under International Fragrance Association (IFRA) guidelines. Oil yield varied with DT, reaching a maximum at 40–80 min (0.54 ± 0.04% and 0.59 ± 0.02%, respectively). Monoterpenes (sabinene, fenchone, and thujone) decreased with prolonged DT, whereas higher molecular weight compounds, including sesquiterpenes (caryophyllene) and diterpenes (hibaene and rimuene) increased. Principal component analysis (PCA) grouped samples into three stages, early (1–10 min), mid (20–80 min), and late (120–480 min), with clear compositional separation (PC1: 68.4%, PC2: 11.8%). As DT increased, the fragrance profile progressively shifted from monoterpene-rich characteristics in the early-stage oils to more persistent aromas associated with sesquiterpenes (caryophyllene, α-cadinol, and α-eudesmol) and diterpenes (hibaene and rimuene) in the late-stage oils. Safety assessment revealed that early-stage oils contained high thujone levels (67.19–71.88%), limiting their allowable use. In contrast, prolonged DTs (≥200 min) reduced thujone content, increasing permissible usage across multiple IFRA categories. Overall, DT significantly influences the oil yield, chemical composition, and regulatory applicability of T. occidentalis oils, with extended distillation enhancing formulation flexibility in cosmetic and fragrance applications. Full article

Fruity natural flavors are widely used in food, cosmetics, and tobacco products, and their flavor profiles directly affect the sensory quality of the final products. However, the volatile organic compound systems in these flavors are highly complex, and severe co-elution among volatile components makes effective component resolution a persistent analytical challenge. In this study, comprehensive two-dimensional gas chromatography–olfactometry–time-of-flight mass spectrometry (GC×GC-O-TOF-MS) was employed to separate and identify volatile odor compounds in three natural fruit flavor extracts: plum, jujube, and grape. A total of 113, 103, and 85 volatile odor compounds were identified from the plum, jujube, and grape extracts, respectively. By progressively adjusting the split ratio, aroma extract dilution analysis was performed, leading to the screening of 14, 11, and 32 aroma-active compounds from the three extracts, respectively. Compounds with high flavor dilution factors were subjected to quantitative analysis, and their odor activity values were calculated. Subsequently, omission and recombination experiments were conducted to confirm the key aroma-active compounds in each extract. The results showed that octanal was a key aroma compound shared by the plum and jujube extracts, while ethyl cinnamate was common to both the plum and grape extracts. Through a molecular sensory science approach and utilizing GC×GC-O-TOF-MS chromatographic separation technology, this study provides a reliable analytical platform for aroma characterization in complex samples. It also establishes a critical theoretical and data foundation for precisely identifying key aroma-active components and implementing targeted aroma modulation to enhance the natural flavor quality of fruits. Full article

This study investigated the influences of geographical origin, harvest season, and plucking position on the chemical composition and flavor characteristics of Hainan Dayezhong black tea. Systematic analysis of basic components, volatile profiles and metabolomes of tea samples collected under different pre-harvest conditions revealed significant variations in polyphenols, flavonoids and catechins, as well as distinct differences in volatile composition. Key aroma-active compounds identified were nerolidol, linalool, benzaldehyde, benzeneacetaldehyde and methyl salicylate, which were determined to be decisive for the characteristic aroma profile of Dayezhong black tea. Untargeted metabolomics further demonstrated that these factors do not merely alter individual metabolite levels, but also reprogram energy metabolism, carbon–nitrogen allocation, and secondary metabolic pathways, resulting in distinct metabolic signatures among samples. From a systematic chemical perspective, this study elucidates the metabolic basis of Hainan Dayezhong black tea quality formation and establishes a scientific foundation for targeted quality optimization through regulation of key components. Full article

Phenolic compounds in Muscat grape juice contribute to antioxidant capacity, functional properties, and sensory quality; however, conventional enzymatic maceration is often limited in efficiency and typically requires elevated temperatures. This study systematically compared pectinase-assisted heat maceration (P45-HM), low-temperature pectinase maceration (P-CM), and low-temperature maceration mediated by the psychrotolerant yeast Metschnikowia pulcherrima (Mp-CM) in Muscat grape juice. Mp-CM significantly enhanced the extraction and transformation of phenolic compounds, with total phenolic and flavonoid contents increasing by 8.01% and 13.14%, respectively, compared with P-CM, and by 27.06% and 55.28%, respectively, compared with P45-HM. Moreover, Mp-CM exhibited higher antioxidant activities, as determined by DPPH, ABTS, and FRAP assays, as well as greater sodium glycocholate-binding capacity than P-CM (p < 0.05). Correlation analysis revealed strong positive correlations between phenolic composition and biological activities. Volatile compounds were analyzed by HS-SPME-GC-MS combined with principal component analysis (PCA), demonstrating distinct aroma profiles. Mp-CM was enriched in terpenes (14.63% higher than P-CM), whereas P-CM was dominated by esters, suggesting that M. pulcherrima possesses a distinct biotransformation capacity that modulates volatile compounds potentially contributing to the characteristic Muscat aroma. These findings indicate that Mp-assisted cold maceration represents an efficient and promising biological maceration strategy for enhancing the quality of grape juice. 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