苹果浓缩汁二次混浊物的形态分析

通过苹果浓缩汁二次混浊物的形态分析以及浊度测定，初步确定混浊物的化学成分，为果汁生产、贮存中混浊的控制提供依据。将二次混浊果汁和后混浊果汁经乙酸双氧铀负染，观察其在透射式电镜下的形态并测定其浊度。结果表明：苹果浓缩汁经-18℃，冷冻8～10h处理后，苹果浓缩汁混浊减轻；再煮沸冷冻的果汁，混浊增加；二次混浊苹果浓缩汁形成的颗粒经乙酸双氧铀负染在透射式电镜下有蛋白质球状颗粒和链状的多酚类颗粒，或自身聚合或相互聚合形成大的颗粒；贮藏6个月的苹果浓缩汁后混浊比二次混浊严重。初步确定苹果浓缩汁的二次混浊物主要是蛋白质和酚类以及两者自身或相互聚合的产物。     

草莓胡萝卜复合澄清汁后浑浊机理研究

为探讨草莓胡萝卜复合澄清汁的后浑浊机理，研究了化学试剂、贮藏温度和顶隙大小对草莓胡萝卜复合澄清汁的澄清度、褐变指数、黄烷醇类多酚含量、可溶性蛋白含量的影响。结果表明：贮藏温度越高，包装顶隙越大，氧气存留越多，随贮藏时间延长，果蔬汁浑浊形成越多，褐变程度越大，黄烷醇类多酚降解程度越大，可溶性蛋白损失越多；果蔬汁中添加尿素和十二烷基磺酸钠(SDS)，都能减少果蔬汁中浑浊的产生，抑制产品褐变，减缓黄烷醇类多酚的降解，减少可溶性蛋白的损失，说明氢键和疏水键都是和浑浊有关的化学键。蔗糖的添加对果蔬汁浑浊的形成没有太     

草莓浑浊汁维生素C降解动力学模型

为了弄清贮藏温度对草莓浑浊汁内维生素C降解的影响,建立其降解动力学模型,为选择草莓浑浊汁的贮藏温度提供依据。该文通过研究草莓浑浊汁贮藏过程中还原型维生素C和氧化型维生素C的降解与贮藏温度、贮藏时间的关系,建立了还原型维生素C和氧化型维生素C降解动力学模型。结果表明：草莓浑浊汁在贮藏过程中还原型维生素C和氧化型维生素C对热不稳定,还原型维生素C和氧化型维生素C降解符合一级反应动力学。经过验证表明该降解动力学模型有效,可用于草莓浑浊汁贮藏温度的选择和预测不同温度下的贮藏期。     

果胶酶对草莓果汁澄清效果的研究

澄清是果汁加工中的关键技术环节之一，利用果胶酶澄清果汁，有快速、简便、效果好等特点，在生产中有重要的应用价值。草莓中因含有果胶物质，制得的果汁易产生浑浊、沉淀等现象，严重影响产品的质量。用果胶酶对草莓果汁进行了单因素澄清试验及最适澄清工艺条件的研究。结果表明，果胶酶用量为0.035～0.075 mL/kg、温度35～45℃、pH 3.0～4.0的条件下澄清草莓果汁，透光率达97%以上，果汁中的可溶性固形物含量基本不变；在单因素试验的基础上，通过正交试验，果胶酶对草莓果汁澄清的最佳工艺条件是：果胶酶用量为0.035 mL/kg，温度为35℃，pH值为3.5。     

贮藏过程中果肉褐变的研究

木奈果实低温贮藏１２ｄ各处理的多酚氧化酶（ＰＰＯ）活性、酚类物质含量和细胞膜透性变化较小。贮藏２４ｄ各处理的细胞膜透性急剧增加,ＰＰＯ活性亦急剧升高,氧化酚类物质而使其含量急剧下降,导致果肉发生褐变。贮藏３６ｄ各处理的ＰＰＯ活性下降,膜透性仍继续增加。在整个贮藏过程中减压处理的ＰＰＯ活性、酚类物质含量和细胞膜透性变化最小,贮藏３６ｄ的果肉褐变率最低     

(木奈)贮藏过程中果肉褐变的研究

(木奈)果实低温贮藏１２ｄ各处理的多酚氧化酶（ＰＰＯ）活性、酚类物质含量和细胞膜透性变化较小。贮藏２４ｄ各处理的细胞膜透性急剧增加,ＰＰＯ活性亦急剧升高,氧化酚类物质而使其含量急剧下降,导致果肉发生褐变。贮藏３６ｄ各处理的ＰＰＯ活性下降,膜透性仍继续增加。在整个贮藏过程中减压处理的ＰＰＯ活性、酚类物质含量和细胞膜透性变化最小,贮藏３６ｄ的果肉褐变率最低     

不同石榴品种果实酚类物质及抗氧化活性研究

为探明石榴不同栽培地区和不同品种间酚类物质含量分布特征,筛选抗氧化能力强的功能型优良品种,以山东、云南、新疆和四川地区8个主栽石榴品种的成熟期果实为试材,利用常规品质分析方法和高效液相色谱技术,对其果实品质、酚类物质和抗氧化能力进行分析。结果表明,石榴品种间果实各品质指标存在显著差异,其中,喀什甜单果质量、可溶性糖和维生素C含量最高,甜绿籽固酸比最高,泰山红可溶性固形物含量最高,红玛瑙可滴定酸含量最高。不同石榴品种果皮中酚类物质含量与抗氧化能力均最高;果汁次之,种子最低。喀什甜果皮和红玛瑙种子中酚类物质含量和DPPH自由基清除率均最高;果汁中花青苷含量和DPPH自由基清除率分别在千籽红和大青皮甜中最高,安石榴苷、没食子酸、鞣花酸、总黄酮和总酚含量在红玛瑙中最高;果皮中安石榴苷含量(平均为135.00 mg·g-1)占总酚的48.94%,是石榴果实中最主要的酚类物质。果实品质指标间、果实品质与酚类物质间存在一定的相关性,安石榴苷、没食子酸、鞣花酸、花青苷、总黄酮和总酚间互为正相关,各指标与DPPH自由基清除率均正相关。红玛瑙、喀什红和千籽红果实的综合品质佳,富含酚类物质,是值得推广和开发利用的优良品种。研究结果为石榴加工产品的研发和新品种选育提供了理论依据。     

基于小角散射的柴油机排气颗粒的孔隙结构分析

为进一步降低柴油机的颗粒排放。针对柴油机的排气颗粒,采用热重分析和同步辐射X射线小角散射的方法,分析了颗粒在氧化过程中的内部特征、孔隙结构参数以及孔隙数量和尺寸分布等随氧化温度的变化规律。结果表明,随着氧化温度的升高,颗粒中电子密度差逐渐增大,颗粒之间的统计平均距离增大,颗粒尺寸逐渐减小;颗粒孔隙分布分维数、截面平均孔径、回转半径以及轴向长度均有明显增加;颗粒孔隙的结构紧密程度下降,随着氧化温度升高,小尺寸孔隙数量逐渐减少,大尺寸孔隙逐渐增加,100℃时的颗粒孔隙尺寸主要分布在6~7 nm,200℃是的颗粒孔隙尺寸主要分布在8~9 nm,400℃的颗粒孔隙尺寸主要分布在12~13 nm,总体上孔隙的尺寸和数量呈上升趋势。利用同步辐射X射线小角散射的方法,掌握颗粒氧化过程中孔隙结构的变化规律,对于丰富颗粒的测量方法提供了借鉴,为完善颗粒的氧化机理提供了相关基础数据。     

高压二氧化碳处理对橙汁货架期的影响(简报)

为了探讨高压CO2加工技术对橙汁货架期的影响,将新鲜的橙汁在温度为37℃,压力60 MPa的高压CO2中处理9 min后,分别在4、15、25和37℃下贮藏,测定果胶甲基酯酶残存相对活性、浑浊度、维生素C残留量和颜色变化。结果表明：在4和15℃下贮藏,橙汁的货架期分别在84和56 d以上;浑浊稳定性比较好;维生素C含量保持在80%以上;在4、15和25℃下贮藏颜色基本上没变化。因此,高压CO2处理橙汁可有效延长产品的货架期,此技术值得在果汁企业中广泛推广。     

枯水期闽江下游水体浑浊空间变化特征及其影响因素分析

采用野外监测与室内分析相结合的方法,对枯水期闽江下游7个断面水质进行分析、研究。结果表明:枯水期闽江下游水体浊度为10.6～330NTU,透明度为0.12～2.22m;悬浮颗粒物含量为2.15～330.2mg/L,其中2μm、2～20μm和20μm分别占5.2%～35.85%、23.2%～76.5%和9.65%～62.6%;溶解氧为3.61～7.78mg/L,叶绿素含量为0.05～3.5μg/L,电导率为152.9～183μs/cm。水体浑浊大体呈现河口高于上游,城区段高于郊区段,感潮段高于非感潮段的空间变化特征。枯水期闽江下游水体浑浊与上游下泄流量减少、潮汐周期性影响、闽江北港段特殊水流形态特征及生活污水排放和局部水土流失等因素有关。研究结果可为闽江下游水质的改善及生态环境保护提供科学依据。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Properties of anaerobically digested and composted municipal solid waste assessed by linking soil mesofauna dynamics and nitrogen modelling

We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.