Palm oil carotenoids are a mixture of alpha- and beta-carotenes, which are used as food colorants. They may also be applied as a functional food ingredient because of the provitamin A activity of alpha- and beta-carotenes and their proposed beneficial roles in the prevention of chronic diseases. This paper discusses the results of an incomplete balanced crossover study with 69 healthy adult volunteers to compare palm oil carotenoids with synthetic beta-carotene in their efficacies to increase plasma levels of carotenoids. Four days of supplementation with natural palm oil carotenoids (7.6 mg/day of alpha-carotene, 11.9 mg/day of all-trans-beta-carotene, 7.5 mg/day of cis-beta-carotene) or synthetic beta-carotene (23.8 mg/day of all-trans-beta-carotene, 4.4 mg/day of cis-beta-carotene), added to a mixed meal, resulted in significant increases in plasma levels of the supplied carotenoids as compared to consumption of a low-carotenoid meal (i.e., 7.2-fold increase in alpha-carotene and 3.5-fold increase in all-trans-beta-carotene following palm oil carotenoids; 6.9-fold increase in all-trans beta-carotene following synthetic beta-carotene). As the carotenoid content differed between the treatments, the relative plasma responses were calculated per milligram of beta-carotene intake. These were similar for the two supplements, suggesting that the presence of alpha-carotene does not affect the bioavailability of beta-carotene from palm oil. It was concluded that 4 days of supplementation with palm oil carotenoids or synthetic beta-carotene improves the plasma beta-carotene status substantially, whereas alpha-carotene is additionally delivered by the palm oil supplement. 相似文献
Oxidation of CH4 in the rhizosphere of rice plants was quantified using (1) methyl fluoride, a specific inhibitor of CH4 oxidation, and (2) measuring changes in plant-mediated CH4 emission after incubation under air, N2, or 40% O2. No significant rhizospheric CH4 oxidation was observed from rice plants in the ripening stage. CH4 emission from rice plants 1 week before panicle initiation increased by 40% if CH4 oxidation in the rhizosphere was blocked. The growth stage of the rice plant is an important factor determining the rhizospheric CH4 oxidation. Fluctuation of rhizospheric CH4 oxidation during the growing season may help to explain the observed seasonal CH4 emission patterns in field studies. Measurements from four rice varieties showed that one variety, Pokkali, had higher rhizospheric CH4 oxidation. This was probably because Pokkali was in an earlier growth stage than the other three varieties. Both in the early and in the late growth stages, incubation under N2 caused a much stronger CH4 flux than inhibition of CH4 oxidation alone. Apparently, N2 incubation not only blocked CH4 oxidation but also stimulated methanogenesis in the rhizosphere. Incubation under a higher O2 atmosphere (40% O2) than ambient air decreased the CH4 flux, suggesting that increasing the oxidation of the rice rhizosphere may help in reducing CH4 fluxes from rice agriculture. The O2 pressure in the rhizosphere is an important factor that reduces the plant-mediated CH4 flux. However, inhibition of methanogenesis in the rhizosphere may contribute more to CH4 flux reduction than rhizospheric CH4 oxidation. 相似文献
A method is described to determine acid and alkaline phosphatase activities from the rate of decomposition of p-nitrophenylphosphate in the presence of large amounts of organic matter, such as occur in the surface layers of soils or in animal wastes. The p-nitrophenol formed is separated by high pressure liquid chromatography on a cellulose column from p-nitrophenylphosphate and other organic compounds present in the soil or waste extract. After separation, p-nitrophenol is measured on-line in a spectrophotometric flow cell at a wavelength of 405 nm. In this way p-nitrophenol concentrations down to 0.1 μm can be measured, making it possible to work with substrate concentrations of 1 μm.
The necessity of correcting the phosphatase activity measured in this way for adsorption of enzyme, substrate (p-nitrophenylphosphate) and product (p-nitrophenol) is discussed.
Acid and alkaline phosphatases are inhibited strongly at phosphate concentrations greater than 0.1 mm, consequently substrate concentrations in the range of 0.01 to 0.1 mm were used.
The method was applied to a number of sandy soils and to pig slurry. Air drying or freeze drying of soils was found to decrease the phosphatase activity. Freeze drying did not affect the phosphatase activity of pig slurry. Michaelis-Menten kinetics were found to apply reasonably well. The resulting kinetic parameters are compared with values from the literature. Phosphatase activities are correlated with organic P and organic matter contents of soils and pig slurry. 相似文献
Heavy sugarbeet harvesters may compact subsoil. But it is very difficult to study this by field experiments that resemble agricultural practice. Therefore, an analysis was made by a finite element method (FEM) for a relevant calcaric fluvial soil profile, the mechanical properties of which were largely known. Measuring data of this Lobith loam soil includes preconsolidation stress, compression index and swelling index, all as a function of depth. Using these three types of soil parameters calculations have been done for tyre sizes, inflation pressures and wheel loads that occur with heaviest sugarbeet harvesters available on the European market in 1999. Because no values on soil cohesion were available, the calculations were done for several cohesion levels. The results include the detection of regions with Mohr–Coulomb plasticity and regions with cap plasticity (compaction hardening). For the soil studied—a typical soil strength profile for arable land with ploughpan in the Netherlands in the autumn of 1977—all studied combinations of wheel load and inflation pressure did not induce compaction in and below the ploughpan. The size of the region with Mohr–Coulomb plasticity decreased with increasing cohesion. It appeared from a sensitivity analysis that, although soil modelling may use a great number of soil parameters, the most important parameters seem to be: preconsolidation stress and cohesion. There is an urgent need for data of these parameters that are measured on a great range of subsoils and subsoil conditions. 相似文献
In the present study, foam-forming and -stabilizing properties of potato proteins were studied using whipping and sparging tests. The soluble potato proteins are mainly composed of patatin and protease inhibitors. The whipping tests showed that less foam was formed from untreated patatin than from the protease inhibitors, but patatin foam was much more stable. The foam-forming properties of patatin could be strongly improved by partial unfolding of the protein. Whipping tests, at both low (0.5 mg/mL) and high (10 mg/mL) protein concentration, also indicated that foams made with an ethanol-precipitated protein isolate were more stable than those made with beta-casein and beta-lactoglobulin. More generally, it can be concluded that when proteins are used as a foaming agent, a high concentration is required, because the protein available is inefficiently used. Also, there are several variables that may all, in different ways, affect both foam formation (amount of foam, bubbles size distribution) and foam stability. These variables include the type and concentration of protein, solvent conditions (pH, I), and the method used to make the foam. 相似文献
Fish oil has been extracted from byproducts of the maatjes (salted) herring production using a pilot plant consisting of a mincer, heat exchanger, and three-phase decanter. The crude herring oil obtained had an initial peroxide value (PV), anisidine value (AV) and free fatty acids (FFA) level of only 3 mequiv of peroxide/kg of lipid, 8.9, and 2.9%, respectively. 5,8,11,14,17-Eicosapentaenoic acid (EPA) and 4,7,10,13,16,19-docosahexaenoic acid (DHA) were present in considerable amounts (99 and 91 g/kg, respectively). During storage of the oil, no photooxidation could be detected. Storage at room temperature led to significant autoxidation over time, apparent from primary and tertiary oxidation products, measured by a decrease of hydroperoxides and an increase of fluorescent compounds (FC). Storage at 50 degrees C resulted in significant increases in secondary (AV) and tertiary oxidation (FC) products. At all storage conditions, the FFA contents remained low (<3%) and the alpha-tocopherol content remained constant. These results open the possibility for fish oil production of good quality using salted herring byproducts. 相似文献
A commercial lot of green coffee, naturally contaminated with ochratoxin A (OTA), was roasted under various conditions, and the effects on its final OTA content were determined. Precautions were taken in sampling the coffee to cope with OTA inhomogeneity. The roasting conditions were kept within the range of commercial practice. Roasting time was varied from 2.5 to 10 min, and the roast color varied from light medium to dark. The differences in OTA reduction between the different levels of roasting times and colors did not reach statistical significance. However, for all roasting conditions, the reduction was highly significant, 69% reduction over the combined results. In total, nine studies by various authors about OTA reduction during coffee roasting are now available. Seven out of these nine reported that the relevant range of OTA reductions was between 69 and 96%. Among these seven,are all four studies that reported using naturally contaminated beans, a sampling procedure adapted to mycotoxin inhomogeneity, and roasting conditions within the range of actual practice. Three different explanations are available for this reduction: physical removal of OTA with chaff, isomerization at the C-3 position into another diastereomer, and thermal degradation with possible involvement of moisture. All three explanations may play a partial role in the OTA reduction during coffee roasting. 相似文献
Nineteen cultivars, with large differences in heading date, were evaluated for their response to septoria tritici blotch in
two experimental setups in Njoro, Kenya. Due to the more or less constant temperatures during the growing season and the overhead
irrigation applied the epidemic conditions were similar over the whole observation period for the early and late cultivars.
In experiment 1 the cultivars were assessed for disease severity at the same moment irrespective of the developmental stage,
while in experiment 2 the cultivars were assessed at the same developmental stage. Measured at the same time, the disease
severity was highest in the early maturing cultivars and lowest in the late maturing cultivars (r = –0.78). When assessed
at the same development stage the disease build up was independent of heading date (r = –0.10) but strongly dependent on resistance
level. There were no indications that early heading cultivars were more susceptible than late heading cultivars.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
Few studies address nutrient cycling during the transition period (e.g., 1–4 years following conversion) from standard to some form of conservation tillage. This study compares the influence of minimum versus standard tillage on changes in soil nitrogen (N) stabilization, nitrous oxide (N2O) emissions, short-term N cycling, and crop N use efficiency 1 year after tillage conversion in conventional (i.e., synthetic fertilizer-N only), low-input (i.e., alternating annual synthetic fertilizer- and cover crop-N), and organic (i.e., manure- and cover crop-N) irrigated, maize–tomato systems in California. To understand the mechanisms governing N cycling in these systems, we traced 15N-labeled fertilizer/cover crop into the maize grain, whole soil, and three soil fractions: macroaggregates (>250 μm), microaggregates (53–250 μm) and silt-and-clay (<53 μm). We found a cropping system effect on soil Nnew (i.e., N derived from 15N-fertilizer or -15N-cover crop), with 173 kg Nnew ha−1 in the conventional system compared to 71.6 and 69.2 kg Nnew ha−1 in the low-input and organic systems, respectively. In the conventional system, more Nnew was found in the microaggregate and silt-and-clay fractions, whereas, the Nnew of the organic and low-input systems resided mainly in the macroaggregates. Even though no effect of tillage was found on soil aggregation, the minimum tillage systems showed greater soil fraction-Nnew than the standard tillage systems, suggesting greater potential for N stabilization under minimum tillage. Grain-Nnew was also higher in the minimum versus standard tillage systems. Nevertheless, minimum tillage led to the greatest N2O emissions (39.5 g N2O–N ha−1 day−1) from the conventional cropping system, where N turnover was already the fastest among the cropping systems. In contrast, minimum tillage combined with the low-input system (which received the least N ha−1) produced intermediate N2O emissions, soil N stabilization, and crop N use efficiency. Although total soil N did not change after 1 year of conversion from standard to minimum tillage, our use of stable isotopes permitted the early detection of interactive effects between tillage regimes and cropping systems that determine the trade-offs among N stabilization, N2O emissions, and N availability. 相似文献
In the southern Benguela upwelling ecosystem off the west coast of South Africa, seabird populations are decreasing dramatically because of reduced availability of pelagic fish. We tested the hypothesis that the west coast fishing industry is competing for the remaining stocks of anchovy and sardine with the largest colony of Vulnerable Cape Gannets (Morus capensis) along the Atlantic coast. Using GPS-tracking of the birds, echo-sounding of pelagic fish, and vessel log books, we located overlap areas between bird foraging ranges, pelagic fish distribution, and fishing activities. We then compared fish catches by gannets and vessels within their joint foraging zones. In October 2007, purse-seine fishing grounds and gannet foraging areas overlapped by only 13%. However, for a 1-month period, the amount of fish removed from this area by purse-seine boats amounted to 41% of the food requirements of the 72,000 gannets breeding on Malgas Island (25% of the world population). The fishery’s catch in this area is significant in terms of its potential impact on gannets, but comprises only 3.6% of total fishery catch. Based on this finding, the rapidly decreasing size of the gannet colony and the stated objectives of South Africa’s Marine Living Resources Act of 1998, the case for considering and experimenting with at-sea ‘no-take’ areas for the purse-seine fishery is strong. Efforts to establish whether ‘no-take’ fishing zones increase food availability for top predators is an important next step in conservation of the southern Benguela Ecosystem. 相似文献