教学课程资源库 更多>>

关键词： Buckwheat kernel   Radio frequency heating   Temperature-time combinations   Pasteurization efficiency   Physicochemical properties  

摘要： Microbial contamination is a persistent problem for grain industry. Many studies have shown that radio frequency (RF) heating can effectively reduce pathogens populations in low moisture foods, but there is a lack on the efficacy to decontaminate natural microbiome. The main objectives of this study were to investigate the effects of different RF heating conditions on natural microbial populations and physicochemical properties of buckwheat. In this study, 30 buckwheat samples collected from 10 different Provinces in China were analyzed for their microbial loads, and the samples with the highest microbial populations were used for further study to select the suitable RF heating conditions. The results showed that microbial loads in tested buckwheat kernels were in the range of 3.4-6.2 log CFU/g. Samples from Shanxi (SX-3) had significantly higher microbial counts than other samples. The selected four temperature-time combinations: 75 degrees C-20 min, 80 degrees C-10 min, 85 degrees C-5 min, and 90 degrees C-0 min of RF heating could reduce microbial counts to <3.0 log CFU/g in buckwheat kernels at 16.5% w.b. moisture content. Furthermore, the reduction populations of the inoculated pathogens (Salmonella Typhimurium, Escherichia coli, Cronobacter sakazakii, and Bacillus cereus) reached 4.0 log CFU/g under the above conditions, and almost 5.0 log CFU/g especially at high temperature-short holding time combinations (85 degrees C-5 min and 90 degrees C-0 min). Besides, physicochemical properties evaluation also showed the insignificant color changes and nutrients loss after RF treatment at 90 degrees C-0 min. Therefore, the RF heating at 90 degrees C-0 min holds greater potential than the other lower temperature-longer holding time combinations for applications in buckwheat pasteurization.

关键词： alkylimidazolium cation   hydrogen bond   ionic liquids   ion-ion interaction   physicochemical properties  

摘要： We focus on a series of protic ionic liquids (PILs) with imidazolium and alkylimidazolium (1R3HIm, R=methyl, ethyl, propyl, and butyl) cations. Using the literature data and our experimental results on the thermal and transport properties, we analyze the effects of the anion nature and the alkyl radical length in the cation structure on the above properties. DFT calculations in gas and solvent phase provide further microscopic insights into the structure and cation-anion binding in these PILs. We show that the higher thermodynamic stability of an ion pair raises the PIL decomposition temperature. The melting points of the salts with the same cation decrease as the hydrocarbon radical in the cation becomes longer, which correlates with the weaker ion-ion interaction inthe ion pairs. A comparative analysis of the protic ILs and corresponding ILs (1R3MeIm) with the same radical (R) in the cation structure and the same anion has been performed. The lower melting points of the ILs with 1R3MeIm cations are assumed to result from the weakening of both the ion-ion interaction and the hydrogen bond.

关键词： Redox reactions   Oxides   Catalysts   Electrical energy   Batteries  

关键词： Particle size  

摘要： Moringa stenopetala, locally known as Shiferraw, is an indigenous vegetable tree native to southern Ethiopia and grown mainly for its food value. This study deals with the investigations of physicochemical characteristics of Moringa stenopetala seeds' oil extracted using solvent extraction with food-grade hexane as a solvent and Analysis of Variance (ANOVA) of the extraction parameters. The seeds were collected from Adama located in Oromia, East Shewa Zone of Ethiopia, and they exhibit the average moisture, ash, fiber, protein, and oil contents of 6.3, 4.2, 2.3, 27.5, and 40.2%, respectively. Temperature, extraction time, and particle size had a significant p < 0.05 effect on the oil yield. According to the Experimental Design Response Surface Methodology (RSM) and ANOVA analysis, the optimum process parameters' combination to find the highest oil yield was particle size of 0.83 mm, the temperature at 78.82 & DEG;C, and extraction time of 5.13 hours. The model predicted oil yield was 39.7 & PLUSMN;0.32%. The oil from Moringa stenopetala seed exhibits physiochemical characteristics of refractive index (40 & DEG;C), 1.4625;viscosity 49.4 Cp;density at 25 & DEG;C, 0.9317 g/cm(-3);saponification value, 191.4;peroxide value, 11.52 millieq O-2/kg;iodine value of 89.21;and Acid Value (AV) 2.21 mg KOH/g. Fourier-transform infrared spectroscopy (FT-IR) analysis shows that the oil contains both ester carbonyl (C=O) functional groups saturated and unsaturated fatty acid. The physicochemical properties of Moringa stenopetala seeds were compared with other edible oil properties such as sesame, groundnut, olive, and sunflower seeds. The result shows that in the future Moringa stenopetala could be used as a substitute for other oil-bearing seeds sources, such as soybean, sunflower, and groundnut.

关键词： Excitons  

摘要： Over the past decade, porous organic polymers (POPs) have emerged as powerful photocatalysts for organic transformations and wastewater decontamination. The surface properties and pore space of POPs have been tailored to find optimal physical dimensions for adsorption and catalysis, whereas playing with the donor-acceptor building units lends them unique prospects for bandgap engineering, beneficial for customized applications including the degradation of simple as well as persistent pollutants. Here in this critical perspective, we focused beyond these generic scenarios and provided a detailed physicochemical explanation for the experimental observations. Considering the invaluable role of excitons, along with mobile electrons and holes, we fundamentally justified the reactivities of POPs with regard to water treatment. Both semiconducting and molecular catalyst approaches have been considered for different types of POPs. Depending on the porosity, structural formation and defects in the POP backbone, the exciton formation, charge separation, charge diffusion, etc. are critically explained, highlighting the influence of the dielectric constant and skeletal polarizability of the material. The translation of this fundamental understanding to various reactive oxygen species generation through charge transfer (e.g., O-2(-)) and exciton-exciton annihilation (e.g., O-1(2)) by proximity-induced FRET or Dexter pathways is discussed. The role of the hydrophilic POP skeleton in overall in-water photochemical applications is also discussed. Finally, the gaps in the current state-of-the-art are considered and the future prospects to mitigate these issues are argued.

关键词： ASTM   gasoline   octane number   oxygenates   volatility  

摘要： Addition of oxygenated additives with gasoline is one of the recent methods to enhance the properties of gasoline and further improve performance of the engines. N-Butanol and Di Isopropyl Ether (DIPE) are having favorable fuel properties and these can be blended with gasoline. In this paper the properties oxygen, density, volatility, octane number and calorific value of the blends obtained from experimental study are discussed in detailed. Oxygenates N-Butanol and DIPE are blended with gasoline individually in a ratio of 10, 20 and 30%vol and named as N10, N20, N30, D10, D20 and D30 respectively. The properties of gasoline-oxygenates blends shows, the use of blends will enhance the combustion process in the engine. Compared to N-Butanol blends, DIPE blends produced higher calorific value and octane number. DIPE shows better gasoline blending properties and it may be used as an oxygenate in petroleum refineries.

关键词： Stoichiometry  

摘要： An inclusion system of embedding ferulic acid into beta-cyclodextrin (FACD) with different host-guest stoichiometries was prepared by a co-precipitation method. Then, the physicochemical properties and release kinetics of the FACD were evaluated. The results of thermal analysis, X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy (FTIR) proved the successful embedding of FA into the beta-cyclodextrin matrix. Four mathematical models were applied to adjust the ferulic acid release profile and identify preferential kinetics. The results of physicochemical properties confirmed the successful formation of the complexes. The loading capacity (LC) and encapsulation efficiency (EE) of the inclusion complex (1 : 0.5) were 41.0 +/- 3.28 mg g(-1) and 52.1 +/- 2.31%, respectively, which were significantly higher than other molar ratios. The release behaviour revealed that loaded FA molecules under various host-guest stoichiometries obey different release models. While lower host-guest stoichiometry (1 : 0.5) provided desirable EE, the moderate host-guest stoichiometry (1 : 1) exhibited faster release behaviour. The FACD inclusion complex could be a promising bioactive material for food preservation.

关键词： Caper shoots   Total polyphenols   Antioxidant activity   Chlorophyll   Carotenoids  

摘要： The cultivation of Capparis spinosa is widespread in the Mediterranean basin. The caper is a perennial and deciduous creeping shrub, of which different aerial parts are edible, such as the flower buds, fruit and caper shoots, however the level of consumption of caper shoots is less widespread. The caper shoots are quite typical of the south-eastern part of Spain and their consumption is usually as a side in salads. The present investigation tries to raise awareness of the nutritional value of this aerial part of the caper plant and promote higher levels of consumption of this specific part, by means of the study of different cultivars located in different geographic zones. According to the present investigation, it has been observed that the tender stems have good biochemical characteristics, providing higher nutritional value than the flower buds and caper fruits. The cultivar Modified Letter Turned CommaORI 1' located in Orihuela (Alicante) has presented the best biochemical characteristics, due to its significantly higher values in polyphenols, flavonoids, flavonols and antioxidant activity. Therefore, it would be worthwhile to encourage the consumption of caper shoots, introducing them as one more ingredient in the Mediterranean diet. The caper is a high value crop, due to its ability to adapt to climate change and drought, in addition to the beneficial properties that the different aerial parts contribute to human health.