电子束和γ射线辐照对象拔蚌品质影响的异同性研究

为探明电子束和γ射线辐照对象拔蚌理化指标和微生物影响的异同性,采用不同剂量的电子束(0、2.1、3.9、6.1、8.0 k Gy)和γ射线(0、2.1、4.2、6.3、8.4 k Gy)辐照真空包装象拔蚌,对其贮藏期内营养成分、p H值、生物胺、菌落总数进行测定。结果表明,利用一定剂量电子束和γ射线辐照均能有效降低象拔蚌的菌落总数,在12 d贮藏期内,2种辐照处理之间菌落总数随辐照剂量的变化趋势以及随贮藏天数的变化趋势无显著差异,其中γ射线的D10=3.2 k Gy,电子束的D10=3.1 k Gy;较之对照,电子束和γ射线辐照对象拔蚌蛋白质、灰分、脂肪和水分含量无显著影响;电子束辐照处理组的p H值在贮藏期内维持在6.80~6.94,而γ射线辐照处理组的p H值维持在6.68~6.92,较之对照组,2种射线辐照处理均可抑制贮藏期内象拔蚌p H值的下降;辐照处理组能够抑制生物胺总量的增长,但电子束和γ射线辐照处理之间,象拔蚌生物胺总量随辐照剂量的变化趋势以及随贮藏天数的变化趋势无显著差别。由此可知,电子束与γ射线辐照均具有应用于象拔蚌鲜食食品加工的潜力,这为辐照应用于象拔蚌提供了科学依据。     

酵母提取物辐照灭菌工艺研究

为研究酵母提取物(YE)最高耐受剂量和最低有效剂量,采用不同剂量的60Co-γ射线(0~10k Gy)辐照YE,研究不同剂量对YE的感观品质、氨基酸含量和微生物生存率的影响。结果表明,当辐照剂量为1.5、3.0、4.0k Gy时,TB11、FB00、FA03 3个批次的YE中微生物含量符合企业标准要求;当辐照剂量超过7 k Gy时,YE有明显的辐照异味产生;当辐照剂量低于8 k Gy时,YE的色泽、口感、氨基酸含量与对照(未辐照)相比无明显变化。酵母提取物中细菌D10为0.7 k Gy,最高耐受剂量为7k Gy,产品箱吸收剂量不均匀度为1.69,故酵母提取物辐照灭菌最低有效剂量不得超过4.1 k Gy,应将产品初始含菌量控制在7.6×106CFU·g-1以内。本研究为酵母提取物辐照灭菌工艺的应用提供了工艺参数。     

多项式拟合法设定泡椒猪皮的辐照杀菌工艺剂量

为探讨多项式拟合法对泡椒猪皮产品辐照杀菌工艺剂量的影响,通过四次项函数式和一次线性函数式决定不同工艺剂量并研究其对泡椒猪皮的辐照效应。结果表明,多项式拟合得到的辐照剂量为6.4 k Gy,比D10值法得到的剂量低9.4%。该剂量可作为泡椒猪皮的工艺剂量,能有效杀灭样品中的微生物,更好地保持产品的色泽、形态、香气、包装等感官品质。因此,使用多项式拟合法设定泡椒猪皮的工艺剂量,能在保证产品合格的前提下尽量降低冗余剂量,降低辐照损伤,提高产品品质和辐照生产效率。本研究结果为推广辐照杀菌技术提供了支撑。     

辐照处理提高猪肉火腿肠保鲜效果

辐照是一种非常有效的食品杀菌保鲜技术,近年来在即食肉制品保鲜方面的应用逐渐引起了人们的关注。为了探讨γ辐照技术对猪肉火腿肠的杀菌保鲜效果,试验采用1、3、5、7、9 k Gy 5个剂量分别对火腿肠进行辐照处理,辐照结束后样品在4℃条件下冷藏,然后跟踪测定其在冷藏过程中脂肪和蛋白质氧化、颜色、p H值、挥发性盐基氮(total volatile basic nitrogen,TVB-N)以及菌落总数的变化,分析不同剂量辐照处理对火腿肠保鲜效果的影响。结果表明,辐照可以显著降低火腿肠脂肪和蛋白质的氧化稳定性,促进其在储藏过程中的氧化。1 k Gy剂量辐照对火腿肠的色泽影响不显著;3~9 k Gy剂量辐照,可以使样品的红度值(a*值)显著降低、亮度值(L*值)显著升高(P0.05),而在冷藏过程中a*值与L*值均随储藏时间的延长而降低,且高剂量辐照组要比低剂量组降低更快一些。火腿肠p H值受辐照影响不显著(P0.05),且在冷藏过程中所有处理组火腿肠的p H值变化也不显著,均在6.0~6.5范围内。5 k Gy剂量辐照即可对猪肉火腿肠中的微生物起到有效抑制作用。     

宠物干粮食品辐照杀菌工艺参数的确定

依照国内外学者的研究结果和国际辐照饲料工艺规范的规定,研究了宠物干粮食品辐照杀菌工艺,确定了各项技术指标,并就主要技术指标的确定依据进行了阐述。该技术规定：辐照前宠物干粮食品细菌总数≤5×104 MPN/100g,霉菌≤4.5×104 CFU/g,沙门氏菌≤1×103 CFU/25g,辐照后细菌总数≤1000 CFU/g,大肠菌群≤30 MPN/100g,霉菌≤25 CFU/g,沙门氏菌不得检出,宠物干粮食品辐照杀菌的最低有效剂量为4.0 kGy,最高耐受剂量为15.0 kGy。辐照产品箱中最小吸收剂量应不小于最低有效剂量,最大吸收剂量应不大于产品的最高耐受剂量。     

小龙虾虾肉辐照后理化指标与蛋白质性质分析

为探讨辐照对小龙虾品质的影响,以小龙虾虾肉为试材,冷冻后经5、10、20k Gy剂量辐照处理,研究分析虾肉理化指标(色泽、质构特性、水解氨基酸含量)与蛋白质性质(表面疏水性、蛋白质浓度、相对分子质量)的变化情况。结果表明,冷冻虾肉辐照后色泽指标(L*、a*与b*)均降低,质构特性(硬度、弹性、黏聚性、胶着度与咀嚼度)随着辐照剂量增大而增加。辐照后虾肉中水解氨基酸含量增加,氨基酸总量均高于未辐照样品。当辐照剂量为5 k Gy时,氨基酸含量达到最高值86.23%,虾肉蛋白表面疏水性最大,蛋白质浓度最高,蛋白质相对分子质量主要分布在55 k Da以下。高剂量辐照对虾肉理化性质影响较大,蛋白质相对分子质量显著降低。本研究结果为小龙虾辐照后的品质变化提供了理论参考。     

辐照对食用槟榔的杀菌效果及品质的影响

以食用槟榔为研究对象,研究辐照对其杀菌效果及品质的影响。结果表明:辐照对食用槟榔杀菌效果明显,当辐照剂量为3.65kGy时,食用槟榔的菌落总数由初始的5.8×105CFU·g-1降低到1.1×103CFU·g-1,霉菌数小于10CFU·g-1,大肠菌群数由4.6×102MPN·g-1降低到3 MPN·g-1以下;当辐照剂量为8.45kGy时,菌落总数、霉菌和大肠菌群均未检出。辐照对食用槟榔中水分、灰分、蛋白质和脂肪含量的影响不显著,对总糖、总酚含量和pH值的影响显著。9.77kGy以下的辐照剂量不会对食用槟榔的色泽、气味、滋味与口感及可接受性产生明显的影响。4~10kGy的辐照剂量能够很好的满足食用槟榔产品的卫生要求。     

电子束辐照对三文鱼品质的影响研究

为确定三文鱼电子束辐照的最佳剂量,以生鲜三文鱼为研究对象,采用0(未辐照)、0.5、1.0、2.0k Gy 4种不同剂量的电子束进行辐照处理,贮藏于0℃下,通过检测贮藏过程中鱼体的挥发性盐基氮、菌落总数、酸价、失重率、色差及质构等指标,研究电子束辐照剂量对三文鱼品质及其货架期的影响。结果表明,电子束辐照可以抑制三文鱼挥发性盐基氮的产生和菌落总数的增长,且辐照剂量越大,效果越明显;辐照剂量越大,贮藏初期的酸价越高,但在贮藏期间较未辐照组稳定,无明显的增大趋势;1.0 k Gy和2.0 k Gy剂量使三文鱼颜色变暗,0.5 k Gy较未辐照组差异不显著;贮藏末期,经过辐照的三文鱼的黏附性相对未辐照组小,硬度、弹性以及咀嚼性与未辐照组无显著差异,各剂量之间也无显著差异。综合各指标,0.5 k Gy剂量的电子束可以更好地保持三文鱼的品质。本研究结果为三文鱼的保鲜提供了有效的技术手段和一定的参考依据。     

~(60)Co-γ射线和电子束辐照对冷鲜鸡保鲜效果的异同性研究

为研究~(60)Co-γ射线和电子束辐照对冷鲜鸡微生物含量的影响及肉品品质的异同性,采用2.5k Gy剂量的~(60)Co-γ射线和电子束辐照处理真空包装冷鲜鸡,对其贮藏期内菌落总数、大肠菌群、丙二醛含量、pH值、嫩度、系水力值、挥发性盐基氮(TVB-N)值、色度进行测定。结果表明,γ射线和电子束辐照处理均能显著降低冷鲜鸡菌落总数,大肠菌群均未检出;2种辐照处理组冷鲜鸡的丙二醛含量、pH值、TVB-N值在整个贮藏期内均呈上升趋势;与对照组相比,2种辐照处理组均显著提高了冷鲜鸡的L*值和a*值,且电子束处理组显著高于γ射线组,对照组b*值在同一贮藏期显著高于2种辐照处理组。由此可知,~(60)Co-γ射线和电子束辐照均对冷鲜鸡的微生物含量和肉品品质产生了显著影响,这为辐照技术应用于冷鲜鸡保藏提供了理论依据。     

植物提取物辐照杀菌工艺研究

检测了几种植物提取物中污染微生物的种类和数量 ,研究了当归提取物中污染微生物的D10 值 ,得出植物提取物辐照杀菌工艺的最低有效剂量为 4 0kGy,最高耐受剂量为 8 0kGy。     

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。     

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.     

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,     

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.     

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.     

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,     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.