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1.
Enantiomeric compositions of chiral terpenes in commercial fruit beverages were examined by solid phase microextraction-gas chromatography (SPME-GC). Optimization of the method was accomplished on the basis of some parameters involved in the extraction, such as heating temperature and extraction time, that provided the highest peak areas, 60 degrees C and 2 min being the optimal values. With the proposed method relative standard deviation (RSD) values from three replicates ranging from 2 to 12% were obtained. The enantiomeric distribution of some terpenes remained constant, whereas other terpenes (linalool, terpinen-4-ol, and alpha-terpineol) exhibited a considerable variation among samples. This can be indicative of the eventual addition of aromas to some fruit beverages.  相似文献   

2.
Olive oil, a traditional food product with thousands of years of history, is continually evolving toward a more competitive global market. Being one of the most studied foods across different disciplines, olive oil still needs intensive research activity to face some vulnerabilities and challenges. This perspective describes some of them and shows a vision of research on olive oil for the near future, bringing together those aspects that are more relevant for better understanding and protection of this edible oil. To accomplish the most urgent challenges, some possible strategies are outlined, taking advantage of the latest analytical advances, considering six areas: (i) olive growing; (ii) processing, byproduct, and environmental issues; (iii) virgin olive oil sensory quality; (iv) purity, authentication, and traceability; (v) health and nutrition; (vi) consumers. The coming research, besides achieving those challenges, would increase the understanding of some aspects that are still the subject of debate and controversy among scientists focused on olive oil.  相似文献   

3.
alpha-Amylases from different origins (wheat, malted barley, fungi, and bacteria) are used extensively to improve breadmaking. However, the enzyme activities, in addition to the differences associated with their origins, are strongly affected by the process conditions and the presence of other compounds in the medium. The activity of different alpha-amylases was tested under different conditions (pH and temperature), and in the presence of some bread ingredients (salt and sugar), some breadmaking additives (ascorbic acid and sodium propionate), and some metabolites (organic acids and saccharides) generated during the fermentation step, to envisage the behavior of these alpha-amylases during the breadmaking process. The alpha-amylase activities were affected to a different extent by the addition of these compounds depending on the enzyme origin. In general, the alpha-amylases from cereals (wheat and malted barley) were less sensitive to the presence of some ingredients, additives, and metabolites. These results show the great variation of the alpha-amylase activity with the process conditions and the importance of its knowledge in the selection of the appropriate alpha-amylase for a specific breadmaking process.  相似文献   

4.
Tea catechins exert many biological effects, including anticancer and antibacterial activities. Also, it is reported that some plant flavonoids exhibit estrogenic activity. In this study, we investigated estrogenic or antiestrogenic activities of catechins in HeLa cells transiently transfected with an estrogen response element (ERE)-regulated luciferase reporter and an estrogen receptor (ER) alpha or ERbeta expression vector. Catechins alone did not induce luciferase (luc) activity in either of the ERs. Addition of 17beta-estradiol (E2) plus epicatechin gallate (ECG) or epigallocatechin gallate (EGCG) at 5 x 10(-6) M resulted in significant decreases in the ERalpha-mediated luc activity compared with that of E2 alone. On the contrary, lower concentrations significantly increased the E2-induced luc activity. Similar effects were observed with tamoxifen. The ERbeta-mediated estrogenic activities were stimulated by catechins. In conclusion, some catechins, particularly EGCG, were antiestrogenic for ERalpha at higher doses, and co-estrogenic for ERalpha at lower doses and for ERbeta. The lower doses were found in human plasma after tea-drinking. In addition, some catechins may be antiendocrine disruptors because they suppressed bisphenol A-induced luc activities.  相似文献   

5.
该文论述了规划设计在水土保持工作中的重要性。认为在新的形势下，应重点抓好以下几方面的规划工作：１．搞好区域规划和小流域综合治理开发规划；２．搞好监督规划；３．搞好城市水土保持规划；４．搞好水土保持产业和行业脱贫致富规划。同时，笔者还对建立水土保持规划设计体系，搞好水土保持规划设计谈了具体意见，并指出：在规划设计中应注意的几个问题。  相似文献   

6.
ABSTRACT

This article briefs agricultural librarians on three key aspects of Colony Collapse Disorder (CCD), a disease involving the virtually total disappearance and presumed annihilation of the adult bee population of hives: (1) the yearly multibillion dollar importance of honeybees as the nation's key crop pollinators and the annual $200 million domestic production and export of honey; (2) the more common bee diseases and well-known hive stressors that current theories of CCD suggest interact with each other in some as yet undetermined combination, perhaps including new pathogens to which most American bees have limited or no immunity; and (3) several bees other than the honeybee that are not currently affected by CCD and that have some potential as partial substitute pollinators for some crops.  相似文献   

7.
The experiments of the United Nations/Economic Commission for Europe (UN/ECE) International Cooperative Programme on effects of air pollution and other stresses on crops and non-wood plants (ICP-Crops) are designed to investigate the effects of ambient ozone pollution on crops and non-wood plants. Each year, participants from approximately 17 European countries conduct a series of coordinated experiments to determine which species develop visible injury following ozone episodes and whether the biomass or yield of sensitive species is reduced. In 1993, ozone injury was only seen at two thirds of sites but in 1994 injury was detected at almost all sites. This coincides with generally higher ozone concentrations measured in that year. Injury was seen on crops including subterranean clover (Trifolium subterraneum L.), white clover (Trifolium repens L.), bean (Phaseolus vulgaris L.), tomato (Lycopersicon esculentum), soybean (Glycine max), watermelon (Citrullus lanatus) and tobacco (Nicotiana tabacum L.) at experimental sites and in some cases, in commercial fields. The application of ethylenediurea (EDU) to some crop species reduced the level of visible injury. At some sites, the yield of EDU-treated bean plants was greater than that of untreated plants where the critical level of ozone for yield reduction was exceeded. Preliminary analysis of ozone concentrations in the days preceding injury indicated a sequential ozone concentration effect. The results are discussed in relation to Level I and Level II mapping of exceedance of the short- and long-term critical levels for ozone.  相似文献   

8.
The generation of pyrazinium radical cations during the early stages of the Maillard reaction has been previously demonstrated. In this study, the effect of food phenolic compounds [4-methylcatechol (4-MeC), (+)-catechin (CAT), and (-)-epigallocatechin-3-gallate (EGCG)] on the fate of these intermediates in Maillard model systems was investigated. Aqueous solutions containing either glyoxal + alanine (GO-A) or glycolaldehyde + alanine (GA-A) were treated with a concentration gradient of each phenolic compound, and quantitative analysis of the resulting pyrazinium radicals in these models was performed using electron paramagnetic resonance (EPR) spectroscopy. CAT and EGCG were observed to affect pyrazinium radical generation rates, in some cases either enhancing or suppressing formation depending on concentration, whereas the simple catechol (4-MeC) had no such effect. A mechanistic study was carried out by LC-MS, which suggested that under some conditions, CAT and EGCG react with imine intermediates via their A-rings, thus influencing the formation of the enaminol radical precursor and, ultimately, pyrazinium radicals. To the authors' knowledge, this is the first study demonstrating imine trapping by phenolic compounds under Maillard conditions and how such phenolic quenching reactions can alter pyrazinium radical formation.  相似文献   

9.
The effects of sewage pollution on the distribution and abundance of some orgnanisms over a period of 4 mo at the Ahmadu Bello University Main Campus sewage treatment plant and Kubanni river were studied. Physico-chemical parameters such as dissolved oxygen; temperature; hydrogen ion concentration (pH); electrical conductivity and chemical oxygen demand influenced by pollution were measured with respect to the population of aquatic organisms. The organisms were used as biological indices to monitor the ecological imbalance caused by the effluent. The variations in concentrations of some heavy metals were also measured. The studies revealed that at the source of pollution there were no organisms except for some insect larva such as Eristalis, Psychoda, and some microscopic algae like Oscillatoria, Anaebaena, and Polysystis. A location (site 5) on Kubanni river just before the confluence of the sewage effluent and the river was taken as the control. There was a wide variety of organisms (crustaceans, rotifers, and fish) at the control point.  相似文献   

10.
The use of solvent-assisted flavor evaporation extraction (SAFE) and purge and trap in Tenax allowed the identification of more than 100 volatile compounds in a sponge cake (SC-e). Gas chromatography-olfactometry (GC-O) of the SAFE extracts of crumb and crust were achieved in order to determine the most potent odorants of SC-e. The change in the traditional dough formulation of SC-e in which eggs were substituted by baking powder (SC-b) as the leavening agent produced important changes in some key aroma compounds. The release curves of some aroma compounds-some of them generated during baking and others added in the dough-were followed by cumulative headspace analysis. In the flavored SC-b, the aroma release curves showed a plateau after 15 min of purge, while the release increased proportionally with the purge time in the flavored SC-e. In general, except for some of the aroma compounds with the highest log P values, the rate of release of most of the added and generated aroma compounds was significantly influenced by the changes in the cake formulation. The higher rates of release found for the aroma compounds in SC-b could contribute to explain its rapid exhaustion of aroma compounds in the purge and trap experiments and might lead to poorer sensorial characteristics of this cake during storage.  相似文献   

11.
The morphological, physical, chemical and mineralogical properties of eight prominent classes of soil developed in the coast aeolianites and sands of Natal are presented. These data and information on soil geography lead to the conclusion that: (i) losses of silica and bases and relative accumulation of iron (the ferrallitic process) have given rise to red and yellow kaolinitic materials; (ii) clay eluviation has given rise to coarse textured topsoils and to B2t horizons; and (iii) the hydromorphic process has caused grey colours in many sandy topsoils, plinthite development at some E/B horizon interfaces and gleying of some B2 horizons. In the soils on the older aeolianites, there is no evidence of either podzolization or the coarser textured topsoil being a younger geological deposit. The development of yellow soils in younger aeolianites may indicate a cooler climate than existed when red materials developed from the older aeolianites.  相似文献   

12.
A technique for assessing the metabolically-active fungal biomass by means of fluorescein diacetate (FDA) staining was recently described (Söderström, 1977). In this note some practical details in the application of this technique to studies of FDA-active fungal biomass in the soil are discussed.  相似文献   

13.
Information is needed on the range of soil water contents for tillage. The objective of the work was to develop methods for the prediction of the soil water contents at which tillage may be done satisfactorily. Three water contents are considered: the lower (dry) limit, the optimum water content, and the upper (wet) limit. This paper makes a synthesis of published results from tillage and soil physics experiments and also includes some new experimental results. The effects of tillage are considered in relation to some “fixed points” including the lower plastic limit, field capacity and a new fixed point “the inflection point”. These considerations lead to methods for prediction of the lower (dry) tillage limit, the optimum water content, and the upper (wet) tillage limit in terms of the parameters of the van Genuchten equation for soil water retention. Predictions can be made in terms of soil composition through the use of pedotransfer functions for the parameters of the van Genuchten equation. The new methods will enable the effects of soil degradation and climate change on tillage work days to be estimated. The results are potentially mappable using geographic information systems.  相似文献   

14.
阐述了沼气技术在农业结构调整中的显著作用，重点就沼气技术对于促进种植业的发展，改善生态环境，促进农村精神文明建设等方面作了阐述，并就进一步大力推广沼气技术提出建议。  相似文献   

15.
Eurasian Soil Science - Water retention curves (WRC) and some physical and chemical properties (particle-size composition, soil density, organic matter content, etc.) were determined for the major...  相似文献   

16.
Some aspects of the genesis of terrae rossae are still subject to controversy while others related to the genesis of the mineral fraction have been studied very little. We have studied four terrae rossae over limestone (two Chromic‐Leptic Luvisols, a Rhodi‐Leptic Luvisol and a Chromi‐Leptic Cambisol) in Sierra Gádor (Almería, southern Spain), in particular the various formation processes by (i) examination of their morphological, analytical and mineralogical characteristics (including crystallochemical parameters of the mica), (ii) examination of the insoluble residue of the gravel and rock, (iii) scanning electron microscopy (SEM) of sand and silt grains, and (iv) examination of the geochemistry of the soil solution. We have investigated the autochthonous or allochthonous nature of the soil material (fine earth and gravel) in relation to the rocky substrate, concluding that both origins are possible. Our SEM study of the morphology of the quartz grains shows that some are insoluble residue and some are probably wind blown from desert and coastal sources. The micas in the fine earth fractions are inherited from the insoluble residue. Comparison of the crystallochemical parameters of micas in the insoluble residue and the soil clay shows that the clay has more SiIV and (Fe, Mg)VI, and less AlIV, AlVI and x (layer charge) than the insoluble residue. It also has fewer polytypes 2M1 and more 1M and has a smaller crystal size, especially in B horizons. The kaolinite is of varied origins including neoformation and inheritance from underlying rock. Some of the kaolinite and some mica has been blown in from elsewhere, probably from desert and coastal sources. The soils have undergone other typical processes of terrae rossae including dissolution of carbonate, illuviation of clay and iron oxides, and rubifaction.  相似文献   

17.
A theoretical model for the microbial degradation of pesticides in soil is presented. This model takes into account an important soil property, the adsorption capacity, and the probable modification of the soil microflora after the pesticide was introduced into the soil.The main assumptions of the model are that: (1) the degradation takes place simultaneously in two ways, by metabolism and by co-metabolism; (2) the pesticide exhibits a lethal effect on a sensitive fraction of the soil microflora; (3) a fraction of this microflora is insensitive and does not degrade the pesticide; (4) the various fractions of the soil microflora can grow at the expense of both the pesticide and soil carbon (metabolizing microorganisms) or of the soil carbon alone (co-metabolizing, sensitive and insensitive microbial populations).Two numerical examples are given to illustrate the soil adaptation phenomenon.The validity of different hypotheses included in the model when applied to the soil system are discussed by comparing the results of the simulations to some experimental data concerning the modification of the degrading soil microflora or by comparing some physico-chemical and biological parameter values used in the calculations to published values.  相似文献   

18.
甜菜夜蛾（Spodoptera exigua）核型多角体病毒（SeNPV）克隆株G1、G3、G4及SeNPV1感染SpIm、BmN4和Ld652y细胞报，均能引起细胞凋亡现象。SpIm细胞感染96h后，大部分细胞死亡，形成葡萄状小泡，但能在个别细胞中形成病毒多角体；BmNr4细胞感染48h后，细胞内颗粒状物质增多，72h后全部死亡，脱壁上浮；Ld652y细胞被G3及SeNPV1感染 72h后解体成颗粒状，而G1、G4只能令部分细胞死亡。Westreren Blot及SlotBlot分析表明：SeNPV克隆株能在SpIm及BmN4细胞中复制病毒DNA，且能在SpIm细胞中形成多角体蛋白，但不能在Ld652y细胞中复制DNA。  相似文献   

19.
The present investigation was undertaken to study how the antioxidative activity (AA) of nonenzymatic browning reactions is changing at the same time that the browning (by the pyrrole polymerization mechanism) is being produced. The antioxidative activities of eight model pyrroles (pyrrole, 1-methylpyrrole, 2,5-dimethylpyrrole, 1,2,5-trimethylpyrrole, 2-acetylpyrrole, 2-acetyl-1-methylpyrrole, pyrrole-2-carboxaldehyde, and 1-methyl-2-pyrrolecarboxaldehyde) as well as the browning reaction of 2-(1-hydroxyethyl)-1-methylpyrrole (HMP) and the dimer (DIM) produced during HMP browning were determined. The results obtained suggest that the AAs observed in nonenzymatic browning reactions are the result of the AAs of the different oxidized lipid/amino acid reaction products formed. Thus, the different pyrrole derivatives produced in these reactions had different AAs, and the highest AAs were observed for alkyl-substituted pyrroles without free alpha-positions. Because some of these pyrrole derivatives are implicated in nonenzymatic browning production and this browning production implies the loss of hydroxyl groups and the transformation of some pyrroles with one type of substitution into others, changes in AA during browning production were observed, and the resulting DIM derivative was more antioxidant than HMP or higher polymers. These results explain the AA observed in fatty acid/protein mixtures after slight oxidation and suggest that, when the pyrrole polymerization mechanism is predominant, slightly browned samples may be more antioxidant than samples in which nonenzymatic browning has been highly developed.  相似文献   

20.
The soil cover pattern on a gentle watershed slope at the Kamennaya Steppe Experimental Farm consists of the areas of typical chernozems, zooturbated chernozems, and leached chernozems evolving into chernozemic-meadow soils; they are oriented along the slope. This soil combination is complicated by the presence of slightly eroded and slightly saline soils. The seasonal overwetting and inundation of the soils are favored by the discharge of the groundwater above the local aquiclude represented by the layer of dark brown calcareous clay at the depth of 1.0–2.2 m from the soil surface and by the concentration of snowmelt runoff in the concave parts of the slope. Seasonal overwetting of the soils leads to the appearance of olive tints and small iron concretions (quasigley features) in the lower horizons; in some cases, proper gley features (bluish coatings) appear in the chernozems. The veinlets of powdery gypsum are formed in the middle-profile horizons of some soils. Salt efflorescence on the surface in some places is also the result of the seasonal overwetting of the soils followed by their intense drying upon the hot and droughty weather conditions.  相似文献   

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