5-hydroxymethylfurfural Research Articles

Immobilization of Heteropolyacids on Zeolite Surface for Catalytic Conversion of Glucose to 5-Hydroxymethyl Furfural (5-HMF)

Immobilization of Heteropolyacids on Zeolite Surface for Catalytic Conversion of Glucose to 5-Hydroxymethyl Furfural (5-HMF)

Ru/TiO2 Catalyzed High‐Yield Synthesis of Furanic Diols by 5‐Hydroxymethylfurfural Hydrogenation with Switchable Selectivity

Abstract5‐Hydroxymethylfurfural (HMF) is a versatile platform molecule that can be derived from biomass feedstocks and catalytically converted into various value‐added chemicals. In this work, selective hydrogenation of HMF is investigated to produce valuable furan‐based diols, namely 2,5‐bis‐hydroxymethylfuran (BHMF) and 2,5‐bis‐hydroxymethyltetrahydrofuran (BHMTHF), using TiO2 supported Ru catalysts. The catalyst performance was fine‐tuned to achieve over 98% yield to BHMF and BHMTHF under optimized reaction conditions with very good recyclability. We pointed out several key factors allowing to maximize the yield towards the respective diols. Features such as the Ru nanoparticle size, the strength of metal‐support interactions and the presence of residual chlorine were found to significantly influence the reaction. A characteristic volcano‐shaped relationship was obtained between the particle size and the catalytic activity giving the highest diol yield for an optimum Ru nanoparticle size of 1.6 nm. Further, metal‐support interactions were found to be responsible for providing optimum Ru‐TiOx interfacial surface sites and chlorine was affecting the electronic properties of Ru nanoparticles, potentially benefiting to the selective formation of BHMF. The reaction time was shown to control the hydrogenation of the furan ring and the selectivity of the reaction, that can be directed optimally towards BHMF or BHMTHF.

Corrective role of endophytic exopolysaccharides from Clerodendrum infortunatum L. on arsenic-induced ovarian steroidogenic dysfunction and associated inflammatory responses

The present investigation aimed to evaluate the therapeutic potential of exopolysaccharides (EPSs) derived from endophytic fungi against arsenic [As(III)]-mediated metabolic and reproductive ailments. Two endophytic fungi, Diaporthe arengae (CleR1) and Fusarium proliferatum (CleR3), were isolated from Clerodendrum infortunatum (Cle), and used for the extraction of two types of EPSs. GC–MS analysis confirmed the presence of hydroxymethyl furfural (HMF) and α-d-glucopyranose in the EPS1 (CleR1) and EPS2 (CleR3), respectively. FTIR analysis revealed the potential As(III)-chelation properties of both EPSs. EPS1 and EPS2 significantly mitigated As(III)-induced oxidative stress and lipid peroxidation by restoring the activities of antioxidative enzymes. EPSs successfully corrected the gonadotropin imbalance and steroidogenic alterations. The downregulation of proinflammatory (NF-κB and TNF-α) and proapoptotic (BAX) mediators and the upregulation of antiapoptotic (Bcl-2) markers were also detected following the treatment with EPSs. Histomorphological restoration of reproductive and metabolic organs was also observed in both the EPS groups. Moreover, the As(III)-induced increase in the immunoreactivity of the androgen receptor (AR) was successfully reversed by these EPSs. Molecular docking predicted that HMF and α-d-glucopyranose of EPS1 and EPS2 interact with the active site of AR by limiting its activity. Hence, EPS could be effective for developing new therapeutic strategies for managing As(III) toxicity.

Antioxidant Property of Different Parts of Palmyra Palm (Borassus flabellifer): A Potential Nutraceutical Food

Worldwide, palmyra palm (Borassus flabellifer) is utilized in cuisine and is renowned for its many nutraceutical qualities, which include anticancer and antioxidant capabilities. There is a connection between cellular free radicals and diseases like atherosclerosis, cancer, and visual impairment. Antioxidants can support cell renewal and potentially lower these hazards. Using the DPPH method, the antioxidant capacity of methanolic extracts from different sections of the Palmyra palm was evaluated. Several nutraceutical substances, including 5-hydroxy methyl furfural, beta-D-glucopyranose 1,6-anhydride, linoleic acid ethyl ester, 9-octadeceneic acid ethyl ester, butylated hydroxytoluene, and stigmasterol, were identified by GC/MS analysis of the crunchy kernel's methanol and hexane extracts. The results show that the crunchy kernel is a valuable addition to food products and has strong antioxidant potential.

QUALITY EVALUATION OF PINE AND BLOSSOM HONEY SAMPLES PRODUCED IN TURKEY: CORRELATION BETWEEN PHYSICOCHEMICAL CHARACTERISTICS

This study presents physicochemical characteristics of 39 honey samples (21 blossom and 18 pine honey) collected during two years from three different geographical regions of Türkiye that differs vastly in climatic conditions and thus plant species. The samples were analysed for δ13C/δ12C stable carbon isotope ratios of honey (δ13Ch) and its protein fraction (δ13Cp), moisture, free acidity, proline and 5-hydroxymethyl furfural (HMF) content, diastase activity and sugar composition. The results showed that C4 sugar content, proline content, diastase activity, acidity values of pine honeys were higher than that of blossom honeys whereas, higher moisture and HMF content were detected for blossom honeys. Besides, geographical region mainly affected the moisture and C4 sugar contents. High correlations between HMF and δ13Ch and δ13Cp; proline and acidity values; fructose and glucose content were determined, and this indicated the robustness of the analysis and quality evaluation among different honey types and regions.

Citric acid/sucrose-modified pMDI for constructing high-performance straw particleboard based on multiple cross-linked networks

Polymeric diphenylmethane diisocyanate (pMDI) is an indispensable material used to produce straw particleboard. However, prolonged exposure to high concentrations of pMDI significantly increases the health risks to relevant professionals. Herein, we report a strategy for reducing safety hazards by partially replacing the pMDI with a bio-based adhesive. An adhesive with multiple cross-linked networks were synthesized using citric acid (CA), sucrose (SU), and pMDI first, and then applied to the preparation of straw particleboard. The amide and esterification reactions between the adhesives and rice straw particles form covalent bonds, enhancing boards adhesion and water resistance. Furthermore, acidic conditions provided by citric acid facilitate to convert SU into 5-hydroxymethyl furfural (5-HMF), which plays a positive role in straw adhesion. Adhesives made with 2.4 % pMDI, 8 %, and 4.8 % SU were used to bond particleboard, achieving internal bond strength, bending strength and elastic modulus of 0.57 MPa, 25.87 MPa, and 3.77 GPa, respectively, whose mechanical properties are comparable to the particleboard prepared with 4 % pMDI. The board showed superb mechanical performances, mould resistance, as well as water resistance. The CA/SU-modified pMDI adhesive system shows significant potential and promising application value in straw particleboard.

Phase effects in zirconia catalysed glucose conversion to 5-hydroxy methylfurfural.

5-(hydroxymethyl)furfural (HMF) is a key biomass derived platform chemicals used to produce fuel precursors or additives and value-added chemicals,synthesised by the cascade isomerisation of glucose and subsequent dehydration of reactively formed fructose to HMF over Lewis and Bronsted acid catalysts respectively. Zirconia is a promising catalyst for such reactions; however, the impact of acid properties of different zirconia phases is poorly understood. In this work, we unravel the role of the zirconia crystalline phase in glucose isomerisation and fructose dehydration to HMF. The Lewis acidic monoclinic phase of zirconia is revealed to preferentially facilitate glucose isomerisation, while the nanoparticulate tetragonal phase possesses Brønsted acid sites which favour fructose dehydration. Synergy between both zirconia phases facilitates cascade HMF production, with both catalysts investigated as physical mixtures in batch and flow reactor configurations. Usinga physical mixture of only 15 wt% m-ZrO2 with 85 wt% t-ZrO2 in either batch or packed bed reactor configuration is sufficient to reach equilibrium conversion of glucose for subsequent dehydration by the t-ZrO2 component. Under continuous flow, a six-fold increase in HMF production was obtained when operating with a physical mixture of m- and t-ZrO2 compared to that from a single bed of t-ZrO2.

Processing of Angelica (Angelica sylvestris L.) into a functional jam with addition of carob and cinnamon extracts: Evaluation of sensorial, physicochemical, and nutritional characteristics and in vitro bioaccessibility of phenolics

AbstractA traditional Angelica jam has been produced from stems of Angelica sylvestris L. growing at the foot of Mount Uludag in Bursa for many years. The aim of this study was to develop new functional formulations of Angelica jam by adding carob and cinnamon extracts, and to evaluate the effect of jam processing and the extracts' addition on the sensory attributes, physicochemical and nutritional characteristics of Angelica jams as well as in vitro bioavailability of phenolics. The main physicochemical properties of the jams including total water‐soluble dry matter (Brix value), pH, invert sugar content, total dietary fiber content, and 5‐(hydroxymethyl) furfural (HMF) ranged between 71.80–72.70 °Bx, 3.65–3.91, 39.30%–49.60%, 0.70–0.90 g/100 g, and 91.00–105.50 mg/kg, respectively. The most abundant minerals were potassium (K), calcium (Ca), magnesium (Mg), phosphorus (P), and iron (Fe) within a concentration range of 80.49–388.67 mg/kg, 111.10–135.00 mg/kg, 24.00–43.28 mg/kg, 7.57–28.06 mg/kg, and 0.52–1.14 mg/kg, respectively. Sensory analysis revealed that general acceptability of Angelica jams in a 9‐point hedonic scale was above 7. The highest antioxidant capacity values of Angelica jam and its functional forms fortified with carob and cinnamon extracts were obtained as 96.68 ± 11.30 mg TE/100 g DM, 248.49 ± 17.78 mg TE/100 g DM, and 193.11 ± 16.06 mg TE/100 g DM, respectively, with the ABTS (2,2′‐azino‐bis‐3‐ethylbenzothiazoline‐6‐sulfonic acid) method. It was observed that the main phenolic compound of the jams was caffeic acid. Depending on the type of extract added into the formulations, trans‐cinnamic acid and gallic acid (GA) became predominant phenolics. Total antioxidant capacity (TAC) of Angelica sylvestris stem decreased by 72%–85% with the heat treatment applied during jam processing. While total phenolic content (TPC) and total antioxidant capacity (measured by the DPPH (1,1‐diphenyl‐2‐picrylhydrazyl) method) increased as a result of intestinal digestion of the jam, it was observed that bioaccessibility of most of the phenolic compounds decreased after intestinal digestion of the jams.

Recent Trends in the Synthesis of Monomers for Furanoate Polyesters and Their Nanocomposites’ Fabrication as a Sustainable Packaging Material

Furanoate polyesters are an extremely promising new class of materials for packaging applications, particularly furanoate-based nanocomposites, which have gained a high interest level in research and development in both academia and industries. The monomers utilised for the synthesis of furanoate-based polyesters were derived from lignocellulosic biomass, which is essential for both eco-friendliness and sustainability. Also, these polyesters have a lower carbon footprint compared to fossil-based plastics, contributing to greenhouse gas reduction. The furanoate-based nanocomposites exhibit enhanced performance characteristics, such as high thermal stability, excellent mechanical strength, superior barrier resistance, and good bacteriostatic rate, making them suitable for a wide range of industrial applications, especially for food-packaging applications. This paper reviews the recent trends in the synthesis routes of monomers, such as the various catalytic activities involved in the oxidation of 5(hydroxymethyl)furfural (HMF) into 2,5-furandicarboxylic acid (FDCA) and its ester, dimethyl furan-2,5-dicarboxylate (DMFD). In addition, this review explores the fabrication of different furanoate-based nanocomposites prepared by in situ polymerization, by melt mixing or solvent evaporation methods, and by using different types of nanoparticles to enhance the overall material properties of the resulting nanocomposites. Emphasis was given to presenting the effect of these nanoparticles on the furanoate polyester’s properties.

Hydrochar and Value-Added Chemical Production Through Hydrothermal Carbonisation of Woody Biomass

This study investigates the optimisation of hydrothermal carbonisation (HTC) parameters for transforming Whitewood biomass into hydrochar, focusing on bioenergy production and valuable chemical extraction as by-products. The optimal carbonisation was achieved at a process temperature of 240 -260 °C, which optimised the higher heating value of the hydrochar to 27-30 kJ/g and ensured a structural integrity similar to lignite coal. Increasing the temperature beyond 260 °C did not significantly enhance the energy content or quality of the hydrochar, establishing 260 °C as the practical upper limit for the HTC process. Residence times between 30 to 60 min were found to have minimal impact on the yield and quality of hydrochar, suggesting significant operational flexibility and the potential to double throughput without increasing energy consumption. The study also revealed that the process water by-product is rich in furan compounds, particularly furfural and hydroxymethyl furfural, with their highest concentration (125 mg/g of feedstock) occurring at 220 °C. The implementation of these findings could facilitate the development of a large-scale HTC facility, significantly reducing reliance on fossil fuels and enhancing economic viability by producing high-energy-density biofuels and high-value chemical by-products.

Novel class of aldehyde reductases identified from Scheffersomyces stipitis for detoxification processes in cellulosic ethanol production industry

The increase in industrialization has led to a significant energy crisis, sparking interest in lignocellulosic biomass for fuel ethanol production because of its renewable characteristics. The complex composition of this biomass requires pretreatment to reduce inhibitors like furfural and hydroxymethylfurfural (HMF), which hinder enzymatic hydrolysis and fermentation, ultimately decreasing ethanol yields. This study investigates the detoxification mechanisms of furan aldehydes in Scheffersomyces stipitis, particularly through the upregulation of genes SsOYE2.2, SsOYE2.7, and SsOYE3.1 under furfural and HMF stress. Enzyme characterization determined that SsOye3.3p is the most active enzyme for reducing both compounds using NADPH. Notably, SsOye2.6p showed the highest catalytic efficiency towards furfural, while SsOye2.8p was optimal for HMF. The study also established the optimal temperature and pH for these enzymatic reactions. Importantly, SsOye2.5p displayed broad substrate specificity, indicating its potential in detoxifying various aldehydes in microbial cells. The findings suggest that genes linked to enhanced enzymatic properties were not significantly induced, indicating that S. stipitis has more substantial potential for furan aldehyde detoxification and can be developed as a chassis organism exhibiting furan aldehyde tolerance. These insights facilitate the development of novel enzymes to counter furan aldehyde inhibitors and the creation of furan aldehyde-tolerant strains via genetic engineering.

Kinetics of Colour, Clarity Changes and HMF Formation in Pear Juice Concentrate During Storage

In terms of providing delicious taste and excellent source of nutritional content, pears are highly consumed fruit all around the world. Pear juice concentrate (PJC) is one of the most frequently used products in the manufacturing processes of beverages, syrup base for canning fruits, vinegar, and wine. Colour, clarity, and the formation of hydroxy methyl furfural (HMF), a mark of Maillard browning reactions, were appraised as quality indices changes of PJC throughout storage. The samples were kept at 47°, 37°, and 27°C for 32 weeks and kinetic criteria were calculated for changes in color, clarity, and the generation of HMF. According to the model of zero-order reaction, the results demonstrated that the quantity of HMF rose linearly with temperature and storage period. The values of clarity and colour were both linearly reduced to align with the zero-order reaction kinetic. The dependence on temperature of the rate constant of the reactions examined and the activation energy values were calculated as 153.14, 93.81 and 61.48 kJ mol-1 for the generation of HMF, clarity, and colour changes with the help of Arrhenius equation.

Comparative analysis of LAB and non‐LAB fermented millet drinks fortified with Chlorella sp.

AbstractThis study investigates the expanding domain of functional beverages crafted from plant‐based milk alternatives. In this study, a total of eight different fermented drinks fortified with beneficial Chlorella sp. and probiotics including Lactobacillus rhamnosus (NCIM 5775) and Saccharomyces cerevisiae (Brewer's yeast) drinks were developed using barnyard millet as the base ingredient due to its rich protein and high‐fibre content in comparison with the other millets in the market. Results revealed that the protein content increases by 2% upon the addition of Chlorella sp., among bacterial samples, with Lactobacillus rhamnosus fermented Unflavoured drink (LRFFD) > Lactobacillus rhamnosus fermented flavoured drink > Lactobacillus rhamnosus fermented with Chlorella sp. > LRFM, and among yeast samples, with Saccharomyces cerevisiae fermented Unflavoured drink (SCFUFD) > Saccharomyces cerevisiae fermented with Chlorella sp. > Saccharomyces cerevisiae fermented flavoured drink (SCFFD) > SCFRM, indicating higher protein content than in typical fermented drink. Fat content was notably low across all samples. Ash and fibre content ranged from 0.23 to 0.27 g and 0.22 to 0.35 g, respectively, for both bacterial and yeast fermented drink. Millet is generally considered a carbohydrate‐rich grain. When fermented, some of the carbohydrates may be broken down by the fermentation process. So, the carbohydrate content was low in fermented millet drink when compared to the nonfermented drink. Energy values varied, with LRFFD and SCFFD containing the highest energy due to incorporation of Chlorella sp. and chocolate flavour. Both LAB and yeast‐fermented drinks demonstrated effective antioxidant activity, with higher total phenolic content, except for non‐Chlorella sp. beverages. GC‐MS analysis identified constituents like hexadecenoic acid and hydroxy methyl furfural (HMF) with anticarcinogenic and anti‐inflammatory properties. Additionally, these samples exhibited elevated antimicrobial activity against test strains. Sensory analysis indicated a preference of SCFFD and LRFFD sample for its good taste as it contains chocolate flavour and the overall acceptability of bacterial fermented beverage was higher compared to the yeast fermented drinks. Therefore, a fermented millet beverage was successfully obtained by the coculture of LAB and Saccharomyces cerevisiae incorporated with Chlorella sp. could increase the product's functional properties.

Reactivity assessment of oligomeric systems associated with crystalline and amorphous cellulose for bioethanol production: a DFT study.

The production of bioethanol from renewable raw materials is a decisive factor in the economic development of many countries. However, the complexity of the processes and the numerous experimental variables involved require a deeper understanding of the chemical reactions that take place during bioethanol production to define optimal parameters. Here, we have employed density functional theory-based calculations to investigate the local reactivity of oligomeric systems by consideringcrystalline and amorphous cellulose models to better understand some details regarding pulp pretreatment processes. Our results evidence a higher chemical susceptibility of amorphous portions of cellulose to chemicals typically employed in acid hydrolysis. Additionally, we observed that glucose monomers coming from cellulose hydrolysis may undergo oxidation, leading to the formation of byproducts such as hydroxymethylfurfural (HMF), acetic acid, formic acid, and levulinic acid. The analysis of local chemical softness indexes indicated that cellulose hydrolysis may be associated with intermediate chemical steps. Finally, we investigated the influence of distinct solvents (dielectric constants) on the local reactivity of the systems, evidencing a relevant role of the solvent dielectric constant for cellulose degradation in glucose. Initial three-dimensional structures were constructed. Pre-optimizations were performed in a Hartree-Fock (HF) approach employing thePM7 semi-empirical hamiltonian. The structures were then re-optimized via density functional theory (DFT). The local reactivity study of the systems was conducted through the condensed-to-atoms Fukui indexes (CAFI). Systematic changes of the dielectric constants were also considered in geometry optimization and CAFI calculations to estimate the influence of solvents on the reactivity of the systems.

Hydroxymethylfurfural adsorption modulating charge separation characteristics of carbon-rich carbon nitrides for simultaneous photocatalytic hydrogen evolution and 2,5-diformylfuran production

Carbon-rich melon-based carbon nitrides (CNs), in which the sp2 N atoms and the terminal C–NH2 within the heptazine rings are partially replaced by the graphitic carbon atoms and C–H terminals, respectively, are synthesized through the condensation of 2,4,6-triaminopyrimidine-added supramolecular complexes comprising melamine and cyanuric acid. Optical characterizations reveal that increasing the C/N ratio in CNs improves their light-harvesting and charge-separation capabilities. Nevertheless, the photocatalytic activities of carbon nitrides reach an optimal level at an appropriate C/N ratio for simultaneous H2 evolution and 2,5-diformylfuran (DFF) production from 5-(hydroxymethyl)furfural (HMF) aqueous solution. Hydrogen evolution from water and DFF production by selective HMF oxidation are driven by photogenerated electrons and holes, respectively. Density functional theory calculations suggest that the adsorption of HMF on carbon-CN dramatically influences the molecular orbital contributions to the lowest singlet excited state, altering its charge separation character and, consequently, the photocatalytic activity. The improvement of charge separation in the optimized CN by HMF adsorption is further confirmed by experimental measurements.

Mechanism insight into α-D-galactopyranose conversion to 5-hydroxymethyl furfural by combining Py-GC–MS experiments and theoretical calculations

Pyrolysis of biomass is a promising technique for producing various chemicals. During the fast pyrolysis of biomass, 5-hydroxymethyl furfural (5-HMF) is a significant product derived from holocellulose, which consists of cellulose and hemicellulose. In this study, the formation mechanism of 5-HMF was systematically revealed by combining fast pyrolysis experiments of 13C-labeled and unlabeled D-galactose and density functional theory calculations that α-D-galactopyranose was selected as the model compound for hemicellulose. Experimental results show the yield and concentration of 5-HMF gradually decrease as the temperature rises (≥400 °C). In addition, the origin of the C atoms in 5-HMF was determined. The aldehyde group and hydroxymethyl are primarily derived from C1 and C6 of D-galactose, respectively. Based on computational results, α-D-galactopyranose prefers to undergo a ring-opening reaction to form acyclic D-galactose with an energy barrier of 166.5 kJ/mol. (2R,3S,E)-2,3,5,6-tetrahydroxyhex-4-enal (C1-i2) and (2R,3S)-2,3,6-trihydroxy-5-oxohexanal (C1-i3) generated by D-galactose are important intermediates for 5-HMF formation. Because C1-i3 can readily form 5-HMF through successive dehydration at 3-OH+2-H site, cyclization, and dehydration at 5-OH+4-H site. In favorable paths, the aldehyde group of 5-HMF all comes from C1 of α-D-galactopyranose, which reasonably explains the experimental results. Overall, this study will be helpful to improve the formation mechanism of 5-HMF and to develop relevant pyrolysis techniques to prepare it.

Detection of adulteration in Iranian grape molasses added glucose/fructose/sugar beet syrups with 13C/12C isotope ratio analysis method.

Grape molasses (GM), produced from grapes, is a traditional Iranian food and is widely consumed in Iran. However, GM adulteration is among the most widespread illegitimate procedures involving contamination of food with foreign materials, such as adding sugar-water solution, date syrup, sugar beet syrup, and grape sauce. This study used stable carbon 13C/12C isotope ratio analysis method to detect adulteration of GM samples with glucose syrups (GS), fructose syrups (FS), and beet sugar syrups (BS) at the ratio of 0%, 10%, 30%, and 50% (by weight). Physicochemical properties of GM including °Brix, conductivity, specific gravity, pH, moisture content, ash content, hydroxymethyl furfural, sugar content, and rheological properties of samples were investigated. The δ13C isotope ratio of the GM was determined as -26.61%, that of the GS as -13.23%, that of the FS as -13.42%, and that of the BS as -16.58%. The δ13C isotope ratio increased by the addition of adulterant syrups to GM. The addition of each adulterant syrup had a different effect on the physicochemical parameters; however, the °Brix and specific gravity had a positive correlation with the δ13C isotope ratio results. The magnitudes of G' and G" increase with an increase in frequency representing the viscoelastic behavior of samples. The obtained results of this study suggest the use of δ13C isotope ratio method as a fast and accurate method to investigate the adulteration of grape molasses.

Pyrolytic conversion of glucose into hydroxymethylfurfural and furfural: Benchmark quantum-chemical calculations.

Quantum chemical methods have been intensively applied to study the pyrolytic conversion of glucose into hydroxymethylfurfural (HMF) and furfural (FF). Herein, we collect the most relevant mechanistic proposals from the recent literature and organize them into a single reaction network. All the transition structures (TSs) and intermediates are characterized using highly accurate ab initio methods and the possible reaction pathways are assessed in terms of the Gibbs energies of the TSs and intermediates with respect to β-glucopyranose, selecting a 2D ideal-gas standard state at 773 K to represent the pyrolysis conditions. Several pathways can lead to the formation of both HMF and FF passing through rate-determining TSs that have ΔG‡ values of ~49-50 kcal/mol. Both water-assisted mechanisms and nonspecific environmental effects have a minor impact on the Gibbs energy profiles. We find that the HMF → FF + CH2O fragmentation has a small ΔrxnG value and an accessible ΔG‡ barrier. Our computational results, which are in consonance with the kinetic parameters derived from lumped models, the results of isotopic labeling experiments and the reported HMF/FF molecular ratios, could be useful for modeling studies including on nonequilibrium kinetic effects that may render more information about product yields and the relevance of the various pathways.

Study of authenticity, quality characteristics and bioactivity in honey samples from different botanical origins and countries

Honey is a widely consumed commodity featuring beneficial nutritional properties resulting in a high market price. Therefore, honey is a target of fraudulent practices and analytical strategies to assess honey quality and origin are highly needed. Within this context, we performed a comprehensive analytical testing for 39 honey samples originating from Greece and other countries. Analytical parameters related to honey quality control (Directive 2001/110/EC) were monitored. In detail, hydroxymethylfurfural (HMF) and diastase activity were measured using spectrophotometric assays. Importantly, 6 samples imported by the American market exceeded the regulatory limit (40 mg/kg). The content of the main honey sugars was monitored using an accredited ultra-high-performance liquid chromatography coupled to evaporative light scattering detector (UHPLC-ELSD) and all samples were in line with the regulatory standards. In addition, chromatographic analysis was performed to determine 23 phenolic compounds as these are bioactive compounds contributing towards the health promoting effects of honey. Besides chemical characterisation, in vitro testing was also performed by monitoring the inhibitory effect of the honey samples towards acetylcholinesterase (AChE) and pancreatic lipase (PNLIP). Indeed, inhibition was noticed and in the case of PNLIP the monitored differences between Greek and samples from other countries were statistically significant. To assess honey sample authenticity, chemometric tools were employed, namely, principal component analysis (PCA), hierarchical cluster analysis (HCA) and linear discriminant analysis (LDA). The multivariate analysis revealed that the taxifolin content may be used as a marker for thyme honey from Cyprus while the total content of gallic and protocatechuic acids could be used as a marker for oak honeys. All in all, implementing several different methods based on different principles (both physicochemical and bioanalytical) in a complex analytical matrix such as honey is a great analytical challenge that we successfully faced and comprehensively demonstrated in this study.

Model-Assisted Optimization of Xylose, Arabinose, Glucose, Mannose, Galactose and Real Hemicellulose Streams Dehydration To (Hydroxymethyl)Furfural and Levulinic Acid.

Conversion of hemicellulose streams and the constituent monosaccharides, xylose, arabinose, glucose, mannose, and galactose, was conducted to produce value-added chemicals, including furfural, hydroxymethylfurfural (HMF), levulinic acid and anhydrosugars. The study aimed at developing a kinetic model relevant for direct post-Organosolv hemicellulose conversion. Monosaccharides served as a tool to in detail describe the kinetic behavior and segregate contribution of hydrothermal decomposition and acid catalyzed dehydration at the temperature range of 120-190 °C. Catalyst free aqueous media demonstrated enhanced formation of furanics, while elevated temperatures led to significant saccharide isomerization. The introduction of sulfuric and formic acids maximized furfural yield and significantly reduced HMF concentration by facilitating its rehydration into levulinic acid (46 mol%). Formic acid additionally substantially enhanced formation of anhydrosaccharides. An excellent correlation between modeled and experimental data enabled process optimization to maximize furanic yield in two distinct hemicellulose streams. Sulfuric acid-containing hemicellulose stream achieved the highest furfural yield after 30 minutes at 238 °C, primarily due to the high Ea for pentose dehydration (150-160 kJ mol-1). Contrarily, formic acid-containing hemicellulose stream enabled maximal furfural yield at more moderate temperature and extended reaction time due to its lower Ea for the same reaction step (115-125 kJ mol-1).