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关键词： Colloid retention   Colloid mobilization   Micromodel   Pore-scale visualization   Solution chemistry   Hydrophobicity  

摘要： Clear understanding of pore-scale mechanisms that control transport and retention of colloids in porous media at different physicochemical conditions is critical to improve design and efficient cleanup methodologies of filter beds. The objective of this work was to investigate the impact of hydrophobicity, solution ionic strength, and pH on colloid retention mechanisms in single-phase and two-phase flow in porous media systems. A series of experiments were conducted using a geometrically representative micromodel. Hydrophilic and hydrophobic colloids were dispersed in water at different solution ionic strength and pH conditions. Findings indicate that hydrophilic colloids exhibit high filtration efficiency as the colloids interact attractively with other colloids and solid-water-interface irrespective of the solution chemistry. However, for hydrophobic colloids, changes in solution chemistry significantly increase colloid retention where the colloid interaction become attractive with the increase in ionic strength and decrease in pH values. Colloids attached to the collector surfaces mobilized by the strong capillary forces induced by the moving gas-water interface and transported along with the interface. However, hydrophilic colloids redeposited on gas-water-solid interfaces or thin water films because of their greater capillary potential. Therefore, greater filtration efficiency is achieved with the hydrophilic colloids compared to the hydrophobic colloids for which the efficiency can be improved by changing the solution chemistry. Moreover, the removal efficiency by the moving gas-water interface was observed to be more for hydrophobic colloids compared to hydrophilic colloids for which the efficiency can be improved by lowering the ionic strength or increasing the pH value. This study indicates that the coupled effects of solution chemistry and colloid hydrophobicity should be taken into account while investigating efficient filtration and cleaning practices fo

关键词： Tilapia   wood smoke   sensory qualities   Mahogany   cinnamon  

摘要： Different preservation and processing techniques have been used to extend the shelf life of fish. Smoking is a technique that enhances the flavor, color, texture, and shelf life of fish. This study was conducted to identify specific smoking conditions for tilapia (Oreochromis niloticus), while comparing the physicochemical and sensory qualities of tilapia smoked using selected wood smokes. Tilapia fillets of the same thickness were obtained, and trials were conducted to identify the best brine concentration, temperature/time combination, and wood material. The fillets were immersed in brine containing 2.5, 5.0, 7.5, 10.0, and 12.5% (w/v) NaCl for 1 hour. Then, fillets were smoked with wood smoke at three different temperatures (50, 60, and 70 degrees C) and three drying times (3, 4, and 5 hours) using a smoking oven. Based on the selected temperature/time combinations, tilapia were smoked using mahogany, cinnamon, or their combination (1:1). Final products were vacuum-packed and stored at 4 degrees C for analysis. Quality changes in sensory attributes were tested by 30 untrained panelists. Microbial quality (Salmonella, Escherichia coli, and total plate count), thiobarbituric acid reactive substances assay, and color were determined during 21 days of chilled storage, and proximate analysis was conducted. Fish brined in 10% (w/v) NaCl and smoked at 60 degrees C for 4 hours using mahogany: cinnamon at 1:1 had the best sensory qualities (p < .05). Microbial counts and lipid oxidation were within the permitted levels, while no Escherichia coli and Salmonella sp. were observed. During the chilled storage, an increase in lightness (40.85 +/- 0.32 to 42.02 +/- 1.22) was observed, whereas the redness (8.86 +/- 0.69 to 6.84 +/- 0.11) was decreased. In conclusion, immersing tilapia fillets in brine containing 10% (w/v) NaCl followed by smoking at 60 degrees C for 4 hours using mahogany: cinnamon at 1:1 can be considered as the best conditions to produce smoked tilapia. Howeve

关键词： 物理化学   科研成果   创新意识  

摘要： 由于物理化学的知识体系与食品、材料、能源、环境、生命等学科密切相连,因此,它不仅是农业大学全校性的化学必修课和基础课,更是培养学生创新思维和科研能力的重要课程。在教育部大力发展“新工科、新农科”建设的新形势下,尝试引入国内外最新的物理化学相关的科技成果,加入与课程相关的内容同时进行讲解,培养学生的创新能力和解决问题的能力,不仅能提高学生对物理化学课程的兴趣,开阔学生的眼界、增长学识,同时也完善了教学体系,教学效果良好。

关键词： 覆盖度   吸附热   反应活性   固体表面  

摘要： 覆盖度是物理化学课程中表面现象部分的重要概念,对学生认识吸附过程,深入理解固体表面的化学反应具有重要的指导意义。然而在教学活动中由于学时限制等因素,对覆盖度概念的讲解不够深入,致使学生不能全面深刻理解该概念。本文以具体事例讲述覆盖度的影响因素及其重要作用,为学生深入理解覆盖度的概念提供了有力的支撑。

关键词： Potato starch   Modification   TPs   Physicochemical properties  

摘要： The physicochemical, rheological properties and structure of potato starch and starch-tea polyphenols (TPs) complex modified by enzyme and alcohol was investigated in this study. Cavities on the modified starch granules and morphology change could be investigated by SEM, while significant birefringence observed in complete granules by polarizing light microscope, but disappeared in crashed starch. TPs inhibited the aggregation of amylose and retrogradation of starch TPs complex, resulting in the decrease of gel strength, and the increase of viscosity and gelatinization stability of starch granules. Fourier transform infrared (FT-IR) spectra showed that intramolecular hydrogen bond could be formed between TPs with modified starch, and the hydrogen bond force formed by starch and TPs was stronger than that between starch molecules. X-ray diffraction (XRD) analysis revealed that three modification methods did not change the crystalline structure of starch, but new diffraction peaks appeared in the four starch-TPs complex, suggesting that the hydrogen bond was incurred by interaction between TPs and amylose to form V-type crystalline. These results demonstrated that the complex formed by TPs and native/modified potato starch could be used in food industrial applications due to the inhibition of starch retrogradation. (C) 2020 Elsevier B.V. All rights reserved.

关键词： Polymorphs   Crystal structure   Hirshfeld surface analysis   Optical band gap   Magnetic susceptibility  

摘要： Two polymorphs of the new complex (C13H22N)(2)[CoBr4] have been prepared. The crystal structures of the polymorphs were determined by X-ray crystallography. Polymorph I belongs to the triclinic system, space group P-1 (No 2), while polymorph II adopts the monoclinic space group P2(1)/c (No 14). The crystal packing is guided by C-H center dot center dot center dot Br hydrogen bonds;these interactions contribute to the overall stabilization of the structures as they connect anions and cations together into a three-dimensional network. The polymorphs present different structure-properties relationships. Hirshfeld surfaces analysis contributes to the identification of the primary intermolecular contacts that guide the packing diagram. The thermal decomposition was studied by DSC, VT-PXRD, TDA and TGA techniques. The optical band gap energy suggests the semiconductor nature of the polymorphs. Temperature dependent magnetic susceptibility measurements in the temperature range of 1.8-310 K reveal that the polymorphs exhibit very weak antiferromagnetic interactions or contributions from single ion anisotropy.

关键词： 物理化学实验   线上教学   考核方式  

摘要： 物理化学实验的教学方法优化是提高教学效果的关键一环。针对目前教学过程中存在的问题,我们采用钉钉和雨课堂辅助实验教学的模式来优化课程资源。我们发现钉钉群上课保存的视频可以永久存放,上课视频可以根据需要下载剪辑,且不需要人员维护,学生在此观看还有统计数据,这是对雨课堂上课效果地有效补充。总之,钉钉和雨课堂联合运用提高了课堂教学效果,调动学习积极性,优化考核方式,为探究以学生为中心的教学模式改革提供参考信息。

关键词： Prawn   Food electronic nose   Physiochemical parameters   Quality analysis  

摘要： Construction of food electronic nose (FEN) for prawn (Macrobrachium rosenbergii) quality rapid assessment assisted with physicochemical parameters was explored in this paper. Sensory analysis, weight, GC/MS, and K value, and microbial were examined to provide the assisting basis for FEN system design. Results indicated that sensory acceptance decreased with the increase in time. The decline of prawn physiochemical parameters was associated with microbiological propagation. The volatile gases emitted by prawn could be utilized for sample quality characterization. FEN successfully discriminated all samples, and presented good detecting accuracy. The method proposed in this work is promising in aquatic products quality rapid analysis.

关键词： Amaranth   Common bean   Protein isolates   Xanthan gum   Compatibility   Electrostatic interaction  

摘要： Vegetables are considered to be a sustainable source of promising biomaterials such as proteins and polysaccharides. In this study, four protein isolates (amaranth protein isolate API, amaranth globulin-rich protein isolate AGR, bean protein isolate BPI, and bean phaseolin-rich protein isolate BPR) were structurally characterized under different pH conditions (2-12) and their compatibility behavior with xanthan gum (XG) in aqueous medium was described. All protein isolates showed beta turn and beta sheet (78.24-81.11%), as the major secondary structures without statistically significant difference under the pH conditions surveyed. Protein isolates show solubility at pH <= 3 (40.4-85.1%) and pH >= 8 (57.6-99.9%) and surface hydrophobicity results suggest protein denaturation at pH <= 3. In the compatibility study, API/XG ratios between 1:1 and 5:1 at pH from 7 to 9 and the BPI/XG ratios from 1:1 to 20:1 at pH 7 form gels that do not require heating nor crosslinking agent addition. Zeta potential results, on the other hand, evidenced that formation of gels is driven by attractive electrostatic interaction of the charged regions of both biopolymers and intermolecular interactions such as hydrogen bonds. (C) 2020 Elsevier B.V. All rights reserved.

关键词： 物理化学   混合教学   教学资源  

摘要： 课程素材的甄选是课程教学准备的重要内容之一。由于物理化学课程具有理论深奥、知识点繁多、推理严密等特点,因此丰富课程的教学资料,加强对《物理化学》课程线上线下的教学设计,对于课程的有效开展具有重要意义。从教学素材的收集、筛选、分类、反馈等方面进行了探讨,为物理化学混合式教学的开展提供保障。