Iron (Fe(2+))-Catalyzed Glucosamine Browning at 50 °C: Identification and Quantification of Major Flavor Compounds for Antibacterial Activity

The conversion of glucosamine to deoxyfructosazine and its impact on bread quality

Bread serves as a crucial medium for developing functional foods. Functional bread enriched with glucosamine (GlcN) can be a dietary supplement to support joint health. This study investigated the retention of GlcN in bread and the formation of deoxyfructopyrazine (DOF) under various formulations. Bread samples containing GlcN and sugar alcohols demonstrated the highest GlcN retention, accounting for 69.7 %-71.0 % of the added GlcN, and exhibited the greatest production of DOF. The moisture distribution in the dough samples and the acetal reaction of sugars with DOF within bread system led to these outcomes. Additionally, bread with these additives displayed a darker and browner color than the control sample containing GlcN alone. Furthermore, 34 distinct flavor substances were identified across all bread samples. The study provides valuable insight for developing functional food utilizing GlcN, especially for baked foods.

Long-term organic carbon preservation enhanced by iron and manganese

The balance between degradation and preservation of sedimentary organic carbon (OC) is important for global carbon and oxygen cycles1. The relative importance of different mechanisms and environmental conditions contributing to marine sedimentary OC preservation, however, remains unclear2-8. Simple organic molecules can be geopolymerized into recalcitrant forms by means of the Maillard reaction5, although reaction kinetics at marine sedimentary temperatures are thought to be slow9,10. More recent work in terrestrial systems suggests that the reaction can be catalysed by manganese minerals11-13, but the potential for the promotion of geopolymerized OC formation at marine sedimentary temperatures is uncertain. Here we present incubation experiments and find that iron and manganese ions and minerals abiotically catalyse the Maillard reaction by up to two orders of magnitude at temperatures relevant to continental margins where most preservation occurs4. Furthermore, the chemical signature of the reaction products closely resembles dissolved and total OC found in continental margin sediments globally. With the aid of a pore-water model14, we estimate that iron- and manganese-catalysed transformation of simple organic molecules into complex macromolecules might generate on the order of approximately 4.1 Tg C yr-1 for preservation in marine sediments. In the context of perhaps only about 63 Tg C yr-1 variation in sedimentary organic preservation over the past 300 million years6, we propose that variable iron and manganese inputs to the ocean could exert a substantial but hitherto unexplored impact on global OC preservation over geological time.

Facile synthesis of chitosan-derived maillard reaction productions coated CuFeO2 with abundant oxygen vacancies for higher Fenton-like catalytic performance

The two shortcomings of the Fenton-like catalyst delafossite-type oxide (CuFeO₂) lie in its spontaneous agglomeration and deactivation under neutral working pH. To remedy these drawbacks, novel Fenton-like catalyst chitosan-derived maillard reaction productions coated CuFeO₂ with abundant oxygen vacancies (OV-CuFeO₂@MRPs) was synthesized by hydrothermal method with no extra chemical reducing agent. The systemic characterization illustrated that richer oxygen vacancies and higher particles dispersion of OV-CuFeO₂@MRPs contributed to better Rhodamine B (RhB) degradation under neutral pH compared to pure CuFeO₂. Cooper antisite defects in OV-CuFeO₂@MRPs were evidenced by X-ray powder diffraction (XRD), fourier transform infrared spectrometer (FTIR), Raman spectra and energy dispersive X-ray spectrometer (EDX) linescan. To keep the charge balance, OV-CuFeO₂@MRPs should form rich oxygen vacancies, which was confirmed by X-ray photoelectron spectroscopy (XPS) and solid-state electron paramagnetic resonance spectrometer (solid-state EPR). Furthermore, the electrochemical impedance spectroscopy (EIS) analysis revealed that oxygen vacancies could improve the electron transfer. Scavenging experiments and electron spin resonance spectroscopy (ESR) analysis demonstrated that OH was main active radical during Fenton-like reaction, and the density functional theory (DFT) calculation verified that the oxygen vacancy could effectively adsorb H₂O₂ and elongate O-O bond of H₂O₂, thus promoting the activation of H₂O₂ into OH.

Probing the interactions of GlcNH2 with boric acid via NMR spectroscopy

The essential role of boronic esters in controlling both the direction and selectivity of chemical reactions as well as their significant function in catalytic activity have been demonstrated for industrially important processes. The specific interaction analyses of the monosaccharide GlcNH2 with boric acid are of interest since monosaccharides serve as model systems for the more sophisticated carbohydrate molecules. The interaction of GlcNH2 with boric acid was systematically investigated by numerous NMR techniques. A 1 : 1 chelate boron complex coordinated at the cis-1,2 position of GlcNH2 was identified as the major species in DMSO-d6 solution via1H and 13C INEPT DOSY NMR spectroscopy. This specific boron nitrogen coordination mechanism was further supported by the 1H-15N HSQC spectra. Variations in the spin-lattice relaxation times (T1) of the 13C1 nucleus also provided quantitative data regarding this non-covalent interactions. This is an application of 1H, 13C INEPT DOSY, 1H-15N HSQC, and relaxation methods to study such aggregations in solutions. These methods have potential applications in the characterization of reactive intermediates in biomass conversions.

The effect of glucosamine and glucosamine caramel on quality and consumer acceptability of regular and reduced salt breakfast sausages

Given the more recent interest in its flavour enhancing potential, the effects of the addition of glucosamine or glucosamine caramel on both technological and consumer acceptability of regular and reduced salt breakfast sausages were studied. A 2 × 3 complete factorial design was used with salt level (regular salt, RS (1.1%) and low salt, LS (0.825%)) and formulation treatment (control, GlcN - glucosamine (1%), CAR - glucosamine caramel (1% GlcN equivalent)) as main effects. Raw or cooked sausages were analyzed for CIE L*, a* and b*, physical and textural properties and consumer acceptance. Different salt levels did not affect the pH of meat batter, while the reduced salt treatment resulted in higher cook loss. On the contrary, addition of GlcN and CAR reduced the pH of sausage with no effect on cook loss. Neither salt levels nor treatment formulation affected the textural attributes of sausages. The inclusion of CAR significantly reduced L* value and increased redness (a*) and yellowness (b*) of cooked sausages. Salt reduction resulted in decreased a* and b* values in raw batter; the effect which disappeared in cooked sausages. Glucosamine caramel increased the overall and flavour acceptability score of low salt breakfast sausages. The present study showed that glucosamine caramel could potentially improve the flavour of low salt breakfast sausage with limited effect on textural attributes.

The effect of amino acids on non-enzymatic browning of glucosamine: Generation of butterscotch aromatic and bioactive health compounds without detectable levels of neo-formed alkylimidazoles

A mixture of glucosamine (GlcN, 15% w/v) and different amino acids in 1:1 M ratio was incubated at 70 °C for 12 h. The resulting GlcN-amino acid caramels were analysed for α-dicarbonyl compounds, polyhydroxyalkyl pyrazines, heterocyclic compound and alkylimidazoles. All the analyses were performed by using HPLC-MS/MS followed by pooling the variables with principal component analysis (PCA). GlcN-Gly caramels generated the greatest amount of butterscotch aromatic compound diacetyl and polyhydroxyalkyl pyrazines (fructosazine and deoxyfructosazine). The potentially toxic heterocyclic compound, 5-hydroxymethylfurfural (HMF) was generated in greater amounts with the GlcN-Arg caramels. However, the toxic alkylimidazoles (4-MEI and THI) were not present in any of the GlcN-amino acid caramels. The results suggest that caramel with butterscotch aroma and bioactivity can be produced with GlcN-amino acid at 70 °C. The PCA performed discriminated the majority of the GlcN-amino acid combinations; GlcN-Gly and GlcN-Ser were best discriminated.

Cold non-enzymatic browning of glucosamine in the presence of metmyoglobin induces glucosone and deoxymyoglobin formation

Glucosamine (GlcN) and GlcN-myoglobin reaction systems were incubated at 4 °C to verify that GlcN can go through non-enzymatic browning at this low temperature, and to test the hypothesis that certain reductones from GlcN non-enzymatic browning can promote the formation of deoxy- and oxymyoglobin from metmyoglobin reduction. Remarkably, alpha-dicarbonyls and self-condensation products, fructosazine and deoxyfructosazine, were produced at this relatively low temperature. The presence of myoglobin shifted GlcN non-enzymatic browning toward the formation of glucosone and fructosazine. When glucosone (250-2000 mg/L) was incubated with myoglobin it contributed to the formation of deoxymyoglobin, indicating its capacity to reduce metmyoglobin. This study opens the possibility of using GlcN in meat products to increase oxy- and deoxymyoglobin and enhance the color of meat.

Effects and mechanism of free amino acids on browning in the processing of black garlic

BACKGROUND

Black garlic is produced by heating raw garlic at a high temperature for a long time without any additives. The thermal processing induces many chemical reactions, such as the Maillard reaction, which causes the color change from white to dark brown. Garlic contains a variety of amino acids, and the effect of each amino acid on browning is not fully understood. This work investigated the effect and mechanism of free amino acids on the browning of black garlic using model solutions containing garlic neutral polysaccharide, hydrolyzed garlic neutral polysaccharide, fructose, and free amino acids.

RESULTS

A significant increase in reducing sugar was detected when garlic neutral polysaccharide was heated with glycine. The browning intensity of garlic neutral polysaccharide-glycine model solution was obviously higher after heating at 80 °C compared with that of garlic neutral polysaccharide solution. The model solution containing histidine had the greatest browning degree. The histidine model has a stable pH value, and almost no 5-hydroxymethylfurfural (5-HMF) was detected.

CONCLUSION

Amino acid can promote the breaking of the garlic neutral polysaccharide chain and can react with the fructose generated to form browning. Histidine has the greatest effect on the browning, because histidine could eliminate the inhibiting effect of organic acid on Maillard reaction due to the buffer ability, and histidine had high reactivity in the late stage of Maillard reaction. © 2019 Society of Chemical Industry.

Improved bactericidal capacity of UV-B radiation against E. coli strains by photosensitizing bacteria with fructosazine - An advanced Maillard reaction product

This study investigated the effect of UV-B irradiation and the combinational effect with glucosamine caramel, fructosazine and riboflavin on the antimicrobial activities against Bacillus subtilis (ATCC 6633) and two strains of Escherichia coli (AW 1.7 and ATCC 25922). The quantum yield of fructosazine was two times less than that of tryptophan, indicating its ability to emit fluorescent light but less efficiently than tryptophan. UV-B treatment alone was efficient to achieve a bactericidal effect for both E. coli stains tested, however no effect was found for Bacillus subtilis for up to 80 mJ/cm² UV-B. The combination of UV-B with photosensitizers fructosazine, glucosamine caramel and riboflavin enhanced the UV-B efficacy against E. coli strains at lower UV-B doses, while Bacillus subtilis ATCC 6633 was more resistant to the treatment combinations. High-performance liquid chromatography showed the production of different fructosazine reaction products occurred during irradiation, including the possible formation of endoperoxides.

Sous-Vide Nonenzymatic Browning of Glucosamine at Different Temperatures

Sous-vide is an increasingly popular method of cooking under controlled conditions of temperature and time inside vacuumed pouches to preserve the nutritional and sensory qualities of food. Sous-vide nonenzymatic browning of glucosamine (GlcN) was investigated at 50, 60, and 70 °C for 12 h. Changes investigated were pH, color, level of browning, and the concentrations of the key Maillard and caramelization reaction products, including α-dicarbonyls and pyrazines. The concentrations of undesired 4-methylimidazole (4-MEI), 2-acetyl-4(5)-tetrahydroxybutyl imidazole (THI), and 5-hydroxymethylfurfural (5-HMF) were also determined. Six types of caramels were produced of unique composition with no detectable levels of 4-MEI. GlcN caramels produced under vacuum were more acidic and lighter in color, containing significantly less flavorful diacetyl, but more fructosazine (FR) as compared to nonvacuum caramels. THI concentration was well below the toxicity levels for all studied caramels. Principal component analyses showed that the incubation temperature played a key role in determining the composition of caramels.

Effect of altitude on biochemical composition and quality of green arabica coffee beans can be affected by shade and postharvest processing method

Although various studies have assessed altitude, shade and postharvest processing effects on biochemical content and quality of coffee beans, data on their interactions are scarce. The individual and interactive effects of these factors on the caffeine, chlorogenic acids (CGA) and sucrose contents as well as physical and sensory qualities of green coffee beans from large plantations in southwestern Ethiopia were evaluated. Caffeine and CGA contents decreased with increasing altitude; they respectively declined 0.12 and 1.23gkg^-1 100m^-1. Sucrose content increased with altitude; however, the altitude effect was significant for wet-processed beans (3.02gkg^-1 100m^-1), but not for dry-processed beans (0.36g kg^-1 100m^-1). Similarly, sucrose content increased with altitude with much stronger effect for coffee grown without shade (2.11gkg^-1 100m^-1) compared to coffee grown under shade (0.93gkg^-1 100m^-1). Acidity increased with altitude when coffee was grown under shade (0.22 points 100m^-1), but no significant altitude effect was observed on coffee grown without shade. Beans grown without shade showed a higher physical quality score for dry (37.2) than for wet processing (29.1). These results generally underline the complex interaction effects between altitude and shade or postharvest processing on biochemical composition and quality of green arabica coffee beans.

Antimicrobial and antioxidant capacity of glucosamine-zinc(II) complex via non-enzymatic browning reaction

Coordination compounds play an important role in the life process, and have been widely used in food, cosmetics and pharmaceutical industry. Herein, we have developed a novel kind of glucosamine-zinc(II) complex (GlcN-ZC) for food additive using non-enzymatic browning reaction. The GlcN-ZC was characterized by FTIR and XRD. Moreover, UV absorbance changes, browning intensity, fluorescence changes, antioxidant activity and antimicrobial assessment of GlcN-ZC were also evaluated. Results showed the GlcN-ZC intermediate compounds were accumulated in non-enzymatic browning while prolonging heating time and melanoidins were produced in the final stage. The fluorescence changes confirmed that fluorophores were formed during the non-enzymatic reaction and fluorescence intensity reached a maximun at 60 min. The highest radical scavenging activity of GlcN-ZC formed after 180 min of heating was 79.2%. Furthermore, GlcN-ZC exhibited excellent antibacterial activity against E. coli and S. aureus. Therefore, GlcN-ZC can be used as a novel promising additive in the food industry.

Inhibitory activity of a Concanavalin-isolated fraction from a glucosamine-peptides reaction system against heat resistant E. coli

Alcalase-derived gelatin hydrolysates were glycated with glucosamine in the presence (+) or absence (−) of transglutaminase (TGase), and their antimicrobial activities toward Escherichia coli AW 1.7 were studied. Glycation treatments were subjected to concanavalin A affinity chromatography to selectively collect the glycopeptide-enriched fractions and the changes in antimicrobial activity were determined. The minimum inhibitory concentration of glycated hydrolysates decreased by 1.2 times compared to the native hydrolysate, with no differences between (+) or (−) TGase treatments. No difference was observed in the dicarbonyl compound concentration between the two glycation methods except that 3-deoxyglucosone was greater in the TGase-mediated reaction. Concanavalin A-retentate, but not the flow-through fractions, significantly improved the antimicrobial activity, however there was no difference between +TGase and −TGase glycated treatments. Purification of the retentate fraction from fluorescent compounds did not improve its antimicrobial activity.

Transport of the Glucosamine-Derived Browning Product Fructosazine (Polyhydroxyalkylpyrazine) Across the Human Intestinal Caco-2 Cell Monolayer: Role of the Hexose Transporters

The transport mechanism of fructosazine, a glucosamine self-condensation product, was investigated using a Caco-2 cell model. Fructosazine transport was assessed by measuring the bidirectional permeability coefficient across Caco-2 cells. The mechanism of transport was evaluated using phlorizin, an inhibitor of sodium-dependent glucose cotransporters (SGLT) 1 and 2, phloretin and quercetin, inhibitors of glucose transporters (GLUT) 1 and 2, transcytosis inhibitor wortmannin, and gap junction disruptor cytochalasin D. The role of hexose transporters was further studied using downregulated or overexpressed cell lines. The apparent permeability (P_a,b) of fructosazine was 1.30 ± 0.02 × 10^-6 cm/s. No significant (p > 0.05) effect was observed in fructosazine transport by adding wortmannin and cytochalasin D. The presence of phlorizin, phloretin, and quercetin decreased fructosazine transport. The downregulated GLUT cells line was unable to transport fructosazine. In human intestinal epithelial Caco-2 cells, GLUT1 or GLUT2 and SGLT are mainly responsible for fructosazine transport.

Fructosazine, a Polyhydroxyalkylpyrazine with Antimicrobial Activity: Mechanism of Inhibition against Extremely Heat Resistant Escherichia coli

Fructosazine is a polyhydroxyalkylpyrazine recently reported to have antimicrobial activity against heat-resistant Escherichia coli AW 1.7. This study investigated fructosazine's antimicrobial mechanism of action and compared it to that of riboflavin. Fructosazine-acetic acid was effective in permeabilizing the outer membrane based on an evaluation of bacterial membrane integrity using 1-N-phenyl-1-naphthylamine and propidium iodide. The uptake of fructosazine by E. coli was pH-dependent with a greater uptake at pH 5 compared to pH 7 for all times throughout 16 h, except 2, 3, and 10 h. Fructosazine generates ¹O₂, which is partially why it damages E. coli. DNA fragmentation was confirmed by fluorescence microscopy, and the fructosazine-acetic acid was the second most intense treatment after riboflavin-acetic acid. Electron microscopy revealed membrane structural damage by fructosazine at pH 5 and 7. This study provides evidence that fructosazine exerts antimicrobial action by permeabilizing the cell membrane, damaging membrane integrity, and fragmenting DNA.

Development and validation of a selective and effective pressurized liquid extraction followed by liquid chromatography-mass spectrometry method for the determination of fructosazine analogues in the ammonia treated extract of Eugenia jambolana Lamarck seeds

This study describes a selective and effective pressurized liquid extraction (PLE) coupled with HPLC-DAD-ESI/MS method for the identification and quantification of three fructosazine analogues (FZAs), fructosazine, 2,6- and 2,5-deoxyfructosazine in Madeglucyl^® (MG) which is an ammonia treated extract of Eugenia jambolana Lamarck seeds, and is the world's first anti-diabetic phytodrug. FZAs were extracted from MG by PLE using methanol as extraction solvent. The PLE extract was then analyzed directly by HPLC-DAD-ESI/MS without cleanup step. Chromatographic separation of these highly related structures was achieved on a porous graphic carbon (PGC) column. The identification of the target FZAs was confirmed by the similar retention time, similar UV and MS spectra to the corresponding pure standards. The quantification was performed by using an electrospray positive ionization mass spectrometry in the selected ion monitoring (SIM) mode. The PLE procedure was optimized and overall method was validated in terms of sensitivity, linearity, selectivity and matrix effect, precision, accuracy and recovery, and stability of the target FZAs in the aqueous solution and in the PLE extracts solution of MG. The developed method was proved to be selective, sensitive, precise, accurate for the quantification of FZAs in MG.