RESUMEN
The profitability and sustainability of future biorefineries are dependent on efficient feedstock use. Therefore, it is essential to valorize lignin when using wood. We have developed an integrated biorefinery that converts 78 weight % (wt %) of birch into xylochemicals. Reductive catalytic fractionation of the wood produces a carbohydrate pulp amenable to bioethanol production and a lignin oil. After extraction of the lignin oil, the crude, unseparated mixture of phenolic monomers is catalytically funneled into 20 wt % of phenol and 9 wt % of propylene (on the basis of lignin weight) by gas-phase hydroprocessing and dealkylation; the residual phenolic oligomers (30 wt %) are used in printing ink as replacements for controversial para-nonylphenol. A techno-economic analysis predicts an economically competitive production process, and a life-cycle assessment estimates a lower carbon dioxide footprint relative to that of fossil-based production.
Asunto(s)
Alquenos , Huella de Carbono , Fenoles , Madera , Biomasa , Carbohidratos , Catálisis , Fraccionamiento Químico , Lignina , FenolRESUMEN
The present chapter describes an accurate and user-friendly method for determining amino acid composition of wheat gluten proteins and their gliadin and glutenin fractions. The method consists of hydrolysis of the peptide bonds in 6.0 M hydrochloric acid (HCl) solution at 110 °C for 24 h, followed by evaporation of the acid and separation of the free amino acids by high-performance anion-exchange chromatography with integrated pulsed amperometric detection (HPAEC-IPAD). In contrast to conventional methods, the analysis requires neither pre- or post-column derivatization nor a time-consuming oxidation or derivatization step prior to hydrolysis. Correction factors account for incomplete release of Val and Ile even after hydrolysis for 24 h and for losses of Ser during evaporation. Gradient conditions including an extra eluent allow multiple sequential sample analyses without risk of Glu accumulation on the anion-exchange column which otherwise would result from high Gln levels in gluten proteins.
Asunto(s)
Aminoácidos/análisis , Gliadina/química , Glútenes/química , Análisis de Secuencia de Proteína/métodos , Triticum/química , Aminoácidos/química , Aniones/química , Cromatografía por Intercambio Iónico/instrumentación , Cromatografía por Intercambio Iónico/métodos , Electroquímica , HidrólisisRESUMEN
The pharaoh ant is a notorious and hard to eradicate pest, which poses a threat in hospitals, spreading pathogens and contaminating sterile equipment. When applied on ants, zeolites adsorb part of their epicuticular wax layer. The ants are then vulnerable to desiccation, since this layer regulates water exchange. We analyzed the chemical composition of this wax layer using GC-MS (Gas Chromatography-Mass Spectrometry). A hexane wash of M. pharaonis foragers resulted in the identification of 53 components, four of which were not previously defined in Monomorium species. Selective adsorption of specific compounds on zeolites assisted in the identification of compounds which could not be separated on the GC column and allowed for the identification of three additional compounds. Zeolites show different affinities for the wax compounds depending on pore structure and chemical composition. Selective adsorption of alkanes on zeolites is also investigated in the fields of refinery processes and catalysis. Pore mouth and key lock adsorption mechanisms and selectivity according to molecular weight and branching, investigated in these fields, are also involved in adsorption processes of epicuticular waxes. The insecticidal activity of a zeolite is related to adsorption selectivity rather than capacity. One of the best adsorbing zeolites showed limited insecticidal activity and can be considered as a non-lethal alternative for epicuticular wax sampling.
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Hormigas/química , Insecticidas/química , Lípidos/análisis , Zeolitas/química , Adsorción , Alcanos/análisis , Alcanos/aislamiento & purificación , Animales , Cromatografía de Gases y Espectrometría de Masas , Lípidos/aislamiento & purificación , Polvos , Ceras/análisis , Ceras/aislamiento & purificaciónRESUMEN
BACKGROUND: Historically, inert insecticidal powders such as diatomaceous earth were researched for pest management applications, and it was revealed that these types of powders killed insects by desiccation. However, data on the critical material properties that affect their efficacy are sparse. The present study investigated the insecticidal effect of powdered materials on the pharaoh ant, a notorious domestic pest. RESULTS: The insecticidal activity of 24 porous materials was tested. Eight of these materials performed better than the benchmark, diatomaceous earth. Zeolite Y and carbon black II performed best, inducing 50% mortality within 40 and 55 minutes, respectively. Statistical analysis of seven material properties revealed that macroporous surface area and Brunauer-Emmett-Teller (BET) specific surface area were most predictive of insecticidal activity. For zeolites and ordered mesoporous silica materials, the most important parameters were, respectively, BET and large mesopore surface area. Finally, gas chromatography-mass spectrometry (GC-MS) analysis confirmed the adsorption of epicuticular hydrocarbons onto the zeolite powders. CONCLUSION: This study shows clear potential for the use of environmentally friendly, inert porous materials as insecticides against the pharaoh ant and identified the key material properties influencing insecticidal activity. The GC-MS data support the hypothesis that the mortality was caused by the removal of the protective epicuticular hydrocarbons. © 2017 Society of Chemical Industry.
Asunto(s)
Hormigas/efectos de los fármacos , Insecticidas/farmacología , Polvos/farmacología , AnimalesRESUMEN
Metal-organic frameworks (MOFs) are investigated for the adsorption of aromatic amino acids l-phenylalanine (l-Phe), l-tryptophan (l-Trp), and l-tyrosine (l-Tyr) from aqueous solutions. After screening a range of water-stable MOFs, the hydrophobic Zr-MOF MIL-140C emerged as the best performing material, exhibiting uptakes of 15 wt % for l-Trp and 20 wt % for l-Phe. These uptakes are 5-10 wt % higher than those of large-pore zeolites Beta and Y. Both single-compound and competitive adsorption isotherms for l-Phe and l-Trp were experimentally obtained at the natural pH of these amino acid mixtures (pH 6.5-7) without additional pH modification. We find that the hydrophobic nature of MIL-140C and the capacity of l-Trp to form hydrogen bonds favor the uptake of l-Trp with its larger indole moiety compared to the smaller phenyl side group of l-Phe. On the basis of literature and vibrational analysis, observations of hydrogen-bonded l-Trp within the MIL-140C framework are evidenced by red- and blue-shifted -NH vibrations (3400 cm-1) in Fourier transform infrared spectroscopy, which were attributed to types N-Hl-Trp···πMIL-140C and N-Hl-Trp···OMIL-140C, respectively. MIL-140C is shown to be recycled at least three times for both aromatic amino acids without any loss of adsorption capacity, separation performance, or crystallinity. Desorption of aromatic amino acids proceeds easily in aqueous ethanol. Substantial coadsorption of negatively charged amino acids l-glutamate and l-aspartate (l-Glu and l-Asp) was observed from a model solution for wheat straw protein hydrolysate at pH 4.3. On the basis of these results, we conclude that MIL-140C is an interesting material for the recovery of essential aromatic amino acids l-Tyr, l-Phe, and l-Trp and of l-Glu and l-Asp from waste protein hydrolysates.
Asunto(s)
Aminoácidos Aromáticos/química , Adsorción , Estructuras Metalorgánicas , AguaRESUMEN
Durum wheat (Triticum durum Desf.) semolina gluten proteins consist of monomeric gliadin and polymeric glutenin and determine the quality of pasta products made therefrom. During pasta drying, glutenin starts polymerizing already below 60 °C (65% relative humidity (RH)), whereas gliadin only is incorporated in the protein network at temperatures exceeding 68 °C (68% RH) through thiol (SH)/disulfide (SS) exchange reactions. Removal of free SH groups in glutenin by adding 2.3 µmol KBrO3 or KIO3 per g dry matter semolina protein (g protein) or 13.8 µmol N-ethylmaleimide/g protein reduces gliadin-glutenin cross-linking during pasta drying and/or cooking and yields cooked pasta of high quality. Introducing free SH groups by adding 13.8 µmol glutathione/g protein increases gliadin-glutenin cross-linking during pasta processing, resulting in cooked pasta of lower quality. We hypothesize that too much gliadin incorporation in the glutenin network during pasta processing tightens the protein network and results in lower cooking quality.
Asunto(s)
Culinaria , Etilmaleimida/química , Calidad de los Alimentos , Gliadina/química , Glútenes/química , Oxidación-Reducción , Polimerizacion , Triticum/químicaRESUMEN
BACKGROUND: There is a growing interest in texturally and nutritionally satisfying vegetable alternatives to meat. Wheat gluten proteins have unique functional properties but a poor nutritional value in comparison to animal proteins. This study investigated the potential of egg white and bovine milk casein with well-balanced amino acid composition to increase the quality of wheat gluten-based protein-rich foods. RESULTS: Heating a wheat gluten (51.4 g)-water (100.0 mL) blend for 120 min at 100 °C increased its firmness less than heating a wheat gluten (33.0 g)-freeze-dried egg white (16.8 g)-water (100.0 mL) blend. In contrast, the addition of casein to the gluten-water blend negatively impacted firmness after heating. Firmness was correlated with loss of protein extractability in sodium dodecyl sulfate containing medium during heating, which was higher with egg white than with casein. Even more, heat-induced polymerization of the gluten-water blend with egg white but not with casein was greater than expected from the losses in extractability of gluten and egg white on their own. CONCLUSION: Structure formation was favored by mixing gluten with egg white but not with casein. These observations were linked to the intrinsic polymerization behavior of egg white and casein, but also to their interaction with gluten. Thus not all nutritionally suitable proteins can be used for enrichment of gluten-based protein-rich foods.
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Caseínas/química , Proteínas en la Dieta/química , Proteínas del Huevo/química , Glútenes/química , Triticum/química , Aminoácidos/análisis , Aminoácidos/química , Animales , Bovinos , Fenómenos Químicos , Pollos , Calor , Carne , Valor Nutritivo , Polimerizacion , SensaciónRESUMEN
Thermolysin hydrolyzates of freshly isolated, extensively stored (6 years, 6 °C, dry) and heated (60 min, 90 °C, in excess water) bovine serum albumin (BSA) samples were analyzed with liquid chromatography (LC) electrospray ionization (ESI) tandem mass spectrometry (MS/MS) using alternating electron-transfer dissociation (ETD) and collision-induced dissociation (CID). The positions of disulfide bonds and free thiol groups in the different samples were compared to those deduced from the crystal structure of native BSA. Results revealed non-enzymatic posttranslational modifications of cysteine during isolation, extensive dry storage, and heating. Heat-induced extractability loss of BSA was linked to the impact of protein unfolding on the involvement of specific cysteine residues in intermolecular and intramolecular thiol-disulfide interchange and thiol oxidation reactions. The here developed approach holds promise for exploring disulfide bond formation and reshuffling in various proteins under conditions relevant for chemical, biochemical, pharmaceutical and food processing.
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Disulfuros/química , Electrones , Albúmina Sérica Bovina/química , Espectrometría de Masas en Tándem/métodos , Secuencia de Aminoácidos , Animales , Bovinos , Cromatografía en Gel , Cromatografía Líquida de Alta Presión , Cisteína/química , Calor , Datos de Secuencia Molecular , Péptidos/química , Agregado de Proteínas , Albúmina Sérica Bovina/aislamiento & purificaciónRESUMEN
Oxidative decarboxylation of amino acids into nitriles was performed using molecular oxygen as terminal oxidant and a heterogeneous ruthenium hydroxide-based catalyst. A range of amino acids was oxidized in very good yield, using water as the solvent.
Asunto(s)
Aminoácidos/química , Nitrilos/química , Oxidantes/química , Oxígeno/química , Rutenio/química , Catálisis , Descarboxilación , Tecnología Química Verde , Oxidación-ReducciónRESUMEN
The oxidative decarboxylation of amino acids to nitriles was achieved in aqueous solution by inâ situ halide oxidation using catalytic amounts of tungstate exchanged on a [Ni,Al] layered double hydroxide (LDH), NH4 Br, and H2 O2 as the terminal oxidant. Both halide oxidation and oxidative decarboxylation were facilitated by proximity effects between the reactants and the LDH catalyst. A wide range of amino acids was converted with high yields, often >90 %. The nitrile selectivity was excellent, and the system is compatible with amide, alcohol, and in particular carboxylic acid, amine, and guanidine functional groups after appropriate neutralization. This heterogeneous catalytic system was applied successfully to convert a protein-rich byproduct from the starch industry into useful bio-based N-containing chemicals.
Asunto(s)
Aminoácidos/química , Nitrilos/química , Catálisis , Descarboxilación , Glútenes/química , Hidrólisis , Oxidación-Reducción , Triticum/químicaRESUMEN
Full baking of earlier partially baked (parbaked) bread can supply fresh bread to the consumer at any time of the day. When parbaked bread loaves were stored at -25, 4 or 23°C, the extent of crumb to crust moisture migration and amylopectin retrogradation differed with storage temperature, and the firming rate was evidently lowest during frozen storage. The extent of crumb to crust moisture migration during parbaked bread storage largely determined the mass of the fresh finished bread, and its crumb and crust moisture contents. Initial NMR proton mobility, initial resilience, the extent of amylopectin retrogradation and changes in firmness and resilience during storage of fully baked bread were affected by its crumb moisture content. The lowest firming rate was observed for finished bread resulting from parbaked bread stored at -25°C, while the highest firming rate was observed for finished bread from parbaked bread stored at 23°C.
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Amilopectina/química , Pan/análisis , Espectroscopía de Resonancia Magnética/métodos , Almacenamiento de Alimentos , Calor , Agua/químicaRESUMEN
High-temperature compression molding of wheat gluten at low water levels yields a rigid plastic-like material. We performed a systematic study to determine the effect of additives with multiple thiol (SH) groups on gluten network formation during processing and investigate the impact of the resulting gluten network on the mechanical properties of the glassy end product. To this end, a fraction of the hydroxyl groups of different polyols was converted into SH functionalities by esterifying with 3-mercaptopropionic acid (MPA). The monofunctional additive MPA was evaluated as well. During low-temperature mixing SH-containing additives decreased the gluten molecular weight, whereas protein cross-linking occurred during high-temperature compression molding. The extent of both processes depended on the molecular architecture of the additives and their concentration. After molding, the material strength and failure strain increased without affecting the modulus, provided the additive concentration was low. The strength decreased again at too high concentrations for polyols with low SH functionalization. Attributing these effects solely to the interplay of plasticization and the SH-facilitated introduction of cross-links is inadequate, since an improvement in both strength and failure strain was also observed in the presence of high levels of MPA. It is hypothesized that, regardless of the molecular structure of the additive, the presence of SH-containing groups induces conformational changes which contribute to the mechanical properties of glassy gluten materials.
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Glútenes/química , Compuestos de Sulfhidrilo/química , Triticum/química , Calor , Estructura Molecular , Peso Molecular , Presión , Conformación ProteicaRESUMEN
Two baking times (9 and 24 min) and storage temperatures (4 and 25 °C) were used to explore the impact of heat exposure during bread baking and subsequent storage on amylopectin retrogradation, water mobility, and bread crumb firming. Shorter baking resulted in less retrogradation, a less extended starch network and smaller changes in crumb firmness and elasticity. A lower storage temperature resulted in faster retrogradation, a more rigid starch network with more water inclusion and larger changes in crumb firmness and elasticity. Crumb to crust moisture migration was lower for breads baked shorter and stored at lower temperature, resulting in better plasticized biopolymer networks in crumb. Network stiffening, therefore, contributed less to crumb firmness. A negative relation was found between proton mobilities of water and biopolymers in the crumb gel network and crumb firmness. The slope of this linear function was indicative for the strength of the starch network.
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Pan/análisis , Culinaria/métodos , Almacenamiento de Alimentos , TemperaturaRESUMEN
Wheat gluten can be converted into rigid biobased materials by high-temperature compression molding at low moisture contents. During molding, a cross-linked protein network is formed. This study investigated the effect of mixing gluten with acid/alkali in 70% ethanol at ambient temperature for 16 h followed by ethanol removal, freeze-drying, and compression molding at 130 and 150 °C on network formation and on types of cross-links formed. Alkaline pretreatment (0-100 mmol/L sodium hydroxide or 25 mmol/L potassium hydroxide) strongly affected gluten cross-linking, whereas acid pretreatment (0-25 mmol/L sulfuric acid or 25 mmol/L hydrochloric acid) had limited effect on the gluten network. Molded alkaline-treated gluten showed enhanced cross-linking but also degradation when treated with high alkali concentrations, whereas acid treatment reduced gluten cross-linking. ß-Elimination of cystine and lanthionine formation occurred more pronouncedly at higher alkali concentrations. In contrast, formation of disulfide and nondisulfide cross-links during molding was hindered in acid-pretreated gluten. Bioplastic strength was higher for alkali than for acid-pretreated samples, whereas the flexural modulus was only slightly affected by either alkaline or acid pretreatment. Apparently, the ratio of disulfide to nondisulfide cross-links did not affect the mechanical properties of rigid gluten materials.
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Ácidos no Carboxílicos/química , Plásticos Biodegradables/química , Glútenes/química , Hidróxidos/química , Indicadores y Reactivos/química , Semillas/química , Triticum/química , Fenómenos Químicos , Módulo de Elasticidad/efectos de los fármacos , Calor , Ácido Clorhídrico/química , Fenómenos Mecánicos , Concentración Osmolar , Compuestos de Potasio/química , Conformación Proteica , Hidróxido de Sodio/química , Solubilidad , Ácidos Sulfúricos/químicaRESUMEN
The concentration and composition of wheat gluten proteins and the presence, concentration and location of cysteine residues therein are important for wheat flour quality. However, it is difficult to identify gluten proteins, as they are an extremely polymorphic mixture of prolamins. We here present methods for cysteine labeling of wheat prolamins with 4-vinylpyridine (4-VP) and iodoacetamide (IDAM) which, as compared to label-free analysis, substantially improve identification of cysteine-containing peptides in enzymic prolamin digests by electrospray ionization--tandem mass spectrometry. Both chymotrypsin and thermolysin yielded cysteine-containing peptides from different gluten proteins, but more proteins could be identified after chymotryptic digestion. In addition, to the best of our knowledge, we were the first to label prolamins with isotope coded affinity tags (ICAT), which are commonly used for quantitative proteomics. However, more peptides were detected after labeling gluten proteins with 4-VP and IDAM than with ICAT.
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Cisteína/química , Glútenes/química , Péptidos/química , Triticum/química , Alquilación , Quimotripsina/química , Espectrometría de Masas , Prolaminas/química , Proteómica , Coloración y EtiquetadoRESUMEN
When Bacillus stearothermophilus α-amylase (BStA), Pseudomonas saccharophila α-amylase (PSA), or Bacillus subtilis α-amylase (BSuA) was added to a bread recipe to impact bread firming, amylose crystal formation was facilitated, leading to lower initial crumb resilience. Bread loaves that best retained their quality were those obtained when BStA was used. The enzyme hindered formation of an extended starch network, resulting in less water immobilization and smaller changes in crumb firmness and resilience. BSuA led to extensive degradation of the starch network during bread storage with release of immobilized water, eventually resulting in partial structure collapse and poor crumb resilience. The most important effect of PSA was an increased bread volume, resulting in smaller changes in crumb firmness and resilience. A negative linear relation was found between NMR proton mobilities of water and biopolymers in the crumb and crumb firmness. The slope of that relation gave an indication of the strength of the starch network.
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Proteínas Bacterianas/metabolismo , Pan/análisis , Culinaria , Proteínas en la Dieta/metabolismo , Almacenamiento de Alimentos , Proteínas de Almacenamiento de Semillas/metabolismo , alfa-Amilasas/metabolismo , Bacillus subtilis/enzimología , Bélgica , Fenómenos Químicos , Proteínas en la Dieta/química , Calidad de los Alimentos , Geobacillus stearothermophilus/enzimología , Estabilidad Proteica , Pseudomonas/enzimología , Proteínas de Almacenamiento de Semillas/químicaRESUMEN
To establish the relationship between biopolymer interactions, water dynamics, and crumb texture evolution in time, proton mobilities in starch and gluten model systems and bread were investigated with NMR relaxometry. Amylopectin recrystallization was observed as an increased amount of fast-relaxing protons, while network strengthening and changes in water levels were noted as a reduced mobility and amount, respectively, of slowly relaxing protons. Amylopectin recrystallization strengthened the starch network with concomitant inclusion of water and increased crumb firmness, especially at the beginning of storage. The inclusion of water and the thermodynamic immiscibility of starch and gluten resulted in local gluten dehydration during bread storage. Moisture migration from crumb to crust further reduced the level of plasticizing water of the biopolymer networks and contributed to crumb firmness at longer storage times. Finally, we noted a negative relationship between the mobility of slowly relaxing protons of crumb polymers and crumb firmness.
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Biopolímeros/química , Pan/análisis , Agua/química , Amilopectina/química , Rastreo Diferencial de Calorimetría , Manipulación de Alimentos/métodos , Glútenes/química , Espectroscopía de Resonancia Magnética , Estructura Molecular , Termodinámica , Difracción de Rayos XRESUMEN
The present paper describes a method for the identification of intact high molecular weight glutenin subunits (HMW-GS), the quality determining proteins from the wheat storage proteome. The method includes isolation of HMW-GS from wheat flour, further separation of HMW-GS by reversed-phase high-performance liquid chromatography (RP-HPLC), and their subsequent molecular identification with electrospray ionization mass spectrometry using a quadrupole-time-of-flight mass analyzer. For HMW-GS isolation, wheat proteins were reduced and extracted from flour with 50% 1-propanol containing 1% dithiothreitol. HMW-GS were then selectively precipitated from the protein mixture by adjusting the 1-propanol concentration to 60%. The composition of the precipitated proteins was first evaluated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis with Coomassie staining and RP-HPLC with ultraviolet detection. Besides HMW-GS (≥65%), the isolated proteins mainly contained ω5-gliadins. Secondly, the isolated protein fraction was analyzed by liquid chromatography-mass spectrometry. Optimal chromatographic separation of HMW-GS from the other proteins in the isolated fraction was obtained when the mobile phase contained 0.1% trifluoroacetic acid as ion-pairing agent. Individual HMW-GS were then identified by determining their molecular masses from the high-resolution mass spectra and comparing these with theoretical masses calculated from amino acid sequences. Using formic acid instead of trifluoroacetic acid in the mobile phase increased protein peak intensities in the base peak mass chromatogram. This allowed the detection of even traces of other wheat proteins than HMW-GS in the isolated fraction, but the chromatographic separation was inferior with a major overlap between the elution ranges of HMW-GS and ω-gliadins. Overall, the described method allows a rapid assessment of wheat quality through the direct determination of the HMW-GS composition and offers a basis for further top-down proteomics of individual HMW-GS and the entire wheat glutenin fraction.
Asunto(s)
Glútenes/química , Glútenes/aislamiento & purificación , Proteoma/química , Triticum/química , Gliadina/química , Gliadina/aislamiento & purificación , Peso Molecular , Espectrometría de Masa por Ionización de Electrospray/métodosRESUMEN
Fermenting yeast does not merely cause dough leavening, but also contributes to the bread aroma and might alter dough rheology. Here, the yeast carbon metabolism was mapped during bread straight-dough fermentation. The concentration of most metabolites changed quasi linearly as a function of fermentation time. Ethanol and carbon dioxide concentrations reached up to 60 mmol/100g flour. Interestingly, high levels of glycerol (up to 10 mmol/100g flour) and succinic acid (up to 1.6 mmol/100g flour) were produced during dough fermentation. Further tests showed that, contrary to current belief, the pH decrease in fermenting dough is primarily caused by the production of succinic acid by the yeast instead of carbon dioxide dissolution or bacterial organic acids. Together, our results provide a comprehensive overview of metabolite production during dough fermentation and yield insight into the importance of some of these metabolites for dough properties.