5-hydroxymethylfurfural Research Articles

Effect of Temperature and Time on the Physicochemical and Sensory Properties of Crystallized Honey.

This research explores the crystallization process of honey during storage with a focus on its dissolution dynamics and essential characteristics. The investigation includes the examination of the effects of heat treatment at different temperatures (45-90 °C) and durations (23-960 min) on the induced crystallization of honey at 14 °C. Various analyses were conducted, including pH, acidity, color, sugar profile, phenolic and flavonoid contents, DPPH-scavenging activity, hydroxymethylfurfural (HMF), viscosity, and sensory attributes. The results indicated a reduction in the moisture content and pH, an increase in acidity, and higher levels of HMF at elevated temperatures. While the ash content remained relatively unchanged, variables such as color, glucose, fructose, total phenol, flavonoid, and antioxidant content exhibited variations with temperature. Viscosity decreased with an increase in temperature, suggesting Newtonian behavior and implying potential colloidal changes. Consumer sensory tests revealed significant differences among samples, with honey treated at 75 °C demonstrating superior physicochemical and sensory attributes. This study offers valuable insights into the dynamics of crystallized honey, providing information for both production practices and understanding consumer preferences.

Transfer learning in near infrared spectroscopy for stingless bee honey quality prediction across different months

Near infrared spectroscopy (NIRS) coupled with machine learning has demonstrated its capability as an efficient secondary measurement method in various applications. However, a NIRS predictive model might be unable to maintain its accuracy when it is applied to samples that were acquired from different periods. Particularly, the qualities of stingless bee honey are affected by various uncontrolled factors, e.g. ecosystem, origins, and weather. Since it is unrealistic to have a NIRS dataset that can represent unforeseen future changes, an algorithm that can adapt existing data for new samples is worth to be investigated. Thus, this study aims to evaluate the feasibility of homogenous transfer learning approaches to overcome data constraints in developing NIRS predictive models of stingless bee honey qualities across different months. First, the near infrared transmittance spectra were acquired across honey samples prior to their respective conventional quality measurements in four different analysis months. Then, data from different analysis months were used as source and target datasets. Next, joint distribution adaptation based partial least square (JDA-PLS) and transfer component analysis based PLS (TCA-PLS) were implemented to establish NIRS predictive models of moisture, hydroxymethylfurfural (HMF), and glucose quality. Results show that the proposed TCA-PLS outperformed JDA-PLS and PLS by achieving the lowest RMSEP of 3.401 % and 0.804 mg/kg in predicting the moisture and glucose of stingless bee honey, respectively, across different months. Lastly, finding shows that both JDA and TCA were inefficacy when the label distributions of the calibration and validation datasets were similar.

THE THERMAL OF PHYTOCHEMICALS AND PHYSICOCHEMICAL PROPERTIES OF KIRAZ AND FINDIK CHERRY LAUREL FRUITS STABILITY (LAUROCERASUS OFFICINALIS L.) AND THEIR MOLASSES

This study aimed to investigate the thermal stability of certain phytochemicals in molasses at temperatures of 50°C, 60°C, and 70°C throughout 6 to 168 hours. Additionally, the chemical makeup of Kiraz (KCLM) and Fındık (FCLM) cherry laurel (Laurocerasus officinalis L.) fruits, as well as their molasses, was examined. The two molasses compositions were different due to the type of fruit used. The soluble dry matter (SDM) and dry matter (TDM) of the molasses ranged from 68.0-68.2% and 72.3-73.1%, respectively. The FCLM had higher values for titratable acidity (TA) (1.201%), hydroxymethylfurfural (HMF) (22.72 mg/kg), Vitamin C (66.83 mg/100 g), phenolics (TP) (5359 mg GAE/100 g), anthocyanin (ACN) (45.27 mg/kg), DPPH-RSA (80%), antioxidant capacity (AC) (33.74 µg TE/g), Hunter L* (31.34), a* (0.96), b* (-0.59), and browning level (BL) (15.20) compared to KCLM. The ANOVA results showed that cultivars, temperature, and storing time significantly affected phytochemicals and physicochemical properties (P <0.05).

Base-free synthesis of renewable furan-2,5-dicarboxylic acid (FDCA) over an earth-abundant magnetic catalyst

Being a biobased alternative to petroleum-based terephthalic acid (TPA), furan-2,5-dicarboxylic acid (FDCA) requires a low-cost and efficient catalytic system for its commercialization. This study describes FDCA production using whey permeate powder (WPP)-derived 5-(hydroxymethyl)furfural (HMF) in a base-free system over a magnetically recyclable catalyst composed of earth-abundant metals (Mn and Fe). The impact of MnCl2·4 H2O loading on the iron core was studied at different levels and found optimal at the ratio of 1:1. The in-situ oxidation of HMF was carried out using ozone and t-BuOOH as the oxidants in a γ-valerolactone (GVL) -water solvent system. It was observed that the ozone pre-treatment (3 h at room temperature) of HMF increased the FDCA yield from 39.7 % (without ozonation) to 60 % at a reaction condition of 130 °C for 2 h. The concentration profiles for the intermediates formed during HMF to FDCA oxidation i.e., 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), furan-2,5-dicarbaldehyde (DFF), and 5-formyl-2-furancarboxylic acid (FFCA) were analyzed at different reaction temperatures to evaluate the reaction kinetics. The kinetic study revealed that the present solvent-catalytic system favored HMFCA formation over DFF due to the requirement of higher activation energy for the latter. The HMF to FDCA catalytic solvent was tested for WPP, which afforded an overall FDCA yield of 14.6 % at 130 °C in 120 min. In addition, the Mn1Fe1 consisted of mixed phases of Mn3O4, Mn2O3, MnO2, Fe2O3, and Fe3O4 and demonstrated variation in oxidation states for Mn (Mn3+↔Mn2+) and Fe (Fe2+↔Fe3+) species.

Feedstock/pretreatment screening for bioconversion of sugar and lignin streams via deacetylated disc-refining

Recent publications have shown the benefits of deacetylation disc-refining (DDR) as a pretreatment process to deconstruct biomass into sugars and lignin residues. Major advantages of DDR pretreatment over steam and dilute acid pretreatment are the removal of acetyl and lignin during deacetylation. DDR does not generate hydroxymethylfurfural (HMF) and furfural which are commonly produced from steam and dilute acid pretreatments. Acetate, lignin, HMF, and furfural are known inhibitors during enzymatic hydrolysis and fermentation. Another advantage of deacetylation is the production of lignin-rich black liquor, which can be upgraded to other bioproducts. Furthermore, due to the lack of sugar degradation during deacetylation, DDR has significantly less sugar loss than other pretreatment methods. Previous studies for DDR have primarily focused on corn stover, but lacked the investigative studies of other feedstocks. This study was designed to screen various DDR process conditions at pilot scale using three different feedstocks, including corn stover, poplar, and switchgrass. The impact of the pretreatment conditions was evaluated by testing hydrolysates for bioconversion to 2,3-butanediol. Pretreatment of biomass by DDR showed high-conversion-yields and 2,3-BDO fermentation production yields. Techno-economic analysis (TEA) of the pretreatment for biomass to sugar was also developed based on NREL’s Aspen Model. This study shows that the cellulose and hemicellulose in poplar was more recalcitrant than herbaceous feedstocks which ultimately drove up the sugar cost. Switchgrass was also more recalcitrant than corn stover but less than poplar.

Physicochemical and antioxidant properties of Apis cerana honey from Lombok and Bali Islands.

Limited honey production worldwide leads to higher market prices, thus making it prone to adulteration. Therefore, regular physicochemical analysis is imperative for ensuring authenticity and safety. This study describes the physicochemical and antioxidant properties of Apis cerana honey sourced from the islands of Lombok and Bali, showing their unique regional traits. A comparative analysis was conducted on honey samples from Lombok and Bali as well as honey variety from Malaysia. Moisture content was found slightly above 20% in raw honey samples from Lombok and Bali, adhering to the national standard (SNI 8664:2018) of not exceeding 22%. Both honey types displayed pH values within the acceptable range (3.40-6.10), ensuring favorable conditions for long-term storage. However, Lombok honey exhibited higher free acidity (78.5±2.14 meq/kg) than Bali honey (76.0±1.14 meq/kg), surpassing Codex Alimentarius recommendations (≤50 meq/kg). The ash content, reflective of inorganic mineral composition, was notably lower in Lombok (0.21±0.02 g/100) and Bali honey (0.14±0.01 g/100) compared to Tualang honey (1.3±0.02 g/100). Electric conductivity, indicative of mineral content, revealed Lombok and Bali honey with lower but comparable values than Tualang honey. Hydroxymethylfurfural (HMF) concentrations in Lombok (14.4±0.11 mg/kg) and Bali (17.6±0.25 mg/kg) were slightly elevated compared to Tualang honey (6.4±0.11 mg/kg), suggesting potential processing-related changes. Sugar analysis revealed Lombok honey with the highest sucrose content (2.39±0.01g/100g) and Bali honey with the highest total sugar content (75.21±0.11 g/100g). Both honeys exhibited lower glucose than fructose content, aligning with Codex Alimentarius guidelines. The phenolic content, flavonoids, and antioxidant activity were significantly higher in Lombok and Bali honey compared to Tualang honey, suggesting potential health benefits. Further analysis by LC-MS/MS-QTOF targeted analysis identified various flavonoids/flavanols and polyphenolic/phenolic acid compounds in Lombok and Bali honey. The study marks the importance of characterizing the unique composition of honey from different regions, ensuring quality and authenticity in the honey industry.

Removal of phenolic inhibitor compounds from hydrolysates and post-fermentation broths by using a hydrophobic magnetic deep eutectic solvent

Hydroxymethylfurfural (HMF), furfural (FF), hydroquinone (HQ), and vanillin (VAN) are among the main inhibitors generated during most of biomass pre-treatments prior to fermentation processes. They are recognized as toxic to several fermentative microorganisms and therefore cause a decrease in biohydrogen or biofuel production (after hydrolysis). Moreover, if they are released into aqueous solutions (after fermentation), they can be detrimental to the ecosystem. In this research, a new method for removing these inhibitor compounds from the broth after hydrolysis and fermentation is proposed. A hydrophobic magnetic deep eutectic solvent (HMDES), based on menthol: nonanoic acid in a mole ratio of 2:1 was prepared and magnetized with Fe3O4 nanoparticles and applied for effective sorption and removal of these inhibitors from the broth after fermentation and for biomass hydrolysates. Parameters affecting sorption, such as pH, volume of the inhibitors, initial concentration of inhibitors, volume of HMDES, temperature, stirring speed, and contact time, were studied and optimized. Under optimum conditions, the removal efficiency for HQ, HMF, FF, and VAN was obtained as 92.97, 86.72, 82.86 and 95.12% for the model samples. In addition, the removal efficiency of real samples after hydrolysis and fermentation for HQ, HMF, FF and VAN were higher than 83.3, 71.42, 69.99 and 76.80%, respectively. The studies on HMDES regeneration revealed that the removal efficiency remained constant even after undergoing 13 cycles of regeneration. The mechanism of inhibitor removal suggests that hydrogen bonding or van der Waals interactions may serve as the predominant factor influencing the extraction process.

Kinetics of Nonenzymatic Browning Reactions in Pumpkin Puree During Storage

Pumpkins (Cucurbita moschata) are a great source of essential nutrients counting vitamins, minerals, carotenoids, and dietary fiber. Due to their healthy composition, it draws consumer attention. Pumpkin puree is used for preparation of baby foods, soups, flour, jam, jellies, and desserts. To assess the main quality parameters of the foods such as color and hydroxymethylfurfural (HMF) formation, CIE-L*a*b* color changes and HMF formation which is also an indicator of Maillard browning reactions were evaluated storing the pumpkin puree at 27°, 37° and 47°C for 17 weeks. Kinetic parameters for HMF formation and color changes were calculated. The findings showed that HMF quantity linearly increased with the temperature and storage duration following the reaction model of zero order. The values of b* coordinate, Lightness, Chroma, and hue lessened linearly as a* coordinate values increased linearly fitting zero order reaction kinetic. By means of Arrhenius equation, the temperature dependency of the rate constant of color variation was demonstrated and the values of the activation energy (kj mol-1) were calculated as 76.15, 30.60, 46.08, 28.44, 27.61 and 38.32 for HMF formation, Lightness, a* coordinate, b* coordinate, Chroma, and hue, respectively.

Efficient and sensitive determination of storage time-temperature marker 5-hydroxy methyl furfural in bee honey based on Fluorescence quenching of human serum albumin

5-hydroxymethyl furfural (HMF) exhibits mutagenic and DNA strand-breaking activity. It is a useful tool to evaluate the effect of heat and time on foodstuffs processing. The fluorescence interaction of HMF with HSA has not been explored to date. Therefore, this work reports the interaction mechanism of HMF with HSA via fluorescence spectroscopy analysis in a simulated physiological environment. The experimental tries showed that HMF intensely quenched the native fluorescence of HSA via the dynamic quenching. According to fluorescence quenching calculations, the binding constants Kb are 1.26x10-4, 2.71x10-4 and 3.19x10-4 M-1 at 298, 303 and 308 K respectively, and the number of binding sites n is almost 1. Thermodynamic parameters values expose that both electrostatic and hydrophobic interactions are accountable for the interaction of HSA and HMF. The presented quenching method for the assay of HMF exhibited a good linearity in the range of 0.1 to 6.66 µg/mL with a detecting limit of 0.0184 µg/mL. These values made the developed method appropriate to be used in the estimation of HMF in samples of bee honey after its extraction using SupelcleanTM ENVI™ -18 SPE Tube. Five bee honey samples show a positive response of HMF after exposing these samples for inappropriate storage or extreme heating.

Regioselectivity and confinement effects for catalytic conversion of carbohydrates within zeolite H-BEA

Zeolites have established the importance during biomass conversion, and H-form zeolites, although extensively used, produce hydroxymethylfurfural (HMF) with low yields. Herein, dispersion-corrected density functional calculations are employed with aim to comprehensively understand glucose conversion to HMF within zeolite H-BEA and unravel the role of confinement effects. The low HMF yields originate from regioselectivity: The preferentially activated O3 and O6 sites are significantly driven to humin precursors, while less reactive O1 and O2 sites lead favorably to HMF. Glucose-to-fructose isomerization occurs only at O5 site, while seems unnecessary for HMF production. Owing to the peculiar confinement effects, HMF precursors are prone to emerge within H-BEA, both upon dehydration and during catalysis, while may turn to be acyclic within aqueous solutions. Direct conversion to levulinic acid without HMF as intermediate thus becomes difficult within acidic zeolites. Results facilitate catalyst design for biomass conversion, and further understanding of regioselective catalysis and confinement effects.

Single Laboratory Validation of Four Methods for Quantification of HMF in Honey

Hydroxymethylfurfural or 5-(hydroxymethyl)-2-furaldehyde (HMF) has been absent or found in honey naturally at very low amount. It is formed in honey mainly by heating process and improper storage conditions. HMF has been reported to have cytotoxic, carcinogenic, and mutagenic effects and thus regulatory agencies in many countries impose restrictions on its maximum levels in honey. Validated methods have been required for effective and specific detection and quantification of HMF in food samples. In this study, a single laboratory validation study was conducted on four quantification methods: direct spectral analysis, High Performance Liquid Chromatography (HPLC) analysis, Seliwanoff and Winkler methods. All methods showed linearity with the lowest R2 value of 0.992. Two method performance parameters, accuracy, and precision were satisfied by each four methods with recovery values at 98.2%, 100.2%, 102.5% and 103.3% and RSDr (relative standard deviation) % values at 6.97%, 6.19%, 2.87% and 0.90% for spectral analysis, Seliwanoff, HPLC and Winkler methods, respectively. Based on the measurement uncertainties of four quantification methods, honey samples spiked with HMF at the final concentration of 0.004mg/0.1g were reported as 0.004 mg/0.1g ± 0.00025 mg/0.1g by spectral analysis, 0.0036 mg/0.1g ± 0.000691 mg/0.1g by Seliwanoff method, 0.004 mg/0.1g ± 0.00045 mg/0.1g by HPLC and 0.0039 mg/0.1g ± 0.00022 mg/0.1g by Winkler methods (k=2, confidence level of 95%). The validated methods can quantify HMF in honey with a target concentration of 0.004 mg/0.1g, specifically and accurately.

A Closed-Loop Biorefinery Approach for the Valorization of Winery Waste: The Production of Iron-Sulfonated Magnetic Biochar Catalysts and 5-Hydroxymethyl Furfural from Grape Pomace and Stalks

In this work, a closed-loop strategy for the management and valorization of winery waste was proposed. The exhausted pomace and grape stalks that are typically obtained from white wine industries were used as a source of simple sugars, namely, glucose and fructose, and of lignocellulosic feedstock for the preparation of selective catalysts for the 5-hydroxymethylfurfural (5-HMF) production from fructose. A novel synthetic procedure was developed for the synthesis of iron-sulfonated magnetic biochar catalysts (Fe-SMBCs). Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), BET surface area, porous structure analysis and determination of total amount of acid sites were performed in order to characterize the physico-chemical properties of the synthesized systems. Then, these heterogeneous catalysts were successfully tested via the dehydration of simple sugars into 5-HMF by using methyl isobutyl ketone (MIBK) and gamma valerolactone (GVL) as co-solvents. The optimum 5-HMF yield of 40.9 ± 1.1%mol with a selectivity of 59.8 ± 2.6%mol was achieved by adopting the following optimized conditions: 0.1 g of catalyst, volume ratio of GVL to H2O = 2 to 1, 403 K, 6 h. In addition, the catalyst was easily recycled using an external magnetic field and used for at least five reaction cycles without significant loss of catalytic activity.

Pushing the Efficiency of the Selective and Base‐Free Air‐Oxidation of HMF by Varying the Properties of Carbon‐Based Supports

AbstractThe selective oxidation of 5‐(Hydroxymethyl)furfural (HMF) to 2,5‐Furandicarboxylic acid (FDCA) is highly attractive for the production of renewable monomers as substitute for fossil‐based monomers. To achieve a sustainable synthesis, we report on advances for a base‐free approach, reducing waste from the process, using air as oxidant and heterogeneous catalysts. Various Carbon‐based supports, which can be bio‐sourced and cost‐efficient, for Pt particles were investigated as they allow for an easy reuse and at the end‐of‐life Pt can be recycled to enable a closed cycle. Commercially available supports with varying properties, which might replace the base, were studied with Pt particles of similar size and loading. Significant differences in the catalytic activity were observed, which were correlated with the O‐functionalities and graphitization degree of the supports derived from Raman spectroscopy, temperature‐programmed desorption, and X‐ray photoelectron spectroscopy. An activated carbon (Norit ROX) rich in quinone/pyrone‐type groups and a carbon black‐based catalyst with graphene‐layers pushed the efficiency with enhanced FDCA‐yields enabling the complete substitution of the homogeneous base. This allows to circumvent the base in this process which together with high selectivity, air as oxidant, a reusable catalyst, and the use of bio‐based feedstock contributes to the sustainability of the production of renewable monomers.

Catalytic action of hydronium-ion in rice straw pretreatment and enhancement of enzymatic hydrolysis and ethanol production

The present investigation will focus on the catalytic effect of hydronium ion during liquid-water/ dilute sulfuric acid/ferric chloride pretreatment (LWP/ SAP/ FCP) on the hydrolysate and pretreated rice straw. The overall pretreatment process has been represented as a sequential catalytic reactions. The temperature range of pretreatment is varied in the range of 140–180 °C and the concentration of dilute sulfuric acid and ferric chloride is 0.1 M. The first order rate constants of xylan and glucan degradation have been determined for LWP/ SAP/ FCP. The maximum xylan and glucan conversion of 96.8% w/wand 31.4%w/w respectively are achieved for FCP at 180 °C. Xylose, glucose, furfural, 5-hydroxymethyl furfural, acetic acid and formic acid appear as the main products for all pretreatments. Only in case of FCP levulinic acid also appears as a hydrolysis product. The thermal characteristics, functional groups, crystallinity, surface morphology of untreated and pretreated rice straw have been evaluated. Among all pretreatment processes under study, the highest values of glucose yield of 78.96% (w/w) using enzymatic hydrolysis and 83.79% of theoretical yield of ethanol using Saccharomyces cerevisiae have been achieved for ferric chloride pretreatment.

Physico-chemical properties of multifloral honey Apis dorsata and monofloral honey of bees Apis mellifera

Physicochemical properties of honey as one of the information about the quality of honey. The type of bee, geographic location, and type of vegetation the source of the honey bee feed influence the physico-chemical properties of honey. This study aims to determine the physico-chemical properties of multifloral honey of Apis dorsata bees and monofloral honey of Apis mellifera bees. The honey samples for this study consisted of 4 multifloral honey samples and 4 monofloral honey samples. Physicochemical parameters of honey include water content, color, pH, acidity, reducing sugars, and hydroxymethylfurfural (HMF). Data were analyzed descriptively and quantitatively. The results of the analysis showed that most of the research honey had a water content above the SNI 8664-2018 standard. Honey that has high levels is easy to ferment and to overcome this by lowering the water content of honey through a dehumidifier. Monofloral honey has an intensity value of 47 to 143 mm Pfund, while multifloral honey has 74 to 100 mm Pfund. The pH value of honey ranges from 3.5 to 4.5. The level of acidity, reducing sugar content, and HMF content of all honey samples in the study complied with SNI-8664. There are differences in the physical and chemical characteristics of multifloral honey and monofloral honey.

Geographical origin authentication of honey produced in the region of Rtanj Mountain (Serbia)

This paper represents the melissopalynological analysis, physicochemical characteristics (moisture, pH, electrical conductivity, free acidity, glucose, fructose, hydroxymethylfurfural (HMF), and colour parameters), polyphenol profile, and sensory properties of Rtanj honey samples (76) harvested during 2019–2021 from different locations in the Rtanj Mountain region (eastern Serbia) with the aim to 1) characterise this meadow honey and 2) obtain markers for its differentiating within the geographical origin protection. The melissopalynological analysis of Rtanj honey revealed many types of pollen, of which the most important belong to the Rosaceae family, especially the Sorbus group. A relatively low value of the colour parameter L* (22.7 ± 0.19–59.8 ± 1.75), the positive a* value of 1.55 ± 0.07–22.3 ± 1.36, and a high content of K (996 ± 376 mg/kg) can be used as markers for its geographical origin authentication, which was confirmed using principal component analysis (PCA). The phenolic profile was evaluated based on the quantification of epicatechin (0.077 ± 0.005 mg/kg), p-coumaric acid (0.316 ± 0.004 mg/kg), ferulic acid (0.524 ± 0.002 mg/kg), naringenin (3.386 ± 0.011 mg/kg), luteolin (0.022 ± 0.006 mg/kg), kaempferol (0.628 ± 0.010 mg/kg), and apigenin (0.120 ± 0.002 mg/kg) using high performance liquid chromatography. The colour of Rtanj honey samples varied from extra white to light amber.

Nutritionally Valuable Components and Heat-Induced Contaminants in Extruded Snack Products Enriched with Defatted Press Cakes.

This research studies the influence of the addition of defatted press cakes (from the production of hazelnut, camelina, pumpkin, and hemp seed oil) on nutritionally important components: fibre, resistant starch, polyphenols, hydroxymethylfurfural (HMF), and acrylamide in directly and indirectly expanded snacks. The amounts of press cakes added to corn grits were 3, 6, and 9%. Extrusion was carried out in a laboratory single-screw extruder. For indirectly expanded products (SCFX), supercritical CO2 was injected during extrusion, and secondary expansion was completed in the microwave oven. The type and content of press cake, as well as the type of product, significantly influenced total polyphenol content and antioxidant activity. Press cakes increased the contents of both soluble and insoluble fibre (from 1.94% d. m. and 1.28% d. m. for extrudates without press cakes up to 3.17% d. m. and 6.94% d. m. for SCFX extrudates with press cakes, respectively), and resistant starch was not markedly influenced by their addition. The influence of the content of press cake on HMF was not significant, whereas the type of cake and the type of extrusion influenced HMF significantly. In a raw mixture of corn grits with 3% of pumpkin press cake, HMF was below the limit of detection, and the highest content was found in the classically extruded sample with the addition of 9% of camelina press cake (580 ppb). In all samples, the acrylamide content was below the limit of detection, indicating that safe products were obtained. This research shows potential for the implementation of supercritical CO2 extrusion in the production of safe, nutritionally improved snack products. Future research might bring about the design of cost-effective processes applicable in the industry.

Meta-analysis of Physicochemical Characteristics in Beekeeping, Wild, and Stingless Bee Honey

The two most extensively beekeeping honeybee species were Apis mellifera and A. cerana. Other species that produced honey, albeit with infrequent cultivation, include A. dorsata, A. florea, and some stingless bees, including Trigona and Melipona. Different types of honeybees were known to affect the quality of honey. Hence, this investigation aimed to conduct a meta-analysis to examine the similarities in honey quality between honey sourced from beekeeping and wild honeybees. Data analysis was performed using the OpenMEE software, facilitating the calculation of effect size and standard error. The effect size and common error data were subsequently organized into separate columns within a CSV file. This CSV file was then imported into the JASP 0.16.2 software to conduct heterogeneity and Egger tests to detect potential publication bias. The findings indicated significant disparities in the quality of honey produced by beekeeping, wild, and stingless bee honey, as determined by various parameters, including pH value, moisture, total sugar, acidity, HMF (hydroxymethylfurfural), and diastase enzyme levels (p < 0.05). According to the results of the meta-analysis, honey from beekeeping exhibited superior quality to that of wild and stingless bees. However, the average values of all parameters still adhered to the established honey quality standards set by the Standar Nasional Indonesia and the International Honey Standard (IHS).
 
 Keywords: honey, honeybees, meta-analysis, physicochemical quality

Novel Furfural-Derived Polyaldimines as Latent Hardeners for Polyurethane Adhesives.

Moisture-curing one-component polyurethane systems in adhesive, sealant, and coating applications may show blister formation upon cure. Blisters can be formed when carbon dioxide, generated in the reaction with isocyanate and water, is trapped in the film. This problem can be mitigated by employing latent hardeners such as blocked polyamines, which are activated upon moisture exposure. The hydrolysis of the latent hardener yields the polyamine that quickly reacts with the isocyanate, forming urea linkages, and then chain extends the polymer. The hydrolysis also releases the blocking agent, which can potentially create an unpleasant odor. In this work, a series of di- and trifunctional aldimines were synthesized from commercially available polyamines, biobased hydroxymethyl furfural, and lauroyl chloride. Hydroxymethyl furfural was first esterified with lauroyl chloride and subsequently condensed with the polyamines to form the aldimines. The application of these novel aldimines in a model moisture-curing system allowed the preparation of blister- and odor-free castings. Based on our results, the mechanical performance of the different aldimines in casting and adhesive applications could be related to the polymer network density. This was dependent on the rate of the aldimine hydrolysis reaction to produce the polyamine. In particular, the use of aldimines prepared from polyether amines and 1,5-diamino-2-methylpentane showed excellent adhesive properties.

Ce‐Modified MgFe−LDH Supported Au Particles: An Efficient Catalyst for Base‐Free Selective Oxidation of 5‐Hydroxymethylfurfural to 2,5‐Furandicarboxylic Acid

Abstract5‐hydroxymethylfurfural (HMF) was selectively oxidized to 2,5‐furandicarboxylic acid (FDCA) using an effective catalytic system made of Au particles supported on Ce‐modified MgFe layered double hydroxide. The structural features and performance of the as‐prepared catalysts were examined using a range of characterizations, and the impact of altering reaction parameters was explored. It was demonstrated that the presence and quantity of Ce and Mg species in the catalyst formulation were the primary determinants of the activity of the Au@Mg−N−M−LDH catalysts (M=Ce, Cu, Mn, Zr, and N=Fe, Al). The catalyst Au@MgFeCe−LDH, loaded with 1 wt % Au, exhibited outstanding catalytic activity in the production of FDCA, achieving complete HMF conversion and 90 % FDCA selectivity. This was accomplished through a two‐step heating procedure, involving initial heating of the reaction medium at 40 °C for 2 hours followed by a subsequent heating at 100 °C for 6 hours, conducted under an oxygen pressure of 5 bar.