Evaluation of the Structural, Physicochemical and Functional Properties of Dietary Fiber Extracted from Newhall Navel Orange By-Products

Ultrasound-assisted enzymatic treatment was used to treat Newhall navel orange peel and residue, and then the structural, physicochemical and functional properties of extracted soluble dietary fibers (SDF) and insoluble dietary fibers (IDF) were investigated. The structural properties were determined using scanning electron microscopy, X-ray diffraction, FT-IR and monosaccharide composition. Among these dietary fibers, residue-SDF showed a more complex structure, while peel-IDF exhibited a looser structure. Four samples showed representative infrared spectral features of polysaccharides, typical cellulose crystalline structure and diverse monosaccharide composition. Furthermore, residue-IDF exhibited higher oil-holding capacity (2.08 g/g), water-holding capacity (13.43 g/g) and nitrite ion adsorption capacity (NIAC) than other three samples, and residue-SDF showed the highest swelling capacity (23.33 mL/g), cation exchange capacity (0.89 mmol/g) and cholesterol adsorption capacity (CAC) among these dietary fibers. In summary, this study suggests that the residue-SDF and residue-IDF could be used as the ideal dietary fibers for application in the functional food industry.

Nitrite content in meat products from the Serbian market and estimated intake

The aim of this study was to determine levels of nitrites in some meat products sold on the Serbian market over a period of 3 years (2018-2020) and to compare results with maximum residue levels as well to discuss dietary exposure of the Serbian adult population to nitrites.A total of 1291 meat product samples, produced by the Serbian meat industry or imported (509 dry fermented sausages, 37 semi-dry fermented sausages, 451 finely minced cooked sausages and 294 coarsely minced cooked sausages), were obtained from the Serbian retail market during 2018-2020.Higher mean levels of nitrite content, expressed as NaNO2, were found in cooked sausages (40.35 mg kg-1, finely minced and 33.75 mg kg-1, coarsely minced) compared to fermented sausages (1.86 mg kg-1 dry fermented and 1.83 mg kg-1, semi-dry fermented).The average dietary exposure to nitrites, expressed as nitrite ion, for the Serbian adult population varies from 0.001 to 0.015 mg kg-1body weight (BW) day-1 and was far below the European acceptable daily intake (0.07 mg kg-1 BW day-1). In conclusion, the concentrations of nitrite in all meat products were below established maximum permitted levels (national and European), indicating that the use of nitrite as a food additive in Serbia is generally in line with existing regulations.

Microbial Fuel Cell as a Bioelectrochemical Sensor of Nitrite Ions

The deteriorating environmental quality requires a rapid in situ real-time monitoring of toxic compounds in environment including water and wastewater. One of the most toxic nitrogen-containing ions is nitrite ion, therefore, it is particularly important to ensure that nitrite ions are completely absent in surface and ground waters as well as in wastewater or, at least, their concentration does not exceed permissible levels. However, no selective ion electrode, which would enable continuous measurement of nitrite ion concentration in wastewater by bioelectrochemical sensor, is available. Microbial fuel cell (MFC)-based biosensor offers a sustainable low-cost alternative to the monitoring by periodic sampling for laboratory testing. It has been determined, that at low (0.01–0.1 mg·L−1) and moderate (1.0–10 mg·L−1) concentration of nitrite ions in anolyte-model wastewater, the voltage drop in MFC linearly depends on the logarithm of nitrite ion concentration of proving the potential of the application of MFC-based biosensor for the quantitative monitoring of nitrite ion concentration in wastewater and other surface water. Higher concentrations (100–1000 mg·L−1) of nitrite ions in anolyte-model wastewater could not be accurately quantified due to a significant drop in MFC voltage. In this case MFC can potentially serve as a bioelectrochemical early warning device for extremely high nitrite pollution.

In-vitro bio-potential and pharmacological studies of newly synthesized Schiff base Cd(II) complex

The post-transition '4d' Cd(II) metal complex were synthesized and characterized by the addition of neutral Schiff base (E)-N-(4-chlorobenzylidene)isonicotinohydrazide) as primary ligand and nitrite ion as mixed ligand. The Schiff base were synthesized with the addition of bio active Isoniazid and 4-chlorobenzaldehyde by eco-friendly technique (water as solvent). The synthesized complex where physically, chemically, spectroscopically and biologically characterized by various Physico-chemical, spectral and biological methods such as micro analytical data, namely elemental analysis & metal estimation, conductivity, Ultraviolet-visible, Infra-Red, Far-Infra Red, and Nuclear Magnetic Resonance (1H &13C) spectral studies. Based on the conductivity and spectral studies, the complex is neutral and non-electrolyte in nature. They have tetrahedral geometry around the Cd(II) metal ion. The in-vitro antibacterial and antifungal activities of Schiff base and Cd(II) complex were screened against E. coli and A. Niger by Agar disc diffusion method using Chloramphenicol and Fluconazole as standard control and DMSO as a solvent control. The results indicate that the complex have more potent than the Schiff base due to the chelation. The pharmacological studies of Schiff base and Cd(II) complex also predicted using a computational method by Swiss ADME software. The lipophilicity and medicinal chemistry importance of the Schiff base and Cd(II) complex were predicted and confirmed by the bio-potential activities.

Nitrate reduction by electrochemical processes using copper electrode: evaluating operational parameters aiming low nitrite formation

This work aims to present different electroreduction and electrocatalytic processes configurations to treat nitrate contaminated water. The parameters tested were: current density, cell potential, electrode potential, pH values, cell type and catalyst use. It was found that the nitrite ion is present in all process variations used, being the resulted nitrite concentration higher in an alkaline pH. The increase in current density on galvanostatic operation mode provides a greater reduction of nitrate (64%, 1.4 mA cm−2) if compared to the potentiostatic (20%) and constant cell potential (37%) configurations. In a dual-chamber cell was tested the nitrate reduction with current density of 1.4 mA cm−2, being obtained the NO3− reduction of 85%. The use of single chamber cell presented 32 ± 3% of nitrate reduction, indicating that in this cell type the nitrate reduction is smaller than in dual-chamber cell (64%). The presence of Pd catalyst with 3.1% wt. decreased the nitrite (1.0 N-mg L−1) and increased the gaseous compounds (9.4 N-mg L−1) formation. The best configuration showed that, by fixing the current density, a highest nitrate reduction is obtained and the pH presents a significant influence during the testes. The use of catalyst decreased the nitrite and enhanced the gaseous compounds formation.

Influence of the heme distal pocket on nitrite binding orientation and reactivity in Sperm Whale myoglobin

Nitrite binding to recombinant wild-type Sperm Whale myoglobin (SWMb) was studied using a combination of spectroscopic methods including room-temperature magnetic circular dichroism. These revealed that the reactive species is free nitrous acid and the product of the reaction contains a nitrite ion bound to the ferric heme iron in the nitrito- (O-bound) orientation. This exists in a thermal equilibrium with a low-spin ground state and a high-spin excited state and is spectroscopically distinct from the purely low-spin nitro- (N-bound) species observed in the H64V SWMb variant. Substitution of the proximal heme ligand, histidine-93, with lysine yields a novel form of myoglobin (H93K) with enhanced reactivity towards nitrite. The nitrito-mode of binding to the ferric heme iron is retained in the H93K variant again as a thermal equilibrium of spin-states. This proximal substitution influences the heme distal pocket causing the pKa of the alkaline transition to be lowered relative to wild-type SWMb. This change in the environment of the distal pocket coupled with nitrito-binding is the most likely explanation for the 8-fold increase in the rate of nitrite reduction by H93K relative to WT SWMb.

The Long-Lasting Story of One Sensor Development: From Novel Ionophore Design toward the Sensor Selectivity Modeling and Lifetime Improvement

The metalloporphyrin ligand bearing incorporated anion-exchanger fragment, 5-[4-(3-trimethylammonium)propyloxyphenyl]-10,15,20-triphenylporphyrinate of Co(II) chloride, CoTPP-N, has been tested as anion-selective ionophore in PVC-based solvent polymeric membrane sensors. A plausible sensor working mechanism includes the axial coordination of the target anion on ionophore metal center followed by the formed complex aggregation with the second ionophore molecule through positively charged anion-exchanger fragment. The UV-visible spectroscopic studies in solution have revealed that the analyte concentration increase induces the J-type porphyrin aggregation. Polymeric membranes doped with CoTPP-N showed close to the theoretical Nernstian response toward nitrite ion, preferably coordinated by the ionophore, and were dependent on the presence of additional membrane-active components (lipophilic ionic sites and ionophore) in the membrane phase. The resulting selectivity was a subject of specific interaction and/or steric factors. Moreover, it was demonstrated theoretically and confirmed experimentally that the selection of a proper ratio of ionophore and anionic additive can optimize the sensor selectivity and lifetime.