杜仲叶总多酚超声波-微波辅助提取及其抗氧化活性研究

采用超声波-微波辅助法优化杜仲叶中总多酚提取工艺,并考察其抗氧化活性。通过Plackett-Burman试验考察了乙醇体积分数、料液比、微波功率、微波处理时间、超声波功率和超声波处理时间6个因素对杜仲叶总多酚提取效果的影响,筛选得到乙醇体积分数、料液比、微波功率和超声波处理时间4个显著影响因素,在此基础上,通过最陡爬坡试验和响应面试验得到最佳提取条件为:乙醇体积分数为46%,料液比为1∶20.70(g∶mL),微波功率为154 W,微波处理时间140 s,超声波功率350 W,超声波处理时间为31 min。在此条件下提取2次总多酚得率达8.491%,与传统溶剂提取法相比,总多酚得率提高33.57%。利用最优工艺得到总多酚提取物,其体外抗氧化试验表明:杜仲叶总多酚提取物对1,1-二苯基-2-三硝基苯肼自由基(DPPH·)、2,2-联氮-二-3-乙基-苯并噻唑-6-磺酸自由基(ABTS·)和羟基自由基(·OH)均有较强的清除能力,其半数抑制质量浓度(IC_(50))分别为31.21、24.50和311.8 mg/L,抗氧化活性与BHT相当,低于Vc。     

苦楝素提取方法的比较研究

对比研究了从苦楝树皮中提取苦楝素的几种方法,通过实验,得出了不同提取方法的最佳条件。超临界CO2萃取在萃取温度45℃、压力20MPa、夹带剂为60%乙醇的情况下萃取2h,苦楝素的萃取率为0.850%;微波辅助提取法,以60%乙醇为溶剂,料液比为1∶9(g∶mL,下同),微波功率340W,辐射时间40s×3次,苦楝素的提取率为0.693%;超声波提取法,以60%乙醇为溶剂,料液比为1∶9,超声波作用时间为30min,超声波功率为200W,苦楝素的提取率为0.715%。将上述3种提取方法与传统的有机溶剂提取法进行详细的比较,结果表明:对于苦楝素提取,超声波提取法最好。     

高黎贡山糯橄榄多酚的提取方法改进及工艺优化

以低温烘干的高黎贡山糯橄榄为原料,采用微波辅助对高黎贡山糯橄榄中的多酚类物质进行提取。在单因素试验的基础上,使用正交试验设计考察了微波时间、微波功率、料液比、乙醇浓度等对多酚提取得率的影响。结果表明,最佳提取工艺条件为微波时间30s、微波功率640W、料液比1︰30g/mL、乙醇浓度50%。该研究结果为高黎贡山糯橄榄中多酚的高效提取和工业化生产提供依据。     

微波辅助提取兴安落叶松木材中阿拉伯半乳聚糖的工艺研究

以兴安落叶松(Larix gmelinii Rupr.)木材的加工剩余物为原料,以水为溶剂,微波辅助提取阿拉伯半乳聚糖.通过对影响提取率的主要因素微波作用时间、微波功率、料液比和木粉粒度等进行正交试验,分析得出微波辅助提取阿拉伯半乳聚糖的较佳工艺参数为10.0 g兴安落叶松木粉,微波功率210 W,微波作用时间35 min,料液质量比1∶35,木粉粒度0.2～0.3 mm时, 阿拉伯半乳聚糖提取率17.47 %,比传统水浴浸提法高1.6 %,时间仅为原来的1/10.用红外和紫外光谱分析两种方法所得产物的化学结构相同,微波辅助提取的粗糖中杂质含量比传统水浴法低.实验结果表明,对于兴安落叶松木材中阿拉伯半乳聚糖的提取,微波辅助提取优于传统水浴浸提法.     

桑叶总多酚筛选和分离纯化工艺研究

采用超声波和微波协同提取桑叶总多酚,Folin-Ciocalte法分析不同品种桑叶的总多酚含量,运用单因素试验和响应面法优化提取工艺,并考察不同种类大孔树脂对桑叶总多酚的纯化效果。结果表明,18个品种桑叶中大墨斗的总多酚质量分数最高,达到2.072%;灃24×苗33总多酚质量分数最低,仅为1.035%。湖桑87桑叶总多酚最佳提取工艺为:1 g桑叶粉末,液料比20∶1(mL∶g),提取时间93 s,微波功率326 W,超声波功率304 W,粗提物得率为14.7%,纯度为10.87%。筛选得到的较适合桑叶总多酚纯化的H103树脂的吸附量为15.57 mg/g,解吸率为88.67%,且较短时间内达到吸附平衡与解吸平衡。上样时吸附柱体积40 mL,上样量15 g粗提物,桑叶总多酚的最佳质量浓度为3 g/L,此时最佳洗脱条件为乙醇体积分数60%、洗脱流速2 mL/min、洗脱体积80 mL,此条件下,桑叶总多酚纯度由10.87%提高到65.45%,纯化过程中桑叶总多酚得率为84.7%。     

超声波辅助提取旱柳树叶中的总黄酮

以旱柳落叶为原料,60 % 乙醇(质量分数,下同)为提取剂,芦丁为标准对照品,研究探索了柳叶中总黄酮的溶剂提取法和超声波辅助提取法的最佳提取条件,并对两种提取方法的提取效果进行了比较.试验表明,溶剂提取法的最佳提取条件为:0.3 g柳叶粉末以60 %乙醇为溶剂,料液比1:35(g:mL,下同),65 ℃提取3次,每次75 min,总黄酮得率3.83%;超声波辅助提取的最佳条件为:0.3 g柳叶粉末以60%乙醇为溶剂,料液比1:35,超声波功率400 W,超声波处理3次,每次30 min,总黄酮得率4.26%.超声波辅助提取比单纯的溶剂提取缩短了60 %的提取时间,得率却提高了11.23 %.     

板栗多糖提取工艺的研究

分别采用热水浸提法、超声波辅助提取法两种工艺提取板栗多糖,经乙醇沉淀、Sevage法除蛋白、有机溶剂脱脂后用蒽酮-硫酸比色法测定其含量,通过单因素试验和正交试验确定不同工艺的最佳提取工艺参数.结果表明:1 g板粟粉,热水浸提法提取板栗多糖的最佳条件为提取温度60℃,提取时间1.5 h,液料比20∶1(mL∶g),板栗多...     

微波和超声波辅助提取桃仁油工艺的比较研究

为了提高桃加工副产物的综合利用,以桃仁为原料,采用微波辅助法和超声波辅助法提取桃仁油,通过单因素和正交试验优化了提取工艺,并对桃仁油的理化性质、脂肪酸组成、主要官能团结构、热力学性质及风味进行分析,以比较不同提取方法对桃仁油成分和性质的影响。研究结果表明:10 g桃仁粉,以石油醚(60～90℃)为提取溶剂,微波辅助提取桃仁油的最佳工艺条件为提取时间25min,温度75℃,微波功率400 W,液料比11∶1(mL∶g),此时桃仁油得率为49.23%;超声波辅助提取桃仁油的最佳工艺条件为温度75℃,液料比11∶1(mL∶g),超声波功率500 W,提取时间40min,此时桃仁油得率为48.56%。2种提取方法的桃仁油得率虽然略低于索氏提取的51.87%,但是提取时间明显缩短、提取效率显著提高。同时2种提取方法所得桃仁油的理化性质、脂肪酸组成、官能团结构、热力学性质及风味等与索氏提取法均无显著差异。桃仁油主要含有油酸、亚油酸和棕榈酸等,其中油酸和亚油酸GC含量最高,二者之和达93%以上。     

油茶籽多酚微波辅助提取响应面法的优化

多酚是油茶籽中重要的活性成分。研究其组成、提取工艺和活性,对于优质茶油的生产具有重要意义。在单因素试验的基础上,采用响应面法就微波辅助提取油茶籽多酚进行了优化试验,优化了提取工艺参数。结果表明:微波功率、微波提取时间、料液比这3个因素对油茶籽多酚提取效果的影响均达到了显著水平;微波功率与微波提取时间、微波功率与料液比、微波提取时间与料液比之间的交互作用显著。利用DesignExpert7.1软件分析得出的油茶籽微波提取的最佳工艺参数为:微波功率,800W;提取时间,35s;料液比为1︰16。在此条件下,用回归模型预测的油茶籽多酚的提取量为19.60mg·g-1,实际测得值为19.02mg·g-1,相对误差为3%。与传统溶剂提取法相比,微波提取法具有时间短、效果好的特点。     

微波辅助提取兴安落叶松木材中阿拉伯半乳聚糖的工艺研究

以兴安落叶松(Larix gmelinii Rupr．)木材的加工剩余物为原料．以水为溶剂，微波辅助提取阿拉伯半乳聚糖。通过对影响提取率的主要因素微波作用时间、做波功率、料液比和木粉粒度等进行正交试验．分析得出微波辅助提取阿拉伯半乳聚糖的较佳工艺参数为10．0g兴安落叶松木粉。微波功率210W。微波作用时间35min。料液质量比1：35．木粉粒度0．2～0．3mm时．阿拉伯半乳聚糖提取率17．47％。比传统水浴浸提法高1．6％，时间仅为原来的1/10。用红外和紫外光谱分析两种方法所得产物的化学结构相同。微波辅助提取的粗糖中杂质含量比传统水浴法低。实验结果表明．对于兴安落叶松木材中阿拉伯半乳聚糖的提取．微波辅助提取优于传统水浴浸提法。     

Growth of Phlebiopsis gigantea in wood of seven conifer species

Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered.     

Growth of Mixed Birch-Coniferous Stands in Relation to Pure Coniferous Stands at Similar Sites in South-eastern Norway

Mean age, mean and top heights and yield were studied in 20 mixed stands of birch ( Betula pubescens Ehrh. and B. pendula Roth) and Picea abies (L.) Karst. and nine mixed stands of birch and Pinus sylvestris L. in south-eastern Norway. Each mixed stand and the adjacent pure coniferous stand (control) were growing under the same site conditions and had not been commercially thinned. There were no significant differences in mean age at breast height or in top heights between birch and conifers in the mixed stands, while mean height was significantly higher for birch than for spruce. A growth index was calculated based on total volume and age at breast height. For the spruce sites the growth in young mixed stands (birch < 17 m) was superior to that of pure spruce, while the difference was insignificant in older stands. The growth index correlated positively with the ratio between generatively and vegetatively regenerated birch trees, and negatively with the age of the oldest species in the mixture and with site quality. For the pine sites there was no significant difference in the growth index between mixed birch-pine and pure pine stands. A mixture effect of birch on the volume yield of spruce or pine could not be demonstrated.     

Defoliation by the Needle-shortening Pine Gall Midge,Thecodiplosis brachyntera,on Pines in Central Sweden

An outbreak of the needle-shortening pine gall midge, Thecodiplosis brachyntera , occurred on Scots pine, Pinus sylvestris (L.) and lodgepole pine, P. contorta (Dougl.) in central Sweden during 1995-1998. The larval feeding of T. brachyntera kills current-year needles and heavy infestation causes severe defoliation. A pattern of fluctuating defoliation among years and sites was found on both pine species. Defoliation was evenly distributed in the crown of P. sylvestris during years of high as well as low infestation; apical whorls had as much defoliation as basal whorls. In P. contorta , however, there was a tendency for defoliation to be concentrated on branches in the most apical whorls. Growth ring increments on P. sylvestris with high levels of defoliation (71%) did not differ from trees with moderate levels (26%) of defoliation. Shoot lengths were significantly shorter, however, on heavily infested trees the year after defoliation.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week⁻¹ for leaves and from 0.0225 to 0.0633 week⁻¹ for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient enrichment capacity and slower decomposition rates which would minimize leaching losses. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions.     

Modelling of adequate pretwist for obtaining straight timber

Abstract

Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral contents and B₁ and B₂ vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B₁ 88 mg 100 g⁻¹, B₂ 187 mg 100 g⁻¹, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations.     

Biogeochemical impacts of clearfelling and reforestation on blanket-peatland streams: II. major ions and dissolved organic carbon

Streams and drains in blanket-peatland forest in western Ireland were sampled weekly over 5 years, 1996–2000, using continuous, depth-proportional passive sampling. Analysis was for pH, alkalinity by Gran titration, anions by IC, metals by ICP, aluminium speciation by loaded-resin exchange, and dissolved organic carbon (DOC) by absorbance at 320 nm.

Effects of felling are identified graphically from two forest drains whose catchments (both about 1 ha) were clearfelled, and partial clearfelling of one larger catchment (somewhat over 1 km²), in summer 1999. Calcium concentrations and alkalinity were increased in the drain- and streamwater from the felled areas. The pH was increased in drains, while in the larger stream, pH range decreased while the mean increased. Phosphorus increased markedly with clearfell, in the absence of recent fertilising, and also increased with fertilising; these results are reported in an accompanying paper. Ammonium-nitrogen concentrations were increased in the two drains with felling, and temporarily decreased in the larger stream. Nitrate increased in some cases. Potassium and manganese concentrations also increased. Concentrations of DOC and organic monomeric aluminium increased gradually, subject to a continuing strong annual cycle. There were no clearfelling effects on concentrations of solphate, suspended solids or inorganic monomeric aluminium. In the two drains (fully clearfelled), concentrations of sodium, chloride and magnesium, and conductivity, were all reduced after felling. Fertilising effects other than for phosphorus were indistinct.

Effects of the combined clearfell–reforestation treatment were testable statistically, using randomised intervention analysis, between two larger streams (1 km²) as a treatment–control comparison. There were statistically significant positive responses in streamwater concentrations of nitrate, potassium, calcium, DOC and aluminium fractions. The implications for management practice depend on whether the loss of nutrients is sustainable for future crop productivity, and whether critical limits and loads of receiving ecosystems are exceeded.     

Effect of Drought on Growth and Mortality of Actively Growing Norway Spruce Container Seedlings Planted in Summer

Survival, root egress and height growth of 13-month-old actively growing Norway spruce ( Picea abies (L.) Karst.) container seedlings exposed to preplanting drying treatments (0, 4, and 8 days) and postplanting drought periods (1, 2, 3, and 4 weeks) were studied in the field between 5 July and 18 August 1999. The mortality of seedlings increased and the height growth and root egress decreased throughout the postplanting drought period. Postplanting performance was also affected by preplanting drying treatments. The results indicate that no risk of excessive mortality and growth restrictions occurs when actively growing seedlings are planted in summer, provided that seedlings are well watered before planting and the drought period does not exceed 3 weeks.     

Rehabilitation of diseased cacao fields in Peru through shade regulation and timing of biocontrol measures

The objective of this case study was to test the effectiveness of biocontrol for the rehabilitation of abandoned, diseased (moniliasis, witches' broom and black pod) cocoa and to develop testable hypotheses regarding the effect of shade and biocontrol timing. Three trial fields differed in their shade regimes. Biocontrol was administered starting either at flowering or pod filling. Disease incidence and yield were compared with cultural control alone. Biocontrol reduced moniliasis from 49% to 25%, independent of the shading regime and application time. Witches' broom was most severe without shade and unaffected by biocontrol. No significant effects on black pod were observed. Although biocontrol increased percentage healthy fruit independent of shading and timing, only the shaded plot with biocontrol from flowering onwards responded with increased yield. Our hypothesis is: 'In the rehabilitation of abandoned cacao, only fields under sustainable shade management and early onset of biocontrol can realise their production potential.' This revised version was published online in June 2006 with corrections to the Cover Date.