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关键词： 物理化学   教学方法   实验教学  

摘要： 针对西部地区少数民族学生的实际情况,我校在物理化学实验教学中,为了提高学生实际动手操作技能和创新能力,加强实验预习、强化实验指导、改进了教学方法、教学内容及教学手段改革的基本思路、建立了现代化的新课程体系。实践证明,我校物理化学实验教学水平有了明显的提高的同时提升了少数民族学生的实验技能和创新创业能力,有助于学生的就业。

关键词： Zinc oxide    nanoparticles   Sol-gel   Bistability   Z-scan technique   Reverse saturable absorption   n- and    p-type ZnO  

摘要： In this study, zinc oxide nanoparticles have been synthesized in the presence of alkali hydroxides (NaOH and KOH) using the Sol-Gel method. The XRD, DLS, Z-scan, and UV-Vis spectroscopy were used to investigate nanoparticles' structural and optical properties. XRD diffraction patterns show enhancement in structural constants by adding sodium and especially potassium atoms. Correspondingly, the bandgap energy reduces because of decreasing the lattice energy. Also, the nonlinear absorption coefficient is measured using the z-scan technique, and it is found that reverse saturable absorption (RSA) is the prominent nonlinear optical phenomenon in this samples upon increasing the power of the incident laser beam and the magnitude of nonlinear absorption coefficient enhance by introducing Na and K atoms into the ZnO (named as NZO and KZO, respectively) crystal lattice. In accordance with the enhancement of nonlinear absorption processes, NZO and KZO are bestowed with optical bistability characteristics, which is beneficial for manufacturing optical switchers.

关键词： antioxidant activity   glycaemic response   pasting   phenolic compounds   starch   viscosity  

摘要： Phenolic compounds have been shown to deliver numerous health benefits. Research has also shown that starch and phenolic compounds interact. This study aimed to investigate the effects of blackcurrant and strawberry powder on the physicochemical and in vitro predicted glycaemic response of sweet potato and potato starches. Sweet potato, or potato, starches were mixed with 0%, 5%, 10% and 15% (w/w) of blackcurrant, or strawberry, powder, to form blackcurrant and strawberry-enriched starch pastes. The results showed that enrichment with 5%, 10% and 15% blackcurrant or strawberry powder for sweet potato and potato starch significantly altered the pasting viscosity and colour profiles (P ), increased the phenolic content and antioxidant activities of starch pastes (P ). Blackcurrant or strawberry powders mixed with sweet potato or potato starches reduced amount of reducing sugar released during in vitro digestion. Addition of 15% blackcurrant powder for the starch exerted stronger in vitro antioxidant and hypoglycaemic properties than that of 15% strawberry powder. Collectively, these findings suggested that addition of blackcurrant or strawberry powder into sweet potato and potato starches manipulated the hypoglycaemic property of pastes.

关键词： Lotus seed starch   Starch-phenolics interactions   Microwave irradiation   Physicochemical properties  

摘要： Lotus seed (LS) has a high starch content and possesses many useful functional properties, which are mainly attributed to its phenolic compound content. The objective of this study was to investigate the effect of microwave irradiation (MW) treatment on the structural and physicochemical properties of a lotus seed starch-chlorogenic acid (CA) blend. MW treatment appeared to promote the formation of LS-CA complexes and the modified starch displayed more rougher structures than native starch. The particle size distribution of starch remained approximately constant when the microwave power was 200 W, but increased sharply with further increases in microwave power;a similar trend was observed in the swelling and solubility of starch. XRD and FT-IR spectra show that MW treatment degraded the ordered crystalline structure of starch, facilitating exposure of the starch chains originally buried in the crystalline and amorphous regions within the grains. During this treatment, CA interacted with starch molecules by hydrogen bonding and form a LS-CA complex, which inhibited the self-assembly process of starch chains. These findings demonstrated the potential use of MW treatment in controlling the storage and processing quality of lotus seed, or other starchy foods rich in polyphenols.

关键词： potato starch   growth   structure   physicochemical properties  

摘要： BACKGROUND Growth stage contributes critically to the physicochemical properties of starches, which make achieving desired functional properties by controlling the growth period possible. Thus, this study investigated the changes in multiscale structure and physicochemical properties of potatoes starches harvested at different growth stages. RESULTS The amylose and phosphate content varied over the growth period, with the ranges 2.756-2.998 g kg(-1) and 0.0058-0.0077 g kg(-1), respectively. The starch granules were round or oval, and the size increased with growth. X-Ray diffraction indicated the B-type crystalline structure of samples. Time-dependent changes in crystallinity were observed. The weight-average molecular weight (M-w) showed a tendency to decrease first and then increase, and presented the lowest M-w (1.105 x 10(8) g mol(-1)) at 35 days. A higher proportion of long chains were noted in starch from earlier harvested potatoes than that in later harvested ones. Differential scanning calorimetry revealed that starch gelatinization temperature decreased, and gelatinization enthalpy decreased from 16.39 to 14.89 J g(-1). All samples possessed weak elastic gel-like structure, and starches harvested at early stage possessed highest viscosity and stronger gel behaviour. Resistant starch showed a decreasing trend on the whole, and presented highest value (10.69%) at earliest harvest time. Starch from the potatoes harvested at 35 days after tuberization exhibited excellent light transmittance (up to 62.47%). CONCLUSION Potato starches harvested at different growth period presented extremely different structures and physicochemical properties. The results will provide fundamental data in terms of changes of potato starch during growth which will affect the choice of harvest time. (c) 2021 Society of Chemical Industry.

关键词： Heating   Gluten   Molecular chain   Aggregation   QCM-D adsorption  

摘要： To understand the heat mediated cross-linking mechanism of gluten in the presence of salt and alkali, the effects of heating on the physicochemical and structural changes of gluten protein was comparatively investigated in this study. Our results showed that the G' value of gluten was mediated by heating, while alkali delayed the transition temperature by approximately 20 degrees C. Salt increased the extensibility of gluten. However, alkali improved gluten strength and toughness. Fluorescence spectroscopy, surface hydrophobicity, and AFM images demonstrated that hydrophobic interactions and aggregations of protein molecular chains were enhanced by both salt and alkali, and heating further promoted these interactions. In addition, alkali reduced the aggregation temperature of large glutenin polymers from 95 to 75 degrees C according to SE-HPLC profiles. RP-HPLC patterns confirmed that alpha- and gamma-gliadin subunits were more susceptible to heat and polymerized after heating at 95 degrees C with alkali. QCM-D results showed that alkali promoted protein-protein interactions in gluten, which was positively correlated with temperature. This study consummates the understanding of heating mediated crosslinking mechanisms of gluten with salt and alkali and provides a more comprehensive theoretical basis for the control of gluten properties and quality of wheat products.

关键词： Fusarium   Pathogenicity   Lesion diameter   Starch   Post-harvest storage  

摘要： Fusarium is a major spoilage fungus of potato tubers during post-harvest storage. The dry rot disease caused by Fusarium species severely affects the harvested potatoes and impose a critical loss to processing industries and consumers. In our experiment, we investigated the occurrence of Fusarium sambucinum (FS) and Fusarium oxysporum (FO) as major storage fungus causing Fusarium dry rot in potato tubers. Further, we performed morphomolecular identification of both the fungi and confirmed their pathogenicity on potato tuber during storage. We evaluated the susceptibility parameters and quality attributes during infection in two popular cultivars namely 'Kufri Pukhraj' (table purpose) and 'Kufri Chipsona 3' (processing purpose). Out of two cultivars, 'Kufri Pukhraj' was shown to have greater susceptibility as compared to 'Kufri Chipsona 3' in terms of lesion diameter, fungus penetration and rot volume during periodic observation of 20, 40 and 60 d of storage. FS was highly aggressive as compared to FO. However, a mixed inoculum of Fusarium species caused higher damage irrespective of cultivars. The physicochemical analysis revealed that fungus infection (individual or mixed inoculum) leads to a reduction in starch and amylose content in both the cultivars after 60 d of storage. Moreover, amylopectin, reducing sugars, sucrose and total soluble sugar content were increased in response to fungal infection in both cultivars. Pearson correlation analysis indicated that lesion diameter and rot volume was negatively correlated (R < -0.80) with starch and amylose content. However, amylopectin, reducing sugar, sucrose and total soluble sugar was positively correlated with susceptibility parameters. This study highlights the impact of storage fungus infection on the nutritional quality parameters of potato tubers which is a critical concern for consumers and processing industries.

关键词： Basalt fiber   acid and alkali corrosion resistance   thermal conductivity   mechanical properties   friction coefficient  

摘要： This paper reviewed the research progress in China on the durability, acid and alkali corrosion resistances, thermal insulation, sound insulation, and hygroscopic properties of basalt fibers (BFs) as well as the physicochemical and mechanical properties of BF-reinforced resin composites. The acidity coefficient and pH value of BFs and glass fibers (GFs) were tested, which showed that BFs had better chemical stability. Scanning electron microscopy observations showed that the acid corrosion of BFs gradually occurred from the outside to the inside, whereas the alkali corrosion of BFs occurred nearly simultaneously both inside and outside. Moreover, the reasons for these results were analyzed from a chemical reaction perspective. BFs met the thermal conductivity and sound absorption coefficient requirements of building thermal insulation and sound absorption materials. The hygroscopicity of BFs was 1/8-1/6 that of GFs, and BFs also had a smaller dielectric loss angle. Tests confirmed that BFRC exhibited great high-temperature resistance. As the short BF content increased, the flexural strength, splitting tensile strength and impermeability of BFRC significantly improved, and an optimal fiber length and content were proposed. A comparison showed that the mechanical properties of BF-reinforced resin were generally better than those of GF-reinforced resin. Finally, this review identified some concepts to be studied in this field and prospects for possible future research directions.

关键词： Thexyldimethyl chlorosilane   Protective effect   Directional modification   Octenyl succinic anhydride   C-3-OS starch  

摘要： A new method of synthesis of C-3 octenyl succinic anhydride-modified corn starch (C-3-OS starch) assisted by thexyldimethyl chlorosilane (TDMS-Cl) was developed for directional modification of starches. The protective effect of TDMS-Cl on carbon 2,6 hydroxyl groups was confirmed by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analysis. The FTIR and H-1 NMR results demonstrated the successful introduction of OSA into starch molecules. Compared with OSA modified starch (OSCS), C-3-OS starch showed higher gelatinization temperatures with a rough surface, irregular shapes, and different size. Moreover, the volume average particle diameters and negative zeta potential of emulsions prepared with C-3-OS-starch were 371.17 nm and -18.7 mV, respectively, which were lower than those of OSCS stabilized emulsion. It has therefore been shown that C-3-OS-starch is more suitable for stabilization of emulsions.

关键词： Edible film   Whey protein isolate   Soy protein isolate   Carboxymethyl cellulose   Film properties  

摘要： The main aim was to discuss the relation between water vapor transmission rate (WVTR) and moisture sorption isotherms (MSIs) of whey protein (WPI), soy protein isolate (SPI), and carboxymethyl cellulose (CMC) films. MSIs obtained using dynamic vapor sorption (DVS) instrument were fitted to GAB, BET, Oswin, Halsey, and Harkins-Jura models, and examined in detail with Peleg approach. BET and Oswin models had the highest R-2 values (0.999). The MSI's data were used to assess water vapor barrier interactions between permeability (P-calculated using WVTR), diffusivity (D), and solubility (S) properties and to compare their feasibility in P = DS simple equation. D and S were calculated using different approaches of Fick's second law and Henry's law. Calculated, measured, and predicted all different P, D, and S presented good operational interchangeability (r = 0.84-0.95). CMC films had the highest WVTR at 1008.06 g/m(2) day;those of WPI and SPI films were 865.79 and 595.71 g/m(2) day at studied condition. The hydrophilicity of CMC films deduced from its high water vapor adsorption capacity might lead to the lowest D among the studied films. This might result in swelling of film matrix and reduction of film porosity. It was interesting to note that films having the highest S-o (128.8 cm(3)/cm(3) cmHg) presented the lowest diffusivity (2.51 x 10(-11) cm(2)/s) with a highest WVTR. Oxygen barrier, mechanical, thermal, and structural measurements were also applied to characterize the films. SPI film was the finest film in terms of its barrier film properties and good film-forming ability.