莲藕的酶促褐变及其贮藏中褐变的控制

为有效控制莲藕褐变,试验研究了温度、pH值、底物浓度以及抑制剂对莲藕多酚氧化酶（PPO）的影响。结果表明：莲藕PPO最适pH值为7.5,最适温度为35℃,以邻苯二酚为底物,米氏常数Km为0.0273 mol/L。亚硫酸钠、抗坏血酸（VC）对莲藕PPO活性具有较好抑制作用,乙酸、柠檬酸、植酸、木瓜蛋白酶、半胱氨酸也对莲藕PPO活性具有一定抑制作用。0.2%VC+2%乙酸+0.03%亚硫酸钠抑制剂处理对莲藕褐变的抑制效果最佳。可以通过浸泡亚硫酸钠和抗坏血酸（VC）、调节pH值、低温贮藏等方法来抑制莲藕PPO活性,控制莲藕褐变。     

甘薯加工过程酶促褐变及控制研究

甘薯加工过程中极易产生酶促褐变。应用分光光度法，研究了甘薯中多酚氧化酶（PPO）的特性及褐变的控制方法。结果表明，甘薯皮部的PPO活性和褐变强度是心部的2倍左右，在pH值为4.5时其活性较低。在甘薯淀粉生产过程中，结合去皮工艺，分别选择添加0.01%～0.05%柠檬酸或0.005%～0.01%抗坏血酸或0.05%～0.1%亚硫酸钠，均可有效控制PPO产生的褐变，提高甘薯淀粉的质量。     

复合护色剂的配制及对鲜切马铃薯片保鲜效果

筛选符合现实鲜切马铃薯片加工需求的复合护色剂,并研究鲜切马铃薯片货架期,防止净菜加工中鲜切马铃薯片的褐变,试验通过L-半胱氨酸,柠檬酸,抗坏血酸对马铃薯多酚氧化酶活性的抑制效果,然后正交试验确定复合护色剂成份以及最佳浓度。对单因素最佳浓度,复合护色剂最佳浓度,以及二氧化氯处理进行货架期试验,测定样品菌落总数,并确定产品有效保藏时间。结果表明：复合护色剂较佳配比为氯化钙0.1%,柠檬酸0.2%,抗坏血酸0.15%。二氧化氯质量浓度40 mg/L浸泡10 min,真空包装低温保藏产品货架期为7 d。     

荔枝护色干制的工艺研究

果皮褐变是荔枝贮藏和加工过程中的常见问题。在探讨了荔枝果皮中引起褐变的主要酶——多酚氧化酶(PPO)特性的基础上着重研究了荔枝干制中的护色工艺。结果表明,荔枝果皮多酚氧化酶的最适温度范围为30～70℃之间;PPO在pH=5.5和pH=7.0左右活性最大。荔枝经90℃,0.2％的柠檬酸溶液中热烫3 min并强制冷却后,用0.2 mol·L^-1抗坏血酸+0.2 mol·L^-1柠檬酸+0.1 mol·L^-1植酸+0.1 mol·L^-1氯化钠+0.2 mol·L^-1亚硫酸氢钠混合液护色处理10 min经脱水干燥制成天然红皮荔枝干。     

甘薯全粉加工中无硫复合护色工艺优化

为了优化甘薯全粉无硫复合护色工艺,该文通过考察柠檬酸、柠檬酸亚锡二钠、植酸、亚硫酸氢钠和抗坏血酸5种护色剂对甘薯全粉色泽的影响,优选出柠檬酸和抗坏血酸作为甘薯全粉加工合适的护色剂;通过正交试验,得到柠檬酸-抗坏血酸无硫复合护色剂的最佳护色工艺为:将10 mm厚的甘薯切片在质量分数为0.3%的柠檬酸和0.1%抗坏血酸的复合护色液中护色处理30 min,可使制得的甘薯全粉亮度值L*达90.58,多酚氧化酶的抑制率达88.13%.研究发现柠檬酸的添加能显著提高抗坏血酸的热稳定性;酶促褐变产物紫外-可见光谱扫描显示,加入复合护色剂后410 nm处吸收峰明显减弱,表明复合护色剂能有效抑制酶促褐变反应的发生;圆二色谱研究表明多酚氧化酶经复合护色剂处理后,酶蛋白二级结构中α-螺旋减少,而β-折叠结构增多,酶蛋白的分子构象被改变,从而降低多酚氧化酶活力.该文为甘薯全粉加工中的无硫复合护色工艺提供了参考.     

石榴果实发育期果皮褐变及相关酶活性变化

为探明石榴果实发育期果皮褐变及其相关酶活性、总酚和抗氧化能力的变化规律及相互关系,以泰山红和泰山三白甜石榴为试材,研究各发育期果皮褐变度、多酚氧化酶(PPO)活性、过氧化物酶(POD)活性、苯丙氨酸解氨酶(PAL)活性、总酚含量和DPPH自由基清除率的变化。结果表明,2个品种果皮褐变度、PPO活性、POD活性、总酚含量和DPPH自由基清除率随着发育天数的增加逐渐降低,均在7月15日达到最高。2个品种果实发育期果皮PAL活性呈先降低后升高再降低的变化趋势,分别在7月15日和9月13日出现峰值。泰山红抗褐变能力高于泰山三白甜,二者分别在9月23日和9月13日采收能减轻褐变的发生。相关性分析表明,PAL、PPO、POD、总酚和DPPH自由基清除率均与石榴果实酶促褐变密切相关,石榴果实酚类物质含量高低与其抗氧化能力极显著正相关。本研究结果为深入揭示石榴果实褐变机理提供了理论依据。     

红熟番茄果实多酚氧化酶酶学特性

多酚氧化酶（Polyphenol oxidase,PPO,EC 1.14.18.1 or 1.10.3.2）与果蔬加工制品的色泽、抗氧化能力关系密切。果蔬PPO酶学特性分析和活性控制越来越受到关注,为设计、开发番茄加工技术和工艺提供理论依据,该文采用光谱法,研究了红熟番茄（Lycopersicum esculentum Mill. cv 918）果实PPO的酶学特性。研究结果表明红熟番茄果实PPO的最适反应pH值是6.0,反应温度是40℃,耐热性较好,50℃加热10 min仍保有88%的活性。红熟番茄果实PPO对一元酚、二元酚和三元酚均有催化氧化能力,最适底物是儿茶酚,其最大反应速率和米氏常数分别是226.30 U/min和 6.00 mmol/L。抗坏血酸、β-巯基乙醇或L-半胱氨酸可抑番茄PPO活性,十二烷基硫酸钠可显著增强其活性。     

快速脱水抑制葡萄干制过程中膜脂过氧化及褐变

为探索脱水速度对无核白葡萄干制过程中膜脂过氧化作用及褐变的影响,以新疆无核白葡萄为试验材料,经过葡萄促干剂处理后,采用快速脱水和缓慢脱水2种处理,质量每减轻10%进行取样,测定脱水过程中果实干基含水率、干燥速率、褐变度、细胞膜透性、丙二醛(malonaldehyde,MDA)含量、脂氧合酶(lipoxygenase,LOX)、超氧化物歧化酶(superoxide dismutase,SOD)、过氧化氢酶(catalase,CAT)、过氧化物酶(peroxidase,POD)、多酚氧化酶(polyphenol oxidase,PPO)活性以及总酚含量的变化。结果表明:与缓慢脱水相比,快速脱水处理显著(P0.05)降低了无核白葡萄褐变度的上升,减少MDA生成量以及膜透性的增加,抑制LOX活性的升高,保持较高的活性氧清除酶SOD、CAT及POD活性及较高的总酚含量,且使PPO活性保持在一个较低的水平。因此认为,快速脱水可以有效地抑制无核白葡萄的膜脂过氧化作用对细胞膜的破坏,保持细胞的完整性,且PPO活性较低,从而减少无核白葡萄脱水褐变的发生。研究结果为快速脱水在无核白葡萄干制中的应用提供参考。     

不同烤烟品种不同成熟度上部叶烘烤特性研究

为明确烤烟叶片上部叶烘烤特性,以K326、毕纳1号、遵烟6号、贵烟1号、贵烟4号、红花大金元(红大)不同成熟度上部叶为材料,研究比较了烘烤或暗箱试验中烟叶失水速率、变黄变褐特性、叶绿素相对含量(SPAD)、颜色值、多酚氧化酶(PPO)活性以及烤后烟叶化学成分含量的差异。结果表明,烘烤和暗箱试验中毕纳1号失水速率较小,红大和贵烟1号失水速率较大,毕纳1号和K326变黄时间最短,红大变黄时间最长;烘烤过程中毕纳1号PPO活性均值低于0.4 U,贵烟1号高于0.5 U;暗箱试验中红大SPAD值较大,其次是遵烟6号和贵烟1号,毕纳1号、贵烟4号、K326较小,红大和遵烟6号颜色值相对较差,毕纳1号变褐较轻,贵烟1号变褐最严重;烤后烟叶毕纳1号、贵烟4号和遵烟6号化学成分含量相对适宜。随着烤烟叶片成熟度的提高,烘烤试验中烟叶变黄时间缩短,PPO活性增加,烤后烟叶总植物碱、总氮含量降低,水溶性总糖、还原糖含量增加;暗箱试验中烟叶变黄、变褐时间缩短,SPAD值减小,颜色较好,但变褐后颜色较差。品种与成熟度不仅影响烟叶的外观表型,而且显著影响其内在生理。不同烤烟品种烘烤特性与化学成分和基因型均密切相关...     

双孢蘑菇护色保鲜技术研究

以双孢蘑菇为试验材料,研究不同的褐变抑制剂对双孢蘑菇保鲜效果的影响，通过正交试验筛选出双孢蘑菇MA贮藏中有利于色泽保持的最适褐变抑制剂配比。研究结果表明，对双孢蘑菇贮藏保鲜效果较好的褐变抑制剂及其浓度为：0.1%的无水亚硫酸钠溶液、0.06%～0.10%的抗坏血酸溶液、0.8～2.6 mmol/L的半胱氨酸溶液；保鲜液最佳配比为2 mmol/L半胱氨酸、0.05%抗坏血酸、0.15%无水亚硫酸钠、浸泡时间8 min。     

葫芦科蔬菜对丛枝菌根真菌依赖性的研究

在盆栽条件下试验研究了5种葫芦科(Cucurbitaceae)蔬菜对2种丛枝菌根(Arbuscular Mycorrhiza，AM)真菌的依赖性。结果表明，AM真菌Glomus mosseae(G.m)和Gigaspora rosea(Gi.r)均能有效地促进葫芦科蔬菜的生长，显著增加叶面积和植株干物质量，提高叶片的光合速率，降低气孔阻力。供试葫芦科蔬菜对菌根的依赖程度顺序为黄瓜＞西瓜＞苦瓜＞葫芦＞南瓜。5种葫芦科蔬菜对AM的依赖性与AM真菌对根系的浸染率呈正相关关系，符合直线回归方程：y=117.19+0.7468x。     

藻(Ziziphus spina-christi)体内外无性繁殖的方法

Christ‘s thorn (Ziziphus spina-christi L. Desf.) is ecologically and economically important in Iran. Since it is a crosspollinated plant with a wide range of genetic variability, an investigation was carried out to determine the best method for mass and clonal propagation. Three vegetative methods were examined, including 1) cutting, where shoots with a 22-25 cm length and three shoot diameters were treated with two culture media; 2) layering, where air layering and trench layering treatments consisted of three growth regulators at three levels of concentration; and 3) tissue culture with nodal segments bearing axillary buds that were removed from shoots of mature trees at different seasons. Several experiments were carried out to determine the best disinfectant chemical, the best culture method, the best season, the appropriate explant characteristics and media type. Rooting was successful only on the sandy beds for cuttings with more than 8.0 mm diameter. For the trench layering method, only one specimen in one replicate rooted a very small root, while for the air layering method, only seedlings with growth regulator treatments rooted successfully. The best season for explant harvesting was determined as mid summer, and among the disinfecting treatments, Ca(OCI)2 at a concentration of 0.5g kg^-1 for 20 minutes was the best. There were no significant differences for shoot weight and length with a Murashige and Skoog (MS) medium with and without a hormone.     

Abundance of Frankia from Gymnostoma spp. in the rhizosphere of Alphitonia neocaledonica, a non-nodulated Rhamnaceae endemicto New Caledonia

The capacity of different soils of New Caledonia to induce nodulation in Gymnostoma poissonianum was studied. The soils were sampled under five Gymnostoma species, Alphitonia neocaledonica (a non-nodulated endemic Rhamnaceae) and Pinus caribea (an introduced species) growing in various ecological conditions. Using G. poissonianum as trap-host, we observed a higher abundance of Frankia from Gymnostoma spp. in the rhizosphere of A. neocaledonica as compared with bare soils and P. caribea rhizosphere. The nodulating capacity of A. neocaledonica rhizosphere was almost similar to that of the five Gymnostoma species (symbiotic host) studied in the same stations. In comparison, bare soils or rhizosphere of P. caribea had poor nodulating capacities. We isolated fourteen Frankia strains from nodules of G. poissonianum after baiting with the rhizospheric soils of five Gymnostoma and A. neocaledonica. Using the PCR/RFLP method, we confirmed the similarity with those already described. Frankia was abundant in the rhizosphere of A. neocaledonica in all the sites studied. One explanation could be a positive tropism of Frankia towards species belonging to families having nodulated species, which is the case of A. neocaledonica endemic in New Caledonia. We can suppose that the non-nodulated plants belonging to these families can excrete some chemical substances able to attract Frankia and to induce its proliferation.     

茄二十八星瓢虫对雷公藤和曼陀罗提取物的敏感性

为研究寄主植物对茄二十八星瓢虫药剂敏感性及体内酶活力的影响,采用浸渍法分别测定了取食茄子、马铃薯、番茄和龙葵的茄二十八星瓢虫幼虫(以下简称幼虫)对雷公藤和曼陀罗提取物的敏感性,用生化方法测定了雷公藤和曼陀罗提取物对幼虫体内乙酰胆碱酯酶(AChE)和主要解毒酶活性的影响。结果表明,雷公藤提取物对取食茄子、马铃薯、番茄和龙葵的幼虫LC50值分别为1.407 9 mg.L-1、1.595 8 mg.L-1、1.464 7 mg.L-1和1.109 7 mg.L-1,相对毒力指数为78.82、69.54、75.76和100;曼陀罗提取物对取食茄子、马铃薯、番茄和龙葵的幼虫LC50值分别为0.641 7 mg.L-1、0.610 3 mg.L-1、0.758 0 mg.L-1和0.488 3 mg.L-1,相对毒力指数为76.09、80.01、64.42和100;取食龙葵的幼虫对2种植物提取物的敏感性显著高于取食茄子、马铃薯和番茄的幼虫。取食4种寄主植物的幼虫体内靶标酶AChE和主要解毒酶谷胱甘肽-S-转移酶(GST)、羧酸酯酶(CarE)、多功能氧化酶(MFO)活力顺序均为茄子>马铃薯>番茄>龙葵。其中,取食番茄和龙葵的幼虫体内AChE和GST活力显著低于取食茄子和马铃薯的幼虫,取食马铃薯、番茄和龙葵的幼虫CarE活力显著低于取食茄子的幼虫,取食4种寄主植物的幼虫MFO活力差异达极显著水平。雷公藤和曼陀罗提取物对幼虫体内AChE和GST、CarE和MFO活性均有抑制作用。其中,对取食马铃薯幼虫的AChE活力抑制作用最强,其次为取食茄子和番茄的幼虫,对取食龙葵的幼虫抑制作用最低。雷公藤和曼陀罗提取物对取食龙葵幼虫CarE活力的抑制作用最强,而对取食马铃薯的幼虫MFO活力的抑制作用最强。寄主植物中的次生物质对解毒酶的诱导或抑制可能是引起药剂敏感性差异的主要原因。     

菲对秀丽隐杆线虫、中杆属和拟丽突属线虫毒性效应研究

采用悉生培养系统,研究不同浓度菲对秀丽隐杆线虫、拟丽突属与中杆属线虫的毒性效应,以及3种线虫对菲的去除作用。结果表明:(1)随着菲浓度的增加,3种线虫存活率逐渐降低。秀丽隐杆线虫在不添加菲的处理中,48 h内出现繁殖,而在添加菲的处理中,即使在最低浓度5 mg/L下,繁殖现象也会消失。中杆属与拟丽突属线虫由于世代时间较长,在本试验周期内均未出现繁殖现象。(2)暴露24 h时,比较不同浓度菲处理下线虫的相对死亡率,得到3种线虫的耐性依次为中杆属线虫≥秀丽隐杆线虫≥拟丽突属线虫,且随菲浓度的增加,秀丽隐杆线虫耐性水平逐渐降低;暴露48 h时中杆属线虫耐性依旧高于拟丽突属,而72 h时中杆属与拟丽突属线虫的耐性趋于一致。(3)3种线虫受菲胁迫后均失去头部正常摆动能力,且秀丽隐杆线虫与拟丽突属线虫体长随菲浓度的增加而逐渐降低。(4)不同种类线虫的添加均能促进菲的去除,不同线虫之间无显著差异。因此,菲会显著抑制3种线虫的存活率和生长发育,抑制秀丽隐杆线虫的繁殖。线虫的存活率受线虫种类、暴露时间、菲浓度及其交互作用的影响显著,其中中杆属线虫对菲的综合耐性最强,3种线虫均能促进溶液中菲的去除。     

开口箭提取物对采后香蕉抗炭疽病菌活性的研究

为探讨植物提取物对香蕉采后病害的防治,采用孢子萌发法和菌丝生长速率测定百合科植物开口箭的甲醇提取物及其乙酸乙酯分部萃取物和正丁醇分部萃取物对香蕉炭疽病菌的离体抗菌活性,选用正丁醇分部萃取物进行耐高温(121℃处理20 min)、紫外光照射(30 W紫外灯距50 cm直射15 h)和酸处理(调节pH 3)的抗菌稳定性研究,并进行了提取物处理香蕉的贮藏防病试验。结果表明,开口箭甲醇提取物及其乙酸乙酯分部萃取物和正丁醇分部萃取物抑制香蕉炭疽病菌孢子萌发的半效应浓度(EC₅₀)分别为1490.27,638.40,1112.65 μg/mL,抑制香蕉炭疽病菌菌丝生长的EC₅₀分别为1262.16,451.02,955.58 μg/mL,正丁醇分部萃取物的抗菌活性不受热、紫外线和酸等因子的影响,用开口箭提取物处理采后香蕉果实,具有明显降低其潜伏性炭疽病发病率的作用。     

重塑Q3黄土K0三轴蠕变特性的试验研究

[目的]研究陕西省延安地区重塑Q_3黄土高填方工程的后期沉降变形特性,为高填方工程的设计、施工提供一定的技术和理论支撑。[方法]通过改进K0三轴蠕变仪,对所取黄土进行了不同压实度、不同含水量、不同竖向应力下的室内土的静止侧压力系数K_0三轴固结排水蠕变试验。[结果]重塑Q_3黄土具有明显的蠕变特性,在低应力条件下,呈现出典型的衰减蠕变;在K_0条件下,随着含水量增大、竖向应力的增大,压实度的减小,蠕变呈增强趋势,蠕变变形量增大;在低水平应力的条件下,土体所受侧向应力与竖向应力成线性关系。[结论]建立了重塑Q_3黄土关于竖向应力的自定义蠕变模型,通过试验数据拟合获得了模型参数,所建模型能很好地描述延安地区重塑Q_3黄土的蠕变特性。     

Growth of Lumbricus terrestris and Aporrectodea caliginosa in an acid forest soil, and their effects on enchytraeid populations and soil properties

A laboratory experiment was carried out to test the hypothesis that the earthworms Lumbricus terrestris and Aporrectodea caliginosa are able to maintain their populations and reproduce in the acid forest soil of a deciduous forest where no lumbricids were found in the field. The experiment was conducted in 45-l containers in which layers of mineral subsoil, humus and organic topsoil collected from the site were established. Both species survived and at least L. terrestris reproduced during the 60 weeks’ incubation. Burrows and middens of L. terrestris were recorded and quantities of litter were consumed. The presence of lumbricids increased the organic matter content of humus, reduced the acidity of the topsoil and humus layers, and suppressed the population of the enchytraeid Cognettia sphagnetorum. A dense population of Enchytraeus albidus was found in L. terrestris middens. It is concluded that edaphic factors do not explain the absence of earthworms, but isolation from cultural landscapes and lack of opportunity to colonize the site from the surroundings is the decisive factor.     

荧光假单胞菌Pf.X16L2与丛枝状菌根真菌Glomus mosseae在小麦根圈内的相互关系

运用发光酶基因标记及其发光强度检测,SDH酶活染色等技术,在根盒－土壤微宇宙及塑料盒栽系统中,研究了发光酶基因（luxAB)标记的荧光假单胞菌菌株Pf.X16L2与丛枝状菌根真菌摩西球孢囊霉Glomus mosseae两者在小麦根圈的相互关系。Gl.mosseae对Pf.X16L2的种群密度和生理活性都有着抑制作用。因而能降低小麦根圈对Pf.X16L2的富集作用,而Pf.X16L2在一定程度上能提高Gl.mosseae的菌根感染率,但会降低菌丝中琥珀酸氢酶（SDH）活性,两者可共同促进小麦中后期的生长。     

Analysis of clonal germplasm from five Saccharum species: S. barberi , S. robustum, S. officinarum, S. sinense and S. spontaneum . A study of inter- and intra species relationships using microsatellite markers

In order to study relationships within and among species of the highly complex polyploid genus Saccharum, 30 clones from 5 species (S. barberi, S. officinarum, S. robustum, S. sinense, and S. spontaneum) and 6 cultivated clones were analyzed using 15 sugarcane simple sequence repeat (SSR) markers and two multivariate statistical methods. The origins of two species, S. barberi and S. sinense, are unclear, and it has been hypothesized that they arose from crosses of S. officinarum × S. spontaneum. S. robustum is suggested to be ancestral to S. officinarum, which, when crossed with S. spontaneum, principally comprise the genomes of commercial cultivars. Although our analyses supported S. robustum as being an ancestor of S. officinarum, and show the composition of commercial clones as expected, our results concerning the species S. barberi and S. sinense indicated them to be much less related to the main Saccharum germplasm pool than previous molecular marker investigations, suggesting that introgression from other genera may exist in their ancestry. The differing results of our analysis of S. barberi and S. sinense are likely attributable to more equal and larger numbers of clones studied in each species. Given the extremely high ploidy, the use of only 15 SSR markers enabled clear distinction of Saccharum species and clones, and also identified likely mislabeled accessions. In addition, the replication of DNA extraction, polymerase chain reactions, and fragment electrophoresis increased the robustness of our analysis.