Acidified sodium chlorite as an alternative to chlorine to control microbial growth on shredded carrots while maintaining quality

Shredded carrots are particularly susceptible to microbial growth and quality deterioration as a result of a large cut surface area to mass ratio. Acidified sodium chlorite (ASC) in the concentration range 500–1200 µL L^?1 has been shown to have stronger efficacy against pathogens and spoilage bacteria than chlorine and does not form carcinogenic products. However, ASC in this concentration range aggravates tissue damage. The objective of this study was to optimize ASC treatment parameters to balance antimicrobial activity with quality retention of shredded carrots. Shredded carrots were immersed for either 1 min in 100, 250 or 500 µL L^?1 ASC solutions or 2 min in 200 µL L^?1 chlorine or water (control). Treated samples were spin‐dried and packaged in polypropylene bags and stored at 5 °C for up to 21 days. Carrots were evaluated at 7‐day intervals for visual appearance, package atmosphere composition (O₂ and CO₂), product firmness, tissue electrolyte leakage and pH. The microbial growth, including total aerobic bacterial counts, total coliforms/Escherichia coli, yeast and mold counts and lactic acid bacterial counts on the products was also determined. Treatments with all concentrations of ASC reduced the aerobic bacterial counts, coliform/E. coli counts, yeast mold and counts and lactic acid bacterial populations by 1.2–2.0 log cfu g^?1 when compared with the water‐washed and unwashed samples. During storage, unwashed samples had a sharp increase in lactic acid bacterial populations accompanied by a sharp decline in pH readings and rapid loss in firmness and tissue integrity; samples washed with 100 µL L^?1 ASC maintained the best overall visual quality, accompanied by the retention of tissue integrity and firmness. Therefore, 100 µL L^?1 was determined as the optimum concentration of ASC for maintaining overall quality and firmness, inhibiting microbial growth and prolonging the shelf‐life of shredded carrots. Copyright © 2006 Society of Chemical Industry     

POROSITY PRESERVATION DUE TO AUTHIGENIC CHLORITE COATINGS IN DEEPLY BURIED UPPER TRIASSIC XUJIAHE FORMATION SANDSTONES,SICHUAN BASIN,WESTERN CHINA

Non‐marine sandstones in the Upper Triassic Xujiahe Formation form an important reservoir unit in the Sichuan Basin, western China. Widespread authigenic chlorite cement is present in the second and fourth members of the formation, referred to as the Xu II and IV members. This study, based on data from 12 wells from three gasfields, focusses on chlorite development and evolution and attempts to evaluate its influence on reservoir quality. Data included results of X‐ray diffraction (XRD) and electron microprobe analyses (EMPA), scanning electron microscopy (SEM), and stable carbon and oxygen isotope analyses. The results showed that chlorite coatings preserve primary pore spaces in the sandstones by inhibiting the nucleation of quartz cements on grain surfaces. Iron for chlorite growth came from the dissolution of Fe‐rich magmatic rocks derived from the palaeo‐Longmenshan fold‐belt, from dissolved and colloidal iron which had been precipitated in the Xujiahe Formation in a fluvio‐deltaic environment, and from compacting mudstones in other pars of the formation. The chlorite initially precipitated from pore waters during eodiagenesis (< 70 °C; < 2 km burial depth). During mesodiagenesis (>70 °C, > 2 km), the chlorite was modified due to exposure to Mg‐rich fluids derived from the underlying carbonate‐dominated Leikoupo Formation. Thus the Mg content of chlorite in the Xu II member increases with depth. However this phenomenon was not observed in the Xu IV member. The effects of authigenic chlorite on the sandstones' petrophysical properties were evaluated from correlations between chlorite content and porosity. Optimum thicknesses for chlorite coatings range from 5 to 10 microns. Thicker or thinner coatings appear to be less capable of preserving primary porosity and permeability.     

油气储层自生伊利石分离提纯微孔滤膜真空抽滤装置与技术

自生伊利石分离提纯是砂岩油气储层自生伊利石K-Ar同位素测年分析的关键技术之一。关于自生伊利石粘土组分的分离,国内外大多是采用高速、超高速离心分离技术。与高速、超高速离心分离技术相比,该文所介绍的微孔滤膜真空抽滤装置与技术具有较为明显的优越性,如操作简便、速度快、效率高、质量好等。文中介绍了装置构成、连接及使用说明、装置特点暨5个方面的技术创新和技术流程,论述了其分离提纯效率和质量以及应用现状和应用前景。5项技术创新克服了以往真空抽滤装置与技术的操作繁琐、效率较低、实用性不强等一系列技术难题,使其可以转化为成型固定设备投入日常生产与科研实验,为自生伊利石分离提纯开创了一种新途径,具有非常广阔的应用前景。      

Sensitivity of antioxidant-deficient yeast to hypochlorite and chlorite

Sodium hypochlorite and sodium chlorite are commonly used as disinfectants, and understanding the mechanisms of microbial resistance to these compounds is of considerable importance. In this study, the role of oxidative stress and antioxidant enzymes in the sensitivity of the yeast Saccharomyces cerevisiae to hypochlorite and chlorite was studied. Yeast mutants lacking Cu-Zn superoxide dismutase, but not mutants deficient in cytoplasmic and peroxisomal catalase, were hypersensitive to the action of both hypochlorite and chlorite. Both compounds depleted cellular glutathione, induced the production of reactive oxygen species and decreased the viability of the cells. The toxicity of hypochlorite and chlorite was abolished by hypoxic and anoxic conditions and ameliorated by thiol antioxidants and ascorbate. The results demonstrated that the action of hypochlorite and chlorite involves the formation of superoxide and peroxide and that SOD1 is protective, probably by limiting the formation of hydroxyl radicals and damage to proteins.     

深埋绿泥石片岩变形特征及稳定性分析

根据锦屏二级水电站绿泥石片岩的特点,在同一断面综合采用变形、应力和钻孔电视多种监测手段,分析围岩内部的力学状态。为了更加深入地认识绿泥石片岩的工程力学特性及其对变形破坏机制的影响,开展单轴和三轴压缩试验、灌浆渗透性试验和三轴流变试验,揭示绿泥石片岩变形、破坏和失稳的多方面原因,并为支护措施的确定提供参考意见。绿片岩洞段的围岩稳定主要取决于衬砌结构能否抵挡流变和遇水软化2种作用导致的挤压效应,通过引入软化系数和退化的Burgers流变模型,从衬砌结构的受力角度对围岩稳定性进行评价,数值计算结果表明衬砌结构具有相当高的安全裕度。     

自生酸酸液体系研究进展及展望

自生酸酸化技术是高温(超高温)低渗致密油气藏主要增产措施之一。对自生酸酸化技术研究进展进行了综合分析,介绍了自生酸的酸岩反应特性,自生酸的主要生酸机理,以及自生有机酸、自生盐酸、自生氢氟酸和复合类自生酸的研究进展,分析了自生酸类型、供氢能力、成本、缓速能力、缓蚀能力等因素对酸化工作液现场应用的影响,并对自生酸在酸化作业中的应用进行了展望。该研究可为自生酸酸化技术的发展和推广应用提供参考。     

4-(2-甲-4-氯苯氧基)丁酸氯化工艺改进—水相氯化法

介绍了以４－（２－甲基苯氧基）丁酸为原料在催化剂存在下用次氯酸钠为氯化剂在水相中氯化制备４－（２－甲－４－氯苯氧基）丁酸的过程。催化剂有高的选择性。整个过程有好的生产环境。该过程也可用于其它２－甲－４－氯苯氧基羧酸类的氯化过程。     

油气储层钾氩定年中的自生粘土矿物提纯技术及意义

该实验尝试了一种从沉积岩中分离提纯自生粘土矿物的方法:反复冷冻-解冻法。其改进之处在于利用渗透于岩石样品中的水,在冷冻的情况下体积膨胀,而使岩石颗粒自然散开。实验的大部分岩样用改进的岩样碎样法分离出的粘土矿物,经扫描电镜及X-射线衍射分析鉴定证实,在<1μm粒级时,粘土组分中不含有碎屑的钾长石,而常规法无法达到这一点。另外,随着分离粒级的减小,粘土组分中碎屑伊利石的含量逐渐减少,在<0.2μm时,大部分组分中碎屑伊利石的含量<5%,有的已不含碎屑伊利石。      

东海盆地西湖凹陷中央背斜带油气运移期次及成藏

利用包裹体测温和成岩矿物伊利石测年数据资料,对东海盆地西湖凹陷中央背斜带油气运移及成藏的基本模式进行了研究。中央背斜带储层流体包裹体明显分为盐水包裹体和有机包裹体,包裹体均一化温度分为3期,其对应的地质时间分别为中中新世、中新世晚期和上新世—第四纪。储层自生伊利石同位素地质年龄自北向南分别为23.5～26.5,18.31～21.86,12.58～13.63 Ma,表明北部油气成藏时间早于中部和南部。综合分析认为中央背斜带发生过早、中、晚3期油气运移和聚集活动,以晚期最为重要,其幕式特征明显。成藏期总体时间长,多期成烃,多次充注,同期不同源,是中央背斜带油气成藏的基本模式。      

国内氯化稀土产品的生产、应用及市场

介绍了我国氯化稀土主要产品的生产、应用、市场状况及今后的发展方向。针对目前存在的问题，提出了几点建议。