HMF Formation Research Articles

HMF formation, diastase activity and proline content changes in bee pollen dried by different drying methods

Bee pollen, as a protein rich and energy enhancing food source, can be used as a valuable complement to our daily diet. In this study, multifloral bee-pollen was dehydrated to a moisture content less than 8% by hot-air (HAD) and vacuum (VD) (300, 500 mbar) drying at 35, 50 and 65 °C, microwave (MWD) and microwave assisted vacuum drying (MW-VD) (500, 675 mbar) at 300, 450, 600 and 900W power levels and freeze drying. The water activity, diastase number (DN), proline and 5-hydroxymethyl-2-furfural (HMF) contents in fresh and dried pollen samples were determined and compared. A greater reduction was observed in DN of samples subjected to MWD and MW-VD at 600 and 900W as compared to other drying treatments. Drying by microwave irradiation at 900W power level caused the highest, almost 72–76%, reduction in DN values. A higher retention of enzyme activity, ranging between 87 and 93%, was observed at 50 °C during HAD and VD. Proline and HMF content were affected by the power level during MWD and MW-VD. A significant reduction in proline content was observed only in microwave treated samples at the highest power level. Except for the highest power level, MW-VD leads to a significant increase in HMF levels ranging between 4.9 and 9.2 mg/kg while HAD and VD provided similar HMF content in samples as compared to fresh pollen.

Catechin-iron as a new inhibitor to control advanced glycation end-products formation during vinegar storage

Vinegar is a kind of popular condiment which has attractive color, flavor and functional properties. However, some potential harmful substances such as advanced glycation end-products (AGEs) will inevitably be generated by Maillard reaction during the brewing process and storage. In our study, it is concluded that catechin can reduce the formation of AGEs in both model vinegar system and the real vinegars. What's more, addition of iron can cooperate with catechin to enhance inhibitory effect up to 92.75 ± 5.24% and 89.77 ± 5.38% in Glu-Ala and Rib-Ala model vinegar system, respectively, and achieved highest inhibitory ratio about 75.52 ± 0.64% in apple vinegar. The corresponding mechanisms included reducing 5-hydroxymethylfurfural (5-HMF) formation and eliminating free radicals in the vinegar. Our study will provide a new idea for the application of catechin-iron as an addictive to assure the safety and the quality of vinegar.

Production of prebiotic 6-kestose using Zymomonas mobilis levansucrase in carob molasses and its effect on 5-HMF levels during storage

Fructooligosaccharides have important potential use in the food industry due to their properties such as solubility in water, stability in acidity of fruit juices and during storage, low-calorie value and prebiotic effects. In this study, for the first time, Zymomonas mobilis levansucrase was used for in situ 6-kestose production in carob molasses. The produced kestose was stable during storage at 20 °C for 4 months. The product was evaluated for color, non-enzymatic browning index and titratable acidity during storage and the quality of the product was found comparable to that of control. Furthermore, the decreased amount of sucrose resulted in the prevention of 5-hydroxymethylfurfural (5-HMF) formation during storage. As a result, carob molasses was converted into a high-quality prebiotic product with decreased sucrose content and reduced 5-HMF quantities, and a new method was developed to prevent 5-HMF formation in fruit juices and molasses.

Changes in Quality Attributes Related to Browning during Storage of Litchi Juice Fermented by Lactobacillus

Litchi juice fermented by Lactobacillus casei was heated (95°C, 1 min) and stored in a dark place at 25°C. Changes in quality attributes (color, 5-hydroxymethylfurfural (5-HMF) phenolic compounds, antioxidant capacity, sugars, free amino acids, and others) related to browning in fermented litchi juice were investigated during the six months of storage. Noticeable visual changes due to browning were observed during storage of fermented litchi juice, especially in the upper part of the juice bottle, and the value of color difference (△E) increased to 7.12±0.04 after six months of storage. The 5-HMF content increased with the increase in storage time, which rose from 0 to 2.31±0.16 mg/L after six months of storage. Five soluble phenolic compounds (rutin, narcissoside, quercetin, kaempferol-rutinose-rhamnoside, and isorhamnetin-rutinose-rhamnoside) were identified in fermented litchi juice, none of which showed a significant decrease (P>0.05), whereas a tendency for total phenolic content to decrease was observed during storage of fermented litchi juice. Adding 0.3 g/L of sodium sulfite can inhibit the browning reaction in fermented litchi juice and decrease the formation of 5-HMF as well as the loss of total phenolics.

PH and lipid unsaturation impact the formation of acrylamide and 5-hydroxymethylfurfural in model system at frying temperature.

The effect of unsaturated free fatty acids (FFAs) and triglycerides (TGs) on the formation of acrylamide and 5-hydroxymethylfurfural (HMF) at frying temperature was investigated. We hypothesized that the nature of the precursors generated by the Maillard reaction in the presence of FFAs and TGs, such as the Amadori product and α-dicarbonyl compounds, would impact acrylamide and HMF formation. Interestingly, the initial pH of the aqueous phase impairs the observed effect of the addition of lipids on the formation of acrylamide. Addition of FFAs and TGs increased acrylamide formation in non-buffered systems (distilled water, pH 4.6), but decreased it in buffered systems (sodium acetate, pH 6.0). Conversely, incorporation of these lipids promoted HMF formation under both conditions. The degree of fatty acid unsaturation played an important role in the formation of acrylamide and HMF. The effect of unsaturated lipids on the acrylamide and HMF was due to lipid oxidation. Statistical correlations were made between acrylamide and HMF formation and α-dicarbonyl compounds in the presence of unsaturated lipids.

Non-enzymatic browning and the kinetic model of 5-hydroxymethylfurfural formation in residual solution of vinegar soaked-soybean

Non-enzymatic browning of vinegar soaked-soybean residual solution was investigated using a model solution. A glycine-fructose-gallic acid model system was proposed by analyzing reducing sugars, amino acids, total phenolics, and pH value of the vinegar soaked-soybean residual solution. Based on the proposed model, the kinetics of 5-hydroxymethylfurfural (5-HMF) formation was also studied. The results showed that Maillard reaction and sugar pyrolysis might be the accurate mechanisms of non-enzymatic browning in vinegar soaked-soybean residual solution. The formation of 5-HMF in the model solution exhibited characteristics of the first-order kinetic model at temperature from 60 to 140 °C. The frequency constant kf was 450.65 /h, and the apparent activation energy Ea was 20.15 kJ/mol. Acetic acid, Fe2+, and Fe3+ significantly enhanced the browning rate and 5-HMF formation; whereas Ca2+, Mg2+, Na+, glucose oxidase, and H2O2 inhibited the browning rate.

Biorefinery processes for the valorization of Miscanthus polysaccharides: from constituent sugars to platform chemicals

A biorefinery scheme was proposed for manufacturing platform chemicals (furfural, denoted F, and 5-hydroxymethylfurfural, denoted HMF) from Miscanthus polysaccharides (including hemicelluloses and cellulose). The feedstock was first subjected to hydrothermal processing, which caused an extensive hemicellulose solubilization, yielding solids enriched in cellulose and aqueous solutions rich in saccharides. The acidic processing of the aqueous solutions in the presence of methyl isobutyl ketone (MIBK), which acted as an extracting agent, led to the formation and the in situ separation of F from pentoses at high molar yields (up to 78%). Moreover, HMF and levulinic acid were obtained from the hexoses released from the feedstock.The cellulose-enriched solids from hydrothermal processing were used as a substrate for HMF manufacture, employing a combination of enzymatic and chemical treatments. The enzymatic hydrolysis yielded glucose (in concentration up to 59 g /L), which was enzymatically isomerized into fructose in the presence of sodium tetraborate at yields up to 80%. Acidic treatments of the resulting reaction media at low temperature (134 °C) in the presence of H2SO4 enabled the formation of HMF at yields about 49%. Under the assayed conditions, glucose remained practically unaltered, facilitating its reutilization in the isomerization stage.

Pathway of 5-hydroxymethyl-2-furaldehyde formation in honey.

5-hydroxymethyl-2-furaldehyde (5-HMF) is an important substance that affect quality of honey and shows toxicity for humans and honey bees. The pathway of 5-HMF formation in honey is still unknown. In this study, we tested the effect of thermal treatment (at 90°C for 4 h) on the formulation of 5-HMF formulation in rapeseed with varied honey composition. 5-HMF content of honey increased at higher water content, Ca2+ and Mg2+ content and lower pH. However, the formation of 5-HMF was not significantly influenced by glucose, fructose, Na+, or K+ contents. Furthermore, different content of proline, the most abundant amino acid in honey (a substance in Maillard reaction), had no effect on 5-HMF formation. Free acids in honey can catalyze fructose and glucose to form 5-HMF. These results suggest that dehydration of glucose or fructose, instead of the Maillard reaction, is the main pathway of 5-HMF formation in honey. This study gives new insights for the mechanisms of 5-HMF formation and provides method for reducing 5-HMF formation during honey processing.

Highly efficient Cr/β zeolite catalyst for conversion of carbohydrates into 5‑hydroxymethylfurfural: Characterization and performance

In the presented work, a series of Cr/β zeolites were prepared and used as bifunctional catalysts with Brønsted and Lewis acidity in the conversion of biomass-derived carbohydrates to 5‑hydroxymethylfurfural (HMF). The physicochemical properties of all catalysts were characterized by ICP-AES, N2 physisorption, solid-state 27Al NMR, XRD, SEM-EDX, UV–Vis, XPS, Raman, NH3-TPD and Py-FTIR techniques. It was found that the catalysts with appropriate total acidity, ratio of Lewis to Brønsted acid sites and acid density appear to be beneficial for HMF formation. Under mild reaction conditions, a superior 72% HMF yield with 83% selectivity was achieved from glucose in the H2O/THF biphasic system by using the 0.4-Cr/β zeolite catalyst. Moreover, the results of the stability evaluation showed that the catalytic activity of the 0.4-Cr/β zeolite was not significantly lost after four consecutive cycles, and the framework remained intact. Therefore, the catalytic approach proposed in this study is believed to provide potential prospects for the production of HMF from biomass material refining in the future.

Formation of 5-hydroxymethylfurfural in industrial-scale apple juice concentrate processing

In industrial-scale apple juice concentrate (AJC) processing, 5-hydroxymethylfurfural (5-HMF or 5-(hydroxymethyl)-2-furaldehyde) is a furanic compound that is formed as an intermediate under certain conditions during thermal treatments applied to foods, especially AJC. Understanding 5-HMF formation is significant, particularly because 5-HMF is undesirable in foods due to its harm to humans’ health, but its presence and content is also an indicator of the processing technique used to prepare the food. The aim of this study was to investigate the changes in 5-HMF and other physicochemical indicators during AJC processing, and to critically analyse the impacts of those physicochemical indicators on the generation of 5-HMF. In this study, 5-HMF content, conventional physicochemical parameters, two monosaccharides, one disaccharide, 18 amino acids, and 12 polyphenols were monitored during 8 crucial stages of AJC production. 5-HMF formed primarily during three thermal processing stages: preconcentration, enzymatic clarification, and quintuple effect concentration. Color value increased, and brown index decreased significantly during processing. Fructose and glucose were the most abundant saccharides present in apple juice. Asparagine and aspartic acid were the two highest contents of amino acids detected, and amino acids contents showed little variation after the resin decolorization stage. Phloridzin content was highest in the original apple fruit, but all polyphenols showed significant variability during processing, especially during adsorption after the resin decolorization stage. The formation of 5-HMF showed a positive correlation with soluble solids content, color value, total sugar, fructose, glucose, glutamic acid, asparagine, threonine, alanine, methionine, proline, gallic acid, and rutin content. The formation of 5-HMF is dependent upon the fructose, glucose and specific amino acids content under acidic and thermal conditions found in industrial-scale AJC processing. Understanding the factors influencing 5-HMF formation can help to control its formation in AJC processing.

Synthesis of 5-hydroxymethylfurfural from glucose using H-Beta catalyst treated with phosphoric acid in one-pot biphasic solvent system

ABSTRACTThe production of 5-hydroxymethylfurfural (5-HMF) from glucose by using phosphoric acid (H3PO4) treated H-Beta zeolite (P-H-Beta) as the catalyst in a one-pot biphasic solvent system is presented. The catalysts with varied contents of H3PO4 over Beta-zeolite were synthesized by wet method and characterized by X-ray diffraction, scanning electron microscopy, fourier transform infrared spectroscopy, and NH3-temperature-programmed desorption. Under the optimized catalytic conditions, the catalyst prepared by the treatment of H-Beta zeolite with 2 M H3PO4 (2P-H-Beta) gave high conversion with almost 54% yield of 5-HMF at 150°C for 90 min reaction time and 0.1:1 mass ratio of catalyst to glucose with the THF/NaCl/H2O solvent system. This resulted from the appropriate acidity of the strong acid sites on the catalyst which promoted the formation of 5-HMF and its effective partition in the biphasic H2O/THF/NaCl solvent system.

Efficient Dehydration of Glucose, Sucrose, and Fructose to 5-Hydroxymethylfurfural Using Tri-cationic Ionic Liquids

Imidazolium predicated room temperature tri-cationic ionic liquid (RTILs) shows highly efficient and selective dehydration of fructose, sucrose, and glucose into 5-hydroxymethylfurfural (5-HMF). The formation of 5-HMF has been investigated using different reaction parameters, such as catalyst weight, reaction time and temperature. Among different reaction parameters, 93% yield of 5-HMF was obtained from fructose in [GLY(mim)3][OMs]3 at 120 °C within 2 h, while 72% and 51% yield of 5-HMF were achieved from dehydration of sucrose, and glucose respectively at 120–140 °C in 3 h to 5 h. In addition, the effect of reaction time, molar ratio, and temperature with CC-SO3H co-catalyst have been discussed. In which, 97%, 77%, and 58% yield of 5-HMF were obtained from fructose, sucrose, and glucose, respectively, in the presence of [GLY(mim)3][Cl]3 and CC-SO3H catalyst at 130–140 °C within 3–5 h. Both catalytic systems showed excellent recyclability for carbohydrates to 5- HMF conversion without any loss in its catalytic activity.

Aqueous-Phase Transformation of Glucose into Hydroxymethylfurfural and Levulinic Acid by Combining Homogeneous and Heterogeneous Catalysis.

Homogeneous (HCl) and heterogeneous catalysts (various zeolites) were combined to enhance the upgrading of glucose into two different platform molecules: 5-hydroxymethylfurfural (HMF) and levulinic acid (LA). β-Zeolite was the most active material for the glucose isomerization to fructose, improving also the activity of HCl for the subsequent steps. Reaction time, temperature, and pH were then modified, identifying 140 °C, 200 ppm of HCl, and 5 h as the optimum conditions for HMF formation (41 % selectivity; 0.06 mol L-1 ) and 140 °C, 400 ppm of HCl, and 24 h for LA formation (34 % selectivity; 0.12 mol L-1 ). This new approach is also relevant because of significant changes to the mechanism for humins formation. All results are successfully fitted to a kinetic model simultaneously considering both catalytic mechanisms.

Dehydration of fructose to HMF in presence of (H3O)xSbxTe(2-x)O6 (x = 1, 1.1, 1.25) in H2O-MIBK

The pyrochlores (H3O)xSbxTe(2-x)O6 (x = 1, 1.1 and 1.25) obtained by ion exchange from KxSbxTe(2-x)O6 oxides were used as catalysts for the conversion of fructose to 5-hydroxymethylfurfural (HMF) in H2O/Methyl isobutyl ketone (MIBK). The structure of the resulting compounds as well as the location of the H3O+ units inside the three-dimensional network, were determined by XRD from powder samples. The effect of factors such as reaction time and temperature on the formation of HMF was studied. A fructose conversion of 99% and a yield of 59% were achieved after 120 min of reaction time and at 150 °C temperature. The percentage of substitution of the cations Sb and Te in the position B of the pyrochlore was determinant to achieve the maximum incorporation of H3O + ions in the pyrochlore structure, which allowed to correlate the density of acidic sites present in the materials and their catalytic activity.

Investigation of the conditions for the formation of 5-Hydroxymethylfurfurol in the production of honey wines and sea-buckthorn wine drinks

The article presents experimental data on some mechanisms for the formation of 5-hydroxymethylfurfural (HMF) in the production of sea-buckthorn wines and wine drinks with the addition of honey. Conducted research is necessary because, despite the unconditionally useful properties of honey, it is possible that it has a high content of such chemicals as heavy metals, alkaloids (even in minimal quantities), as well as HMF, the unwanted effect of the latter on the body is mutagenic, genotoxic, organotoxic effects, accompanied by inhibition of a number of metabolic enzymatic processes in the living cell, in addition, the concentration of HMF is used as a parameter characterizing the freshness of honey. In this regard, the Codex Alimentarius Commission has set a maximum limit for HMF in honey - 40mg/kg (80 mg/kg for honey originating from tropical regions), ensuring that honey is not subjected to intense heating during processing and is safe for consumption. Thus, the identification of the kinetic patterns of formation of HMF will allow establishing the optimal parameters for the production of high-quality and safe honey wines and sea-buckthorn wines. It is shown that when preparing this group of drinks, the heating temperature of the product (at the stages of preparing the wort, pasteurizing the finished drink, etc.) should not exceed 60°C with a total heating time of not more than 6 hours and the content of total titrated acids in the drink not more than 7g/dm 3 . The research has scientific and practical significance for beverage producers who use natural honey and vegetable raw materials with high acidity in production, as well as for the regions of Russia engaged in industrial production of honey, since the creation of scientifically based technologies and modes of its storage and processing will improve quality and safety of food produced on its basis.

Conversion of fructose into furfural or 5-hydroxymethylfurfural over HY zeolites selectively in γ-butyrolactone

Furfural is one of the most valuable biomass platform compounds which is typically prepared from hemicellulose. Conversion of cellulose and its derived hexoses, which are the most abundant resource in nature, to furfural, is a big challenge. The amount of the reactive form (fructofuranose) which was beneficial to the formation of furfural and HMF, was increased when the solvent transformed from water to γ-butyrolactone (GBL)-water. The GBL promoted the adsorption of fructose on HY. The transfer of fructose from the solution to the channels of HY was enhanced with the introducing of GBL in solvent. The HY zeolite with apertures of 7.4 Å was found to promote the formation of acyclic fructose from cyclic fructose (8.6 Å) in the synergy with GBL. The Brønsted acid sites in the channels of HY favored the selective cleavage of the CC bond in acyclic fructose to xylose, and promoted the following dehydration of xylose to furfural, simultaneously. The furfural yield was increased while the 5-hydroxymethylfurfural (HMF) yield was decreased with the decrease of the Brønsted acid sites density. The maximum furfural yield was 37.8% over HY-3, while the maximum HMF yield was 69.2% over HY-1 in the conversion of fructose in GBL-water solvent. In addition, the etherification of HMF was the main factor for the low HMF yield and carbon balance in fructose conversion in GBL-water solvent.

Conversion of Sucrose into Lactic Acid over Functionalized Sn-Beta Zeolite Catalyst by 3-Aminopropyltrimethoxysilane.

The utilization of sucrose, an easily accessible disaccharide, in the production of a versatile platform chemical lactic acid (LA), is more attractive than a monosaccharide. In this work, we report a modification approach by 3-aminopropyltrimethoxysilane to introduce an amino group onto the surface of the Sn-Beta Lewis acid catalyst. Using the modified catalyst, a maximum LA yield of 58% was achieved under optimal hydrothermal conditions (190 °C, 4 h) from sucrose, along with a complete conversion and a reduced 5-hydroxymethylfurfural (HMF) yield of 8% compared to Sn-Beta. To evaluate the role of the amino group, different substrates were used as the reactants to produce LA. The experimental results suggested that both fructose and glucose were crucial intermediates in the initial 2 h, whereas glucose is the sole reactant after 2 h. Upon modification, not only the hydrolysis of sucrose was promoted, but the side reaction of HMF formation was also suppressed.

Production of 5-Hydroxymethylfurfural from D-Fructose in Low-Transition-Temperature Mixtures Enhanced by Chloride Anions and Low Amounts of Organic Acids.

The use of safe and sustainable solvents able to solvate reagents and to catalyze their reactions at temperatures below 100 °C is an innovative strategy to develop future lignocellulosic biorefineries. Many low-transition-temperature mixtures (LTTMs) have been investigated for this purpose. Among them, natural deep eutectic solvents (NADESs) have been proposed as cheap and renewable alternatives to ionic liquids for the synthesis of bio-based chemical building blocks. We compare herein the ability of several organic acids/choline chloride/water LTTMs to perform D-fructose dehydration to 5-hydroxymethylfurfural (5-HMF). The addition of chloride salts as well as an increased proportion of choline chloride promotes 5-HMF formation, which seems to indicate a beneficial effect of chloride anions on D-fructose dehydration. Besides improving selectivity by at least 10 %, increasing the choline chloride/acid ratio could enhance the biodegradability of the LTTMs. Unlike other acidic components, maleic and citric acids are especially selective at early D-fructose conversion. Maleic acid was the most selective acidic component among the tested chemicals, achieving an 80 % 5-HMF molar yield in 1 h at 90 °C.

Catalytic Conversion of Carbohydrates into 5‐Ethoxymethylfurfural by a Magnetic Solid Acid Using γ‐Valerolactone as a Co‐Solvent

AbstractSelective conversion of carbohydrates to fuels and fine chemicals is of great importance for biorefinery. However, development of efficient solid acidic catalysts which perform stably for this process is still challenging. Herein, we reported a novel carbon‐based solid acidic catalyst, prepared via hydrothermal carbonization of glucose followed by magnetization of Fe3O4 and sulfonation of H2SO4, which can serve as an efficient and recyclable catalyst in the catalytic dehydration of fructose to 5‐hydroxymethylfurfural (HMF) and subsequent etherification of 5‐ethoxymethylfurfural (EMF) with ethanol from various carbohydrates. The effects of reaction conditions (temperature, time, solvents, catalyst amount, and γ‐valerolactone (GVL) concentration) were optimized affording to a maximum EMF yield of 67.4 % at 120 °C, 55 wt % catalyst loading based on starting fructose and 60 vol.% of GVL in ethanol after 24 h of reaction. Noticeably, GVL promotes the formation of EMF and HMF reducing the extent of side reactions. Recycling experiments showed that the catalyst could be easily separated with a magnet and reused up to 4 consecutive times without significant loss of activity. The present work opens a way to synthesize reusable and cost‐effective solid acidic catalysts from biomass wastes and may contribute to a holistic approach for biomass valorization.

Determination of 5-hydroxymethylfurfural (5-HMF) in Expired Pharmaceutical Syrups by Using HPLC-DAD Method

The Maillard reaction product 5-hydroxymethylfurfural (5-HMF) is formed under acidic conditions by the dehydration of sugars in carbohydrate-based food and pharmaceutical products during heating and storage. As pharmaceutical syrup formulations contain sugar and are stored under room temperature, they provide favorable conditions for the formation of 5-HMF. The long-term storage of syrup bottles after their cap has been opened and the unintentional use of expired syrups can lead to the formation of undesirable products such as 5-HMF in medications. Although legal limits have been established for 5-HMF content in pharmaceutical preparations, these levels may exceed those limits in hot climates or under inappropriate storage conditions. The present study detects and measures 5-HMF levels in expired pharmaceutical syrups through the HPLC-DAD (High Performance Liquid Chromatography with Diode Array Detection) method, and investigates the effects on 5-HMF levels of the 72-hour storage of syrups at temperatures of 40˚C. The 5-HMF level in syrups stored at room temperature varied between 1.34 μg/mL to 15.63 μg/mL, while in syrups stored at higher temperatures, the levels ranged from 2.24 μg/mL to 18.24 μg/mL. This indicated that 5-HMF content in syrups stored at 40 ˚C was higher than those measured in syrups stored at room temperature, although the increase was not found to be statistically significant (p>0.05). In addition to measuring the amount of 5-HMF in pharmaceutical syrups, this study also examined the changes in the levels of this dehydration product in syrup formulations under hot climates and according to storage conditions.