ABSTRACT
Oxygen scavengers are valuable active packaging systems because several types of food deterioration processes are initiated by oxygen. Although the incorporation of oxygen scavenger agents into the polymeric matrices has been the trend in recent years, the release of volatile organic compounds (VOC) as a result of the reaction between oxygen and oxygen scavenger substances is an issue to take into account. This is the case of an oxygen scavenger based on a trans-polyoctenamer rubber (TOR). In this work, the design of an oxygen scavenger multilayer system was carried out considering the selection of appropriate adsorbents of VOCs to the proposed layer structure. Firstly, the retention of some representative organic compounds by several adsorbent substances, such as zeolites, silicas, cyclodextrins and polymers, was studied in order to select those with the best performances. A hydrophilic silica and an odor-adsorbing agent based on zinc ricinoleate were the selected adsorbing agents. The principal VOCs released from TOR-containing films were carefully identified, and their retention first by the pure adsorbents, and then by polyethylene incorporated with the selected compounds was quantified. Detected concentrations decreased by 10- to 100-fold, depending on the VOC.
ABSTRACT
The generation of oxygen from electrolysis in gel electromembrane extraction (G-EME) causes a negative error when applied to the analysis of easily oxidized species such as nitrite. Nitrite in G-EME is oxidized by oxygen to nitrate, leading to the negative error and the impossibility of simultaneous analysis. In this work, the application of oxygen scavengers to the acceptor phase of the G-EME system was attempted to minimize the oxidation effect. Several oxygen scavengers were selected and examined according to their compatibility with ion chromatography. The mixture of sulfite and bisulfite (14 mg L-1) showed the highest efficiency in preventing the oxidation of nitrite to nitrate. Under the optimized conditions, a good linear range was obtained (10-200 µg L-1; R2 > 0.998) with a detection limit of 8 µg L-1 for both nitrite and nitrate. This method was applied to the simultaneous determination of nitrite and nitrate in sausage samples.
Subject(s)
Nitrates , Nitrites , Electrolysis , Membranes, ArtificialABSTRACT
Polymer gel plugging is an effective technique for gas mobility control in flue gas flooding reservoirs. However, the performance of polymer gels is extremely susceptible to the injected flue gas. A reinforced chromium acetate/partially hydrolyzed polyacrylamide (HPAM) gel, using thiourea as the oxygen scavenger and nano-SiO2 as the stabilizer, was formulated. The related properties were evaluated systematically, including gelation time, gel strength, and long-term stability. The results indicated that the degradation of polymers was effectively suppressed by oxygen scavengers and nano-SiO2. The gel strength would be increased by 40% and the gel kept desirable stability after aging for 180 days at elevated flue gas pressures. Dynamic light scattering (DLS) analysis and Cryo-scanning electron microscopy (Cryo-SEM) revealed that nano-SiO2 was adsorbed on polymer chains by hydrogen bonding, which improved the homogeneity of gel structure and thus enhanced the gel strength. Besides, the compression resistance of gels was studied by creep and creep recovery tests. The failure stress of gel with the addition of thiourea and nanoparticles could reach up to 35 Pa. The gel retained a robust structure despite extensive deformation. Moreover, the flow experiment indicated that the plugging rate of reinforced gel still maintained up to 93% after flue gas flooding. It is concluded that the reinforced gel is applicable for flue gas flooding reservoirs.
ABSTRACT
We present an optochemical O2 scavenging system that enables precise spatiotemporal control of the level of hypoxia in living cells simply by adjusting the light intensity in the illuminated region. The system employs rhodamine containing a selenium or tellurium atom as an optochemical oxygen scavenger that rapidly consumes O2 by photochemical reaction with glutathione as a coreductant upon visible light irradiation (560-590â nm) and has a rapid response time, within a few minutes. The glutathione-consuming quantum yields of the system were calculated as about 5 %. The spatiotemporal O2 consuming in cultured cells was visualized with a hypoxia-responsive fluorescence probe, MAR. Phosphorescence lifetime imaging was applied to confirmed that different light intensities could generate different levels of hypoxia. To illustrate the potential utility of this system for hypoxia research, we show that it can spatiotemporally control calcium ion (Ca2+ ) influx into HEK293T cells expressing the hypoxia-responsive Ca2+ channel TRPA1.
Subject(s)
Hypoxia , Oxygen , Humans , HEK293 Cells , Reactive Oxygen Species , GlutathioneABSTRACT
Nowadays, the strong increase in products consumption, the purchase of products on online platforms as well as the requirements for greater safety and food protection are a concern for food and packaging industries. Active packaging brings huge advances in the extension of product shelf-life and food degradation and losses reduction. This systematic work aims to collect and evaluate all existing strategies and technologies of active packaging that can be applied in food products, with a global view of new possibilities for food preservation. Oxygen scavengers, carbon dioxide emitters/absorbers, ethylene scavengers, antimicrobial and antioxidant active packaging, and other active systems and technologies are summarized including the products commercially available and the respective mechanisms of action. © 2022 Society of Chemical Industry.
Subject(s)
Anti-Infective Agents , Food Packaging , Food Preservation , AntioxidantsABSTRACT
The commercialization of amperometric or voltammetric biosensors that operate at potentials lower than -0.2 V vs SHE has been hindered by the need for anoxic working conditions due to the interference of molecular oxygen, whose electrochemical reduction can potentially mask other redox processes and generate reactive oxygen species (ROS). A deoxygenation step must be thus integrated into the analytical process. To this end, several (bio)chemical oxygen scavenging systems have been proposed, such as the bi-enzyme system, glucose oxidase/catalase. Still, a few issues persist owing to enzyme impurities and the formation of oxygen reactive species. Here in, we propose a new mono-enzymatic oxygen scavenging system composed of a multicopper oxidase as a single biocatalytic oxygen reducer. As a model, we used bilirubin oxidase (BOD), which catalyzes the direct reduction of oxygen to water in the presence of an electron donor substrate, without releasing hydrogen peroxide. Both the direct electron transfer and mediated electrochemical approach using different co-substrates were screened for the ability to promote the enzymatic reduction of oxygen. An optimal combination of BOD with sodium ascorbate proved to be quick (5 min) and effective. It was subsequently employed, as a proof-of-concept, in a voltammetric biosensor based on a multiheme cytochrome c nitrite reductase, which performs the reduction of nitrite to ammonia at potentials below -0.3 V vs SHE. The nitrite biosensor performed well under ambient air, with no need for a second enzyme to account for the build-up of oxygen reactive intermediaries.
Subject(s)
Biosensing Techniques , Ammonia , Ascorbic Acid , Catalase , Glucose Oxidase/chemistry , Hydrogen Peroxide , Nitrites , Oxidation-Reduction , Oxidoreductases Acting on CH-CH Group Donors , Oxygen/chemistry , Reactive Oxygen Species , WaterABSTRACT
Commercially available oxygen scavengers used to prevent lipid autoxidation, microbial growth and enzymatic browning in food products present several issues, which include the usage of metals and their moisture dependence to work properly. We present the synthesis and characterization of a moisture-independent oil-based oxygen scavenging system comprised of linseed oil and silica nanoparticles. The system was synthesized via sol-gel chemistry and was characterized using morphological analysis (SEM, AFM, TEM, and N2 adsorption/desorption), oil-loading analysis (TGA), and surface analysis (ζ-potential and ATR-FTIR). Performance of the system was evaluated through headspace measurements and reproducibility of synthetic procedure was verified using six replicates. Nanoparticles showed the desired spherical shape with a diameter of (122.7 ± 42.7 nm) and mesoporosity (pore diameter = 3.66 ± 0.08 nm), with an encapsulation efficiency of 33.9 ± 1.5% and a highly negative ζ-potential (-56.1 ± 1.2 mV) in basic solution. Performance of the system showed a promising high value for oxygen absorption of 25.8 ± 4.5 mL O2/g of encapsulated oil (8.3 ± 1.5 mL O2/g of nanocapsules) through a moisture independent mechanism, which suggests that the synthesized system can be used as an oxygen scavenger in dry atmosphere conditions.
ABSTRACT
The EFSA Panel on Food Contact Materials, Enzymes and Processing Aids (CEP) assessed the safety of the combined use of cyclooctene homopolymer (PCOE) and cobalt stearate (CoS) intended as a oxygen scavenger in the packaging of all kinds of food stored at room temperature or below for up to 6 months. The CoS is the oxidation catalyst and the PCOE is intentionally oxidised for the oxygen scavenging function. They are incorporated into a plastic layer that is intended to be either in direct or indirect contact with the food. The potential migration of cobalt and cyclooctene monomer were below their respective specific migration limit (SML). The potential migration of PCOE non-oxidised oligomeric low molecular weight fraction (LMWF) < 1,000 Da was estimated to be up to â â â â â The Panel concluded that this fraction does not raise concern for genotoxicity potential and that the no observed adverse effect level (NOAEL) derived from a subchronic toxicity study would ensure a margin of exposure large enough to not raise a safety concern. However, the Panel considered the analysis of the oxidised PCOE LMWF not sufficiently comprehensive, i.e. that additional oxidation products of different nature may be formed, and that the limit of detection corresponding to ca. â â â â â for individual substances is too high. The oxidised PCOE LMWF was not covered by the genotoxicity tests or the 90-day study on the PCOE oligomers. The assessment of the identified potential oxidised migrants was considered conclusive, but not that of the migrants having remained undetected. Therefore, the CEP Panel was not able to conclude on the safety of the proposed use of cyclooctene homopolymer and cobalt stearate together as active substances in a layer for scavenging oxygen, either in direct contact with the food or separated from the food by a passive layer of polymer.
ABSTRACT
Oxygen tension varies during placental and fetal development. Although hypoxia drives early trophoblast invasion, low placental oxygen levels during pregnancy show association with pregnancy complications including fetal growth restriction and preeclampsia. JEG-3 cells are often used as a trophoblast model. We studied transcriptional changes of JEG-3 cells on a uterine leiomyoma derived matrix Myogel. This might be the closest condition to the real uterine environment that we can get for an in vitro model. We observed that culturing JEG-3 cells on the leiomyoma matrix leads to strong stimulation of ribosomal pathways, energy metabolism, and ATP production. Furthermore, Myogel improved JEG-3 cell adherence in comparison to tissue culture treated plastic. We also included PDMS microchip hypoxia creation, and observed changes in oxidative phosphorylation, oxygen related genes and several hypoxia genes. Our study highlights the effects of Myogel matrix on growing JEG-3 cells, especially on mitochondria, energy metabolism, and protein synthesis.
ABSTRACT
Modified calcium carbonates (MCC) are inorganic mineral-based particles with a large surface area, which is enlarged by their porous internal structure consisting of hydroxyapatite and calcium carbonate crystal structures. Such materials have high potential for use as carriers for active substances such as oxygen scavenging agents. Oxygen scavengers are applied to packaging to preserve the quality of oxygen-sensitive products. This study investigated the potential of MCC as a novel carrier system for unsaturated fatty acids (UFAs), with the intention of developing an oxygen scavenger. Linoleic acid (LA) and oleic acid (OA) were loaded on MCC powder, and the loaded MCC particles were characterized and studied for their oxygen scavenging activity. For both LA and OA, amounts of 20 wt% loading on MCC were found to provide optimal surface area/volume ratios. Spreading UFAs over large surface areas of 31.6 and 49 m2 g-1 MCC enabled oxygen exposure and action on a multitude of molecular sites, resulting in oxygen scavenging rates of 12.2 ± 0.6 and 1.7 ± 0.2 mL O2 d-1 g-1, and maximum oxygen absorption capacities of >195.6 ± 13.5 and >165.0 ± 2.0 mL g-1, respectively. Oxygen scavenging activity decreased with increasing humidity (37-100% RH) and increased with rising temperatures (5-30 °C). Overall, highly porous MCC was concluded to be a suitable UFA carrier for oxygen scavenging applications in food packaging.
ABSTRACT
In this study, the oxygen scavenger layer (OSL) is proposed as a back channel in the bilayer channel to enhance both the electrical characteristics and stability of an amorphous indium-gallium-zinc oxide thin-film transistor (a-IGZO TFT) and also to enable its fabrication at low temperature. The OSL is a hafnium (Hf)-doped a-IGZO channel layer deposited by radio-frequency magnetron cosputtering. Amorphous IGZO TFTs with the OSL, even if annealed at a low temperature (200 °C), exhibited improved electrical characteristics and stability under positive bias temperature stress (PBTS) compared to those without the OSL, specifically in terms of field-effect mobility (31.08 vs 9.25 cm2/V s), on/off current ratio (1.73 × 1010 vs 8.68 × 108), and subthreshold swing (0.32 vs 0.43 V/decade). The threshold voltage shift under PBTS at 50 °C for 10,000 s decreased from 9.22 to 2.31 V. These enhancements are attributed to Hf in the OSL, which absorbs oxygen ions from the a-IGZO front channel near the interface between a-IGZO and the OSL.
ABSTRACT
The aim of this study was to develop a double function active packaging material for nuts. The packaging solution, on the one hand, integrated polybutadiene (PB) as an oxygen scavenger and, on the other hand, it incorporated peanut aroma (PA) to improve customer's sensorial experience. Different formulations based on low density polyethylene (LDPE), commercial PA (5 wt %) and PB at two levels (5 wt % and 13 wt %) were obtained by cast film extrusion. The obtained films were compared in terms of their mechanical, structural, optical and thermal properties confirming a plasticizing effect of PA and PB resulting in an increase in the ductility of the polymer and in a slight decrease in the thermal properties, maintaining their transparency. Regarding the oxygen capacity of the films, values of 4.4 mL and 2.7 mL O2 g-1 film were obtained for PE/PA/PB13 and PE/PA/PB5, respectively, after 6 days proving the suitability of the UV irradiation treatment in improving the oxygen absorption capacity of PB without the need of a metal catalyst. The aroma retention capacity into the polymer matrix was also evaluated in the developed formulations. The incorporation of PB in 13 wt % into a LDPE matrix improved the PA retention. This behavior was attributed to the ability of PB in enhancing cross-linking of LDPE as the concentration of PB increases. The results suggested the potential of PE/PB/PB13 films as oxygen scavenger and aromatic food packaging system to offer protection against lipid oxidation in nuts.
ABSTRACT
An amperometric trimethylamine N-oxide (TMAO) biosensor is reported, where TMAO reductase (TorA) and glucose oxidase (GOD) and catalase (Cat) were immobilized on the electrode surface, enabling measurements of mediated enzymatic TMAO reduction at low potential under ambient air conditions. The oxygen anti-interference membrane composed of GOD, Cat and polyvinyl alcohol (PVA) hydrogel, together with glucose concentration, was optimized until the O2 reduction current of a Clark-type electrode was completely suppressed for at least 3 h. For the preparation of the TMAO biosensor, Escherichia coli TorA was purified under anaerobic conditions and immobilized on the surface of a carbon electrode and covered by the optimized O2 scavenging membrane. The TMAO sensor operates at a potential of -0.8 V vs. Ag/AgCl (1 M KCl), where the reduction of methylviologen (MV) is recorded. The sensor signal depends linearly on TMAO concentrations between 2 µM and 15 mM, with a sensitivity of 2.75 ± 1.7 µA/mM. The developed biosensor is characterized by a response time of about 33 s and an operational stability over 3 weeks. Furthermore, measurements of TMAO concentration were performed in 10% human serum, where the lowest detectable concentration is of 10 µM TMAO.
Subject(s)
Biosensing Techniques , Methylamines/analysis , Electrodes , Escherichia coli , Glucose Oxidase , Humans , OxygenABSTRACT
A biotrickling filter (BTF) was combined with a microbial fuel cell (MFC) to remove ethyl acetate from exhaust gas while generating electricity in the process. The results indicated that the use of carbide porous ceramic rings (CPCR) as auxiliary anodes produced more biomass and exhibited a high average removal efficiency (98%), making it a superior microorganism growth carrier compared with carbon coke. When CPCR was used as the cathode in the BTF-MFC, the maximum power density (PD) was 5.64-14.8% of that achieved when carbon cloth was used as the cathode, revealing that CPCR is not a suitable cathode. The maximum elimination capacity (EC) and output voltage of the two-stage BTF-MFC (tBTF-MFC) were only 69.4% and 68.4% of those of the single-stage BTF-MFC (sBTF-MFC), presumably because of voltage reversal. Although the output voltage and EC in the tBTF-MFC were less than those in the sBTF-MFC, the follow-up field application involves stacking multiple small MFCs to remove high-concentration pollutants and generate a high power output. Additionally, continuously adding sodium sulfite decreased the average dissolved oxygen; generated an averaged closed-circuit voltage of 477 mV; and produced a maximum PD of 71.7 mW/m3. These findings demonstrated that the aforementioned method can effectively improve the problem of oxygen and MFC anodes competing for electrons, thus delivering a method that enhances MFC performance through controlling the amount of oxygen in practical applications.
Subject(s)
Bioelectric Energy Sources , Carbon , Electricity , Electrodes , OxygenABSTRACT
Among the factors that adversely influence the viability of probiotics, the oxygen content of the product and the permeation of oxygen molecules through the packaging system have a noticeable role in the viability loss during the manufacture and storage of fermented milk products. The objective of this study was to examine the qualitative attributes of probiotic yogurt containing different O2 scavengers, including the commercial O2 absorber and cysteine-ascorbic acid. Bifidobacterium lactis BIA-7 and B. longum BIA-8 were used as probiotic strains for the production of bio-yogurts. The biochemical parameters, including the changes in pH, titratable acidity, redox potential and incubation time, were determined throughout the fermentation period at 30-min intervals. Also, the changes in viable count, pH, redox potential, titratable acidity, and dissolved oxygen were evaluated at 7-day intervals during the 28 days of refrigerated storage. In addition, the evaluation of rheological and sensory properties measured in the freshly made samples was carried out. The results showed that the utilization of different oxygen scavengers has an effective impact on the decrement of oxygen content and improvement of probiotic viability. As such, the population of B. lactis in the treatments containing various oxygen scavengers was maintained above 7 log CFU/mL throughout the refrigerated storage. Notwithstanding the effective function of cysteine-ascorbic acid in the enhancement of viability, the containing treatments had not only weaker gel structure probably due to short incubation time (360 min) and fast acidification [22.20-22.35 (ËD/min) × 10-2], but also lower sensory acceptance. Overall, the yogurt treatment containing commercial O2 scavenger and B. lactis indicated a great potential for the industrial applications. To the best of our knowledge, there is no study on the efficiency of commercial O2 absorber as a potential factor to maintain the viability of probiotics in yogurt.
Subject(s)
Cultured Milk Products , Probiotics , Bifidobacterium , Fermentation , YogurtABSTRACT
Purified walnut oil (PWO) microparticles with Capsul® (C, encapsulating agent), sodium alginate (SA) as outer layer and ascorbic acid (AA) as oxygen scavenger were obtained by spray drying using a three-fluid nozzle. AA was incorporated in the inner infeed (PWO-C(AA)/SA), in the outer infeed (PWO-C/SA(AA)) and in both infeed (PWO-C(AA)/SA(AA)). PWO-C(AA)/SA (4.56 h) and POW-C(AA)/SA(AA) (2.60 h) microparticles showed higher induction period than POW-C/SA(AA) (1.17 h), and lower formation of triacylglycerol dimers and polymers during storage (40 °C). Therefore, AA located in the inner infeed improved the oxidative stability of encapsulated PWO by removing the residual oxygen. AA in the SA outer layer did not improve the oxidative stability of encapsulated PWO since oxygen diffusion through the microparticles was limited and/or AA weakened the SA layer structure. The specific-location of AA (inner infeed) is a strategy to obtain stable spray-dried polyunsaturated oil-based microparticles for the design of foods enriched with omega-3 fatty acids.
ABSTRACT
Emulsion templated norbornadiene is cured via ring-opening metathesis polymerization yielding macroporous poly(norbornadiene) foams of 76% porosity exhibiting appealing stiffness combined with considerable ductility. The foams are readily oxidized in the presence of air at room temperature exhibiting an oxygen uptake capacity of more than 300 mg O2 g-1 foam. In closed volumes of air, a final oxygen level of a maximum of 0.0005 vol%, that is, 5 ppm(v) can be achieved after several hours at room temperature. The synergism of the porous morphology and the chemical nature of the polymer allows for the first example of an organic oxygen scavenger material with properties distinctly surpassing the state-of-the art in the field.
Subject(s)
Norbornanes/chemistry , Oxygen/chemistry , Polymers/chemistry , Styrenes/chemistry , Emulsions , Microscopy, Electron, Scanning , Polymerization , PorosityABSTRACT
Nitrous oxide is an important greenhouse gas and there is a need for sensitive techniques to study its distribution in the environment at concentrations near equilibrium with the atmosphere (9.6 nM in water at 20 °C). Here we present an electrochemical sensor that can quantify N2O in the nanomolar range. The sensor principle relies on a front guard cathode placed in front of the measuring cathode. This cathode is used to periodically block the flux of N2O towards the measuring cathode, thereby creating an amplitude in the signal. This signal amplitude is unaffected by drift in the baseline current and can be read at very high resolution, resulting in a sensitivity of 2 nM N2O for newly constructed sensors. Interference from oxygen is prevented by placing the front guard cathode in oxygen-consuming electrolyte. The sensor was field tested by measuring an N2O profile to a depth of 120 m in the oxygen minimum zone of the Eastern Tropical North Pacific Ocean (ETNP) off the coast of Mexico.
ABSTRACT
The photon induced radical-initiated polymerization in polymer gels can be used for high-resolution tissue equivalent dosimeters in quality control of radiation therapy. The dose (D) distribution in radiation therapy can be measured as a change of the physical measurement parameter T2 using T2-weighted magnetic resonance imaging. The detection by T2 is relying on the local change of the molecular mobility due to local polymerization initiated by radicals generated by the ionizing radiation. The dosimetric signals R2 = 1/T2 of many of the current polymer gels are dose-rate dependent, which reduces the reliability of the gel for clinical use. A novel gel dosimeter, based on methacrylic acid, gelatin and the newly added dithiothreitol (MAGADIT) as an oxygen-scavenger was analyzed for basic properties, such as sensitivity, reproducibility, accuracy and dose-rate dependence. Dithiothreitol features no toxic classification with a difference to THPC and offers a stronger negative redox-potential than ascorbic acid. Polymer gels with three different concentration levels of dithiothreitol were irradiated with a preclinical research X-ray unit and MR-scanned (T2) for quantitative dosimetry after calibration. The polymer gel with the lowest concentration of the oxygen scavenger was about factor 3 more sensitive to dose as compared to the gel with the highest concentration. The dose sensitivity (α = ∆R2/∆D) of MAGADIT gels was significantly dependent on the applied dose rate D Ë (≈48% reduction between D Ë = 0.6 Gy/min and D Ë = 4 Gy/min). However, this undesirable dose-rate effect reduced between 4-8 Gy/min (≈23%) and almost disappeared in the high dose-rate range (8 ≤ D Ë ≤ 12 Gy/min) used in flattening-filter-free (FFF) irradiations. The dose response varied for different samples within one manufacturing batch within 3%-6% (reproducibility). The accuracy ranged between 3.5% and 7.9%. The impact of the dose rate on the spatial integrity is demonstrated in the example of a linear accelerator (LINAC) small sized 5 × 10 mm2 10 MV photon field. For MAGADIT the maximum shift in the flanks in this field is limited to about 0.8 mm at a FFF dose rate of 15 Gy/min. Dose rate sensitive polymer gels likely perform better at high dose rates; MAGADIT exhibits a slightly improved performance compared to the reference normoxic polymer gel methacrylic and ascorbic acid in gelatin initiated by copper (MAGIC) using ascorbic acid.
ABSTRACT
A baseline dip caused by the reduction of dissolved oxygen in samples has been a source of trouble in the analysis of major monosaccharides (galactose, glucose, mannose, and fructose) in the high-performance anion-exchange chromatography with pulsed amperometric detection system. This study attempted three different methods to remove the baseline dip from the resulting chromatograms, and among the approaches, sodium sulfite was found to act as the best oxygen scavenger. Clean chromatograms were obtained by adding at least 3â¯mg/mL sodium sulfite to samples, which removed the baseline dip and improved the accuracy of sugar analysis. Although sodium sulfite does not influence analytical sensitivity, it can cause a reduction of sugar retention; however, retention time can be recovered by washing with 200â¯mM sodium hydroxide solution. Results demonstrated that sodium sulfite is an effective means either to remove the baseline dip for low concentration analysis under 1â¯mg/L, or to separate the target sugar from the baseline dip by retention time rearrangement.