Activity and process stability of purified green pepper (Capsicum annuum) pectin methylesterase     

Castro SM  Van Loey A  Saraiva JA  Smout C  Hendrickx M 《Journal of agricultural and food chemistry》2004,52(18):5724-5729

Pectin methylesterase (PME) from green bell peppers (Capsicum annuum) was extracted and purified by affinity chromatography on a CNBr-Sepharose-PMEI column. A single protein peak with pectin methylesterase activity was observed. For the pepper PME, a biochemical characterization in terms of molar mass (MM), isoelectric points (pI), and kinetic parameters for activity and thermostability was performed. The optimum pH for PME activity at 22 degrees C was 7.5, and its optimum temperature at neutral pH was between 52.5 and 55.0 degrees C. The purified pepper PME required the presence of 0.13 M NaCl for optimum activity. Isothermal inactivation of purified pepper PME in 20 mM Tris buffer (pH 7.5) could be described by a fractional conversion model for lower temperatures (55-57 degrees C) and a biphasic model for higher temperatures (58-70 degrees C). The enzyme showed a stable behavior toward high-pressure/temperature treatments.  相似文献   

Aroma quality differentiation of pyrazine derivatives using self-organizing molecular field analysis and artificial neural network   总被引：2，自引：0，他引：2  

Klocker J  Wailzer B  Buchbauer G  Wolschann P 《Journal of agricultural and food chemistry》2002,50(14):4069-4075

The encoding of various aroma impressions and the distinction between different aroma qualities are unsolved problems, as differences between aroma impressions can be described only in a qualitative but not in a quantitative manner. As a consequence, classifications of various aroma qualities cannot easily be performed by standard QSAR methods. To find a proper way to encode aroma impressions for SAR studies, a total of 50 pyrazine-based aroma compounds showing the aroma quality of earthy, green-earthy, or green are analyzed. Special attention is thereby turned on the mixed aroma impression green-earthy. Classifications on the whole data set as well as on smaller subsets are calculated using self-organizing molecular field analysis (SOMFA) and artificial neural networks (ANNs). SOMFA classifies between two or three aroma impressions, leading to models satisfying in predictive power. ANN analysis using multilayer perceptron network architecture with one hidden layer and nominal output as well as genetic regression neural network) with two hidden layers and numerical output both lead to a rather good performance rate of 94%.  相似文献   

Nutrition education for illiterate children in southern Madagascar--addressing their needs, perceptions and capabilities     

Mahr J  Wuestefeld M  Ten Haaf J  Krawinkel MB 《Public health nutrition》2005,8(4):366-372

OBJECTIVE: A Knowledge, Attitudes and Practices (KAP) study was conducted in three villages of Bekily District in southern Madagascar prior to the implementation of a health education programme with children. The participatory learning concept of the Child-to-Child approach was followed to involve the children in the planning and implementation of the programme, which was covered by the German Agency for Technical Cooperation. DESIGN: To this effect, qualitative research methods such as Participatory Learning and Action techniques (focus group discussions, mapping and matrix ranking, etc.) were applied. SUBJECTS: The survey was conducted between August and December 1999. It involved a total of 55 school-aged children (6-14 years) along with 21 mothers and 34 fathers, representing different ethnic groups and educational backgrounds. RESULTS: The results show that children's KAP related to health and nutrition strongly reflect those of adults. They are not aware of a possible link between bad hygiene and the occurrence of diseases. According to them, diarrhoea or malaria is caused by consuming too large amounts of certain foods. Even if they know about certain elementary hygiene behaviours, they do not practise this in their everyday life. CONCLUSION: A major objective of the health education programme for children should be to tackle the discrepancy between hygiene-related knowledge and behaviour. Through the participatory study approach the children revealed their ability to contribute to the programme development. In using appropriate communication channels, the Child-to-Child health education programme is expected to influence the health behaviours of both adults and children. The health education programme should be combined with a literacy programme to address the children's desire to learn reading and writing.  相似文献   

Endomycorrhizae in a newly cultivated acidic meadow: Effects of three years of barley cropping,tillage, lime,and phosphorus on root colonization and soil infectivity   总被引：2，自引：0，他引：2  

Chantal Hamel  Yolande Dalpé  Claude Lapierre  Régis R. Simard  Donald L. Smith 《Biology and Fertility of Soils》1996,21(3):160-165

The dynamics of mycorrhizae under disturbance created by crop production is not well understood. A 3-year experiment was undertaken on a nutrient-poor and acidic land that had last been cultivated in the early 1970s. We observed the effects of cropping spring barley (Hordeum vulgare L.) under four P-fertilizer levels and four levels of lime, in a minimum (rototillage), a reduced (chisel), or a conventional tillage system, on the mycorrhizal receptiveness of the host (maximum level of mycorrhizal colonization, as measured at harvest) and soil infectivity most probable number method. The host receptiveness decreased with time, while crop yields and soil infectivity increased simultaneously with time. Liming increased mycorrhizal colonization of barley roots and soil infectivity. P additions decreased root colonization but did not significantly affect the most probable number valuse. Slightly higher soil infectivity estimates were found under reduced tillage.  相似文献   

Erfassung der Mineralstoffverteilung in Wurzelnähe durch getrennte Analyse von Rhizo- und Restboden     

L. Hendriks  A. Jungk 《植物养料与土壤学杂志》1981,144(3):276-282

Estimation of the nutrient distribution around plant roots by separate analysis of rhizo and bulk soil A procedure is described to separate rhizo soil from bulk soil. For this purpose the living plant roots along with the strongly adhering soil are taken out of the surrounding soil. After a short period of drying, roots are separated from rhizo soil by gently sifting. Chemical analysis of the samples has shown that the nutrient content of rhizo soil usually differs markedly from bulk soil. Phosphate and potassium content of the rhizo soil of wheat and maize is lower than in bulk soil. Percentagewise, these differences are higher by using water as an extractant when compared to the slightly acid lactate or formate solutions. The water soluble calcium content of several wheat fields was in most cases higher in the rhizo than in the bulk soil. In sandy soil the depletion zone of phosphate does not exceed the length of the root hairs markedly whereas in the case of potassium it does. This is concluded from data showing that the potassium content, but not the phosphate content, was decreased in the bulk soil if compared to the uncropped soil. In heavier loess soils the nutrient concentrations of rhizo and bulk soil were not always found to be markedly different. It is assumed that the depletion zones are smaller than in sandy soils. In addition, because of aggregation, rhizo soil cannot be separated from bulk soil as neatly as in sandy soils. Therefore, in heavier soils the method does not yield satisfactory results.  相似文献   

Comparison of the chemical composition of extracts from Scutellaria lateriflora using accelerated solvent extraction and supercritical fluid extraction versus standard hot water or 70% ethanol extraction     

Bergeron C  Gafner S  Clausen E  Carrier DJ 《Journal of agricultural and food chemistry》2005,53(8):3076-3080

The aqueous extract of American skullcap (Scutellaria lateriflora L. (S. lateriflora), Lamiaceae) has been traditionally used by North American Indians as a nerve tonic and for its sedative and diuretic properties. Recent reports stated that flavonoids and possibly amino acids are responsible for the anxiolytic activity. As a part of our search for environmentally friendly solvents to extract the active components from medicinal plants, we used S. lateriflora in a comparison of accelerated solvent extraction (ASE) using water, and supercritical fluid extraction (SFE) using CO2 and 10% EtOH as modifier, at different temperatures. Flavonoids and amino acids were quantified by HPLC-UV and HPLC-MS, respectively. The flavonoid content was compared with conventional extraction methods (hot water extraction and 70% ethanol). The use of ASE at 85 degrees C with water as solvent gave the best results for flavonoid glycosides and amino acids, whereas SFE gave higher yields of flavonoid aglycones. However, the results obtained for total flavonoids were not significatively superior to hot water extraction or 70% aqueous EtOH extract.  相似文献   

Degradation pathway of dicyclanil in water in the presence of titanium dioxide. Comparison with photolysis     

Goutailler G  Guillard C  Faure R  Païssé O 《Journal of agricultural and food chemistry》2002,50(18):5115-5120

The solar photolytic behavior of the pesticide 4,6-diamino-2-cyclopropyl-pyrimidine-5-carbonitrile, currently known as dicyclanil, has been mimicked in a photoreactor operating with an artificial light flux. The rate and pathway of degradation were performed. An additional study, using TiO(2) photocatalysis, has been achieved in order to determine the efficiency of photocatalysis to degrade the molecule. The catalyst was titania Degussa P-25. The aim of this article was the identification of the intermediate products formed during the irradiation, to establish the degradation pathway of dicyclanil. The kinetics of the reactions were followed by liquid chromatography with a diode array detector (LC-DAD). Most of the organic compounds occurring during the photodegradation have been identified by means of liquid chromatography and mass spectrometry coupled techniques (HPLC-MS). Additional analyses were carried out to evaluate the mineralization rates into nitrate and ammonium ions.  相似文献   

The metabolism of [14C]aldicarb in the root of sugar beet plants     

Jean Rouchaud  Chantal Moons  Joseph A. Meyer 《Pest management science》1981,12(5):548-556

Sugar beet plants were grown in the field, after in-furrow application of [¹⁴C]- aldicarb (3 kg of aldicarb ha^?1) at planting. The ripe sugar beet plants were harvested, and the roots were analysed. The roots were fractionated according to a procedure similar to the normal beet-sugar manufacturing process. Expressed as a proportion of the total radioactivity incorporated into the root, the pulp contained 29.7%, the lime cake 9.7%, the crystallised sugar 17.7% (which gave, with the radioactivity found in the sugar in the molasses, a total of 20.7% of the radioactivity in the total sugar), and the molasses, 42.9%. A part of the labelled carbon from the radio- active aldicarb and its metabolites had thus been metabolised and incorporated into sugar molecules. Except for the radioactivity in the sugar and in the lime cake from the processing, the proportion of radioactive non-conjugated organosoluble compounds was very low (2.6%), and perhaps partially corresponded to the very low amount of aldoxycarb (aldicarb sulphone) in the root (less than 0.001 mg of [¹⁴C]-aldicarb equivalents kg^?1 fresh weight). Hydrolysis of the molasses yielded free radioactive 2-methyl-2-(methylsulphinyl)propan-1-ol (3.1%), 2-mesyl-2-methyl-propan-I-ol (8.9%) and 2-mesyl-2-methylpropionic acid (12.0%) which had been conjugated to plant constituents in the root. The corresponding concentrations (expressed as mg of [¹⁴C]aldicarb equivalents kg^?1 fresh weight of root) were 0.004, 0.011, and 0.016, respectively. No aldicarb, aldicarb sulphoxide or aldoxycarb (nor the corresponding nitrile, generated from aldicarb during the fractionation procedure) was liberated by the hydrolysis, indicating the absence of conjugates of these compounds in the root.  相似文献   

The Dutch elm disease Summary of fifteen years hybridisation and selection work (1937–1952)     

Dr Johanna C. Went 《European journal of plant pathology / European Foundation for Plant Pathology》1954,60(2):109-127

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The effect of temperature on formation and abortion of flower buds in gynoecious cucumber plants     

Johanna L.F. van der Vlugt 《Scientia Horticulturae》1983,20(4):323-328

Plants were grown at 15, 21 or 27°C. Fewer buds were formed at high than at low temperature. At all 3 temperatures, some of the buds aborted. However, the differences in numbers of buds between temperatures did not disappear. Transfer of the plants from 27 to 21°C did not raise the number of buds formed in nodes of which the leaf primordia had already been formed. Therefore, it is plausible that the number of flower buds is determined at a very early stage of node development.  相似文献