Search Results (338)

2,5-bis(hydroxymethy)lfuran (BHMF), a renewable compound with extensive industrial applications, can be obtained by selective hydrogenation of the C=O group of 5-hydroxymethylfurfural (HMF), a platform molecule derived from lignocellulosic biomass. In this work, we perform kinetic modeling of the selective liquid-phase hydrogenation of HMF to BHMF over a Cu/SiO₂ catalyst prepared by precipitation–deposition (PD) at a constant pH. Physicochemical characterization, using different techniques, confirms that the Cu/SiO₂–PD catalyst is formed by copper metallic nanoparticles of 3–5 nm in size highly dispersed on the SiO₂ surface. Before the kinetic study, the Cu/SiO₂-PD catalyst was evaluated in three solvents: tetrahydrofuran (THF), 2-propanol (2-POH), and water. The pattern of catalytic activity and BHMF yield for the different solvents was THF > 2-POH > H₂O. In addition, selectivity to BHF was the highest in THF. Thus, THF was chosen for further kinetic study. Several experiments were carried out by varying the initial HMF concentration (C⁰_HMF) between 0.02 and 0.26 M and the hydrogen pressure (P_H2) between 200 and 1500 kPa. In all experiments, BHMF selectivity was 97–99%. By pseudo-homogeneous modeling, an apparent reaction order with respect to HFM close to 1 was estimated for a C⁰_HMF between 0.02 M and 0.065 M, while when higher than 0.065 M, the apparent reaction order changed to 0. The apparent reaction order with respect to H₂ was nearly 0 when C⁰_HMF = 0.13 M, while for C⁰_HMF = 0.04 M, it was close to 1. The reaction orders estimated suggest that HMF is strongly absorbed on the catalyst surface, and thus total active site coverage is reached when the C⁰_HMF is higher than 0.065 M. Several Langmuir–Hinshelwood–Hougen–Watson (LHHW) kinetic models were proposed, tested against experimental data, and statistically compared. The best fitting of the experimental data was obtained with an LHHW model that considered non-competitive H₂ and HMF chemisorption and strong chemisorption of reactant and product molecules on copper metallic active sites. This model predicts both the catalytic performance of Cu/SiO₂-PD and its deactivation during liquid-phase HMF hydrogenation. Full article

Soy sauce (SS) is one of the most popular condiments in the world. However, Nε-carboxymethyl-lysine (CML) and 5-hydroxymethylfurfural (5-HMF), harmful Maillard reaction products, are present in SS. Worse still, their primary sources in SS production remain unclear, and their contents increase during the consumption of heated SS. In this study, CML and 5-HMF were simultaneously monitored, and thermal treatment and the addition of natural product were used to simultaneously reduce their contents during SS production and consumption. During SS production, CML and 5-HMF primarily originated from the raw materials used in SS production, Maillard reactions during fermentation, and the addition of food additives. Also, CML and 5-HMF were simultaneously found in commercial light soy sauce, dark soy sauce, and infant SS, and thermal treatment could increase their contents. Fortunately, additional thermal treatment of semi-finished SS (especially raw sauce and rude light SS) and appropriate concentrations of (−)-epicatechin (100 μM) and ascorbic acid (5 μM), respectively, added to SS for direct and heated consumption, could simultaneously reduce the CML and 5-HMF contents. This study highlights the presence of CML and 5-HMF in SS and proposes practical methods to simultaneously minimize their contents during production and consumption. Full article

5-Hydroxymethylfurfural (HMF) is a versatile platform molecule with the potential to replace many fossil fuel derivatives. It can be obtained through the dehydration of carbohydrates. In this study, we present a simple and cost-effective microwave-assisted method for producing HMF. This method involves the use of readily available sucrose as a substrate and glucose-derived bifunctional hydrochars as carbocatalysts. These catalysts were produced via hydrothermal carbonisation using thiourea and urea as nitrogen and sulphur sources, respectively, to introduce Brønsted acidic and basic sites into the materials. Using a microwave reactor, we found that the S, N-doped hydrochars were active in sucrose dehydration in water. Catalytic results showed that HMF yield depended on the balance between acidic and basic sites as well as the types of S and N species present on the surfaces of these hydrochars. The best-performing catalyst achieved an encouraging HMF yield of 37%. The potential of N, S-co-doped biochar as a green solid catalyst for various biorefinery processes was demonstrated. A simple kinetic model was developed to elucidate the kinetics of the main reaction pathways of this cascade process, showing a very good fit with the experimental results. The calculated rate constants revealed that reactions with a 5% sucrose loading exhibited significantly higher fructose dehydration rates and produced fewer side products than reactions using a more diluted substrate. No isomerisation of glucose into fructose was observed in an air atmosphere. On the contrary, a limited rate of isomerisation of glucose into fructose was recorded in an oxygen atmosphere. Therefore, efforts should focus on achieving a high glucose-to-fructose isomerisation rate (an intermediate reaction step) to improve HMF selectivity by reducing humin formation. Full article

Black garlic is a thermally processed product derived from fresh garlic through controlled high-temperature and -humidity conditions. During this process, the formation of 5-hydroxymethylfurfural (5-HMF), a potentially harmful byproduct, is a major quality and safety concern in food processing. This study systematically investigated the distributions of 5-HMF and key process-related biochemical components in black garlic samples from three major production regions in China—Jiangsu, Yunnan, and Shandong. Additionally, correlations between 5-HMF and biochemical components—reducing sugars, amino acids, and organic acids—were analyzed to inform process optimization strategies. Results showed significant regional variation in 5-HMF content, with Jiangsu black garlic exhibiting the highest levels, followed by Yunnan and Shandong (p < 0.05). Partial least squares regression analysis (PLSR) indicated that the key biochemical factors regulating 5-HMF accumulation are primarily organic acids. Among them, citric acid was identified as the most important negative regulator (VIP = 3.11). Although acetic acid (VIP = 1.38) and malic acid (VIP = 1.03) showed positive correlations with 5-HMF, aspartic acid (VIP = 0.41) and fructose (VIP = 0.43) exhibited a weak positive correlation, and arginine (VIP = 0.89) showed weak negative correlations, their effects were far less significant than that of citric acid. Based on these findings, we propose a potential strategy for reducing 5-HMF content in black garlic—selecting raw material cultivars with higher endogenous citric acid levels or exploring the exogenous addition and regulation of citric acid during processing. This study provides a theoretical foundation for understanding the accumulation mechanism of 5-HMF in black garlic and suggests new potential regulatory directions for controlling its content. Full article

2,5-Furandicarboxylic acid (FDCA) is a bio-based platform chemical with high potential to replace terephthalic acid in polymer production, particularly for polyethylene furanoate (PEF), a biopolymer with superior thermal and barrier properties. This study investigates the selective oxidation of 5-hydroxymethylfurfural (HMF) into FDCA using nickel-based heterogeneous catalysts, aiming at a cost-effective and sustainable alternative to noble metal catalysts. A series of nickel oxide catalysts were synthesized and screened. The NiOx catalyst synthesized without thermal treatment via Route B showed the best performance, achieving a FDCA yield of 11.77%, selectivity of 27.41%, and concentration of 0.9 g/L under preliminary conditions. Reaction kinetics revealed that the controlled addition of NaClO enhanced FDCA yield by 2.28 times. Optimization using a 2³ factorial design identified the optimal conditions as 6% (w/v) catalyst concentration, 25 °C, and a NaClO:HMF molar ratio of 12:1, leading to 34.14% yield and 42.57% selectivity. The NiOx catalyst maintained its activity over five successive cycles, indicating good recyclability. Moreover, NiOx demonstrated catalytic activity with crude HMF derived from glucose dehydration, confirming its practical applicability. These results support the potential of nickel-based catalysts in sustainable FDCA production, contributing to the advancement of bio-based polymer synthesis. Full article

The electrochemical oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) coupled with water electrolysis for green hydrogen production is a promising strategy to address energy crises and environmental pollution. Despite the suitable adsorption energy for HMF due to their partially filled d-band electronic structures, Ni- or Co-based oxides/hydroxides still face challenges in insufficient activity and stability. In this study, a porous heterogeneous nickel cobalt oxide/hydroxide growth on nickel foam (NF), which is defined as NF@NiCo-H/O, was developed via immersion in concentrated alkali solution. Compared with the single-component NiCo oxides, the NF@NiCo-H/O catalyst exhibits a lower application potential of only 1.317 V, 1.395 V, and 1.443 V to achieve current densities of 20, 50, and 100 mA cm⁻², respectively, in an alkaline solution containing HMF. Additionally, it demonstrates rapid reaction kinetics with a Tafel slope of 27.6 mV dec⁻¹ and excellent cycling stability. Importantly, the presence of more high-valent Ni³⁺-O species on the catalyst surface contributes to its exceptional selectivity for 2,5-furandicarboxylic acid (86.7%), Faradaic efficiency (93.1%), and conversion rate (94.4%). This catalyst provides some theoretical guidance for the development of biomass electrooxidation catalysts for sustainable energy and chemical production. Full article

This study investigates the effects of electric field pretreatment parameters such as electric field strength (0.1–0.2 kV/cm), waveform (sinusoidal vs. square), and application mode (continuous vs. pulsed) on the quality attributes of dried Fuji apple slices, including ascorbic acid (vitamin C) retention, β-carotene content, and hydroxymethylfurfural (HMF) formation. Electric-field-treated samples were compared to untreated controls after convective drying at 75 °C. Results revealed that vitamin C was significantly influenced by waveform, with sinusoidal waves preserving about 27% more vitamin C than square waves, likely due to reduced oxidative degradation from gentler electroporation. Conversely, square waves caused the highest β-carotene losses (25% vs. control), attributed to prolonged peak voltage destabilizing carotenoids. HMF formation was reduced by 10–23% in electric-field-treated samples compared to controls, linked to accelerated drying rates limiting Maillard reaction time. Low electric field strengths (0.1–0.15 kV/cm) enhanced antioxidant activity; however, higher intensities showed a potential decline. The square waveform had a more detrimental effect on phenolic compounds than the sinusoidal waveform. These findings suggest that low electric field pretreatment, particularly with sinusoidal waveforms at 0.2 kV/cm, enhances drying efficiency while balancing nutrient retention and HMF mitigation, offering a promising strategy for producing high-quality dried fruits. Full article

This study systematically investigated the evolution of color values and the reaction kinetics of the Maillard reaction in membrane-clarified sugarcane juice during the vacuum evaporation process, providing a theoretical basis for pigment regulation in white sugar production. Content changes in the reactants (sucrose, glucose, fructose, and free amino acids), the precursors of melanoidins including 3-deoxyglucosone, 5-hydroxymethylfurfural, glyoxal, methylglyoxal, carboxymethyl lysine, and melanoidin, were monitored during the thermal processing of membrane-clarified sugarcane juice (MCSJ), and the reaction mechanism was investigated via kinetic modeling. The zero-level, first-level, and second-level kinetic models could represent the change in L* and b*, and the zero-level kinetic model best fit the change in a* and ΔE*. The multi-response kinetics revealed that the main pathway of melanoidins in MCSJ model systems was that glucose and fructose were mutually isomerized into 1,2-enediol to generate 3-DG and then degraded to produce 5-HMF. Subsequently, 5-HMF further reacted to produce melanoidins. Full article

This study compares the physicochemical properties of Royal Gala apple snacks fresh and processed using different methods: solar-dried (SD), oven-dried at 65 °C (OD65°) and 85 °C (OD85°) and two commercial brands (CC—commercial apple C and CF—commercial apple F). Evaluated parameters included color, microstructure, acidity, sugar content, phenolic compounds, antioxidant activity, and the presence of heat-induced compounds such as 5-hydroxymethylfurfural (5-HMF) and acrylamide. Commercial samples showed more pronounced color changes and a denser microstructure, with higher browning index (BI) values. The ratio of soluble solids to titratable acidity, an indicator of sensory acceptance, was more influenced by drying methods than temperature. Total phenolic content was highest in fresh apples (123.68 mg GAE/100 g d.m.) and decreased across all drying methods, particularly in solar-dried (SD) samples (78.57 mg GAE/100 g d.m.). Antioxidant activity followed a similar trend, although SD samples performed better than expected, likely due to the retention of certain bioactive compounds. Fresh apples had the highest sugar content (43.25 mg/100 g d.m.), followed by CC (33.81 mg/100 g d.m.), OD65° (33.37 mg/100 g d.m.), CF (31.56 mg/100 g d.m.), OD85° (25.92 mg/100 g d.m.) and SD (25.01 mg/100 g d.m.). Commercial samples were sweeter and darker, with detectable levels of 5-HMF and acrylamide. The findings highlight that drying method significantly affects snack quality. While solar- and oven-dried samples better preserve bioactive compounds, industrial processes enhance sweetness and visual appeal but increase the formation of potentially undesirable compounds. These results are valuable for both consumers and producers aiming to balance sensory quality with nutritional and food safety considerations in dried apple products. Full article

Grape seeds are a major by-product of the winemaking industry and a great source of bioactive compounds such as polyphenols and proteins. These compounds have a wide range of applications including those in nutraceutical products and cosmetics and within the wine industry itself. Subcritical water extraction (SWE) was explored as a global method to valorize grape seed by-products for their different bioactive compounds in the context of waste valorization, green chemistry (solvent-free extraction), and circular economy. A Box–Behnken design was applied to generate mathematical responses and the ANOVA analysis determined the optimal extraction conditions (pressure, temperature, and time of extraction) for different responses such as total polyphenol content (TPC), antioxidant activity (AA), and total protein (Tprot). Extraction temperature was found to be the most significant factor influencing all responses while pressure had no significant impact on them. Optimal conditions were derived from the mathematical models for each response. For polyphenol extraction, the optimal conditions were as follows: 170 °C and 20 bar for 39 min with 288 mg GAE/g DM. To achieve the highest AA, SWE parameters should be set at 165 °C and 20 bar for 51 min with 332 mg TROLOX/g DM. For the extraction of proteins, it is necessary to work at 105 °C and 20 bar for 10 min (78 mg BSA/g DM) to preserve protein functionality. In comparison, conventional solvent extraction was unable to outperform SWE with values under the SWE results. Given the high content of polyphenols found in the extracts, an HPLC analysis was conducted. The following compounds were detected and quantified: protocatechuic acid (7.75 mg/g extract), gallic acid (6.63 mg/g extract), delphinidin chloride (1.44 mg/g extract), catechin (0.36 mg/g extract), gentisic acid (0.197 mg/g extract), and some epicatechin (0.07 mg/g extract). Additionally, Maillard reaction products (MRPs) were detected at high temperatures, with 5-hydroxymethylfurfural (5-HMF) appearing in extracts processed at 165 °C and above. The presence of MRPs, known for their antioxidant and bioactive properties, may have contributed to the increased AA observed in these extracts. These findings are significant because a solvent-free extraction process like SWE offers a sustainable approach to repurposing winemaking by-products, with potential applications in the wine and food industries. Full article

5-Hydroxymethylfurfural (HMF) is a versatile carbohydrate-derived platform chemical that has been used for the synthesis of a number of commercially valuable compounds. In this study, several chromium (Cr)-doped, biomass-derived hydrochar catalysts were synthesized via the one-pot method using starch, eucalyptus wood, and bagasse as carbon sources. Then, the performance of these synthesized materials for the catalytic conversion of glucose into HMF was evaluated by, primarily, the yield of HMF. The synergistic interactions between the Cr salt and the different biomass components were investigated, along with their effects on the catalytic efficiency. The differences in the catalytic activity of the synthesized materials were analyzed through structural characterization, as well as assessments of the acid density and strength. Among the catalysts, Cr₅BHC₁₈₀ derived from bagasse presented the highest activity, achieving an HMF yield of 64.5% in an aqueous solvent system of dimethyl sulfoxide (DMSO) and saturated sodium chloride (NaCl) at 170 °C after 5 h. After four cycles, the HMF yield of Cr₅BHC₁₈₀ decreased to 38.7%. Characterization techniques such as N₂ adsorption–desorption and Py-FTIR suggested that such a decline in the HMF yield is due to pore blockage and acid site coverage by humic by-products, as demonstrated by the fact that regeneration by calcination at 300 °C restored the HMF yield to 50.5%. Full article

Red beetroot (Beta vulgaris L.) is a nutritionally rich root vegetable. It is a potential alternative raw material for pestil, a traditional fruit-based snack. This study aimed to develop a healthy beetroot-based pestil using traditional boiling (95 °C) and novel pretreatment methods, including thermosonication and microwave processing, with and without additional concentration steps. The effects of these methods on heat treatment period, hydroxymethylfurfural (HMF) formation, and the physicochemical, sensorial, nutritional, and chemometric profiles of pestils were evaluated. The beetroot-based snack formulated in this study was hedonically acceptable (≥5/9) and rich in essential minerals (Ca, K, Na, P, Mg) and trace elements (Zn, Fe, Mn), as determined by inductively coupled plasma–mass spectrometry. Total antioxidant capacity (CUPRAC) ranged from 113.11 to 870.78 mg Trolox^® equivalent/100 g dry matter (DM). Total phenolic, flavonoid, and betalain contents varied between 220.6–313.8 mg gallic acid equivalent/100 g DM, 365.08–517.46 mg rutin equivalent/100 g DM, and 314.40–488.66 mg/kg, respectively. Major flavonoids identified and quantified included epicatechin, rutin, isoquercitrin, taxifolin, and quercetin, while major phenolic acids identified were chlorogenic acid, ferulic acid, caffeic acid, o-salicylic acid, p-coumaric acid, and vanillin, using liquid chromatography–electrospray tandem mass spectrometry. Reducing the soluble solids content of the pestil pulp from 40 to 20 Brix degrees, in combination with thermosonication and microwave treatments, significantly shortened the processing time by 10–67%. This approach also reduced the HMF content to the limit of quantification (LOQ). Pretreatment methods significantly (p < 0.05) affected the levels of minerals and bioactive compounds in the pestils. These findings highlight the importance of process optimization to improve overall safety and the nutritional quality of the pestil. Full article

Metal carbonyl clusters, which can be seen as monodispersed and atomically defined nanoparticles stabilized by CO ligands, were used to prepare Ru-based catalysts with tuned basic properties to conduct the 5-hydroxymethylfurfural (HMF) aerobic oxidation to produce 2,5-furandicarboxylic acid (FDCA) in base-free conditions. The controlled decomposition of the carbonyl cluster [HRu₃(CO)₁₁]⁻, a methodology not yet applied to Ru catalysts for this reaction, on different supports focusing on controlling and tuning the basic properties of support allowed the formation of small Ru nanoparticles with a mean diameter of around 1 nm. The catalytic systems obtained resulted in more activity in the HMF oxidation than those prepared through a more common salt-impregnation technique, and the deposition of Ru nanoparticles on materials with basic functionalities has allowed avoiding the use of basic solutions in the reaction. The characterization by CO₂-TPD of Mg(Al)O catalysts obtained from decomposition of layered double hydroxide hydrotalcites with different composition and activation has allowed disclosure of an important correlation between the selectivity of FDCA and the fraction of weak basic sites, which is decreased by the calcination treatment at increased temperature. Full article

This study evaluated the potential of pectin (PEC)-based coatings, enhanced with olive leaf extract (OLE) and chitosan nanoparticles (CH-NPs), to mitigate the formation of harmful compounds during the frying of French fries. The research compared deep fat and hot air frying methods. Initial characterization of the coating solutions included assessing zeta potential, Z-Average, polydispersity index, and antioxidant capacity. The inclusion of OLE and CH-NPs significantly boosted antioxidant activity, reaching 78.9%, without substantially altering zeta potential or Z-Average characteristics. Notably, hot air frying induced significantly higher levels of acrylamide (ACR) and hydroxymethylfurfural (HMF) compared to deep fat frying. However, the application of the developed coatings demonstrated a marked reduction in both ACR and HMF across both frying techniques. Furthermore, the coatings, particularly PEC with OLE and CH-NPs, effectively decreased oil absorption by 55% while simultaneously increasing moisture content. The sensory evaluation indicated that the panelists liked the deep-fat-fried fries significantly more compared to hot air frying. Deep-fat frying led to an elevated browning index, which was significantly counteracted by the application of the coatings. These findings underscore the importance of informing consumers about the potential for increased ACR and HMF formation during hot air frying, despite its advantages in reducing fat content, to ensure informed dietary choices. Full article

The use of alternative flours is becoming more common in the food industry to enhance the nutritional and sensory properties of baked goods. However, these changes may also affect the formation of acrylamide, a potentially carcinogenic and genotoxic compound generated in foods heated above 120 °C. This study evaluated the acrylamide-forming potential of 16 flours from cereals, pseudocereals, legumes, fruits, and roots. Samples were analyzed for acrylamide precursors—reducing sugars and free asparagine—and tested in model dough systems with and without added glucose. All samples were baked at 150 °C for 30 min. Hydroxymethylfurfural (HMF) was also determined as a marker of thermal damage. In water-hydrated systems, acrylamide was only detected in wheat, rye, and coconut flours (23–61 µg/kg). When glucose was added, acrylamide levels increased in all systems except cassava. Lentil flour produced the highest levels (154 µg/kg), while corn flour showed the lowest (20 µg/kg). HMF levels followed a similar trend, with lentil flour again showing the highest content (232.3 mg/kg). These results highlight the importance of evaluating acrylamide formation when using non-wheat flours, especially in formulations containing sugars. Additional mitigation strategies may be needed to ensure the safety of these innovative food products. Full article