Search Results (2,615)

Yellowing is the key processing technology of yellow tea, and environmental conditions have a significant impact on the yellowing process. In this study, volatile compounds of the yellowing process under different environmental conditions were analyzed by GC–MS. Results showed that a total of 75 volatile compounds were identified. A partial least squares discriminant analysis (PLS-DA) determined that 42 of them were differential compounds, including 12 hydrocarbons, 8 ketones, 8 aldehydes, 6 alcohols, and 8 other compounds, and compared the contents of differential compounds under the conditions of 40 °C with 90% humidity, 50 °C with 50% humidity, and 30 °C with 70% humidity, then analyzed the variation patterns of hydrocarbons under different yellowing environmental conditions. A 40 °C with 90% humidity treatment reduced the content of more hydrocarbons and increased the aldehydes. The content of 3-hexen-1-ol was higher when treated at 50 °C with 50% humidity and was consistent with the results of sensory evaluation. This study could provide a theoretical basis for future research on the aroma of yellow tea. Full article

Small bifunctional molecules are attractive for use as models in different areas of knowledge. How can their functional groups interact in solids? This is important to know for the prediction of the physical and chemical properties of the materials based on them. In this study, two new hydrogen-bonded organic frameworks (HOFs) based on sterically demanding molecular compounds, bis(1-hydroxy-2-methylpropane-2-aminium) sulfate (1) and 2-methyl-4-oxopentan-2-aminium hydrogen ethanedioate hydrate (2), were synthesized and fully characterized by means of FTIR and NMR spectroscopies, as well as by X-ray powder diffraction and thermogravimetric analyses. Their molecular and crystal structures were established through single-crystal X-ray diffraction analysis. It was shown that both compounds have a layered structure due to the formation of a 2D hydrogen-bonding network, the layers being linked by systematically arranged Van der Waals contacts between the methyl groups of organic cations. To unveil some dependencies between the chemical nature of bifunctional molecules and their solid structure, Hirschfeld surface (HS) analysis was carried out for HOFs 1, 2, and their known congeners 1-hydroxy-2-methylpropan-2-aminium hemicarbonate (3) and 1-hydroxy-2-methylpropan-2-aminium (1-hydroxy-2-methylpropan-2-yl) carbamate (4). HS was performed to quantify and visualize the close intermolecular atomic contacts in the crystal structures. It is clearly seen that H–H contacts make the highest contributions to the amino alcohol based compounds 1, 3 and 4, with a maximal value of 65.2% for compound 3 having CO₃²⁻ as a counterion. A slightly lower contribution of H–H contacts (64.4%) was found for compound 4, in which the anionic part is represented by 1-hydroxy-2-methylpropan-2-yl carbamate. The significant contribution of the H–H contacts in the bifunctional moieties is due to the presence of a quaternary carbon atom with a short three-carbon chain. Full article

Polyethylene mulching film, which is widely utilized in arid and semi-arid agriculture, leaves residual pollution. A novel approach to addressing this issue is microbial degradation. To screen the strains that degrade polyethylene efficiently and clarify the effect of degrading strains on the turnover of soil organic carbon, a polyethylene-degrading fungus PF2, identified as Trichoderma asperellum, was isolated from long-time polyethylene-covered soil. Strain PF2 induced surface damage and ether bonds, ketone groups and other active functional groups in polyethylene, with 4.15% weight loss after 30 days, where laccase plays a key role in the degradation of polyethylene. When applied to soil, the Trichoderma-to-soil weight ratios were the following: B1: 1:100; B2: 1:200; B3: 1:300 and B4: 1:400. Trichoderma asperellum significantly increased the cumulative CO₂ mineralization and soil organic carbon mineralization in the B1 and B2 treatments compared with the control (B0). The treatments B1, B3 and B4 increased the stable organic carbon content in soil. An increase in the soil organic carbon content was observed with the application of Trichoderma asperellum, ranging from 27.87% to 58.38%. A positive correlation between CO₂ emissions and soil organic carbon was observed, with the soil carbon pool management index (CPMI) being most correlated with active organic carbon. Trichoderma treatments improved the CPMI, with B3 showing the most favorable carbon retention value. Thus, Trichoderma asperellum not only degrades polyethylene but also contributes to carbon sequestration and soil fertility when applied appropriately. Full article

Myofibrillar proteins primarily consist of myosin, actin, myogenin, and actomyosin. These proteins form complex networks within muscle fibers and are crucial to the physical and chemical properties of meat. Additionally, myofibrillar proteins serve as significant substrates for the adsorption of volatile flavor compounds, including aldehydes, alcohols, ketones, and sulfur and nitrogen compounds, which contribute to the overall flavor profile of meat products. A series of chemical reactions occur during the processing, storage, and transportation of meat products. Oxidation is one of the most significant reactions. Oxidative modification can alter the physical and chemical properties of proteins, ultimately impacting the sensory quality of meat products, including flavor, taste, and color. In recent years, considerable attention has been focused on the effects of protein oxidation on meat quality and its regulation. This study investigates the impact of myofibrillar protein oxidation on the sensory attributes of meat products by analyzing the oxidation processes and the factors that initiate myofibrillar protein oxidation. Additionally, it explores the control of myofibrillar protein oxidation and its implications on the sensory properties of meat products, providing theoretical insights relevant to meat processing methods and quality control procedures. Full article

In this study, we investigated the mechanical and tribological properties of the layer-by-layer structure of additively manufactured implant-grade Polyether Ether Ketone (PEEK) through the Material Extrusion (ME) process as a potential substitute for artificial joints. The effective elasticity modulus of the anisotropic 3D-printed PEEK was determined to be 2.505 GPa along the vertical and horizontal build orientations. The lubricated friction and wear performance were assessed using a pin-on-disk test under various loads, including 14, 30, 50, and 70 N, with a sliding speed of 50 mm/s over a total distance of 1 km at 37 °C. The contact parameters between the hemispherical steel pin and 3D-printed PEEK disks, involving contact pressures over the circle of contact, were observed to increase as the load increased. The results indicated that the wear coefficient exhibited a rise from $1.418{ \times 10}^{-5}$ to $2.089{ \times 10}^{-1}$ as the applied loads increased, signaling a shift from mild to severe wear regimes. Fetal Bovine Serum (FBS) as a lubricant exhibited a mixed mechanism, ascertained through the Stribeck curve, as well as a minimum fluid film thickness of 1.346 nm under an isoviscous–elastic regime, as calculated by the maximum load. Moreover, the mechanism governing wear during sliding, influenced by both normal axial and shear loads, primarily involved adhesion. Full article

Patients with Alzheimer’s disease and related dementia (ADRD) are faced with a formidable challenge of focal amyloid deposits and cerebral amyloid angiopathy (CAA). The treatment of amyloid deposits in ADRD by targeting only oxidative stress, inflammation and hyperlipidemia has not yielded significant positive clinical outcomes. The chronic high-fat diet (HFD), or gut dysbiosis, is one of the major contributors of ADRD in part by disrupted transport, epigenetic DNMT1 and the folate 1-carbon metabolism (FOCM) cycle, i.e., rhythmic methylation/de-methylation on DNA, an active part of epigenetic memory during genes turning off and on by the gene writer (DNMT1) and eraser (TET2/FTO) and the transsulfuration pathway by mitochondrial 3-mercaptopyruvate sulfur transferase (3MST)-producing H₂S. The repeat CAG expansion and m⁶A disorder causes senescence and AD. We aim to target the paradigm-shift pathway of the gut–brain microbiome axis that selectively inhibits amyloid deposits and increases mitochondrial transsulfuration and H₂S. We have observed an increase in DNMT1 and decreased FTO levels in the cortex of the brain of AD mice. Interestingly, we also observed that probiotic lactobacillus-producing post-biotic folate and lactone/ketone effectively prevented FOCM-associated gut dysbiosis and amyloid deposits. The s-adenosine-methionine (SAM) transporter (SLC25A) was increased by hyperhomocysteinemia (HHcy). Thus, we hypothesize that chronic gut dysbiosis induces SLC25A, the gene writer, and HHcy, and decreases the gene eraser, leading to a decrease in SLC7A and mitochondrial transsulfuration H₂S production and bioenergetics. Lactobacillus engulfs lipids/cholesterol and a tri-directional post-biotic, folic acid (an antioxidant and inhibitor of beta amyloid deposits; reduces Hcy levels), and the lactate ketone body (fuel for mitochondria) producer increases SLC7A and H₂S (an antioxidant, potent vasodilator and neurotransmitter gas) production and inhibits amyloid deposits. Therefore, it is important to discuss whether lactobacillus downregulates SLC25A and DNMT1 and upregulates TET2/FTO, inhibiting β-amyloid deposits by lowering homocysteine. It is also important to discuss whether lactobacillus upregulates SLC7A and inhibits β-amyloid deposits by increasing the mitochondrial transsulfuration of H₂S production. Full article

Methyl ethyl ketone (MEK) is among the most extensively utilized solvents in various industrial applications. In this study, we present a highly efficient synthesis route for MEK via the decarboxylation of biomass-derived levulinic acid, using potassium persulfate (K₂S₂O₈) and silver nitrate (AgNO₃) as key reagents. The specific roles of AgNO₃ and K₂S₂O₈ were thoroughly investigated. Additional silver species, such as Ag₂O and AgO, were also detected during the reaction. X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) analyses provided evidence of the evolution of solid phases throughout the reaction. Based on these findings, we propose a radical decarboxylation mechanism initiated by the generation of sulfate radicals (SO₄•⁻) through the catalytic breakdown of K₂S₂O₈ by AgNO₃. This mechanistic understanding, combined with a parametric study, enabled us to achieve an unprecedented level of levulinic acid conversion (97.9%) and MEK yield (86.6%) with this system, surpassing all previously reported results in the literature. Full article

Seed cakes, by-products from the cold press extraction of vegetable oils, are valuable animal feed supplements due to their high content of proteins, carbohydrates, and minerals. However, the presence of anti-nutrients, as well as the rancidification and development of aflatoxins, can impede their intended use, requiring alternative treatment and valorisation methods. Thermal treatment as a procedure for the conversion of seed cakes from walnuts, hemp, pumpkin, flax, and sunflower into valuable products or energy has been investigated in this paper. Thermogravimetry shows the particular behaviour of seed cakes, with several degradation stages at around 230–280 and 340–390 °C, before and after the typical degradation of cellulose. These are related to the volatilisation of fatty acids, which are either free or bonded as triglycerides, and with the thermal degradation of proteins. Torrefaction at 250 °C produced ~75–82 wt% solids, with high calorific values of 24–26 kJ/g and an energy yield above 90%. The liquid products have a complex composition, with most parts of the compounds partitioning between the aqueous phase (strongly dominant) and the oily one (present in traces). The structural components of seed cakes (hemicelluloses, cellulose, and lignin) produce acetic acid, hydroxy ketones, furans, and phenols. In addition to these, most compounds are nitrogen-containing aromatic compounds from the degradation of protein components, which are highly present in seed cakes. Full article

Heart failure (HF) is a growing concern due to the aging population and increasing prevalence of comorbidities. Despite advances in treatment, HF remains a significant burden, necessitating novel therapeutic approaches. Sodium–glucose cotransporter 2 inhibitors (SGLT2is) have emerged as a promising treatment option, demonstrating benefits across the entire spectrum of HF, regardless of left ventricular ejection fraction (LVEF). This review explores the multifaceted mechanisms through which SGLT2is exert cardioprotective effects, including modulation of energy metabolism, reduction of oxidative stress, attenuation of inflammation, and promotion of autophagy. SGLT2is shift myocardial energy substrate utilization from carbohydrates to more efficient fatty acids and ketone bodies, enhancing mitochondrial function and reducing insulin resistance. These inhibitors also mitigate oxidative stress by improving mitochondrial biogenesis, reducing reactive oxygen species (ROS) production, and regulating calcium-signaling pathways. Inflammation, a key driver of HF progression, is alleviated through the suppression of proinflammatory cytokines and modulation of immune cell activity. Additionally, SGLT2is promote autophagy, facilitating the clearance of damaged cellular components and preserving myocardial structure and function. Beyond their glucose-lowering effects, SGLT2is provide significant benefits in patients with chronic kidney disease (CKD) and HF, reducing the progression of CKD and improving overall survival. The pleiotropic actions of SGLT2is highlight their potential as a cornerstone in HF management. Further research is needed to fully elucidate their mechanisms and optimize their use in clinical practice. Full article

Aroma in food plays an important role in food perception and acceptance, which depends on various mixtures of volatile organic compounds (VOCs). Moreover, VOCs are of great significance for aroma identification. In this study, headspace solid-phase microextraction (HS-SPME) combined with gas chromatography–mass spectrometry (GC-MS) technology was used to determine the VOCs in 10 pear syrups. A total of 127 VOCs were quantitatively determined, including 9 common VOCs and 46 characteristic VOCs of 10 pear syrups. The pear syrups were divided into three categories by cluster analysis, and thirty-eight differential VOCs were obtained using orthogonal partial least squares discrimination analysis (OPLS-DA) and fourteen key VOCs were selected by odor activity value (OAV). It was revealed that the key and common aroma components of pear syrups were butanoic acid, methyl ester, 2-methyl-, methyl ester and Hexanoic acid, and ethyl ester. The characteristic and differential VOCs were 10-Undecen-1-ol, Hexadecanal, n-Propylacetate, Cyclohexanol, 5-methyl-2-(1-methylethyl)-, (1S,2R,5S)-, Methional, Disulfide, dimethyl, 8-Nonenoic acid, ethyl ester, Naphthalene, 1,2-dihydro-1,1,6-trimethyl-, 3H-Purin-6-amine, N,N,3-trimethyl-, 2-Octanol,2,6-dimethyl-, Furyl hydroxymethyl ketone, Heptane, 2,2,4,6,6-pentamethyl-, and Butanoic acid,2-methyl-,methyl ester. The above results showed that different pear syrups had rich diversity in aroma compounds, with some components being shared among them while others are exclusive to specific syrups. Full article

A novel and controllable synthesis of thioacetals/thioketals and β-sulfanyl ketones mediated by the reaction of aldehyde/acetone with thiols has been developed. In this protocol, β-sulfanyl ketones can be generated without the prior preparation of α, β-unsaturated carbonyl compounds. A variety of thiols reacted with aldehyde/acetone and provided the corresponding thioacetals/thioketals and β-sulfanyl ketones in good to excellent yields, respectively. This protocol is operationally simple, mild, and atom-economical, providing controllable access to thioacetals/thioketals and thia-Michael addition products under mild conditions. Full article

Lignin valorisation into chemicals and fuels is of great importance in addressing energy challenges and advancing biorefining in a sustainable manner. In this study, on the basis of the high microwave absorption performance of carbon nanotubes (CNTs), a series of copper-oxide-loaded CNT catalysts (CuO/CNT) were developed to facilitate the oxidative depolymerization of lignin under microwave heating. This catalyst can promote the activation of hydrogen peroxide and air, effectively generating a range of reactive oxygen species (ROS). Through the application of electron paramagnetic resonance techniques, these ROS generated under different oxidation conditions were detected to elucidate the oxidation mechanism. The results demonstrate that the ^•OH and O₂^•− play a crucial role in the formation of aldehyde and ketone products through the cleavage of lignin C_β-O and C_α-C_β bonds. We further evaluated the catalytic performance of the CuO/CNT catalysts with three typical lignin feedstocks to determine their applicability for lignin biorefinery. The bio-enzymatic lignin produced a 13.9% monophenol yield at 200 °C for 20 min under microwave heating, which was higher than the 7% yield via hydrothermal heating conversion. The selectivity of G-/H-/S-type products was slightly affected, while lignin substrate had a noticeable effect on the selective production. Overall, this study explored the structural characteristics of CuO/CNT catalysts and their implications for lignin conversion and offered an efficient oxidation approach that holds promise for sustainable biorefining practices. Full article

This review discusses the progress of research on sulfonated poly(ether ether ketone) (SPEEK) and its composite membranes in proton exchange membrane fuel cells (PEMFCs). SPEEK is a promising material for replacing traditional perfluorosulfonic acid membranes due to its excellent thermal stability, mechanical property, and tunable proton conductivity. By adjusting the degree of sulfonation (DS) of SPEEK, the hydrophilicity and proton conductivity of the membrane can be controlled, while also balancing its mechanical, thermal, and chemical stability. Researchers have developed various composite membranes by combining SPEEK with a range of organic and inorganic materials, such as polybenzimidazole (PBI), fluoropolymers, and silica, to enhance the mechanical, chemical, and thermal stability of the membranes, while reducing fuel permeability and improving the overall performance of the fuel cell. Despite the significant potential of SPEEK and its composite membranes in PEMFCs, there are still challenges and room for improvement, including proton conductivity, chemical stability, cost-effectiveness, and environmental impact assessments. Full article

Objectives: This study investigated the efficacy of wheat peptide supplementation compared to regular proteins in elite cross-country skiers, providing insights into the metabolic and performance effects of these supplements in order to guide athletes in selecting optimal energy sources for training and competition. Methods: Nineteen healthy male cross-country skiers were enrolled and assigned to either the peptide group (PEP, n = 9) or the protein group (PRO, n = 10). A four-week intervention study involving supplementation with wheat peptides/regular proteins was conducted, and pre- and post-intervention assessments were performed to evaluate exercise capacity and metabolic profiles. Results: The study found that the PEP group and the PRO group showed distinct within-group effects on exercise performance. The PEP group demonstrated improved aerobic capacity, including better performance in 10 km roller skating, an increased lactate threshold, and reduced resting blood lactate levels. The PRO group enhanced anaerobic capacity, such as improved sprint time, hexagon test performance, and lactate clearance. Metabolomic analysis revealed specific metabolic pathways affected in each group, with the PEP group showing impacts on the α-linolenic acid pathway and the PRO group on ketone body synthesis and degradation as well as vitamin B6 metabolism. Conclusions: Our findings indicate that wheat oligopeptides and regular proteins have comparable effects on exercise performance. However, the wheat peptides may offer greater advantages in enhancing aerobic capacity. No significant variations were observed in blood metabolite profiles between the two groups, but distinct metabolic pathways exhibited different responses. Full article

Background: Resistant starches, such as high-amylose maize starch and resistant potato starch (RPS), have prebiotic effects that are linked to improved metabolism at >15 g/day, but the effects at lower doses have not been reported. Methods: We performed an exploratory post hoc analysis of free fatty acids (FFAs), bile acids (BAs), and ketone bodies in serum previously collected from a randomized, double-blind, placebo-controlled clinical trial evaluating the effects of one- and four-week consumption of 3.5 g/day RPS versus a placebo using two-way ANOVA adjusted by pFDR. Associations between week 4 changes in FFAs, BAs, and ketone bodies were assessed by Pearson’s correlations. Results: RPS consumption reduced total FFAs relative to the placebo, including multiple unsaturated FFAs and octanedioic acid, with reductions in taurine- and glycine-conjugated secondary BAs also detected (q < 0.05). No changes in ketone bodies were observed (q > 0.05). Changes in 7-ketodeoxycholic acid (r = −0.595) and glycolithocholic acid (r = −0.471) were inversely correlated with treatment-induced reductions in FFAs for RPS but not the placebo, suggesting the effects were from the prebiotic. Shifts in β-hydroxybutyrate were further correlated with FFA changes in both treatments (q < 0.05). Conclusions: These findings demonstrate that low doses of RPS positively influence fatty acid metabolism in humans, reducing circulating levels of FFA and conjugated BAs. Full article