甘薯淀粉糖苷表面活性剂的合成及性能研究

以甘薯淀粉、乙二醇、长链醇(C8~10醇、C12醇、C12~14醇)为原料,在2 000 L反应釜中采用转糖苷法合成了系列淀粉糖苷类表面活性剂。该产品25℃时表面张力为32 mN/m左右,并且具有两个cmc值点,第一个cmc值点表面张力约为35 mN/m,第二个cmc值点表面张力为24~28 mN/m。保湿性优于丙三醇及其它市售保湿产品,12 h后失水率低于30%,24 h后失水率为33.35%。具有较好的稳泡性,一定的乳化性。红外、气相色谱表征,该系列产品为淀粉糖苷类表面活性剂。     

Influence of physicochemical and structural characteristics of chitosan flakes on molybdate sorption

This study investigates the effect of deacetylation degree and molecular weight of chitosan on molybdate sorption on both raw and glutaraldehyde crosslinked samples. It appears that the physicochemical parameters affect the crystallinity of the samples: a high crystallinity reduces the accessibility of both water and metal ions to the amine binding sites. Both equilibrium and kinetic performances are thus influenced. The crosslinking by glutaraldehyde decreases sorption performances for large size particles while it does not influence sorption for the smallest. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 571–580, 1998     

Effects of pretreatments on properties of microwave-vacuum drying of sweet potato slices

Abstract

Pretreatments of blanching (BL); osmotic dehydration at 35°Brix of sucrose (OD); ultrasound in distilled water (UD), and ultrasound-assisted osmotic dehydration (UO) were carried out for microwave-vacuum drying (MVD) orange- and purple-flesh sweet potato slices, and effects on their properties were investigated in this study. UO had improvements effects on water loss, solid gain, and relaxation time of the samples compared to other pretreatments. Low-field nuclear magnetic resonance results offered a view of water state concerning the effects of different pretreatments on sweet potato. UD treatment following by BL showed a long relaxation time corresponding to the weaker degree of bound hydrogen proton or the greater freedom degree of hydrogen comparing to other pretreated samples. Differential scanning calorimetry parameters appeared to be sensitive to pretreatments by increased Tg value compared to blanched sample. The value of Tg shows that it does not depend only of the water content but also on the experimental conditions (pretreatments). The dried sweet potato exhibited amorphous structures as evidenced by the X-ray diffractograms due to the BL treatment and MVD. Concentration of total phenolics and anthocyanins were high in purple sweet potatoes, whereas content of vitamin C and total carotenoid were high in orange ones. Application of UO is suitable for retention of bioactive compound and stability of MVD sweet potato slices.     

食品胶对甘薯淀粉糊黏度性质的影响

研究了在淀粉乳浓度6%(质量分数)条件下,分别添加相当于淀粉干基质量分数1%、2.5%、5%的瓜尔胶、纯化魔芋微粉、卡拉胶、羧甲基纤维素(CMC)、黄原胶5种食品胶对甘薯淀粉糊黏度性质的影响.结果表明,不同浓度的胶体对淀粉糊黏度性质的影响程度不同,瓜尔胶和魔芋微粉对淀粉的协同作用特别强;卡拉胶和CMC在低浓度时对淀粉糊性质影响不明显,高浓度较明显.不同添加量的食品胶都降低甘薯淀粉的起糊温度和回生值,而且黄原胶对甘薯淀粉起糊温度降低程度最大.     

红薯中硒含量的测定

以超声波辅助红薯的消解过程以及硒与邻苯二胺的络合、萃取过程,利用紫外光谱法测定硒的含量。结果表明,硒在0～1.60μg/mL含量范围内具有良好的线性关系,相关系数为0.999 9。回收率达96.0%～100.7%。该方法使样品的消解时间大为缩短,并加快了硒的络合萃取过程。     

红薯淀粉浆在水解过程中的黏度

淀粉是由直链结构与支链结构构成结晶与非结晶的颗粒结构.在淀粉水解过程中的水链与链链的能量结构具有一定的变化规律.本文对红薯淀粉浆水解过程中的黏度进行了研究,找到了黏度与直链、支链淀粉的关系,发现了糊化过程的黏度急剧增加,并用特定的复合水解酶实现了常温水解的低黏度过程.     

Mechanical properties of graphite flakes and spherulites measured by nanoindentation

The mechanical properties of graphite flakes and spherulites in cast iron were measured by nanoindentation. The spherulites had a significantly lower Young’s modulus and hardness than the graphite flakes. This was attributed to the faulty growth morphology and the presence of foreign particles (impurities) in the spherulites as detected in the micro Raman spectroscopy and confirmed by the different deformation behaviours of the flakes and spherulites.     

微波辅助提取甘薯叶中黄酮类化合物的工艺研究

甘薯叶中黄酮类化合物具有抗癌、降血压、降血脂、清除自由基等作用,可用于医学上的癌症、冠心病、脑血栓的防治及食品工业中的抗氧化剂等。采用微波协助浸提法提取甘薯叶中的黄酮类化合物,以甘薯叶中总黄酮含量为指标,考察乙醇浓度、料液比、微波萃取时间、微波输出功率等单因素的影响,并结合正交实验设计对提取工艺条件加以优化与改进。所得最佳提取工艺条件为:乙醇体积分数为60%、料液质量比为1∶25、微波输出功率为400W、萃取时间为6min,总黄酮质量分数达到83.68mg/g。与传统的溶剂加热回流法和超声波辅助提取甘薯叶中的总黄酮相比,微波协助浸提法大大缩短了提取时间,提取效率较高,所用有机溶剂量少,极大地降低了提取成本。     

Tribological properties of polymer composites with diamond-like carbon flakes

Composites of epoxy resin with diamond-like carbon (DLC) flakes were fabricated. The DLC flakes were prepared from a DLC film deposited by chemical vapor deposition on an aluminum substrate. The tribological properties of composites were evaluated in air and water environments using a reciprocating friction tester and an AISI 440C mating ball. The friction coefficient of the epoxy composite decreased from 0.90 to 0.69 in air and from 0.71 to 0.29 in water with the addition of DLC flakes. The specific wear rate of the composite also decreased from 5 × 10^? 5 to 7 × 10^? 6 mm³/N m in air and from 4 × 10^? 5 to 4 × 10^? 6 mm³/N m in water. In contrast, the wear of the mating ball increased. Furthermore, the tribological properties of DLC flakes as an additive in water were evaluated. The suspension of powdered DLC in water reduced the friction coefficient of epoxy resin against the AISI 440C mating ball. Furthermore, the wear of the resin was negligibly small, although severe abrasive wear on the mating ball was observed.     

Physical characteristics of sweet potato pulp/polycaprolactone blends

Sweet potato pulp (SSP) obtained as a by‐product from starch extraction was blended with polycaprolactone (PCL) to prepare a biodegradable plastic material. In the blends, PCL was used as a reinforcing agent. The SPP/PCL blends were prepared by compression‐molding under high temperature and pressure, at different SPP/PCL ratios, and the mechanical properties of the molded specimens were tested. Matrix structure and thermal properties were measured by using a Fourier transform infrared (FTIR) spectrophotometer, scanning electron microscope (SEM), differential scanning calorimetry (DSC), and thermogravimetric analyzer (TGA). Mechanical properties (tensile and flexural properties) were also measured to find the most suitable ratio in a SSP/PCL blend. During compression molding of the SPP/PCL blends under high pressure and temperature, chemical reaction occurred between SPP and PCL, and thus, thermal stability and mechanical strength of the blends increased and water uptake decreased. Also, by increasing the PCL content in the blend, the matrix in the blend became more homogeneous, and consequently, mechanical strength of the molded specimen increased. At 7/3 or 6/4 weight ratio of SSP/PCL, water uptake of the molded specimen became substantially less than that at 8/2. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 861–866, 2004     

Thermodynamic modeling of the sorption of organic chemicals in thermoplastics and elastomers

The amount of solute sorbed per unit weight of sorbent, q_e, and the equilibrium solubility (partition) coefficient were measured using a gravimetric method for various types of organic chemicals in thermoplastics and elastomers. A thermodynamic model was derived to predict the activity-dependent partition coefficient and q_e for a wide range of organic chemicals. The thermodynamic model produced a better fit to the measured q_e values than did the Flory–Huggins equation. Partition coefficients and q_e increased with increase in activity. For nonpolar compounds, q_e increased logarithmically but decreased for polar compounds with an increase in the saturation organic chemical vapor concentration. Elastomers had 14–28 times greater q_e values than did thermoplastics. A structure–activity relationship was found to accurately predict the partition coefficient for liphophilic organic chemicals at a specific activity. © 1993 John Wiley & Sons, Inc.     

Attraction of adult sweet potato weevils,Cylas formicarius elegantulus (Summers), (Coleoptera: Curculionidae), to sweet potato leaf and root volatiles

A dual-choice olfactometer was developed to study the responses of sweet potato weevils,Cylas formicarius elegantulus (Summers), to volatiles from the sweet potato,Ipomoea batatas (L.) Lam. Both males and females were attracted by volatiles from sweet potato leaves and a methylene chloride leaf extract. Females, but not males, responded to volatiles from storage roots and a methylene chloride root extract. Leaves and storage roots from four sweet potato cultivars (Centennial, Jewel, Resisto, and Regal) were attractive to female weevils; however, the attractant response varied with cultivar. GC profiles from leaf and root extracts, and GC-MS analysis of leaf extract, for Jewel cultivar enabled the volatile peaks to be identified as sesquiterpenes.     

Feeding and oviposition preferences of sweet potato weevil,Cylas formicarius elegantulus (Summers), on storage roots of sweet potato cultivars with differing surface chemistries

Cores from sweet potato [Ipomoea batatas (L.) Lam.] storage roots (Centennial, Jewel, Resisto, and Regal cultivars) were presented to sweet potato weevils [Cylas formicarius elegantulus (Summers) (Coleoptera; Curculionidae)] in multiple-choice, limited-choice, and no-choice bioassays. Centennial, a susceptible cultivar in field-plot experiments, was preferred for feeding and oviposition by female weevils in choice bioassays, and for ovi-position in no-choice bioassays, compared to three other cultivars. Analysis of root surface chemistry showed a tentatively identified triterpenol acetate in Centennial, which was not found in the more resistant cultivars; another root surface component was found in higher concentrations in the more resistant cultivars.     

施肥对甘薯生长发育及产量效益的影响

在豫东潮土研究施肥对甘薯产量、生产情况的影响,分析不同施肥处理的产量及经济效益。结果表明,甘薯应不施或少施N肥,补施P、K肥;单施P、K肥分别比对照增产2.23%和1.16%,单施N肥比对照减产0.02%;N、P、K配合施用最佳配方是N_5P_9K_(10),其效益最高,为44 251.0元/hm~2,比对照增收355.3元/hm~2,鲜产量为30 713.9 kg/hm~2,比对照增产4.96%,分别比单施N、P、K增产4.98%、2.67%和3.75%。     

鲜食甘薯最佳施肥量的田间试验

为改善甘薯品质、提高产量和增加无公害甘薯的上市率,通过肥料的"3414"田间肥效试验来确定鲜食甘薯的最佳施肥量和配比。试验结果:中产地667 m2N、P2O5、K2O最佳施肥量分别为10、7、13.5 kg,低产地为6.5、13.62、12.62 kg。     

回收PET瓶片/接枝PE反应共混物的形态及性能

利用有反应活性的各种接枝聚乙烯(PE)作为回收聚对苯二甲酸乙二酯(PET)瓶片的改性剂,使接枝PE上的活性酐基与PET的端羟基在不同的挤出设备中熔融反应,制备相分散均匀、力学性能较好的PET基工程塑料.结果表明,挤出设备的选择对混合效果影响较大,缩聚型反应挤出机和双螺杆挤出机比普通单螺杆挤出机具有更优良的混合效果;各种接枝PE的改性效果优劣次序是:马来酸酐接枝线型低密度聚乙烯,马来酸酐接枝低密度聚乙烯,马来酸酐接枝高密度聚乙烯;接枝PE添加质量分数为20%时,可大幅度提高反应共混物的冲击性能.     

Thermodynamic and mechanistic characterization of water sorption in homogeneous and asymmetric cellulose acetate membranes

The water sorption isotherms for homogeneous and asymmetric cellulose acetate membranes have been measured at different temperatures. Subtle differences between the water sorption isotherms for asymmetric and homogeneous membranes have been interpreted by suggesting that capillary condensation contributes significantly to sorption in asymmetric membranes at high activities and also to an intriguing excess sorption observed in homogeneous membranes at intermediate activities. This model has been supported by the experimentally determined values of the enthalpy and entropy changes associated with sorption.     

Processing and mechanical properties of new hierarchical metal-graphene flakes reinforced ceramic matrix composites

Hierarchical tantalum-graphene flakes reinforced zirconia (3Y-TZP) ceramic matrix composites were fabricated by wet processing route and freeze drying followed by spark plasma sintering (SPS). The microstructures and mechanical properties were investigated. The results show that graphene and Ta particles are homogeneously dispersed in the ceramic matrix and the optimum sintering temperature for complete densification of composites and thermal reduction of the graphene oxide is 1500 °C. The addition of dual reinforcements of tantalum microflakes and graphene nanoflakes results in significant improvement in the mechanical properties of the ZrO₂ matrix. Approximately a 30% increase in flexural strength vs the zirconia-Ta composite and a 175% increase in fracture toughness vs the monolithic zirconia have been achieved by introducing 0.5 vol% GO and 20 vol% Ta particles.     

Hot air drying of purple-fleshed sweet potato with contact ultrasound assistance

A drying technique using a combination of a contact ultrasound apparatus and a hot air dryer is developed to investigate the strengthening effect of contact ultrasound on hot air drying. The effects of drying parameters such as ultrasound power and drying temperature on drying characteristics, effective moisture diffusivity (D_eff), microstructure, glass transition temperature (T_g), rehydration ratio, and color difference are discussed. The results show that the application of contact ultrasound causes a significant acceleration of internal mass transfer, and higher ultrasound power applied leads to faster drying rate. The effect of ultrasound power on drying rate decreases along with the reduction of moisture content during drying process. The increase in drying temperature significantly reduces drying time but has a little negative influence on the strengthening effect of ultrasound. D_eff values range from 1.0578?×?10^?10 to 5.4713?×?10^?10?m²/s in contact ultrasound-assisted hot air drying of purple-fleshed sweet potato and increase significantly with an increase in drying temperature as well as ultrasound power. The microstructure of purple-fleshed sweet potato is greatly different at different ultrasound powers during contact ultrasound-assisted hot air drying and shows more microchannels and dilated intercellular spaces in the cross-section of purple-fleshed sweet potato micrographs at higher ultrasound power. Contact ultrasound application during hot air drying could improve the mobility of water and consequently reduce glass transition temperature. Lower color difference and higher rehydration ratio could be achieved as drying temperature decreases and ultrasound power increases. The increase in contact ultrasound power could reduce energy consumption of drying process up to 34.60%. Therefore, contact ultrasound assistance is a promising method to enhance hot air drying process.     

二氯磷酸苯酯的热力学性质

应用比重瓶法、乌氏黏度计法和静态法分别测定了二氯磷酸苯酯(PDCP)的密度、黏度和饱和蒸汽压,通过对实验数据的关联,发现密度随温度的变化适合于二次多项式,黏度随温度的变化适合于Andrade方程,饱和蒸汽压随温度的变化适合于Antoine方程,为工业化生产提供基础性数据。