Atmospheric sulfate aerosols contribute significantly to air pollution and climate change. Sulfate formation mechanisms during winter haze events in northern China have recently received considerable attention, with more than 10 studies published in high-impact journals. However, the conclusions from in-field measurements, laboratory studies, and numerical simulations are inconsistent and even contradictory. Here, we propose a physically based yet simple method to clarify the debate on the dominant sulfate formation pathway. Based on the hazes evolving in the synoptic scale, first, a characteristic sulfate formation rate is derived using the Eulerian mass conservation equation constrained by in situ observations. Then, this characteristic value is treated as a guideline to determine the dominant sulfate formation pathway with a 0D chemical box model. Our observation-derived results establish a linkage between studies from laboratory experiments and chemical transport model simulations. A convergent understanding could therefore be reached on sulfate formation mechanisms in China\'s wintertime haze. This method is universal and can be applied to various haze conditions and different secondary products.

Volatile sulfur compounds (VSCs) significantly influence food flavor and garner considerable attention in flavor research due to their low sensory thresholds, diverse odor attributes, and high reactivity. Extensive research studies have explored VSC formation through thermal processes such as the Maillard reaction, thermal pyrolysis, oxidation, and enzymatic reactions. However, understanding of the specific reaction mechanisms and processes remains limited. This is due to the dispersed nature of existing studies, the undefined intermediates involved, and the complexity of the matrices and processing conditions. Given these limitations, the authors have shifted their focus from foods to sulfides. The structure, source, and chemical characteristics of common precursors (sulfur-containing amino acids and derivatives, thiamine, thioglucoside, and lentinic acid) and their corresponding reactive intermediates (hydrogen sulfide, thiol, alkyl sulfide, alkyl sulfenic acid, and thial) are provided, and the degradation mechanisms, reaction rules, and matrix conditions are summarized based on their chemical characteristics. Additionally, the VSC formation processes in several typical foods during processing are elucidated, adhering to these identified rules. This article provides a comprehensive overview of VSCs, from precursors and intermediates to end products, and is crucial for understanding the mechanisms behind VSC formation and managing the flavor qualities of processed foods.

Tea is widely consumed in both beverages and food. Epigallocatechin gallate (EGCG) is the most crucial active ingredient in tea. Currently, knowledges on transformation processes of EGCG during tea processing are lacking. Understanding the chemical reactions of EGCG and its products during tea processing is important for assessing the safety of tea-containing food. Here, we revealed the formation of persistent free radicals (PFRs) from EGCG under the influence of heating and light irradiation, which was substantiated with evidence. These PFRs exhibited stability for >30 min in simulated gastric fluid. Furthermore, we observed potential effects of these PFRs on DNA damage and cell cytotoxicity in vitro. By combining electron paramagnetic resonance spectrometer with Fourier transform ion cyclotron resonance mass spectrometry, we elucidated the pathways involved in free radical formation. These findings are expected to contribute to a comprehensive understanding of free radical chemistry in tea-containing food.

Microemulsions are thermodynamically stable, optically isotropic, transparent, or semi-transparent mixed solutions composed of two immiscible solvents stabilized by amphiphilic solutes. This comprehensive review explores state-of-the-art techniques for characterizing microemulsions, which are versatile solutions essential across various industries, such as pharmaceuticals, food, and petroleum. This article delves into spectroscopic methods, nuclear magnetic resonance, small-angle scattering, dynamic light scattering, conductometry, zeta potential analysis, cryo-electron microscopy, refractive index measurement, and differential scanning calorimetry, examining each technique\'s strengths, limitations, and potential applications. Emphasizing the necessity of a multi-technique approach for a thorough understanding, it underscores the importance of integrating diverse analytical methods to unravel microemulsion structures from molecular to macroscopic scales. This synthesis provides a roadmap for researchers and practitioners, fostering advancements in microemulsion science and its wide-ranging industrial applications.

Staple foods serve as vital nutrient sources for the human body, and chewiness is an essential aspect of food texture. Age, specific preferences, and diminished eating functions have broadened the chewiness requirements for staple foods. Therefore, comprehending the formation mechanism of chewiness in staple foods and exploring approaches to modulate it becomes imperative. This article reviewed the formation mechanisms and quality control methods for chewiness in several of the most common staple foods (rice, noodles, potatoes and bread). It initially summarized the chewiness formation mechanisms under three distinct thermal processing methods: water medium, oil medium, and air medium processing. Subsequently, proposed some effective approaches for regulating chewiness based on mechanistic changes. Optimizing raw material composition, controlling processing conditions, and adopting innovative processing techniques can be utilized. Nonetheless, the precise adjustment of staple foods\' chewiness remains a challenge due to their diversity and technical study limitations. Hence, further in-depth exploration of chewiness across different staple foods is warranted.

Tropospheric ozone (O3) is mainly produced through a series of photochemical reactions of nitrogen oxides (NOx) and volatile organic compounds (VOCs). The reaction process presents complex non-linear relationships. In this work, datasets of atmospheric ozone and volatile organic compounds (VOCs) observed during the summer of 2018 in Nanjing were used. Combining with the framework for 0-D atmospheric model-master chemical mechanism (F0AM-MCM), the characteristics of photochemical reactions for ozone (O3) formation in Nanjing during the O3 episode days and non-episode days were investigated. The results showed that φ(O3) and φ(TVOCs) in the O3 episode days were 47.8×10-9 and 49.0×10-9, respectively, exceeding those in the non-episode days by factors of 1.8 and 1.6. Furthermore, F0AM, the empirical kinetic modeling approach (EKMA), and relative incremental reactivity (RIR) were utilized for the calculation of ozone chemical sensitivity. It was found that O3 formation in Nanjing was attributed to both VOCs and NOx limitation. In addition, the modeled ·OH and HO2 concentrations in the O3 episode days were 1.3 and 1.8 times higher than those in the non-episode days. The higher formation and loss rates of ·OH and HO2 were also found during O3 episode days. These findings reflected that the enhancements of atmospheric oxidation capacity resulted in increased production rates of O3, providing an explanation for the enhancements of O3 concentrations in Nanjing during the O3 episode days. The findings also improved the understanding of the O3 photochemical characteristics over Nanjing in the summer during the O3 episode days.

The pronounced perception of off-odors poses a prevalent issue across various categories of food ingredients and processed products, significantly exerting negative effects on the overall quality, processability, and consumer acceptability of both food items and raw materials. Conventional methods such as brining, marinating, and baking, are the main approaches to remove the fishy odor. Although these methods have shown notable efficacy, there are simultaneously inherent drawbacks that ultimately diminish the processability of raw materials, encompassing alterations in the original flavor profiles, the potential generation of harmful substances, restricted application scopes, and the promotion of excessive protein/lipid oxidation. In response to these challenges, recent endeavors have sought to explore innovative deodorization techniques, including emerging physical processing approaches, the development of high-efficiency adsorbent material, biological fermentation methods, and ozone water rinsing. However, the specific mechanisms underpinning the efficacy of these deodorization techniques remain not fully elucidated. This chapter covers the composition of major odor-causing substances in food, the methodologies for their detection, the mechanisms governing their formation, and the ongoing development of deodorization techniques associated with the comparison of their advantages, disadvantages, and application mechanisms. The objective of this chapter is to furnish a theoretical framework for enhancing deodorization efficiency through fostering the development of suitable deodorization technologies in the future.

Synthesis of methylsilsesquioxane aerogels by ambient pressure drying instead of supercritical drying has recently emerged as a major trend, but the issues of low mechanical strength and unstable performance still need to be resolved. This work reveals the microscopic formation mechanisms of gel skeleton based on the kinetic characteristics of methyltrimethoxysilane (MTMS) precursor hydrolysis and the associated sol-gel reactions. The effects of oxalic acid concentration (cOA) and hydrolysis time of MTMS solution (th) on the gelation time, morphologies, microstructures, chemical structure, and compression properties of the as-synthesized methylsilsesquioxane aerogels are investigated. The optimal cOA and th are 38.4 mmol/L and 120 min, respectively, endowing the methylsilsesquioxane aerogels with a compression strength of 0.170 MPa and a maximum compression strain of 61.2%. Precise control of the hydrolysis conditions ensures the formation of branched particle-to-particle networks, which is crucial for maximizing the compression properties of methylsilsesquioxane aerogels synthesized under industry-relevant conditions.

Substituted polycyclic aromatic hydrocarbons (SPAHs) are a type of emerging pollutant that widely exist in the environment, which also exhibit carcinogenicity, mutagenicity, and teratogenicity. These pollutants belong to toxic pollutants because of their similar structures to polycyclic aromatic hydrocarbons (PAHs). Their environmental behavior and ecological risk have attracted increasing attention. Based on a literature review, we found a new breakthrough in the source, distribution, behavior, and risk of SPAHs with comparison to traditional pollutants PAHs. This paper reviewed the current research progress on the environmental occurrence and photochemical behavior of SPAHs. Their sources, formation mechanisms, and distribution characteristics in the multimedia environment were highlighted, and the photochemical transformation kinetics, pathways, and affecting factors of SPAHs in water, ice, and other media were discussed. Furthermore, the research prospects about the environmental behavior and risk of SPAHs were proposed.

The thermal processes of materials containing decabromodiphenyl ether (BDE-209) normally result in the exposure of BDE-209 to high-temperature environments, generating a series of hazardous compounds. However, the evolution mechanisms of BDE-209 during oxidative thermal processes remain unclear. Thus, this paper presents a detailed investigation on the oxidative thermal decomposition mechanism of BDE-209 by utilizing density functional theory methods at the M06/cc-pVDZ theoretical level. The results show that the barrierless fission of the ether linkage dominates the initial degradation of BDE-209 at all temperatures, with branching ratio over 80%. The decomposition of BDE-209 in oxidative thermal processes is mainly along BDE-209 → pentabromophenyl and pentabromophenoxy radicals → pentabromocyclopentadienyl radicals → brominated aliphatic products. Additionally, the study results on the formation mechanisms of several hazardous pollutants indicate that the ortho-phenyl-type radicals created by ortho-C-Br bond fission (branching ratio reached 15.1% at 1600 K) can easily be converted into octabrominated dibenzo-p-dioxin and furan, which require overcoming the energy barriers of 99.0 and 48.2 kJ/mol, respectively. The O/ortho-C coupling of two pentabromophenoxy radicals also acts as a non-negligible pathway for the formation of octabrominated dibenzo-p-dioxin. The synthesis of octabromonaphthalene involves the self-condensation of pentabromocyclopentadienyl radicals, followed by an intricately intramolecular evolution. Results presented in this study can enhance our understanding of the transformation mechanism of BDE-209 in thermal processes, and offer an insight into controlling the emissions of hazardous pollutants.