Search Results (518)

Furan-2-yl substituted ethenes and conjugated butadienes containing two geminal electron-withdrawing groups, as well as phenylbutadienes with two electron acceptors, were synthesized from the corresponding aldehydes and various β-dicarbonyl compounds via aldol condensation. Reactions of these ethenylfurans and methyl 3-(benzofuran-2-yl)propenoate with arenes in triflic acid (TfOH) yield arylated 2,3-dihydrofurans and 2,3-dihydrobenzofurans, representing a novel synthetic approach to these dihydro derivatives. In contrast, analogous reactions of furanyl- and phenylbutadienes result in carbon–carbon bond cleavage through retro-aldol and related acid-promoted processes. We propose plausible multistep mechanisms and cationic intermediates for these transformations. The synthesized furans and related compounds, at a concentration of 64 μg/mL, exhibit moderate antimicrobial activity against the yeast-like fungus Candida albicans. Full article

Fresh fruits are highly perishable products whose acceptance depends not only on external appearance and firmness, but also on the preservation of taste and aroma. This review addresses the relationship between active packaging and the maintenance of fruit sensory quality, with special emphasis on the volatilome as a dynamic marker of aroma integrity. The first part examines how taste and aroma are formed during ripening through the interaction of sugars, organic acids, phenolics, amino acids, and a wide range of volatile compounds, including fatty-acid-derived esters and aldehydes, terpenoids, carotenoid-derived norisoprenoids, phenylpropanoids, sulfur-containing compounds, and glycosidically bound precursors. It then analyzes how these traits deteriorate during packaged shelf life through temperature effects, refrigerated and room-temperature storage, microbial and enzymatic activity, mechanical damage, and packaging-atmosphere imbalance, showing that visual and sensory shelf life do not necessarily decline together. The second part reviews how active packaging can preserve—or unintentionally distort—this volatilome, covering modified-atmosphere and gas-regulating systems, antimicrobial and ethylene-managing systems based on released essential oils, sulfur dioxide and ethanol emitters, oxygen and carbon dioxide regulators, moisture absorbers, multi-active combinations, and packaging-adjacent edible coatings. A recurring principle emerges: every active function is double-edged, as an intervention that delays spoilage or senescence may itself add exogenous notes or trigger fermentative off-flavors unless it is tuned to a sensory compatibility threshold. The packaging material is also decisive, since paper and cardboard buffer humidity and interact weakly with aroma compounds, whereas high-barrier polymers sustain a modified atmosphere but can scalp esters and terpenes; conversely, releasing volatiles compatible with the native aroma can act as an aroma-positive strategy that restores characteristic notes. Active packaging should therefore be evaluated not only by conventional quality parameters, but also by headspace gas evolution, sugar/acid balance, odor-active volatiles, off-flavor markers, and sensory validation, together with consumer acceptance, odor-threshold relevance, migration and safety considerations, and kinetic matching between active-agent release, fruit respiration, and flavor evolution. Full article

New methylenecyclobutane-derived allylboranes, diisopropyl(2-methylenecyclobutyl)borane and chiral (+)-diisopinocampheyl(2-methylenecyclobutyl)borane undergo rapid equilibration via facile [1,3]-B sigmatropic shifts that interconvert the endocyclic and exocyclic isomers. Both endocyclic isomers react with the Soai aldehyde, 2-(3,3-dimethylbut-1-yn-1-yl)pyrimidine-5-carbaldehyde, affording a single diastereomer of the corresponding homoallylic alcohol. With the achiral reagent the reaction is regio- and diastereoselective, yielding exclusively one diastereomer of the racemic alcohol in 83% yield. With the chiral reagent, the reaction is enantioselective, providing optically active (RR)-alcohol in 87% yield and 89% ee, demonstrating the synthetic potential of the new chiral organoboron reagent. The regio- and diastereospecific allylboration with the achiral reagent and the regio-, diastereo- and enantioselective allylboration with the novel chiral reagent, as well as their reactions with pyrimidinic aldehyde yielding new alcohol, were analyzed computationally, revealing the origins of high selectivity in dynamic multicomponent reaction mixtures. The exocyclic isomers are unreactive due to the universally high barriers of allylboration reactions with their participation. Relative stabilities of all intermediates and transition states are regulated by the effectiveness of weak non-covalent interactions in the corresponding species. X-Ray crystallographic analysis of the racemate, consisting of (RR) and (SS) enantiomers, confirmed its constitution and relative configuration, whereas the absolute configuration of the chiral compound was assigned on the basis of the DFT calculation results. The chiral alcohol was tested as a catalyst in the Soai reaction, which afforded a racemic product. Full article

Sequential non-thermal and thermal processing offers a route to jointly adjust the functionality, color/volatile profile and immunoreactivity of gluten-containing systems. This study aimed to evaluate the effects of sequential ultrasound-assisted enzymatic hydrolysis, wheat/rice starch incorporation and microwave heating on soluble gluten hydrolysate–starch composites, and to probe the underlying starch–gluten interactions. Gluten hydrolysates were blended with wheat or rice starch and microwave-heated to induce the Maillard reaction. Sequential processing enriched the <1 kDa peptide fraction (2.34%→13.05–14.99%) and raised ABTS·⁺ scavenging (0.25→0.40 mM Trolox/g). After starch compounding and microwaving, the composites exhibited increased protein-normalized TEAC (0.07–0.08 to 0.10–0.13 mM per mg/mL protein) and released more ninhydrin-reactive amino groups (>55 μmol/mg protein) after in vitro digestion. All microwave composites remained pale (L* > 94), with the coupled treated rice-starch composite showing the lowest color difference (ΔE = 0.25). GC-FID/electronic-nose profiling with PCA–DFA showed that the coupled treated composites retained a native cereal-like volatile profile, marked by the green/malty aldehyde 3-methylbutanal and hexanal, with only mild roasted-type Maillard volatiles and the clearest separation for rice starch. The lowest residual R5-reactive gluten reached 8.31–9.82 ppm for the coupled treated groups. Docking provided putative models of multi-site starch binding near immunodominant gliadin sequences (e.g., QQPYP, LQPFP) via Glu/Gln–glucose hydrogen bonds and hydrophobic contacts, with more diverse binding modes for rice starch. Overall, the sequential treatment improved functional and volatile properties and lowered R5-detectable immunoreactivity for composites, offering a process reference for the development of balanced gluten-derived functional ingredients and special dietary food formulations. Full article

Dissolved organic matter (DOM) in the water column and sediments in coal mining subsidence areas considerably affects the carbon cycle and ecological environment. This study analyzed the spectral characteristics, material composition, and molecular transformation of DOM in the water column and sediments of a coal mining subsidence area in Huaibei, China, using ultraviolet–visible absorption spectroscopy, three-dimensional fluorescence spectroscopy combined with the parallel factor analysis (PARAFAC) model, and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). The DOM concentration (11.99 ± 4.73 mg/L) and the degree of DOM humification in the sediment were higher than those (9.54 ± 0.68 mg/L) in the water column. The PARAFAC model revealed three chemical components: fulvic acid–like, protein-like, and humus-like substances. DOM in the water column is primarily derived from endogenous inputs, characterized by low humification and high biological activity. In contrast, DOM in the sediments primarily originates from external inputs. FT-ICR MS analysis revealed that lignin-like (50.80–67.02%), protein-like (13.18–18.38%), and lipid-like (5.74–10.39%) components are the main DOM constituents in the water column and sediments, with lignin content in the water column (66.16%) being higher than that in the sediments (55.09%). Paired mass difference network analysis identified redox reactions as the predominant reactions in the water column and sediments, converting aldehydes or carbonyl compounds into acids or alcohols. This study elucidates the composition and transformation characteristics of DOM in the water column and sediments in coal mining subsidence areas, providing a scientific foundation for the protection and management of aquatic ecosystems. Full article

Linear α-olefins derived from Fischer–Tropsch (FT) synthesis serve as critical feedstocks for high-grade polyolefin production, yet residual oxygenated compounds severely compromise polymerization efficiency and product quality. This study reports the modification of 13X zeolite via Mg/K bimetallic ion exchange to enhance its adsorptive performance for deep oxygenate removal. It is found that Mg/K modification enhances surface polarity and acid sites without destroying the zeolite framework. Adsorption capacity follows the order of Mg/K-13X > Mg-13X > 13X. The process fits the Langmuir isotherm and pseudo-second-order kinetics, indicating monolayer chemical adsorption. Thermodynamic results reveal spontaneous and exothermic adsorption. In fixed-bed tests with 1-hexene and 1-octene, oxygenates are reduced below 5 ppm within 270 min. Breakthrough curves are well-fitted by the Thomas model, with aldehydes breaking through first and alcohols last, owing to polarity-driven adsorption selectivity. After 40 regeneration cycles, the oxygenate removal efficiency remains above 90.72%, confirming exceptional stability and reusability. Mg/K-13X thus represents a highly efficient and robust adsorbent for the deep purification of FT-derived α-olefins. Full article

This study examined the effect of grape ripening on the distillate quality of Hetianhong table grapes across three stages of maturity (17, 20, and 24 °Brix). Through the application of HS-SPME-GC-MS, a total of 72 volatile aroma compounds were identified. As the grapes matured from 17 to 24 °Brix, there was an 8.48-fold increase in volatile fatty acids, accompanied by a rise in ester concentrations, while significant reductions were observed in naphthalene derivatives, aldehydes/ketones, and terpenols. Notably, the distillate at 20 °Brix demonstrated the highest concentration of higher alcohols, the richest aroma and superior sensory attributes. The 2-methyl-1-propanol concentration was 15.70 times greater at 20 °Brix than at 24 °Brix, while octanoic acid concentration was 97.93 times higher at 20 °Brix compared to 17 °Brix. Overall, Hetianhong table grapes are ideal for distilled spirits, with optimal maturity modulating the final flavor profile. This research supports value-added processing of these grapes. Full article

This study characterized the pattern and timing of post-cooking quality deterioration in durum wheat held at 25, 35, and 45 °C by performing physicochemical, microbiological, and volatile compound analyses combined with a sensorially defined off-odor onset endpoint. The bulk moisture content remained high throughout holding at all temperatures. Titratable acidity increased from 1.49 to 2.15, and pH at off-odor onset decreased from 6.63 to 6.49 with increasing temperature. Off-odor was detected after 50, 45, and 34 h at 25, 35, and 45 °C, respectively. Microbial growth was fastest at 35 °C (μ_max = 0.0651 h⁻¹). Thiobarbituric acid reactive substances (TBARS) values were slightly lower at 45 °C than at 25 °C, despite the shorter holding duration, whereas lipid oxidation-derived volatile aldehydes declined more sharply over the same comparison. This pattern, together with the earliest off-odor onset occurring at 45 °C, suggests that non-lipid-derived volatiles increasingly drive off-odor perception as holding temperature increases. Gas chromatography–mass spectrometry (GC–MS)-based relative odor activity value (ROAV) analysis identified 2-methoxy-4-vinylphenol, 2,4-decadienal, 2-nonenal, 2,3-butanedione, nonanal and 2-methoxyphenol as the principal contributors to the aroma profile. These findings indicate that off-odor development during post-cooking holding results from a temperature-dependent interplay between microbial and chemical deterioration pathways and provide a basis for optimizing holding time and temperature to delay off-odor onset and limit quality losses in bulgur production. Full article

Asian local chickens are often perceived as more palatable than commercial broilers, with stronger taste and longer aftertaste, but the biochemical basis of this eating quality remains unclear. Using Japanese local chicken meat as the main example and other Asian local chicken studies as context, this hypothesis-generating review develops a hypothesis centered on arachidonic acid. The core hypothesis is that higher arachidonic acid content may partly explain why local chicken meat is perceived as more palatable. Available Japanese data show that local chicken meats generally contain higher arachidonic acid proportions than commercial broiler meat. However, higher arachidonic acid content alone cannot explain why the meat is perceived as more palatable. A previously proposed hypothesis links lipid-derived volatile aldehydes to kokumi through activation of the calcium-sensing receptor. This route is treated cautiously here, because volatile aldehydes may be lost during cooking and have not yet been shown to remain in cooked chicken meat at concentrations that influence eating quality. Instead, this review proposes a second validation route. Arachidonic-acid-rich lipid pools generate 4-hydroxy-2-nonenal and related compounds that are less volatile and more likely to remain in edible fractions than short-chain aldehydes. These compounds are introduced here only as plausible downstream oxidation products that may help connect meat lipid composition with kokumi-related or aftertaste-related perception. This review emphasizes production context, meat-quality traits, and sensory evaluation as the primary basis for interpreting fatty-acid differences, with chemical hypotheses presented only as exploratory routes for future validation. Full article

Liupao tea (LPT), one of China’s representative fermented dark teas, develops its unique “red, heavy, aged, and mellow” flavor characteristics. This review provides a comprehensive update on LPT aroma, integrating analyses of volatile organic compounds (VOCs), associated microorganisms, odor-active compounds (OACs), and metabolic pathways of key odor-active compounds (KOACs). With over 2000 VOCs documented, predominated by alcohols (368), hydrocarbons (357), and ketones (351), the total for LPT substantially exceeds the approximately 1000 compounds typically reported for other dark teas. By combining sensory evaluation with techniques such as gas chromatography–olfactometry (GC-O) and odor activity value (OAV), KOACs, predominantly comprising alcohols, aldehydes, and methoxybenzene derivatives, were identified as key contributors to the floral, fruity, aged, stale and other notes that define LPT’s characteristic aroma. The formation of the aroma compounds is closely linked to microbial metabolism and the enzymatic activities generated by microorganisms. Fungi, including Aspergillus, Rhodotorula, Geosmithia, Wallemia, Penicillium, Blastobotrys, Fusarium, and Xeromyces, and bacteria, including Burkholderia, Ralstonia, and Achromobacter, serve as the primary functional microorganisms driving fermentation and aging. This review provides a comprehensive framework for understanding the chemical and microbial complexity of LPT aroma. Full article

This study evaluated carob (Ceratonia siliqua L.) flour as a functional ingredient for improving the nutritional and sensory properties of wheat-based biscuits. Mature carob pods collected from eastern Algeria were processed into fine flour and characterized for physicochemical properties, antioxidant activity, and volatile and phenolic profiles. GC–MS analysis revealed a complex volatile profile dominated by organic acids, aldehydes such as furfural and benzaldehyde, and Maillard-derived compounds, including 2-acetylpyrrole and furfuryl alcohol, associated with caramel and cocoa-like aromas. LC-MS profiling identified several flavonoids and phenolic acid derivatives, including quercetin-, myricetin-, and kaempferol-glycosides, as well as gallic acid glucoside, confirming the high antioxidant potential of carob flour. Biscuits were formulated by substituting wheat flour with 30% and 60% carob flour. Sensory evaluation revealed significant increases in color intensity, caramel odor, sweetness, and chocolate-like flavor (p ≤ 0.05), with the 30% substitution achieving the highest overall acceptability. These sensory attributes were associated with the volatile and phenolic profiles, particularly the presence of Maillard-derived furans and flavonoid compounds. These findings demonstrate that carob flour can enhance the sensory characteristics and contribute to the functional potential of biscuits, supporting its use as a natural cocoa substitute and source of bioactive compounds in bakery products. Full article

To investigate sex-specific differences in gonad quality and flavor characteristics of the sea urchin Heliocidaris crassispina, female and male gonads were compared using proximate composition, colorimetry, E-tongue, E-nose, LC-MS, and HS-SPME-GC-MS. No significant sex differences were observed in wet weight, test diameter, gonadosomatic index, moisture, or crude fat, whereas female gonads showed higher crude protein content, lightness, and yellowness. E-tongue and E-nose analyses revealed distinct sex-dependent taste and odor fingerprints. Metabolomics identified 366 differential non-volatile metabolites and 53 differential volatile metabolites, mainly involving lipids, organic acids and derivatives, dipeptides, nucleotide-related compounds, hydrocarbons, terpenoids, aldehydes, ketones, and esters. Female gonads were enriched in phospholipids, lysophospholipids, dipeptides, and nucleotide precursors, whereas male gonads contained higher levels of acylcarnitines, hydroxy fatty acids, 3-carene, and hydrocarbons. These findings provide metabolomic evidence for sex-dependent flavor differences and support quality evaluation of sea urchin products. Full article

Goat and sheep meat are highly regarded in the market for their unique flavor qualities. In this study, lipidomics technology was employed to compare the lipid differences in the longissimus dorsi muscle among 8-month-old Saanen dairy goats (DYG, n = 6), Shaanbei white cashmere goats (CAG, n = 6), and Tan sheep (TSH, n = 6). Electronic nose analysis was performed solely on the DYG samples, while the E-nose data for the CAG and TSH groups were referenced against previously published literature. The results indicated that aldehydes, ketones, methyl derivatives, and inorganic sulfides constituted the predominant stable volatile flavor compounds in the DYG muscle. Principal component analysis (PCA) and partial least square discriminant analysis (PLS-DA) revealed clear breed-dependent clustering and separation. Cluster analysis revealed that CAG and TSH groups exhibited highly similar lipid expression patterns, whereas the DYG group showed a distinct profile. Specifically, in the DYG group, SM (d18:1/20:3) and S1P (t17:0) were significantly increased, while most triglycerides (TG) were decreased and diglyceride DG (18:0/16:0) was increased. Additionally, multiple phosphatidylcholines (PC) and phosphatidylethanolamines (PE) were significantly reduced in the DYG group. This study revealed unique lipid signatures in the DYG group muscle compared with CAG and TSH groups, providing a theoretical basis for deciphering the lipid regulatory mechanisms underlying meat quality and flavor formation in goats and sheep. Full article

Prior studies on Ganoderma lucidum spore oil (GLSO) rarely systematically explored its storage oxidative deterioration mechanism via multi-marker combined characterization. This study innovatively integrated the Schaal oven accelerated storage test and dual-NMR detection (LF-NMR and ¹H NMR) to evaluate the oxidative stability of GLSO over 60 d. Dynamic changes in routine oxidation indices, glycerol core aldehydes (GCAs), phytosterols and their triterpenoid biosynthetic precursors, fatty acids and volatile compounds were synchronously tracked. Results revealed complex fluctuating accumulation of primary and secondary oxidation products; non-volatile GCAs exhibited continuous monotonic growth and acted as reliable markers for severe GLSO oxidation. Unsaturated fatty acids and phytosterols and their triterpenoid biosynthetic precursors degraded in a structure-dependent pattern, with phytosterols and their triterpenoid biosynthetic precursors degradation sensitivity ranked as squalene > lanosterol > β-sitosterol. Correlation analysis clarified the intrinsic linkage between fatty acid substrates and oxidation derivatives. This work innovatively reveals the complete lipid oxidation pathway of GLSO, offering novel theoretical references and multi-index evaluation strategies for quality control and preservation of high-grade GLSO products. Full article

Background: Polygodial (9), a drimane sesquiterpene dialdehyde from Drimys winteri, has not previously been examined against carbohydrate-hydrolyzing enzymes. Methods: Regioselective Wittig olefination at C12 gave the enoate 10; reduction of the remaining C11 aldehyde with NaBH₄ was followed by spontaneous intramolecular conjugate addition, affording the annellated tetrahydrofuran 12a and the bridged ether 12b. Results: All three derivatives inhibited α-glucosidase and α-amylase more strongly than the parent compound. Compound 12a was the most active α-glucosidase inhibitor (IC₅₀ = 53.98 ± 3.0 µM, against 90.36 ± 4.0 µM for acarbose) and, in docking, the only derivative to occupy the acarbose-binding site of the enzyme (−8.1 kcal/mol). However, this 12a–α-glucosidase pose was not maintained during the 200 ns simulations. The enoate 10 was the most active α-amylase inhibitor (IC₅₀ = 42.32 ± 2.1 µM, against 78.24 ± 3.9 µM for acarbose; −8.5 kcal/mol). Over 200 ns of molecular dynamics, the 10–α-amylase complex remained associated, with binding attributed by MM-GBSA mainly to van der Waals and lipophilic terms. Conclusions: Converting the dialdehyde into an enoate or a cyclic ether increases carbohydrase inhibition and determines which of the two enzymes is preferentially inhibited. Full article