Volatile Oxidation Research Articles

Influence of processing of seitan, tempeh, and firm regular tofu on protein and lipid oxidation and Maillard reaction products formation

The impact of production and cooking on protein oxidation, lipid oxidation and Maillard reaction products (MRPs) generation was evaluated for firm regular tofu, tempeh, and seitan, three plant-based alternatives to meat products. Tofu showed higher content of protein-bound carbonyls (25.5 ± 5.4 nmol/mg protein) indicating higher degree of protein oxidation, while seitan exhibited the lowest content of MRPs like N(6)-carboxymethyllysine, as revealed by LC-MS/MS. Through determination of the peroxide value and thiobarbituric acid reactive substances as well as analysis of volatile oxidation compounds by GC–MS, an overall higher lipid oxidation level was found in tofu. Likewise, a mean 92.2 % depletion of naturally occurring antioxidant tocopherol, assessed by HPLC-DAD, was observed in tofu. Furthermore, acrylamide was detected in tofu at 196.0 ± 15.4 μg/kg after frying at 190 °C. This study, therefore, concluded that practices used in tempeh and seitan processing are promising strategies to limit oxidation and Maillard reactions in food.

Oxidation protection efficiency of the combination of Minthostachys mollis K. and Origanum vulgare L. essential oils with "chain-breaking" and "termination-enhancing" antioxidant mechanisms.

The use of antioxidants is known to reduce lipid oxidation. This study aimed to assess the interaction of two antioxidant mechanisms, namely, "chain-breaking" and "termination-enhancing" by combining natural antioxidants derived from "oregano" (Origanum vulgare L.) and "peperina" (Minthostachys mollis K.) essential oils (EOs) in an accelerated oxidation process of sunflower oil at 60°C. Concentrations of 0.05% w/w (1) and 0.02% w/w (2) of the combined oregano and peperina EOs were evaluated. Chemical and volatile oxidation markers were determined in comparison with the pure compounds, an antioxidant-free control, and a BHT-treated sample (0.02% w/w). Although the combinations exhibited lower oxidation indicator values (Anisidine≈136) compared to the control (Anisidine≈213), no evidence of a synergistic effect was observed (Anisidine: Oregano 1≈52; Oregano 2≈199; Peperina 1≈155; Peperina 2≈153), indicating that the combination did not enhance their antioxidant activity beyond that of the pure EOs. Thus, evaluating these combinations in other food matrices is important. PRACTICAL APPLICATION: Food oxidation is one of the main causes of food spoilage, and the search for natural antioxidants has become a necessity for society's increasing food knowledge and consumption preference. The research is focused on demonstrating that not only natural phenolic compounds with a "chain-breaking" mechanism have efficient antioxidant activity but also non-phenolic terpenes using the "termination enhancer" mechanism are efficient, but also the combination of them, which provides more alternative antioxidants for industrial applications.

Textured vegetable protein from flaxseed press cake and pea – syntonizing chemical and structural properties

Flaxseed press cake (FS) was mixed with pea protein isolate and low-moisture twin-screw-extruded to valorize the oil production side stream as meat analogue. Water input, FS content, barrel temperature, and throughput were varied in a Box-Behnken design to test these factors’ influences on extrusion response parameters (pressure, temperature, mechanical energy input), lipid oxidation product and process contaminant formation (by liquid chromatography and head-space gas chromatography mass spectrometry), and mechanical properties of the TVPs.The water input was identified as the strongest influencing factor, reducing shear forces in the extruder and thereby reducing mechanical energy input, pressure, and temperature and affecting several TVP properties. Volatile lipid oxidation products from enzymatic oxidation in the raw materials are decomposed and steam-stripped during extrusion. Higher melt temperatures and lower water contents enhance this effect and promote the formation of masking “roasted” flavour compounds. However, acrylamide (<100 µg/kg) and trans-fatty acids (<0.4 g/kg) are also formed under flavour-improving conditions and TVP hardness is reduced. FS increases TVP density and reduces expansion and hardness. Reconciling mitigation of undesired chemical compounds and meat-like mechanical properties (at 16-18% water, 55-65% FS, mass flows <8 kg/h), a FS-based TVP can be created, combining nutritional and sustainability benefits of FS.

Templated synthesis of holy MIL-125(Ti) for the boosted photocatalytic performance in volatile organic compound oxidation and water treatment

This study presents the synthesis of hierarchically porous holy MIL-125(Ti) (H-MIL-125(Ti)) photocatalyst via a polystyrene (PS)-directed templating approach combined with solvent evaporation self-assembly (SESA). Sacrificial PS microsphere templates facilitated the formation of a macroporous structure, acting as temporary placeholders during metal–organic frameworks (MOF) crystallization. Removal of the templates created a complementary porous network within MIL-125(Ti), yielding a hierarchical pore architecture comprising inherent micropores and templated macropores. Characterization techniques revealed a high surface area (1204 m2 L−1) and optimal band gap (3.2 eV). Photoelectrochemical studies demonstrated efficient charge carrier generation and separation, with high average photocurrent density (4.5 mA cm−2) and low charge transfer resistance (27.5 Ω cm2). H-MIL-125(Ti) exhibited excellent photocatalytic activity for degrading various (volatile)organic pollutants under visible light, highlighting the importance of rational design and synthesis strategies in optimizing the performance of advanced porous materials.

Tailored engineering of intracrystalline mesopores for boosting multicomponent volatile organic compounds simultaneous deep oxidation

Developing effective catalysts for the removal of VOCs from air is crucial for mitigating air pollution. However, the catalytic performance is often constrained by mass transfer limitations due to the mismatch between the molecular dimensions of VOCs and the pore sizes of the catalysts. Herein, we report a hierarchically porous siliceous zeolite catalyst (Pt@S-1-meso) synthesized via a reversed-phase microemulsion method, featuring abundant silanol nests and mesopores to facilitate VOCs diffusion. Using o-xylene and propane as probe molecules, we demonstrate that Pt@S-1-meso exhibits superior catalytic activity toward o-xylene achieving 90 % conversion at 159 °C, compared to its purely microporous counterpart (Pt@S-1), which achieved 90 % conversion at 179 °C. Remarkably, this diffusion enhancement persisted even in the presence of smaller propane molecules. Mechanistic studies revealed that the silanol nests in Pt@S-1-meso effectively enrich o-xylene near the Pt nanoparticles and involve in the reaction pathway, promoting its catalytic degradation with a high turnover frequency of 2.34 × 10−2 s−1, significantly outperforming conventional microporous zeolites (1.22 × 10−2 s−1). This hierarchical pore engineering provides a promising strategy for developing efficient VOC abatement catalysts by overcoming mass transfer limitations for large molecules.

Coated oregano essential oil and cinnamaldehyde compounds supplementation improves growth performance, enhances immune responses, and inhibits cecal Escherichia coli proliferation of broilers.

Plant essential oils are unstable due to high volatility and easy oxidation, while microencapsulation provides a potentially effective strategy for increasing the stability of natural essential oils and preserving their function. This study examined the effects of feeding coated oregano essential oil and cinnamaldehyde (COEC) compounds on growth, immune organ development, intestinal morphology, mucosal immune function, and the cecal microbiota populations of broilers. Three hundred one-day-old male Arbor Acres broiler chicks were organized into 5 groups: 1) negative control fed basal diet alone (NC), 2) positive control receiving basal diet plus 50mg/kg of chlortetracycline (CTC), 3) basal diet plus 150mg/kg COEC (COEC150), 4) plus 300mg/kg COEC (COEC300), and 5) plus 450mg/kg COEC (COEC450). The supplement trial was continued for 42 d. The results showed that CTC, COEC300, and COEC450 treatments decreased the feed conversion ratio of broilers both in the starter and whole experiment phases, increased the height of jejunal villi at 21 d and the number of goblet cells and IgA-producing cells at 21 or 42 d compared with NC group (P < 0.05). Members of the COEC300 treatment group had a higher thymus weight index and jejunum length index than birds of NC or CTC groups at 21 d (P < 0.05). CTC and all COEC treatments decreased malondialdehyde content in jejunal mucosa at 42 d (P < 0.05). The population of Escherichia coli (E. coli) in the cecal digesta at 21 d was lower in the CTC, COEC300, and COEC450 treatment groups compared with the NC group (P < 0.05). In contrast to the CTC group, COEC supplementation dose-dependently accelerated body weight gain, improved jejunal morphology, decreased malondialdehyde content in jejunal mucosa, increased numbers of jejunal goblet cells and IgA-producing cells, and decreased the E. coli population in cecal digesta at 21 or 42 d (P < 0.05). Thus, we concluded that feeding broiler chickens with 300 or 450mg/kg in antibiotic-free diets can improve growth performance, enhance immune responses, and inhibit the proliferation of cecal pathogenic bacteria.

Contribution of plastic solid components to volatile organic compounds formation during plastics combustion

The combustion of plastic waste releases volatile organic compounds (VOCs) that are harmful to human health. However, information on the micro-mechanisms of VOC formation remains lacking. Here, the study hypothesized and verified the relationship between VOC formation and solid component degradation during plastics combustion. The VOCs released during plastics combustion exhibit characteristics such as low carbon content (nc< 10), volatility (9μgm-3 < log10C0 < 11μgm-3), and medium oxidation degree (−1.5 <OSC¯ < −0.5). The dominant VOCs ketones/aldehydes/acids (33-43%) may be attributed to the depolymerization of the polymer structure of plastics, the oxidation of C-O/C=O groups, and the secondary cleavage of gaseous oxygen-containing macromolecules. The VOCs released from the combustion of polyethylene terephthalate (PET) and poly(butyleneadipate-co-terephthalate) (PBAT) contained more aromatics than polyethylene (PE) and polypropylene (PP). And the temperature response of aromatics released from PET and PBAT lagged other VOCs compared that of PP and PE. However, compared to biomass thermal conversion, combustion of plastics releases fewer aromatics and nitrogenous compounds. Collectively, this work shows that the formation mechanisms of VOCs contributed by the solid components during plastic combustion are similar for PET and PBAT due to their similar chemical structures. The proposed mechanism in this paper will provide insight into the control of contaminants during plastic combustion.

Biogenic secondary organic aerosol participates in plant interactions and herbivory defense.

Biogenic secondary organic aerosols (SOAs) can be formed from the oxidation of plant volatiles in the atmosphere. Herbivore-induced plant volatiles (HIPVs) can elicit plant defenses, but whether such ecological functions persist after they form SOAs was previously unknown. Here we show that Scots pine seedlings damaged by large pine weevils feeding on their roots release HIPVs that trigger defenses in neighboring conspecific plants. The biological activity persisted after HIPVs had been oxidized to form SOAs, which was indicated by receivers displaying enhanced photosynthesis, primed volatile defenses, and reduced weevil damage. The elemental composition and quantity of SOAs likely determines their biological functions. This work demonstrates that plant-derived SOAs can mediate interactions between plants, highlighting their ecological significance in ecosystems.

Unraveling the Impacts of Germination on the Volatile and Fatty Acid Profile of Intermediate Wheatgrass (Thinopyrum intermedium) Seeds.

Intermediate wheatgrass (IWG) is a promising perennial grain explored for mainstream food applications. This study investigated the effects of different germination temperatures (10, 15, and 20 °C) and durations (2, 4, and 6 days) on IWG's volatile and fatty acid (FA) profiles. A method using headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was optimized through response surface design to extract the volatile compounds, achieving ideal extraction conditions at 60 °C for 55 min. Multiple headspace extraction (MHE) was used for volatile compound quantification. Fifty-eight compounds were identified and quantified in IWG flour, mainly alcohols, aldehydes, hydrocarbons, terpenes, esters, organic acids, and ketones. The main FAs found were linoleic acid (C18:2), oleic acid (C18:1), palmitic acid (C16:0), and linolenic acid (C18:3). Principal component analysis showed a direct correlation between volatile oxidation products and FA composition. Germination at 15 °C for 6 days led to a reduced presence of aldehydes and alcohols such as nonanal and 1-pentanol. Therefore, optimized germination was successful in reducing the presence of potential off-odor compounds. This study provides valuable insights into the effects of germination on IWG flour, showing a way for its broader use in food applications.

Enhanced cyclic oxidation resistance of Metcoloy II coated ASTM A53 Grade B steel by electric arc thermal spray

This study evaluates the enhanced cyclic oxidation resistance of Metcoloy II coatings applied to ASTM A53 Grade B steel substrates using electric arc thermal spray, across temperatures ranging from 500 °C to 700 °C. The research identifies distinct performance differences between coated and uncoated samples under cyclic oxidation conditions. Initially, both sample types exhibited mass increases due to oxide formation. However, uncoated samples developed non-protective iron oxides, while Metcoloy II coatings formed a protective layer of chromium and nickel oxides. During 500 oxidation cycles at 500 °C, uncoated samples showed a rapid mass increase, indicative of accelerated oxidation, whereas Metcoloy II coatings experienced a controlled mass gain, reflecting effective protection by chromium and aluminum oxides. At 700 °C, the mass variation trends were similar for both types initially; however, uncoated samples suffered significant mass loss due to iron oxide volatilization, emphasizing their susceptibility. Conversely, Metcoloy II coatings exhibited a reduced but steady mass increase, indicating their resilience under high-temperature conditions. Microstructural analysis confirmed the presence of a protective oxide layer in the coated samples, which is essential for reducing substrate oxidation. Although challenges such as coating detachment and thinning were observed, particularly at higher temperatures, Metcoloy II coatings maintained their protective role. This study highlights the coating's effectiveness in extending the lifespan of steel substrates subjected to cyclic oxidation, providing valuable insights for optimizing protective coatings in demanding industrial applications and advancing material science strategies for enhanced durability.

Effects of papain hydrolysate of Pseudosciaena crocea roe on the physical and oxidative stability of water-in-oil emulsions

This study investigates the effects of hydrolysates from Pseudosciaena crocea roe on the physical and oxidative stability of oil-in-water emulsions, emphasizing the structure-activity relationship between peptide structure and emulsifying properties. The results showed that, compared to other proteases, hydrolysates prepared with papain (PCRHs) at moderate degrees of hydrolysis (DH 4.68% and 6.8%) exhibited superior emulsifying activity index (EAI) and emulsifying stability index (ESI). PCRHs with DH of 4.68%, 6.8% formed smaller particle sizes (89.8 ± 3.52 nm, 112 ± 2.65 nm) and more stable emulsions. EAI and ESI of PCRHs were significantly negatively correlated with emulsion particle size and significantly positively correlated with surface hydrophobicity, amino acid composition, relative molecular mass, random coil content and total sulfhydryl groups. Additionally, although PCRHs with DH of 4.68% produced smaller and more stable emulsion particles, PCRHs with DH of 6.8% significantly inhibited primary and secondary lipid oxidation products formation. Correlation analysis revealed that emulsions with smaller particle sizes exhibited poorer oxidative stability, and secondary volatile oxidation products better reflected the oxidative stability of emulsions. Therefore, hydrolysates from Pseudosciaena crocea roe protein with moderate hydrolysis, particularly PCRHs with DH of 6.8%, demonstrate potential as natural emulsifiers to maintain the physical and oxidative stability of oil-in-water emulsions.

Impact of Nonthermal Plasma Treatment on the Oxidation of Lipids with Different Unsaturation Degrees.

Nonthermal plasma (NTP) treatment of food presents a new technology for the industry but raises concerns about lipid oxidation due to the presence of reactive species. Considering the critical role of the degree of unsaturation in lipid oxidation, this study investigates NTP-induced oxidation across various unsaturated lipids. These lipids are six oil samples primarily containing one of the following methylesters: oleate, linoleate, linolenate, arachidonate, eicosapentaenoate, and docosahexaenoate. Samples were treated with a nonthermal surface dielectric barrier discharge. Plasma-induced effects were first examined by classical lipid oxidation indicators, such as the peroxide value and p-anisidine value. The specific volatile oxidation products, including hexanal, nonanal, trans-2-hexenal, and methyl 9-oxononanoate, were determined to further elucidate the impact of ozone-related oxidation. Monitoring the production of selected nonvolatile oxidation products, such as epoxy-, oxo-, and hydroxy fatty acid methylesters, confirmed that plasma treatment facilitated the decomposition of lipid hydroperoxide. Generally, the level of plasma-induced oxidation increased in parallel with the unsaturation degree of the studied samples, except for the quantity of individual volatile carbonyls. The long-term effect of NTP treatment was investigated by a stability test, revealing that the oxidative stability depended on the input gas of plasma treatment, the sensitivity of the treated sample, and the presence of antioxidants. Except for the focus on the NTP impact, this study offered a case study of a comprehensive investigation into lipid oxidation.

Double layer packaging based on active black chickpea protein isolate electrospun nanofibers and intelligent salep film containing black chickpea peel anthocyanins for seafood products

In this study, a double-layer active and intelligent packaging system was developed based on two main natural macromolecules i.e. protein and carbohydrate with green perspective. Firstly, the salep-based films containing different concentrations (0–8 % w/w) of the inclusion complex of β-cyclodextrin/black chickpea anthocyanins (βCD/BCPA) were produced. The salep film containing 8 % of βCD/BCPA complex was specified as the optimized film sample based on its performance as a color indicator. The electrospinning of black chickpea protein isolate nanofibers (BCPI NFs) containing citral nanoliposomes (NLPs) was done on the optimized salep film. The cross-sectional field emission scanning electron microscopy approved the creation of double-layer structure of the developed film. The study of chemical and crystalline structure, as well as the thermal properties of the film exhibited the physical attachment of BCPI electrospun NFs on salep film. The effectiveness of the developed system was studied in detection of spoilage and increasing the shelf life of seafood products, including shrimp and fish fillet. The performance of the intelligent layer in detection of freshness/spoilage was acceptable for both seafood products. In addition, the active layer of the film controlled the changes of pH, total volatile basic nitrogen, oxidation, and microbial load in samples during storage time.

Hot corrosion behavior of Mo–Si–Ti alloys

AbstractThe hot corrosion behavior of two ternary Mo–Si–Ti alloys (eutectic Mo–20.0Si–52.8Ti (at.%) and eutectoid Mo–21.0Si–34.0Ti (at.%)) was investigated at C and C for up to 100 h. Both Mo‐based alloys evidenced a hot corrosion attack, resulting in a uniform attack of the substrate surface. The higher Ti content of the eutectic alloy significantly reduced the formation of solid and volatile Mo oxides compared with the eutectoid alloy. After 24 h at C, the corrosion products formed on the eutectic alloy were only one‐tenth the thickness of the layers formed on the eutectoid alloy. The corrosion products were examined with optical and electron microscopy. Semiquantitative electron probe micro analysis and X‐ray diffraction measurements were used to identify the formed phases. The underlying corrosion mechanisms comprising not only hot corrosion‐induced fluxing but also oxidation‐induced pesting are discussed in detail.

The surface chemistry of the atomic layer deposition of ruthenium on aluminum and tantalum oxide surfaces

The surface chemistry of Ru atomic layer deposition (ALD) processes based on the use of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)ruthenium(III) (Ru(tmhd)3) and either molecular oxygen or atomic hydrogen on aluminum oxide films was characterized by a combination of surface-sensitive techniques. The thermal decomposition of the Ru metalorganic precursor was determined, by using a combination of reflection-absorption infrared spectroscopy (RAIRS), temperature programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS), to start below 400 K and to take place in a stepwise fashion over a wide range of temperatures. Gas-phase products from this chemistry include 2,2,6,6-tetramethyl-3,5-heptanedione (the protonated ligand, Htmhd; in a TPD peak at 520 K), isobutene (540 K; indicating the fragmentation of the organic ligands), and other products from isomerization and/or aldol condensation (650 and 730 K). This chemistry is accompanied by the reduction of the Ru3+ ions in two stages, involving the loss of some of their ligands and their direct bonding to the substrate first (between 500 and 600 K) and a full reduction to a metallic state later on (600–700 K). ALD cycles using either molecular oxygen or atomic hydrogen resulted in the slow build-up of Ru on the surface, but the co-deposition of carbon could not be avoided, at least in the initial cycles, while the alumina surface was still exposed. With O2, the Ru atoms alternate between partially-oxidized (after the O2 exposures) and zero-valent (after the Ru(tmhd)3 doses) states, and some Ru loss in the form of the volatile RuO4 oxide was seen after the second half of the ALD cycles; neither the Ru oxidation state alternation nor the elimination of some Ru from the surface were observed when using H·. The deposited Ru was determined, by combining results from angle-resolved XPS (ARXPS) and low-energy ion scattering (LEIS) experiments, to grow as 3D nanoparticles rather than as a layer-by-layer 2D film, presumably because the Ru precursor preferentially adsorbs (and decomposes more cleanly) on the metal surface. A discussion is provided of the implications of these results for the design of ALD processes.

Responses of fine particulate matter (PM2.5) air quality to future climate, land use, and emission changes: Insights from modeling across shared socioeconomic pathways

Air pollution induced by fine particulate matter with diameter ≤ 2.5 μm (PM2.5) poses a significant challenge for global air quality management. Understanding how factors such as climate change, land use and land cover change (LULCC), and changing emissions interact to impact PM2.5 remains limited. To address this gap, we employed the Community Earth System Model and examined both the individual and combined effects of these factors on global surface PM2.5 in 2010 and projected scenarios for 2050 under different Shared Socioeconomic Pathways (SSPs). Our results reveal biomass-burning and anthropogenic emissions as the primary drivers of surface PM2.5 across all SSPs. Less polluted regions like the US and Europe are expected to experience substantial PM2.5 reduction in all future scenarios, reaching up to ~5 μg m−3 (70 %) in SSP1. However, heavily polluted regions like India and China may experience varied outcomes, with a potential decrease in SSP1 and increase under SSP3. Eastern China witness ~20 % rise in PM2.5 under SSP3, while northern India may experience ~70 % increase under same scenario. Depending on the region, climate change alone is expected to change PM2.5 up to ±5 μg m−3, while the influence of LULCC appears even weaker. The modest changes in PM2.5 attributable to LULCC and climate change are associated with aerosol chemistry and meteorological effects, including biogenic volatile organic compound emissions, SO2 oxidation, and NH4NO3 formation. Despite their comparatively minor role, LULCC and climate change can still significantly shape future air quality in specific regions, potentially counteracting the benefits of emission control initiatives. This study underscores the pivotal role of changes in anthropogenic emissions in shaping future PM2.5 across all SSP scenarios. Thus, addressing all contributing factors, with a primary focus on reducing anthropogenic emissions, is crucial for achieving sustainable reduction in surface PM2.5 levels and meeting sustainable pollution mitigation goals.

Volatile tin oxide memristor for neuromorphic computing

The rise of neuromorphic systems has addressed the shortcomings of current computing architectures, especially regarding energy efficiency and scalability. These systems use cutting-edge technologies such as Pt/SnOx/TiN memristors, which efficiently mimic synaptic behavior and provide potential solutions to modern computing challenges. Moreover, their unipolar resistive switching ability enables precise modulation of the synaptic weights, facilitating energy-efficient parallel processing that is similar to biological synapses. Additionally, memristors' spike-rate-dependent plasticity enhances the adaptability of neural circuits, offering promising applications in intelligent computing. Integrating memristors into edge computing architectures further highlights their importance in tackling the security and efficiency issues associated with conventional cloud computing models.

Determination of 2-MIB and rancid-related volatile lipid oxidation products in hybrid catfish (Clarias macrocephalus × Clarias gariepinus) with an automated HS-SPME-GC–MS-QTOF-arrow technique

A headspace solid–phase microextraction (HS-SPME) method coupled with gas chromatography/mass spectrometry with quadrupole time-of-flight (GC/MS-QTOF) was developed for analysis of volatile off-odor compounds, i.e., earthy/musty (2-methylisoborneol, 2-MIB) and rancid (aldehydes and alcohols), from farmed hybrid catfish (Clarias macrocephalus × Clarias gariepinus). The most efficient extraction of targeted volatiles was provided by 50 min at 70 °C with a CWR-PDMS fiber and 3 g of fish diluted to 5 mL with 1.5 g NaCl (30 % saturated NaCl). The maximum time-delay before extraction was 8 h to avoid spoilage and lipid oxidation during analysis. The final method showed good linearity, intraday repeatability of 5–9 %, interday reproducibility of 5–12 % and recoveries of 94–112 %. The implementation part proved that the developed method gave accurate quantitative results for oxidation-derived volatiles, several with high correlation to thiobarbituric acid reactive substances (TBARS). Altogether, our study provided an effective SPME-GC–MS method for the extraction and analysis of important off-odor compounds in catfish mince.

Investigation of scale formation and degeneration of silicide coating on Nb–Si based alloy in the temperature range from 1250 °C to 1560 °C

Nb silicide coatings modified with active elements have good oxidation resistance, but there is a lack of systematic research on their oxidation behavior at high temperatures above 1250 °C. The aim of this work is to investigate the oxidation behavior of an Al–Y modified silicide coating on Nb–Si based alloy in the temperature range from 1250 °C to 1560 °C. After oxidation at 1250 °C, the scale displays a typical layered structure consisting mainly of a TiO2 outer layer, an amorphous SiO2 matrix layer embedded with TiO2 and ZrSiO4, and an inner layer consisting of SiO2 and Cr2O3. Above 1350 °C, the evaporation reaction of Cr2O3 into CrO3 (g) is significantly accelerated and Cr2O3 disappeared gradually with temperature or time. The TiO2 layers covering on the scales formed at 1250–1500 °C grow along the crystallographic orientation of [100]. The micropores formed on the surface of TiO2 should be attributed to the further oxidation of Cr2O3 into volatile oxide CrO3 (g). The scales exhibit a similar structure consisting mainly of a SiO2 glass matrix embedded with ZrSiO4 and a surface TiO2 layer until 1500 °C. Above the eutectic temperature of SiO2–TiO2 system, the scale is mainly composed of a matrix layer of SiO2–TiO2 eutectic embedded with block TiO2 particles, and a thin SiO2 interface layer at 1560 °C. The degeneration path of the (Nb,X)Si2 coating is (Nb,X)Si2 → (Ti,Nb)5Si4 → γ-(Nb,X)5Si3.

Chemical and physical changes induced by cold plasma treatment of foods: A critical review.

Cold plasma treatment is an innovative technology in the food processing and preservation sectors. It is primarily employed to deactivate microorganisms and enzymes without heat and chemical additives; hence, it is often termed a "clean and green" technology. However, food quality and safety challenges may arise during cold plasma processing due to potential chemical interactions between the plasma reactive species and food components. This review aims to consolidate and discuss data on the impact of cold plasma on the chemical constituents and physical and functional properties of major food products, including dairy, meat, nuts, fruits, vegetables, and grains. We emphasize how cold plasma induces chemical modification of key food components, such as water, proteins, lipids, carbohydrates, vitamins, polyphenols, and volatile organic compounds. Additionally, we discuss changes in color, pH, and organoleptic properties induced by cold plasma treatment and their correlation with chemical modification. Current studies demonstrate that reactive oxygen and nitrogen species in cold plasma oxidize proteins, lipids, and bioactive compounds upon direct contact with the food matrix. Reductions in nutrients and bioactive compounds, including polyunsaturated fatty acids, sugars, polyphenols, and vitamins, have been observed in dairy products, vegetables, fruits, and beverages following cold plasma treatment. Furthermore, structural alterations and the generation of volatile and non-volatile oxidation products were observed, impacting the color, flavor, and texture of food products. However, the effects on dry foods, such as seeds and nuts, are comparatively less pronounced. Overall, this review highlights the drawbacks, challenges, and opportunities associated with cold plasma treatment in food processing.