冷藏过程中调味料对海鲈鱼片品质的影响

目的 研究复合调味料对海鲈鱼片贮藏品质的影响,以期为海鲈鱼的保鲜提供理论指导和技术支持.方法 以海鲈鱼片为研究对象,采用花椒、桂皮、八角、白酒、生姜、食盐等6种调味料及其复合物的溶液浸渍海鲈鱼片,测定4℃贮藏条件下海鲈鱼片的鲜度和质构指标的变化.结果 单一调味料液处理可使鱼片的鲜度和质构指标变化减缓,其中桂皮调味料液处理有效延缓了鱼片的菌落总数、pH值、硫代巴比妥酸(TBA)值、挥发性盐基氮(TVB-N)值和K值的上升.经复合调味料液处理后,鱼片的各项鲜度指标均有所改善,且自由水的含量显著降低,持水力比未处理鱼片高出8％,改善了鱼肉的持水性.结论 6种调味料复合后具有协同抗菌性能,保鲜性能较好,可有效延缓海鲈鱼的蛋白质分解和脂肪氧化,延长货架期至12 d.     

SrTiO3复合氧化膜对铝阳极箔比容的影响

用柠檬酸盐溶液浸渍沉积法在腐蚀铝箔上制备出SrTiO3-Al2O3复合氧化膜,研究了处理液中Ti和Sr离子浓度与柠檬酸含量、浸渍处理时间、退火温度以及退火时间对铝箔比容的影响.实验结果表明最佳工艺参数为:处理液中Ti和Sr离子浓度分别为3×10-3mol/L,浸渍时间为10分钟,退火温度在550℃、退火时间为1小时.另外,实验结果也表明,处理液中柠檬酸含量对比容的影响不大.使用该工艺,可使腐蚀铝箔的比容提高15%.该复合膜有希望用作电解电容器的电介质.     

纳米银抗菌包装对虾仁冷藏过程中品质的影响

目的制备一种可用于水产品冷藏保鲜包装的纳米银抗菌薄膜,并测定其保鲜性能。方法将纳米银母粒与低密度聚乙烯颗粒混合,并通过吹膜机生产纳米银质量分数为1%,2%的抗菌活性薄膜,通过测定pH值、TBARS值、TVB-N值、菌落总数等指标来分析纳米银抗菌活性薄膜对虾仁贮藏的效果。结果随着薄膜中纳米银含量的提高,抗氧化能力和抑菌能力也相应提高。与低密度聚乙烯薄膜相比,该薄膜的抑菌能力和抗脂质氧化能力可提高50%左右,冷藏虾仁的货架期可延长2 d。结论纳米银抗菌薄膜具有抗菌和抗氧化的作用,并可延长虾仁在冷藏过程中的保质期,有望成为一种新型的虾仁包装材料。     

FG/CS逐层复合保鲜涂膜对三文鱼鱼片品质的影响

目的为了提高复合涂膜对三文鱼鱼片的保鲜性能,获得具有高效长效缓释性能的生物保鲜材料。方法以亚麻籽胶(FG)和壳聚糖(CS)为成膜材料,丁香酚(EG)和月桂精油(LEO)为保鲜剂,采用流延法制备逐层FG/CS+EG/FG+LEO复合涂膜。以三文鱼鱼片为研究对象,评估复合涂膜的保鲜性能。结果 FG/CS+EG/FG+LEO复合涂膜能够显著抑制三文鱼鱼肉中微生物的生长,提高鱼肉持水力,延缓脂肪氧化、蛋白质分解和色差值的变化进程。结论 EG和LEO复配使用具有一定的协同增效作用,同时,多层涂膜组成的缓释体系有效地延长了生物保鲜剂的作用时间,使EG和LEO对鱼片的保鲜效果更好,其中FG/CS+EG/FG+LEO复合涂膜的保鲜效果最优,可使生鲜三文鱼鱼片的货架期从7 d延长至13 d。     

堇青石载镍催化剂对燃烧合成碳纳米管的影响

借助于硝酸镍溶液, 利用浸渍法在堇青石表面均匀负载镍催化剂颗粒, 在甲烷扩散火焰中活化并催化生成碳纳米 管. 实验结果表明, 生成的多壁碳纳米管直径为30～50nm, 长度约为十几微米, 空腔比较小, 管壁石墨结晶结构良好.提高浸渍液浓度, 催化剂颗粒尺寸明显变大, 但对碳纳米管的形态影响比较小. 延长浸渍时间, 可使催化剂颗粒密度提高, 碳纳米管出现成束生长现象. 结合碳管成核生长过程和火焰燃烧的特点, 探讨了催化剂对于碳纳米管生长的影响机制.     

蓄水渗膜导水纤维的研制

选取植物纤维、动物纤维和化学纤维分别与环境友好性高分子复合成膜进行包装水渗水试验,初步选取了植物纤维作为蓄水渗膜导水纤维材料.为了提高植物纤维的导水性能,制膜前对其进行预处理,在常温、50、100℃温度下分别用不同浓度的自制预处理剂浸泡处理后,观察纤维的微观形貌和测量纤维的拉伸性能,发现在常温下预处理剂的浓度为14%时纤维的亲水性及拉伸性提高,微观形貌好,常温下使用14%的预处理剂浸渍30min后制备的纤维可作为蓄水渗膜的导水纤维.     

原料浸渍工艺对十二醇/木塑复合相变材料影响的研究

以十二醇为相变基元,通过真空浸渍、常压浸渍和超声浸渍等3种工艺使木粉的多孔腔体吸附十二醇,再与聚丙烯共混,制备出十二醇/木塑复合相变材料。通过力学性能测试、差示扫描量热和循环性能分析,研究了不同浸渍工艺对木粉吸附相变剂及复合相变材料综合性能的影响。结果表明:超声浸渍工艺负载十二醇的含量比常压的提高了9.6%,比真空的提高了2.2%。超声处理木粉有利于提高木塑复合相变材料的力学性能,超声浸渍处理后制备的材料相变焓比常压浸渍的提高了6.21J/g。循环测试结果表明,常压浸渍的材料相变焓损失率达到69.17%,而超声浸渍和真空浸渍分别为11.93%和14.97%。     

超疏水铜网的制备及其在油水分离中的应用

将铜网浸渍于一定浓度的氯化铜和硫代硫酸钠的混合液中反应一定时间,从而在铜网表面构筑了微米级颗粒粗糙表面,并用一定浓度的正十二硫醇对其进行疏水修饰,制备出了具有超疏水特性的铜网。并探讨了浸渍温度、浸渍时间、浸渍液配比、修饰浓度、修饰时间对铜网疏水性的影响。在浸渍温度50℃,浸渍时间4h,浸渍液配比1∶1,修饰浓度10mmol/L,修饰时间10min的条件下得到了疏水性最好的铜网。用扫描电子显微镜、X射线粉末衍射仪、接触角测量仪对所制备的铜网表面形貌、化学组成、疏水性能进行了表征,并用4种油水混合物探究了所制备铜网的分离效果。结果表明,所制备的铜网具有超疏水性,接触角可达154°,并且成功应用于不同油水混合物的分离,分离效率均在96%以上。     

基于煤沥青质族组分的陶瓷-炭复合膜制备

以煤全组分族分离所得的沥青质族组分为新型前躯体材料,采用浸渍法在陶瓷支撑体上涂膜,再经干燥和炭化制备出陶瓷-炭复合膜,并主要考察了成膜条件对其性能的影响.结果表明:随着沥青质溶胶浓度、涂膜次数和浸渍时间的增加,复合膜孔隙率和水渗透率降低,对Fe(OH)3胶体截留效果增强；适当提高涂膜液温度和干燥温度,也能使复合膜更致密均匀,改善其孔结构和分离性能；根据对Fe(OH)3的截留结果,得到的最佳制备条件为:沥青质溶胶浓度为336.7g/L,浸渍涂膜2次,浸渍时间为35min,涂膜温度为55℃,干燥温度为80℃.     

ZrO_2-AC电极材料制备工艺的确定及性能表征

采用浸渍-焙烧法对活性炭(AC)进行载锆改性,选取浸渍浓度、浸渍时间和焙烧温度为影响因子,以比电容为评价指标,通过单因素和正交试验确定ZrO_2-AC电极材料的最佳制备工艺,利用BET、SEM、EDS及FT-IR对载锆前后活性炭材料进行性能表征。结果表明:ZrO_2改性活性炭的最佳工艺参数为浸渍浓度1.5mol/L,浸渍时间16h,焙烧温度500℃;活性炭负载ZrO_2后比电容增加了72.6%,比表面积降低了12.75%;ZrO_2-AC电极材料的表面及孔道出现絮状和颗粒状的ZrO_2,Zr元素的质量分数为16.8%,表面形成Zr—O键的含氧官能团。活性炭负载ZrO_2后加速了电极双电层的形成,提高了电极材料的电化学性能,可作为电吸附除盐的电极材料。     

Packaging for freshness and the prevention of discoloration of fish fillets

Fillets of various kinds of fish are currently packed in thin films (e.g. polyvinyl chloride) for sale at supermarkets; however, these fillets are not necessarily fresh or of good quality. Packed fillets must be certified for safety, freshness and quality, because sensory judgement is difficult. In order to understand how the freshness and colour of red fish meat can be retained, the methods of packaging were examined. It was known that for freshness the packed fillets must be kept at a low temperature, but discoloration of red meat could not be prevented by this alone. However, discoloration of red-meat fish, such as yellowtail and oceanic bonito, can be prevented by packing with nitrogen gas (N₂).     

Effect of pre-treatment with carbon monoxide and film properties on the quality of vacuum packaging of beef chops

Beef chops (longissimus dorsi) were pre-treated with 5% carbon monoxide (CO) − 95% N₂ for 24 h, vacuum packed in thermo-contractile bags and stored at 0 ± 2°C. Shelf life, as determined by the viable aerobic bacterial load, was 11 weeks. Vacuum-packed chops with heat-contractile film produced a smaller drip loss, had a more intense red colour and higher colour stability under storage than chops with non-heat-contractile film. Chops pre-treated with CO were redder during all the storage period than controls without CO. The pre-treatment did not affect pH, water-holding capacity, drip loss or rancidity of the meat stored in vacuum. Copyright © 2008 John Wiley & Sons, Ltd.     

Preservation of freshness of yellowtail fillet packaged using carbon dioxide-nitrogen gas mixture

Gas-exchange packaging was studied as a method of maintaining the freshness of fish-farm-cultured yellowtail, and its effectiveness was examined. The fish-farm-cultured yellowtail was processed into three layers (two fillets plus bones). Half of these fillets were wrapped using co-extruded ethylene vinyl acetate/polyvinylidene chloride/polyolefin film. The gas used, which was sealed into the packaging, was a mixture of nitrogen and carbon dioxide (N₂/CO₂:60/40). Packages were kept at 5°C. The other half of the fillets were packaged in stretch-wrap made of PVC, for comparison. The effectiveness of both types of packaging on maintaining freshness was examined. Results show that stretch-wrap-packaged yellowtail suffered discoloration of the dark meat sections and a degeneration of quality during the first day of preservation. Discoloration was extremely marked by the 3rd day and the fish was completely valueless as merchandise. In contrast, gas packaging of yellowtail prevented rapid discoloration, maintained taste and texture, and suppressed the growth of bacteria, to give a 3-4-day shelf-life for the fish which was to be used subsequently as sashimi.     

Singular intensity factors at bimaterial anisotropic interfaces

The singular intensity factors at bimaterial anisotropic interfaces in bonded joints with composite adherends are found by using a hybrid method based on numerical and elasticity solutions. The method is applicable to the solution of problems having complex geometry, loading and boundary conditions, which is the case in typical composite structures. Results are given in terms of the singular intensity factor, which is a generalization of the stress intensity factor commonly used with cracks. Both closed and open wedges, which are found, respectively, in bonded joints with or without adhesive fillets, are considered. Equivalent singular intensity factors in modes I, II and III are defined, and the results indicate that the mode III factor, which arises due to out-of-plane coupling, is negligible in all cases studied. Moreover, use of the Erdogan–Sih failure criterion indicates that the direction of crack propagation in lap joints with fillets remains constant beyond a very small region near the point of singularity, while for joints without fillets crack initiation always occurs in a direction parallel to the adhesive–adherend interface.     

Effect of chitosan‐propolis edible coatings on stability of refrigerated cachama (Piaractus brachypomus) vacuum‐packed fish fillets

The effect of chitosan‐based coatings containing ethanolic extracts of propolis (EEPs) on the quality of chill‐stored, vacuum‐packed fillets of cachama, an emerging aquaculture species of fish native to the Amazon basins, was evaluated. Coatings were prepared by adding propolis to chitosan following two different strategies: (1) incorporation of microencapsulated EEP and (2) direct incorporation of EEP. Fillets were dip‐coated, vacuum‐packed in medium‐oxygen barrier bags, stored at 4°C, and their quality was evaluated during 20 days, by monitoring lipid oxidation indexes, physicochemical parameters, microbiological quality indicators, texture profile, and sensory acceptance. Chitosan‐EEP coatings significantly increased the time stability of physicochemical, microbiological, and sensory quality indicators of the fish meat compared with control treatments (uncoated vacuum‐packed fillets). In particular, the secondary lipid oxidation of the coated muscles was 12% to 15% lower compared with uncoated samples after 12 days; pH and total volatile base nitrogen (TVB‐N) presented a slower increase in the coated samples; and a greater inhibition of coliforms was observed between days 8 and 16. The chitosan‐EEP coatings had a positive effect in both texture stability and sensory acceptance of the products during storage. Moreover, chitosan coatings with encapsulated EEP had better impact on the evaluated sensory quality parameters. The results indicate that the combination of the barrier properties of chitosan with the bioactive properties of propolis compounds against oxidative free radicals and microbiological deterioration allowed for the edible coatings to extend the shelf life of this aquaculture product with respect to conventionally vacuum‐packed fillets.     

CNTs添加对MmMn0.4Co0.7Al0.3Ni3.4贮氢合金负极性能的影响

对商用MmMn_0.4Co_0.7Al_0.3Ni_3.4贮氢合金中添加多壁碳纳米管(CNTs)、Ni的电化学性能进行了研究.结果表明,CNTs的加入可以提高电极的放电容量和初始活化性能,合金中添加CNTs、CNTs+Ni的电极完全活化只需11个循环,其最大放电容量分别为255、271mAh/g.而添加Ni的电极则需24个循环才达到最大容量(245mAh/g);合金中添加CNTs、CNTs+Ni的电极具有更高的放电平台和更好的高倍率放电性能(HRD),在1000mAh/g放电电流下,添加CNTs、CNTs+Ni、Ni以及未添加电极的HRD值依次为80.5%、83.9%、66.9%和62.4%,线性极化和电化学阻抗测试表明,CNTs的加入可有效减少欧姆电阻、提高电极表面的电荷迁移速率,更有利于在大电流下进行放电.     

细菌纤维素及其复合材料在环境领域应用的研究进展

细菌纤维素(Bacterial cellulose, BC)是一种由微生物发酵产生的细胞外多糖,作为一种新型的环境友好生物材料,细菌纤维素具有高纯度、高吸水性,优异的机械强度及生物相容性高等优点,在生物医学、化工及食品等诸多领域展现出广阔的应用前景。本文系统性地介绍了BC的结构和特性,对BC的制备工艺和影响因素进行了总结,并分析了化学改性、原位改性和纳米材料复合改性等改性方法对BC的结构与特性的影响,对BC在环境处理技术(吸附、过滤、光催化)中的应用进展进行了概述,最后对BC的研究进展及其发展方向进行了总结和展望。      

Analysis of singular regions in bonded joints

Singular regions in bonded joints with geometric and material stress singularities are studied by expressing the displacement and stress fields in the neighborhood of the singularity by means of eigenfunction expansions which are in terms of unknown coefficients. These coefficients are found by matching displacements with those from a finite element analysis at points remote from the singularity. Expressions for the eigenfunction expansions are given explicitly for bonded joints with and without fillets (closed and open wedges). The results are not limited to stress intensity factors at the point of singularity, but can include stress values at any point near the singularity. It was found that two singular terms exist in all cases, and that, for joints with adhesive fillets and E ₁/E ₂>7, failure is governed by the term associated with the second lowest eigenvalue, while the lowest eigenvalue controls the failure of joints without fillets. It was also found that the calculation of stresses using only the singular terms provided a good approximation to the actual stresses over a distance of about one-fifth the adhesive thickness. The method was also used in conjunction with the Erdogan–Sih maximum stress failure criterion to determine the initial angle of crack propagation for bonded joints with and without fillets. This revealed that the direction of the maximum principal stress in the adhesive, which is also the direction of crack propagation, for joints with fillets remains essentially constant beyond a very small region near the point of singularity, while for joints without fillets crack propagation always occurs in a direction parallel to the adhesive/adherend interface.