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排序方式: 共有400条查询结果,搜索用时 31 毫秒
1.
Andreas Gruber Jolanda Zimmermann Gerhard Wieser Walter Oberhuber 《Annals of Forest Science》2009,66(5):503-503
2.
Helmut Saucke Britta Schultz Rainer Wedemeyer Nadine Liebig Olaf Zimmermann Peter Katz 《Gesunde Pflanzen》2011,63(4):183-189
The cabbage whitefly,Aleyrodes proletella, has developed to a key pest in brassica vegetable crops throughout Germany. In a 3-year project we investigated a biotechnical approach employing netting (0.8?×?0.8 mm meshsize) in combination with the native parasitoidEncarsia tricolor in an inoculative-inundative approach in organic Brussels sprouts under field conditions. In small scale plot experiments continuous netting from transplanting in May till October alone reduced whitefly larval densities by 77 % at peak infestation in all years. Remaining whitefly infestation under net was associated with the necessity of temporary net removal for the purpose of mechanical weeding, which caused primary whitefly infestation. Release of mass rearedE. tricolour under net at the first signs of larval infestation significantly increasedA. proletella-parasitation and reduced infestation compared to netted controls without release. Furthermore, at highest dosage in 2009,E. tricolor had a significant enhancing effect on raw yield and the quality level of marketable yield. Additional on-farm experiments without netting in 2008 and 2009 confirmed the control potential ofE. tricolor. Although the most important project mile stones have been achieved, namely (a)E. tricolour-establishment under net and in the open field, (b) enhanced parasitation corresponding with pest density decline and (c) a positive impact on yield and quality parameters, further research will be necessary. The focus should be on the initial infestation period, optimizing the timing, frequency and required dosage. 相似文献
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4.
Bellion P Hofmann T Pool-Zobel BL Will F Dietrich H Knaup B Richling E Baum M Eisenbrand G Janzowski C 《Journal of agricultural and food chemistry》2008,56(15):6310-6317
Apples represent a major dietary source of antioxidative polyphenols. Their metabolic conversion by the gut microflora might generate products that protect the intestine against oxidative damage. We studied the antioxidant effectiveness of supernatants of fermented apple juice extracts (F-AEs, 6 and 24 h fermentation) and of selected phenolic degradation products, identified by HPLC-DAD-ESI-MS. Cell free antioxidant capacity of unfermented apple juice extracts (AEs) was decreased after fermentation by 30-50%. In the human colon carcinoma cell line Caco-2, F-AEs (containing <0.5% of original AE-phenolics) decreased the reactive oxygen species (ROS) level more efficiently than the F-blank (fermented without AE) but were less effective than the respective AEs. Similarly, antioxidant effectiveness of individual degradation products was lower compared to respective AE constituents. Glutathione level was slightly increased and oxidative DNA damage slightly decreased by fermented AE03, rich in quercetin glycosides. In conclusion, F-AEs/degradation products exhibit antioxidant activity in colon cells but to a lesser extent than the respective unfermented AEs/constituents. 相似文献
5.
An analytical approach for the detection and quantification of cocoa butter equivalents (CBEs) in milk chocolate is presented. It is based on (i) a comprehensive standardized database covering the triacylglycerol composition of a wide range of authentic milk fat (n=310), cocoa butter (n=75), and CBE (n=74) samples and 947 gravimetrically prepared mixtures thereof, (ii) the availability of a certified cocoa butter reference material (IRMM-801) for calibration, (iii) an evaluation algorithm, which allows a reliable quantification of the milk fat content in chocolate fats using a simple linear regression model, (iv) a subsequent correction of triacylglycerols deriving from milk fat, (v) mathematical expressions to detect the presence of CBEs in milk chocolate, and (vi) a multivariate statistical formula to quantify the amount of CBEs in milk chocolate. The detection limit was 1% CBE in chocolate fat (0.3% CBE in milk chocolate, having a fat content of 30%). For quantification, the average error for prediction was 1.2% CBE in chocolate fat, corresponding to 0.4% in milk chocolate (fat content, 30%). 相似文献
6.
The most important active compound in garlic is alliin. Sulfur (S) fertilization was shown to significantly increase the alliin concentration in garlic cloves, while high nitrogen (N) levels had an adverse effect. The effect of graded N and S application on the storage life of garlic has been paid little attention so far. A bifactorial field trial with 4 levels of N and S was conducted in a randomized block design. At harvest, 40 bulbs per treatment were stored under terms comparable to the storage conditions in average households (20 °C, dry, and dim) for 83 days. Every 3 weeks, samples were analyzed for their alliin and water content. The alliin concentration in peeled garlic cloves increased during storage from on average 9.2 mg g(-1) dry weight at harvest to 21.4 mg g(-1) dry weight after 83 days of storage. S fertilization increased the alliin concentration by a factor of 2.3 from 11.4 mg g(-1) in the control treatment to 26.6 mg g(-1) dry weight at the highest S level of 45 kg ha(-1) after 83 days of storage. N fertilization decreased by a trend of the alliin content. Fertilizer rates had only a minor influence on water losses from bulbs at short-term storage. After 83 days of storage, water losses were by trend lower at higher S levels, and this relationship proved to be significant when no N was applied. Best quality in terms of high alliin contents was obtained during the entire storage time at an S level of at minimum 30 kg ha(-1) S if no N was applied. The results show that the physiological S demand of 15 kg ha(-1) S for optimum yield is lower than the S requirement of 30 kg ha(-1) S for a longer storage life. 相似文献
7.
Dorfner R Ferge T Kettrup A Zimmermann R Yeretzian C 《Journal of agricultural and food chemistry》2003,51(19):5768-5773
The formation of 4-vinylguaiacol, guaiacol, and phenol during coffee roasting was monitored in real-time, using resonance enhanced multiphoton ionization and time-of-flight mass spectrometry. A model is proposed, based on two connected reaction channels. One channel, termed the "low activation energy" channel, consists of ester hydrolysis of 5-FQA followed by decarboxylation of the ferulic acid to form 4-vinylguaiacol, and finally polymerization at the vinyl group to form partly insoluble polymers (coffee melanoidins). The second "high activation energy" channel opens up once the beans have reached higher temperatures. It leads to formation of guaiacol, via oxidation of 4-vinylguaiacol, and subsequently to phenol and other phenolic VOCs. This work aims at developing strategies to modify the composition of coffee flavor compounds based on the time-temperature history during roasting. 相似文献
8.
Aguilar-Cisneros BO López MG Richling E Heckel F Schreier P 《Journal of agricultural and food chemistry》2002,50(26):7520-7523
By use of headspace SPME sampling and a PLOT column, on-line capillary gas chromatography-isotope ratio mass spectrometry was employed in the combustion (C) and the pyrolysis (P) modes (HRGC-C/P-IRMS) to determine the delta(13)C(VPDB) and delta(18)O(VSMOW) values of ethanol in authentic (n = 14) and commercial tequila samples (n = 15) as well as a number of other spirits (n = 23). Whereas with delta(13)C(VPDB) values ranging from -12.1 to -13.2 per thousand and from -12.5 to -14.8 per thousand similar variations were found for 100% agave and mixed tequilas, respectively, the delta(18)O(VSMOW) data differed slightly within these categories: ranges from +22.1 to +22.8 per thousand and +20.8 to +21.7 per thousand were determined for both the authentic 100% agave and mixed products, respectively. The data recorded for commercial tequilas were less homogeneous; delta(13)C(VPDB) data from -10.6 to -13.9 per thousand and delta(18)O(VSMOW) values from +15.5 to +22.7 per thousand were determined in tequilas of both categories. Owing to overlapping data, attempts to differentiate between white, rested, and aged tequilas within each of the two categories failed. In addition, discrimination of tequila samples from other spirits by means of delta(13)C(VPDB) and delta(18)O(VSMOW) data of ethanol was restricted to the products originating from C(3) as well as C(4)/CAM raw materials. 相似文献
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10.
Farmers in Ghana use a variety of soil‐fertility management practices to optimize the benefits of shifting cultivation and/or to intensify their production. The research question was to analyze the relationship between these practices and the availability of the production factors land, labor, and capital. A farm survey along a gradient through SW Ghana showed that there is only a weak link between the intensification of traditional farming systems, population pressure, and reduced fallow periods as long as shifting cultivation is possible and common. Even where fallow periods reach a cut‐off point, farmers might look for land in remoter areas or invest in off‐farm activities. Only where market proximity supports the production of high‐value crops, investment flows are used to maintain continuous cultivation on favorable production sites, especially those with water access. The results verify the validity of the framework of agricultural‐systems dynamics in W Africa, developed by the International Institute of Tropical Agriculture (IITA) and the importance to distinguish between population‐driven and market‐driven situations. Both meet in periurban areas, which make them hot spots for research and development, while support for intensification is likely to fail where markets are far and shifting cultivation still an option. 相似文献