教学课程资源库 更多>>

关键词： powder   Ultrasound-assisted extraction   Freeze drying   Spray drying   Platycodin D  

摘要： Platycodon grandiflorus (Jacq.) ***. roots (PGR), a Chinese herb with medicinal and edible value, was powdered by freeze drying (FD) and spray drying (SD) after maceration extraction (ME) or ultrasound-assisted extraction (UAE) to develop a new functional food product. Four PGR powders were obtained namely ME-FD, ME-SD, UAEFD, and UAE-SD and their powder quality, structural properties, and functionalities were evaluated. UAE-FD powder had the highest powder recovery (85.3 +/- 5.79%) and also presented better hydration properties due to the larger particle size compared with other three PGR powders. Four PGR powders exhibited similar thermal decomposition process, molecular structure, amorphous characteristics, amino acids composition, and taste profiles. Furthermore, the UAE-FD PGR powders presented the highest Platycodin D (3.68 +/- 0.04 mg/g), total phenolic (2.84 +/- 0.11 mg GAE/g), and total flavonoids content (2.11 +/- 0.14 mg RE/g), resulting in best antioxidant activity (58.67 +/- 2.42 mu mol Trolox/g). Therefore UAE-FD is an environment-friendly technique for the production of functional PGR powder with improved nutritional and redispersion properties.

关键词： Kombucha   Zijuan tea   Attractive color   Anthocyanins   Antioxidant activity  

摘要： Zijuan tea is a representative anthocyanin-rich tea cultivar in China. In this study, Zijuan tea was used to produce a novel kombucha beverage (ZTK). The physicochemical, sensory properties, and antioxidant activity of ZTK were compared with that of black tea kombucha (BTK) and green tea kombucha (GTK). Results indicated that after fermentation, the color of ZTK changed from yellowish-brown to salmon-pink, because its anthocyanins (4.5 mg/L) appeared red in acidic conditions. Meanwhile no significant changes of color were observed in BTK and GTK. The dynamic changes of pH, biomass, and concentrations of sugars, amino acids, and main organic acids were similar in three kombucha beverages, except catechins showing different trends. Moreover, ZTK showed the highest overall acceptability score, antioxidant activity, and concentration of volatiles among the three kombucha beverages. Therefore, Zijuan tea is suitable for the preparation of kombucha beverage with attractive color and health benefits.

关键词： Starch   Self-assembly   Curcumin  

摘要： Pullulanase debranching and subsequent hydroxypropylation were applied to prepare a series of dual-modified starches (Hydroxypropylated debranched starch, HPDS) with different degrees of hydroxypropyl substitution. Their structural and physicochemical properties varied with the degree of hydroxypropyl substitution, and all HPDS exhibited the ability to self-assemble into well-shaped nanospheres (100-150 nm, PDI < 0.2). These HPDS nanospheres were attempted to encapsulate curcumin with the aim of improving the bioavailability, solubility and stability of curcumin. Their structural characteristics, thermal stability, iodine staining, morphology, safety, encapsulation efficiency, in vitro gastrointestinal release behavior, and anti-inflammatory activity were evaluated. The results showed that curcumin could be effectively encapsulated into the HPDS nanospheres, and the encapsulation efficiency, water solubility and physical stability were positively correlated with the degree of hydroxypropyl substitution. After encapsulation, the water solubility and physical stability of curcumin could be increased up to 226-fold and 6-fold, respectively. The HPDS nanospheres also exhibited good safety (including hemolysis and cytotoxicity) and sustainable release of curcumin. Evaluation of anti-inflammatory activity showed that the activity of curcumin-encapsulated HPDS was enhanced by 170% compared to unencapsulated curcumin. These suggest that HPDS nanospheres encapsulation may be a more suitable option for the development of functional foods containing bioactive compounds.

关键词： black carbon   cold climate   airport   winter accumulation   winter boundary layer   impact of COVID-19 lockdown  

摘要： Black carbon (BC) plays an important role in climate and health sciences. Using the combination of a year real-time BC observation (photoacoustic extinctiometer) and data for PM2.5 and selected co-pollutants, we herein show that annual BC Mass concentration has a bi-modal distribution, in a cold-climate city of Montreal. In addition to the summer peak, a winter BC peak was observed (up to 0.433 mu g/m(3)), lasting over 3 months. A comparative study between two air pollution hotspots, downtown and Montreal international airport indicated that airborne average BC Mass concentration in downtown was 0.344 mu g/m(3), whereas in the residential areas around Montreal airport BC Mass values were over 400% higher (1.487 mu g/m(3)). During the numerous snowfall events, airborne BC Mass concentration decreased. High-resolution scanning/transmission electron microscopy with energy dispersive X-ray spectroscopy analysis of the snow samples provided evidence that airborne BC particles or carbon nanomaterials were indeed transferred from polluted air to snow. During the COVID-19 lockdown, the BC concentration and selected co-pollutants, decreased up to 72%, confirming the predominance of anthropogenic activities in BC emission. This first cold-climate BC data set can be essential for more accurate air quality and climate modeling. About one-third of the Earth's land surface receive snow annually, the impact of this study on air quality, health and climate change is discussed.

关键词： Microplastics   Wastewater treatment plants   Aging behavior   Physicochemical characteristics   Adsorption capacities  

摘要： Despite a wealth of information on removal of the microplastics (MPs) in wastewater treatment plants (WWTPs), little attention has been paid to how wastewater treatment process affect the MP physicochemical and adsorption characteristics. In this study, changes in physicochemical property of three MPs, i.e. polyamide (PA), polyethylene (PE) and polystyrene (PS) through the wastewater pipeline, grit and biological aeration tanks were investigated. The results show that compared with virgin MPs, the treated MPs have higher specific surface area and O content, and lower C and H contents, and glass transition temperature, implying that the three treatments cause the chain scission and oxidation of the MPs. Cd adsorption capacities of the MPs are higher than the corresponding virgin MPs after sulfidation in the pipeline (SWPN) and biological treatment in aeration tank (BTAT). Pearson correlation analysis shows that the increase is mainly resulted from the enhancement of the O-containing groups on the MPs. However, Cd adsorption capacities of the MPs decrease after mechanical abrasion in grit tank (MAGT), corresponding to the decrease in carbonyl index. Two dimensional FTIR correlation spectroscopy demonstrates that the N\\H bond in the PA plays a more important role than C\\H bond in the adsorption of Cd, but only change of the C\\H bond is found in the PE and PS. The findings provide new insights into the effect of WWTPs on the MP aging and physicochemical characteristics. (c) 2021 Elsevier B.V. All rights reserved.

关键词： Cobalt-doped (Co-doped) Gd2O3   chemical precipitation   physico-chemical characteristics   photo-physical study  

摘要： Gd2-xCoxO3-delta (where x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) nanoparticles were synthesized by a simple chemical precipitation method. XRD data revealed the presence of a cubic crystalline structure in the samples. FTIR data showed a peak at 441 cm(-1) which is due to Gd-O vibration mode. Particle size analysis indicated particles in the range of 290.5-616.6 nm. SEM studies revealed agglomeration of particles. The presence of cobalt dopant with varying compositions was further confirmed from EDX. The band gap of Gd(2-x)Co(x)O(3-delta)was found to be in the range of 3.57 - 4.93 eV.

关键词： Copper   Catalysts   Catalytic reactions   Oxidation   Doping  

摘要： Selective catalytic reduction (SCR) systems are important technical means of mitigating NOx emissions for diesel engines. The major challenge of this technique is to improve the low-temperature activity of the catalyst during engine cold start and the thermal stability on repeated exposure to high-temperature exhaust. A two-stage SCR system with a Cu-SSZ-13 catalyst was analyzed with SCR sample experiments and NH3 oxidation experiments. The effects of copper content, doping metals, structural arrangement, NO2/NOx ratio, and NH3/NOx ratio (ANR) on the NOx conversion reaction at different temperatures were investigated. Furthermore, the Cu-SSZ-13 catalyst activity was characterized by Fourier transform infrared spectroscopy, H-2 temperature-programmed reduction, and X-ray diffraction. The results showed that the low-temperature catalytic performance first increased with increasing copper content and decreased with a further increase. The optimal value of copper content was around 3.4%. The thermal stability of Cu(S)SZ-13 catalysts decreased with the increase in the copper content. The temperature window of the high NOx conversion rate was widened by doping Zr/Mn/Ce, and the temperature window was widened by 15.1-33.1%. The two-stage SCR system was compared with a single SCR, which showed that the NH3 oxidation rate increased by 46.9-88.7%, the NOx conversion rate increased by 67.7-85.5%, and T-90 was optimized by 3.3-13.5% during engine cold start. This made the total NOx conversion rate to maintain a high level above 80% at temperatures over 500 degrees C. An appropriate NO2/NOx ratio and ANR could improve the NOx conversion rate at a low-temperature range.

关键词： UF   PF   wheat flour   wheat starch   wheat protein   viscosity   ABES   buffer capacity  

摘要： The use of additives for resins modification is common practice in wood-based panel industry and wheat flour has been one of the most widely used extenders for decades. The amount of wheat flour to be added is determined through a sense of proportion, mainly based on experience, as systematic scientific studies on the effect of its individual components are limited. In this study, we added wheat flour, wheat starch and wheat protein as extenders in various quantities to urea (UF) and phenol formaldehyde (PF) resins and analysed their structure, pH value and buffer capacity through closely examining their interaction with the resins as well as their effect on viscosity and bonding strength development. As a result, wheat protein proved to be the most effective on both resins. Despite influencing adhesive properties in uncured state, no effect on the curing behaviour of the resins could be observed.

关键词： Polarization  

摘要： Barium strontium titanate BaxSr1-xTiO3 (BSTO) has been widely used in nano devices due to its unique ferroelectric properties and can be epitaxially grown on a SrTiO3 (STO) support, with a reduced lattice and thermal mismatch. In this work, we developed a ReaxFF reactive force field verified against quantum mechanical data to investigate the temperature and composition dependency of BSTO in non-ferroelectric/ferroelectric phases. This potential was also explicitly designed to capture the surface energetics of STO with SrO and TiO2 terminations. Our molecular dynamics simulations indicate that when the percentage of Sr increases, the phase transition temperature and the polarizations of the BaxSr1-xTiO3 system decrease monotonically. In addition, as the oxygen vacancy concentration enhances, the initial polarization and the phase transition temperature of the system drop significantly. Furthermore, our simulation results show that charge screening induced by adsorption of water molecules on TiO2 terminated surfaces leads to an increased initial polarization.

关键词： Chitosan   Molecular weight   Antioxidant activity   beta-carotene   Nanoemulsion   Layer-by-layer technique  

摘要： In this research, three various Mw of chitosan (CS)-gallic acid (GA) conjugates were synthesized, characterized, and used for improvement of physicochemical stability of 0-carotene (BC) nanoemulsion (NE) by layer-by-layer technique. GA conjugation degrees were in the following order: HCS (125.6 mg/g) > MCS (102.3 mg/g) > LCS (74.6 mg/g) at GA:CS mass ratio of 0.5:1. Three varying Mw of CS-GA conjugates exhibited pronouncedly higher antioxidant abilities than native CS. For native CS, antioxidant abilities increased with the decrease of Mw. However, HCS-GA conjugate showed the highest antioxidant activity, due to the higher GA conjugation degrees and decreased intramolecular hydrogen bonds and crystallinity in HCS-GA conjugate. CS-GA conjugates substantially improved BC chemical stability in NE than CS and BC retentions were in the following order: HCS-GA (76.8%) > MCS-GA (68.3%) > LCS-GA (53.4%) after 30 days storage. The results obtained may provide some useful information for the applications of CS-GA conjugates for nutraceuticals stabilization in food systems.