Furan Formation Research Articles

EFFECT OF UV-C TREATMENT ON MICROBIAL POPULATION AND BIOACTIVE COMPOUNDS OF ORANGE JUICE USING MODIFIED REACTOR BASED ON DEAN VORTEX FLOW

The aim of the present study was to investigate the effectiveness of UV-C treatment using a modified UV-C reactor based on Dean vortex flow. Parameters taken into account were total aerobic bacteria count and yeast and mould counts, antioxidant capacity, total phenolic content, 5-HMF content, furan formation and sensory attributes. A UV-C treatment with 68.75 mJ/cm2 led to 2.21-log CFU/ml and 1.13-log CFU/ml reduction of TMAB and YM count, respectively. DPPH radical scavenging activity and total phenolic content of UV-C treated orange juice significantly decreased. However, UV-C induced reduction of HMF was observed. UV-C treatment would be a beneficial method to eliminate or decrease the HMF content if HMF were present in the juice as a consequences of obtained results. pH and °Brix remained constant after UV-C treatment. No furan formation was detected and no significant change observed in the quality attributes in regards to appearance and colour.

Transformation of 3-(Furan-2-yl)-1,3-di(het)arylpropan-1-ones to Prop-2-en-1-ones via Oxidative Furan Dearomatization/2-Ene-1,4,7-triones Cyclization.

The approach to 3-(furan-2-yl)-1,3-di(het)arylprop-2-en-1-ones based on the oxidative dearomatization of 3-(furan-2-yl)-1,3-di(het)arylpropan-1-ones followed by an unusual cyclization of the formed di(het)aryl-substituted 2-ene-1,4,7-triones has been developed. The cyclization step is related to the Paal–Knorr synthesis, but the furan ring formation is accompanied in this case by a formal shift of the double bond through the formation of a fully conjugated 4,7-hydroxy-2,4,6-trien-1-one system or its surrogate.

Effects of processing parameters on furan formation in canned strawberry jam

The formation mechanism of furan has been studied extensively in model systems, however, furan formation in real foods are complex and far from being fully understood. In this study, the effects of acid-regulating agent (citric acid), sugar addition (glucose, fructose and sucrose) and thickening agents (xanthan gum, κ-carrageenan and pectin) on furan levels in strawberry jams were studied; meanwhile the formation pathway of furan in canned strawberry jam was proposed by carbon module labeling (CAMOLA) technique. Our results suggested low pH promoted furan formation in strawberry jam. Besides, fructose produces more furans than sucrose and glucose, and the addition of xanthan gum reduced furan levels significantly. The kinetic data showed that ascorbic and dehydroascorbic acid degradation followed first-order kinetics while rate of furan formation followed zero-order kinetics. This study presented the possibility of mitigating furan formation in canned strawberry jams by optimization of processing parameters and addition of xanthan gum.

Water-Mediated Catalytic Decarboxylation Enabled Polysubstituted Furans and Allylic Alcohols with Exclusive (E)-Configurations.

A water-mediated catalytic decarboxylation process toward the formation of polysubstituted furans and (E)-allylic alcohols has been reported. This protocol features wide functional group tolerance, easy operation, and only CO2-byproduct generation. These reactions can be performed on a large scale open to air under extremely ambient conditions. A range of control experiments revealed the crucial role of the water for the successful conversions as well as the origin of the chemoselectivity and exclusive stereoselectivity.

Effects of pH on headspace volatiles and properties of Maillard reaction products derived from enzymatically hydrolyzed quinoa protein-xylose model system

The enzymatically hydrolyzed quinoa protein (E-HQP) was used as a main precursor of a wide range of thermal process flavours. Identification of the volatile compounds generated from the reaction of E-HQP-xylose model mixture at different initial pH values (5, 6, 7, 8 and 9) was performed using a solid phase microextraction - GC-MS technique. The content of free amino acids, colour intensity and radical scavenging activity of the Maillard reaction products (MRPs) formed at each pH were determined. The results revealed a great influence of the pH values on chemical composition and odour profile of the generated volatiles. The studies showed that low pH favoured formation of furans, furanones and cyclopentanones. In contrast, the pyrazines comprised the highest yield of the total volatiles at pH 9. A positive correlation was found between increasing the pH values and browning intensity of MRPs. The antioxidant activity of MRPs and total content of free amino groups showed a gradual decrease by increasing the pH. A correlation was found between the antioxidant activity of MRPs and the volatile compounds generated at each pH. Principle component analysis clearly elucidated a distinct separation among the investigated E-HQP-xylose model mixtures based on the volatile compounds generated at different pH.

Gentle Sterilization of Carrot-Based Purees by High-Pressure Thermal Sterilization and Ohmic Heating and Influence on Food Processing Contaminants and Quality Attributes.

Pressure-enhanced sterilization (PES) and ohmic heating (OH) are two emerging sterilization techniques, currently lacking implementation in the food industry. However, both technologies offer significant benefits in terms of spore inactivation using reduced thermal intensity in food products, as well as minimized effects on sensory and nutritional profiles. In this study, PES and OH were tested based on possible food safety process windows in comparison to thermal retorting, to optimize the food quality of carrot-based purees. The following parameters related to food quality were tested: texture, carotenoid content, color, and detectable amount of food processing contaminants (FPC) formed. Application of the innovative sterilization techniques resulted in a better retention of color, texture, and carotenoids (for PES) as well as a reduced formation of food processing contaminants. Importantly, a significant reduction in the formation of furan and its derivates was observed, compared to the retorted samples. Hence, both sterilization technologies showed promising results in the mitigation of potential toxic processing contaminants and retention of quality attributes.

Niobium phosphates as bifunctional catalysts for the conversion of biomass-derived monosaccharides

The direct conversion of glucose and xylose into HMF and furfural is more efficient using a combination of Lewis and Brønsted acids. Herein, niobium phosphates were prepared with different compositions, which affect its surface acidity and, consequently, the catalytic activity. The catalysts with a high P/Nb molar ratio presented a low molar ratio between Lewis and Brønsted acid sites (L/B ratio), while those with low P/Nb molar ratio displayed a high L/B ratio. NbP-2, the sample with the highest L/B ratio, showed the highest reaction rate for both HMF and furfural formation. It was found, indeed, that the reaction rate for monosaccharides conversion and furans formation correlate linearly with the L/B ratio. The results presented not only introduce niobium phosphates with a high L/B molar ratio as promising catalysts for HMF and furfural production but also provide fundamental knowledge that will guide the design of other bifunctional heterogeneous catalysts.

Formation of furan in baby food products: Identification and technical challenges

Furan is generally produced during thermal processing of various foods including baked, fried, and roasted food items such as cereal products, coffee, canned, and jarred prepared foods as well as in baby foods. Furan is a toxic and carcinogenic compound to humans and may be a vital hazard to infants and babies. Furan could be formed in foods through thermal degradation of carbohydrates, dissociation of amino acids, and oxidation of polyunsaturated fatty acids. The detection of furan in food products is difficult due to its high volatility and low molecular weight. Headspace solid-phase microextraction coupled with gas chromatography/mass spectrometer (GC/MS) is generally used for analysis of furan in food samples. The risk assessment of furan can be characterized using margin of exposure approach (MOE). Conventional strategies including cooking in open vessels, reheating of commercially processed foods with stirring, and physical removal using vacuum treatment have remained unsuccessful for the removal of furan due to the complex production mechanisms and possible precursors of furan. The innovative food-processing technologies such as high-pressure processing (HPP), high-pressure thermal sterilization (HPTS), and Ohmic heating have been adapted for the reduction of furan levels in baby foods. But in recent years, only HPP has gained interest due to successful reduction of furan because of its nonthermal mechanism. HPP-treated baby food products are commercially available from different food companies. This review summarizes the mechanism involved in the formation of furan in foods, its toxicity, and identification in infant foods and presents a solution for limiting its formation, occurrence, and retention using novel strategies.

Method for Disposal of Landfills in Sparsely Populated Areas of Russia

The development of a mobile waste incineration plant designed for the recovery of garbage dumps located near towns and villages, from where the removal of garbage to the city to the incineration plant is not profitable due to the large remoteness of small settlements from the city. The installation has two combustion zones: in the 1st zone, the combustion process of solid municipal waste (MSW) is achieved at temperatures up to 600 °C, and in the second zone – up to 1200 °C. Afterburning of flue gas to reduce the formation of dioxins, furans and soot is provided.

Acetylene vs ketones on the route to base-promoted assembly of furans or 6,8-dioxabicyclo[3.2.1]octanes and cyclopentenols: a quantum-chemical study

The electronic characteristics of substrates (α,β-unsaturated ketones) and reagents (carbanions of ketones and ethynide ions), as well as thermodynamic and kinetic characteristics both their interaction and the formation of final products have been evaluated using the B2PLYP/6-311+G**//B3LYP/6-31+G* and B3LYP/6-311++G**//B3LYP/6-31+G* quantum-chemical approaches. Reactivity indices that adequately describe the electrophilic and nucleophilic properties of the substrates and reagents are proposed. It has been shown that, regardless of the nature of substrates and reagents, the formation of cyclopentenols and furans is thermodynamically favorable, while the presence of bulky substituents leads to an increase in energy during the formation of 6,8-dioxabicyclo[3.2.1]octanes and explains in this case their absence in products. The calculated activation barriers of the competing reactions of the nucleophilic addition of ethynide ions and ketone carbanions to the double C=C bond of α,β-unsaturated ketones are correlated with the observed reaction direction and the proposed reactivity indices.

Effects of Modified Activated Carbon on Microwave-Accelerated Organosolv Fractionation of Rice Husk.

Organosolv fractionation is a promising approach for the separation of lignocellulosic components in integrated biorefineries where each component can be fully valorized into valuable platform chemicals and biofuels. In this study, microwave-accelerated organosolv fractionation was developed for the modification of lignocellulosic fractionation of rice husk. The fractionation condition was optimized for 1 h with the microwave irradiation at 300 W using a ternary solvent mixture composed of 24%:32%:44% water/ethanol/methyl isobutyl ketone. The effects of mineral acids (HCl, H3PO4, and H2SO4) and heterogeneous acid promoters (HCl, H3PO4, and H2SO4 impregnated over activated carbon) on the efficiency and selectivity of product yields (i.e., glucan, hemicellulose-derived products, and lignin) were also investigated. It was found that the use of H3PO4–activated carbon as the promoter showed superior performance on the fractionation of rice husk components, resulting in 88.8% recovery of cellulose, with 63.8% purity in the solid phase, whereas the recovery of hemicellulose (66.4%) with the lowest formation of furan and 5-hydroxymethyl furfural and lignin (81.0%) without sugar cross-contamination was obtained in the aqueous ethanol phase and organic phase, respectively. In addition, the morphology structure of fractionated rice husk presented 2.6-fold higher surface area (5.4 m2/g) of cellulose-enriched fraction in comparison with the native rice husk (2.1 m2/g), indicating the improvement of enzyme accessibility. Besides, the chemical changes of isolated lignin were also investigated by Fourier-transform infrared spectroscopy. This work gives pieces of information into the efficiencies of the microwave strategy as a climate neighborly elective fractionation method for this serious starting material in the biotreatment facility business.

Process modeling of chemical looping combustion (CLC) of municipal solid waste

Chemical Looping Combustion (CLC) of MSW could serve as a potential treatment method for the disposal of MSW and the recovery of energy because it can inhibit dioxins and furans formation that is associated with the traditional treatment (incineration). This study evaluated the chemical looping combustion of MSW composition (Paper + Plastics) at different ratios using Chemcad® process simulation software. The process simulation was done for two different CLC processes namely Chemical Looping Oxygen Uncoupling (CLOU) and In-situ Gasification CLC (IG-CLC). Plastic samples used include polyvinyl chloride (PVC), high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyethylene terephthalate (PET), polystyrene (PS) and polypropylene (PP). The results showed a promising CO2 yield (higher degree of CO2 capture) with the IG-CLC process having a higher CO2 yield (90–100%) than the CLOU process (30–80%) for the individual paper and plastic sample and the paper/plastic blends. For the combustion efficiency, the CLOU process was marginally higher than the IG-CLC process for all the plastics and the paper and while the IG-CLC process had higher combustion efficiency (30–75%) for the blends than the CLOU process (25–70%). Chlorine formation was used to measure the amount of dioxin formed; less chlorine means less dioxin formation. The results showed that the amount of chlorine formed decreases when paper and plastics were blended for all the different plastics except in PVC which increased for both CLOU and IG-CLC processes.

Dioxins and furans toxicity during the photocatalytic remediation of emerging pollutants. Triclosan as case study

The benefits of wastewater remediation technologies are offset in those cases where, as a result of operating conditions, harmful compounds are formed in the degradation routes of the original organic pollutants. This may be the case for the application of some advanced oxidation processes to wastewater containing precursors of dioxins and furans, as previously reported in the application of electrochemical and Fenton oxidation to degrade Triclosan and 2-chlorophenol. This work reports for the first time a detailed kinetic analysis of the formation of dioxins and furans during the photocatalytic treatment of aqueous samples containing 5-Chloro-2-[2,4-dichlorophenoxy] phenol, commercially known as Triclosan. After analysis of the PCDD/Fs concentration, the toxicity of the samples has been determined in terms of toxic equivalents (TEQ). TEQ values have been calculated, first with the group of 17 congeners with higher toxicity. Finally, a multivariable analysis and linear regression have been applied to reduce the significant number of congeners and optimize the analytical effort.

Thermal decomposition and isomerization of furfural and 2-pyrone: a theoretical kinetic study.

We have studied the decomposition and isomerization of furfural in the gas phase using quantum chemical and statistical reaction rate theory techniques. This work uncovers a variety of new reaction channels in furfural pyrolysis that lead to formation of the experimentally observed products, including CO2, which was previously unexplained. In addition to the known mechanism for furan + CO production, furfural is shown to isomerize directly to 2-pyrone, with a barrier height of 69 kcal mol-1, from where it can decompose to vinylketene + CO (highest barrier of 65 kcal mol-1) or to CO2 + 1,3-cyclobutadiene (highest barrier of 66 kcal mol-1). Alternative pathways to vinylketene + CO and 4-pyrone are also described. An RRKM theory/master equation model is developed to describe reactions on the C5O2H4 surface and used to simulate the decomposition kinetics of furfural and 2-pyrone. For both molecules, decomposition at 1400-2100 K is dominated by the formation of furan + CO, which represents around 75% of the total products, compared to around 19% and 6% for vinylketene + CO and total CO2, respectively. The model also predicts significant formation of stabilized 2-pyrone under these conditions. Rate coefficient expressions are reported as a function of both temperature and pressure for the main decomposition and isomerization channels identified in the pyrolysis of furfural and 2-pyrone, to facilitate detailed chemical kinetic modelling of these important oxygenated hydrocarbons.

Estimation of Life Cycle of Distribution Transformer in Context to Furan Content Formation, Pollution Index, and Dielectric Strength

Distribution transformer is the most vital component in the power system. Failure of a transformer leads to loss of revenue besides affecting the reliability of power supply to consumers. It can lead to the non-availability of the transformer for a long duration. Due to this, it is important to maintain the good quality of mineral oil. Thus, if the quality of the mineral oil is reduced then its dielectric strength/quality is degraded. Finally, it can affect the services of the transformer, in terms of continuity of power supply. This paper entails the development of a mathematical MATLAB/Simulink model which able to calculate the life cycle of distribution transformer and exact oil changing frequency. With the help of proposed Matlab/Simulink models, the plot curves between furan content formation versus time, pollution index versus time, and dielectric strength of oil versus time are also prepared. The article methodology uses the newly proposed equations, that are in accordance with IEEE standards: IEEE Guide for Loading Mineral-Oil-Immersed Transformers and Step-Voltage Regulators (IEEE Std. C57.91-2011) and IEEE Guide for the Reclamation of Insulating Oil and Criteria for Its Use (IEEE Std C57.637-2015). Then the case study for a 100 kVA distribution transformer is realized. So, with the input values in the Simulink model of load current of the transformer, dielectric constant of oil and flash point of oil we can estimate the life of the distribution transformer. Harmonic load factor in our research work is not included, in order to reduce influence of harmonic load we need to installed the active filter, which is not covered in this paper.

Insight into Tar Formation Mechanism during Catalytic Pyrolysis of Biomass over Waste Aluminum Dross

Tar is one of major products from biomass pyrolysis. Its formation mechanism in a catalytic pyrolysis system comprising pine sawdust and waste aluminum dross (AD) is investigated with the aid of analytical methods including thermogravimetric analysis (TG), Nuclear Magnetic Resonance (NMR), electron paramagnetic resonance (EPR), and gas chromatography coupling with mass spectrometry (GC-MS). The results show that AD plays a vital role in cleavage of C-O bonds to enhance selective formation of furans, ketones, and phenols. The catalytic pyrolysis is initiated by active C-O-M intermediate formation that accelerates C-O bond cleavage and generates great amounts of free radicals to 1020 spins/g at 300–500 °C. Compared with pure pine pyrolysis, the percentage of glucosidic bonds from cellulose decreases from 14.00% to 9.66% at 500 °C; the etherified guaiacyl is more actively ruptured and disappears at 700 °C. Furans and ketones increase from 17.45% to 22.23% and 6.71% to 10.80% at 500 °C, respectively. Phenols increase from 66.75% to 71.57%. The preferential production of higher value-added products via catalytic pyrolysis between biomass and industrial wastes may bring new insight to the simultaneous valorization of agricultural, municipal, and industrial waste.

Catalytic fast Co-Pyrolysis of sewage sludge−sawdust using mixed metal oxides modified with ZSM-5 catalysts on dual-catalysts for product upgrading

Catalytic fast co-pyrolysis of sewage sludge and sawdust was performed using Py/GC-MS for pyrolytic product upgrades. Metal oxides (NiO and MoO3) and ZSM-5 catalysts had been introduced into single catalytic pyrolysis. The combination of NiO + MoO3 in mixed metal oxides (MMOs) was modified with ZSM-5 under a dual-catalyst with different catalytic layouts. In the pyrolysis process, the metal oxides specifically promoted the formation of phenols, ketones, and furans. ZSM-5 was proven to be more effective in producing aromatic hydrocarbons and phenols and in reducing the oxygenated compounds. The combination of MMOs with ZSM-5 effectively improved product distribution by increasing the production of aromatics and phenols. MMOs promoted the aromatics selectivity of undesirable PAHs (70.5%), however, the addition of ZSM-5 to MMOs appeared to reduce and inhibit the formation of PAHs by 0.85%. The highest yield of aromatics was obtained by the layout of the ZSM-5/MMO dual catalysts layout which was 21.6%. Dual catalysts of MMOs and ZSM-5 in separated layout created promising effects in further increasing the production of aromatic hydrocarbons and phenols compared to the mixture of MMOs modified ZSM-5.

In situ Fe3O4 nanoparticles coating of polymers for separating hazardous PVC from microplastic mixtures

Poly(vinyl chloride) (PVC) poses great challenges to the recycling of plastic wastes since it highly deteriorates the properties of other plastics and induces the formation of hazardous chlorinated dioxins and furans. For the first time, we developed a novel hydrophilization method of polymers, the in situ magnetite (Fe3O4) nanoparticles (NPs) coating, to facilitate the flotation separation of PVC from microplastic mixtures. A homogeneous Fe3O4 NPs layer was selectively fabricated on the surface of non-PVC microplastics via a facile in situ coprecipitation method. This obviously decreased the contact angle of non-PVC microplastics by approximately 30° due to the plenty of hydroxyl groups on the surface of Fe3O4 NPs. However, the fabrication was not observed on the surface of PVC due to the weak interaction between Fe3+/Fe2+ and the surface of PVC. In this regard, the application of in situ Fe3O4 NPs coating in the flotation separation of PVC was systematically optimized using Box-Behnken design of response surface methodology. Quadratic models were generated to predict the floatability of microplastics, ascertain the effect of independent and interacted parameters, and numerically optimize the separation efficiency. Under optimum conditions, the Removalrate, Purity, and Recovery of PVC were 100.0%, 99.6%, and 100.0%, respectively. This study provides novel insights into the surface hydrophilization of polymers and shows promising prospects for facilitating the recycling of plastic wastes.

Pyrolysis Temperature Effect on Compositions of Neutral Nitrogen and Acidic Species in Shale Oil Using Negative-Ion ESI FT-ICR MS.

Negative-ion electrospray ionization (ESI) Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was used to study the effect of the pyrolysis temperature (400, 430, 460, 490, and 520 °C) on acidic and neutral nitrogen species in Huadian shale oil. To more accurately analyze the influence, shale oils produced during the heat-up stage were abandoned. The results show that because of the influence of polymerization and cracking reactions, the increase in temperature increases the content of pyrrole, thiophene, furan, phenol, and aromatic ring cores and decreases the content of carboxylic acid, respectively. Among all the heteroatom compounds identified from negative-ion ESI FT-ICR MS, the relative abundance of N1O1, N1O2, N1O3, N2, N2O1, O1, O3, O1S1, and N1S1 species increases, whereas that of O2 and O4 species decreases as the pyrolysis temperature increases. The decrease in the O2 species can be attributed to carboxylic acid with a double-bond equivalence (DBE) value of 1, whereas the increase in the O2 species with DBE values of 7 and 9 can be attributed to the formation of furan, phenol, and aromatic ring by the polymerization reaction at higher pyrolysis temperatures. Although the effect of the reaction temperature on the molecular composition of acidic and neutral nitrogen species is complex, still characteristic rules are found in this study.

Optimization and Validation of HS-SPME-GC-MS for the Determination of Furan and Alkylfurans in Chocolate-Based Products: Impact of Tempering and Laser Printing.

Furan and its alkyl substituted (2-methylfuran, 3-methylfuran, 2,3-dimethylfuran, 2,5-dimethylfuran) are found in a range between ppm to sub-ppb levels in many foodstuffs undergoing heat treatments like coffee, chicory, or even chocolate. Two major objectives are presented. First, we aim at optimizing and validating a HS-SPME-GC-MS method for the quantification of five alkylfurans in chocolate. Second, we focus our study on measuring the quantitative impact of engraving technique on the formation of furan and its derivatives in chocolate, from the raw callets to processed end-products. HS-SPME-GC-MS method operating in SIM mode and using isotope dilution technique with deuterated homologue internal standards was used to quantify alkylfurans in chocolate. Good repeatability (RSD% = 0.1-8%, in duplicate) and intermediate precision (RSD% = 1.7-7%, n = 6) were obtained for these five process contaminants at 10, 25, and 50 µg/kg. Trueness was varying between 81 and 109%. LoQ ranged from 0.48 to 2.50 µg/kg. Relative expanded measurement uncertainties ranged from 6 to 30%. Finally, tempering is responsible for a 24% increase in furan contamination, while the laser engraving technique results in an additional 31% increase in furan. A similar trend was also observed for 2-methylfuran and 3-methylfuran, whereas no significant increases were observed for 2,3-dimethylfuran and 2,5-dimethylfuran. A reliable and sensitive method of HS-SPME-GC-MS was reported for the first time for the analysis of furan and four alkylfurans in chocolate. This paper demonstrated that engraving using laser-based techniques can increase the levels of these compounds by up to 30%.