Combination of Sodium Chlorite and Calcium Propionate Reduces Enzymatic Browning and Microbial Population of Fresh-Cut “Granny Smith” Apples

ABSTRACT: Tissue browning and microbial growth are the main concerns associated with fresh-cut apples. In this study, effects of sodium chlorite (SC) and calcium propionate (CP), individually and combined, on quality and microbial population of apple slices were investigated. “Granny Smith” apple slices, dipped for 5 min in CP solutions at 0%, 0.5%, 1%, and 2% (w/v) either alone or in combination with 0.05% (w/v) SC, were stored at 3 and 10 °C for up to 14 d. Color, firmness, and microflora population were measured at 1, 7, and 14 d of storage. Results showed that CP alone had no significant effect on the browning of cut apples. Even though SC significantly inhibited tissue browning initially, the apple slices turned brown during storage at 10 °C. The combination of CP and SC was able to inhibit apple browning during storage. Samples treated with the combination of SC with CP did not show any detectable yeast and mold growth during the entire storage period at 3 °C. At 10 °C, yeast and mold count increased on apple slices during storage while CP reduced the increase. However, high concentrations of CP reduced the efficacy of SC in inactivating E. coli inoculated on apples. Overall, our results suggested that combination of SC with 0.5% and 1% CP could be used to inhibit tissue browning and maintain firmness while reducing microbial population. Practical Application: Apple slices, which contain antioxidants and other nutrient components, have emerged as popular snacks in food service establishments, school lunch programs, and for family consumption. However, the further growth of the industry is limited by product quality deterioration caused by tissue browning, short shelf-life due to microbial growth, and possible contamination with human pathogens during processing. Therefore, this study was conducted to develop treatments to reduce microbial population and tissue browning of “Granny Smith” apple slices. Results showed that an antimicrobial compound, sodium chlorite, is effective in not only eliminating microbes but also inhibiting tissue browning of apple slices. However, the compound caused tissue softening and its antibrowning effect was short-lived, lasting only for a few days. Combination of the compound with a calcium-containing food additive was able to improve firmness and freshness of apple slices while reducing population of Escherichia coli artificially inoculated on samples and inhibiting the growth of yeast and mold during storage.     

砂岩储层中自生伊利石定年分析油气藏形成期

砂岩储集层中自生伊利石仅在流动的富钾孔隙水介质环境下才能形成,烃类流体注入储集层后自生伊利石形成便会中止;因此,烃类流体进入储层时间不可能早于自生伊利石的形成时间.利用K/Ar同位素地质年代学方法分析塔里木盆地D区石炭系油藏和J区三叠系凝析气藏二个砂岩储集层的自生伊利石形成时间,分别为24.3～31.8Ma和44.3～49.2Ma,反映油气藏形成期前者为渐新世,后者为始新世.     

Oxidation character of chlorite from Byrapur chromite deposit,India — A57Fe Mössbauer evaluation

Chlorite occurring in tremolite-chlorite schist rock of Byrapur chromite deposit of southern India has been investigated by⁵⁷Fe Mössbauer spectroscopy along with XRD, IR and EPMA analyses. From XRD and EPMA results the chlorite is identified as clinochlore. The fit of Mössbauer spectrum (at room temperature) shows five symmetric doublets for iron. Based on hyperfine parameters three doublets are assigned to Fe²⁺ attrans andcis positions of talc layers, and Fe²⁺ at brucite layer. The remaining two doublets are attributed to Fe³⁺ attrans position and Fe³⁺ at tetrahedral site. The Mössbauer result suggests that the Fe³⁺ in octahedral sites of this chlorite was caused by oxidation after chloritization. The chlorite of Byrapur area was less oxidized compared to the chlorite of Sukinda chromite deposit of eastern India.     

致密砂岩自生伊利石的成因及其对相对优质储层发育的影响——以川西地区须四段储层为例

川西地区须家河组四段为典型的致密砂岩储层,砂岩骨架颗粒中岩屑含量高而长石含量极低。自生黏土矿物主要为伊利石和高岭石,其中自生伊利石呈碎屑颗粒包膜、充填于次生粒内溶孔中的网状集合体和充填于粒间的非网状集合体3种方式产出。第一种为早期形成的蒙脱石经伊蒙混层转化而来;第二种由埋藏期钾长石的伊利石化作用形成;第三种由钾长石和早期形成的高岭石在深埋期间通过伊利石化作用形成。自生伊利石的形成对致密砂岩中相对优质储层的发育具有双重影响。它能降低储层的渗透率,影响储层质量,但颗粒包膜伊利石可以阻止石英次生加大的形成从而保护原生孔隙,埋藏成岩过程中蒙皂石-伊利石的转化反应以及钾长石和高岭石的伊利石化作用能促进钾长石的溶解形成次生孔隙。因此,自生伊利石的形成对于砂岩原生孔隙的保存和次生孔隙的发育具有积极作用,因而有利于相对优质储层的形成。     

Effectiveness of Individual or Combined Sanitizer Treatments for Inactivating Salmonella spp. on Smooth Surface, Stem Scar, and Wounds of Tomatoes

ABSTRACT: Unwaxed, green tomatoes ('Florida 47' cultivar) were contaminated with Salmonella and then treated with aqueous solutions of sodium hypochlorite (HOCl; 200 ppm), acidified sodium chlorite (ASC; 1200 ppm), peroxyacetic acid (PAA; 87 ppm), or chlorine dioxide gas (ClO₂; total 100 mg). Additionally, a combined treatment of immersion in HOCl, followed by immersion in ASC and then exposure to ClO₂ gas was investigated. Tomatoes were spot inoculated with a 5-strain Salmonella cocktail on smooth surfaces, stem scar tissue, or puncture wounds. A 3 replicate set of each of the sample groups was stored at 20 °C and 95% relative humidity (RH) and retested after 5 d. Greater than 4.0-log unit reductions of Salmonella spp. inoculated on the smooth surface of the tomatoes were seen for all aqueous sanitizer treatments, with Salmonella populations below the detection limit after 5 d of storage. All aqueous treatment groups showed > 1.0-log unit reductions in Salmonella at the stem scar and >2.0-log unit reduction at puncture wounds. The ClO₂ gas treatment reduced Salmonella to undetectable levels at the stem scar, but had no apparent effect on populations inoculated in puncture wounds. The combined treatment resulted in a 3.0-log unit reduction of inoculated Salmonella at puncture wounds. In all cases except for treatment with chlorine, surviving Salmonella populations did not increase after the 5 d of storage. Results of this study suggest the combined treatment was most effective for minimizing the risk of Salmonella contaminated on tomatoes.     

不同结构羧甲基纤维素对绿泥石的抑制作用及机理

通过浮选、吸附量测试及动电位测量,研究不同结构的羧甲基纤维素对绿泥石浮选的影响,并考察其作用机理。结果表明,绿泥石具有一定的天然可浮性,羧甲基纤维素对绿泥石的浮选具有抑制作用,抑制效果随矿浆pH的升高而增大。羧甲基纤维素的结构对其抑制作用效果影响较大,羧甲基纤维素的取代度越低,分子量越高,对绿泥石的抑制效果越强。动电位测量及吸附量测试结果表明,在弱碱性pH条件下,绿泥石表面荷负电,羧甲基纤维素分子中的羧甲基也荷负电,二者之间存在阻碍羧甲基纤维素吸附的静电排斥作用,羧甲基纤维素取代度越低,分子量越大,在绿泥石表面吸附量越高,对绿泥石的抑制效果越强。     

反应条件对颗粒活性炭吸附亚氯酸盐的影响

采用烧杯试验探讨了水溶液中颗粒活性炭(GAC)对亚氯酸盐(ClO-2)的去除特点。结果表明:GAC投加量越大,去除率越高;当投加比大于1∶1、反应120 min时,去除率可达100%;ClO-2初始浓度小于5 mg/L时,受GAC表面与溶液中ClO-2浓度差的影响,ClO-2去除率随初始浓度增加而迅速升高;在pH的影响下,会改变GAC表面的电性,酸性条件下带正电,促进GAC对ClO-2的去除,反之碱性条件下抑制ClO-2的去除;GAC吸附ClO-2为自发吸热的物理吸附反应,温度低于20℃时受温度影响较大,温度在20℃以上时,几乎不影响ClO-2去除效果;搅拌强度对ClO-2去除基本不产生影响,只需要GAC与ClO-2充分接触即可;粒度主要影响去除速率,充分反应的条件下,粒度对ClO-2去除效果影响较小。     

邻帮预裂爆破在司家营铁矿的应用研究

近年来的爆破实践表明,随着司家营露天铁矿开采深度的逐渐增大,不同区段不同岩性的边坡岩体已经出现了不同程度的失稳现象。基于压缩应力波和准静态气体压力共同作用理论, 应用兰格弗斯的研究结果,对在强风化绿泥岩中进行的邻帮预裂爆破的爆破技术参数选取进行了基本分析和讨论,同时根据在司家营铁矿进行的工业应用试验及其结果,提出了选取邻帮预裂爆破技术参数的基本原则, 并且取得了较好的预裂效果和降震效果。     

湖泊沉积物的矿物组成、成因、环境指示及研究进展

湖泊沉积物是不同地质、气候、水文条件下各类碎屑、黏土、自生/生物成因矿物以及有机物质等的综合体。沉积矿物蕴含着丰富区域和全球环境演变信息,如湖水的化学组成、流域构造、气候、水文以及人类活动的相互作用等。相关信息可以赋存在矿物外部微形貌、内部微结构、化学组成、物理和化学性质、同位素组成、谱学特征、成因以及共生组合等方面。因此,湖泊科学的许多关键课题都离不开矿物学,特别是在利用湖泊沉积物进行区域及过去全球变化研究中,深入的机理研究归根到底都要涉及矿物学,如流域化学风化作用、粒度组成、生物壳体化学组成、测年材料的选择等。然而,由于湖泊沉积物中矿物的多源性、复杂性,如何有效提取和解译其中的环境信息,是一项长期困扰研究者的课题,湖泊沉积矿物学的研究往往被许多研究者所忽视,中国的相关研究也较为薄弱。笔者综述了湖泊沉积物中碎屑、黏土、自生/生物矿物的矿物组合、特征、成因在(古)环境反演中的作用及最新研究进展,提出除了继续加强对湖泊沉积物中矿物来源、成因和古环境示踪的深入研究以外,矿物相间的转变及其对湖水和孔隙水组成的响应、一些非晶质或隐晶质及低丰度矿物相在湖泊化学和动力学中的作用也是很有潜力的研究领域,最后提出了研究中存在的一些问题、面对的挑战以及对研究前景的展望。     

有机稳定性二氧化氯初步研究

对有机稳定性二氧化氯溶液(稳定液)进行了初步研究,确定了稳定液的制备方法。并且通过对稳定液指标的测定、氯元素存在形态分析、反应物比例的测定及红外光谱分析,提出在稳定液中ClO2可能以配位化合物的形式存在,并给出了产物可能的分子结构。