Antioxidant capacity, vitamin C, phenolics, and anthocyanins after fresh storage of small fruits.

Fresh strawberries (Fragaria x ananassa Duch.), raspberries (Rubus idaeus Michx.), highbush blueberries (Vaccinium corymbosum L.), and lowbush blueberries (Vaccinium angustifolium Aiton) were stored at 0, 10, 20, and 30 degrees C for up to 8 days to determine the effects of storage temperature on whole fruit antioxidant capacity (as measured by the oxygen radical absorbing capacity assay, Cao et al., Clin. Chem. 1995, 41, 1738-1744) and total phenolic, anthocyanin, and ascorbate content. The four fruit varied markedly in their total antioxidant capacity, and antioxidant capacity was strongly correlated with the content of total phenolics (0.83) and anthocyanins (0.90). The antioxidant capacity of the two blueberry species was about 3-fold higher than either strawberries or raspberries. However, there was an increase in the antioxidant capacity of strawberries and raspberries during storage at temperatures >0 degrees C, which was accompanied by increases in anthocyanins in strawberries and increases in anthocyanins and total phenolics in raspberries. Ascorbate content differed more than 5-fold among the four fruit species; on average, strawberries and raspberries had almost 4-times more ascorbate than highbush and lowbush blueberries. There were no ascorbate losses in strawberries or highbush blueberries during 8 days of storage at the various temperatures, but there were losses in the other two fruit species. Ascorbate made only a small contribution (0.4-9.4%) to the total antioxidant capacity of the fruit. The increase observed in antioxidant capacity through postharvest phenolic synthesis and metabolism suggested that commercially feasible technologies may be developed to enhance the health functionality of small fruit crops.     

Ion chromatographic determination of chloride in mustard sauces.

A new, simple, precise, and rapid ion chromatography (IC) method has been developed to determine chloride in mustard sauces using a mixture of phthalic acid, acetone, and water adjusted to pH 5.0 as eluent. Conductometric detection was carried out. The retention time for chloride was 1.5 min. Linearity was obtained up to a concentration level of 100 mg/L NaCl. The method was statistically evaluated for accuracy and precision after being used to assay the chloride from mustard sauces. Within the same samples, the chloride levels obtained by IC were compared with the sodium concentrations quantified by atomic absorption spectrophotometry.     

Flavonoid constituents of Chorizanthe diffusa with potential cancer chemopreventive activity

An ethyl acetate-soluble extract of Chorizanthe diffusa was found to exhibit significant antioxidant activity, as judged by scavenging stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals and inhibition of 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced free radical formation with cultured HL-60 cells. Bioassay-directed fractionation of this extract using the DPPH antioxidant assay as a monitor led to the isolation of five structurally related flavonoids (1-5), including the novel compound 5,8,3',4',5'-pentahydroxy-3, 7-dimethoxyflavone (1). Isolates 1-5 demonstrated varying degrees of antioxidant or antimutagenic activity. Two of the compounds, 5,7,3', 4'-tetrahydroxy-3-methoxyflavone (2) and quercetin (4), were subsequently found to inhibit carcinogen-induced preneoplastic lesions in a mouse mammary organ culture model. Inhibitory activity of this type is known to correlate with cancer chemopreventive effects in full-term models of tumorigenesis.     

Comparison of the bioavailability of natural palm oil carotenoids and synthetic beta-carotene in humans

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.     

Mobility of the herbicide pyrithiobac through intact soil columns

The relative mobility of pyrithiobac [sodium 2-chloro-6-(4, 6-dimethoxypyrimidin-2-ylthio)benzoate], a new herbicide used for postemergence control of broadleaf weeds in cotton (Gossypium hirsutum), was evaluated and compared against that of bromide (Br(-)) tracer on four soils representative of cotton-growing regions using intact soil columns under saturated flow conditions. Pyrithiobac breakthrough curves were asymmetrical in shape with significant tailing and displaced to the left of 1 pore volume in the Houston Black clay (fine, montmorillonitic, thermic Udic Pellustert), Orelia fine sandy clay loam (fine-loamy, mixed, hyperthermic Typic Ochraqualfs), and Ships silty clay (very-fine, mixed, thermic Udic Chromustert) soils. Breakthrough of pyrithiobac in the Hidalgo sandy loam soil (fine-loamy, mixed, hyperthermic Typic Calciustoll) was delayed and more symmetrical, with peak pyrithiobac concentration reached after 1.2 pore volumes. The immobile pore water (IPW) fractions estimated from the Br(-) breakthrough curves ranged from 20 to 87% of total pore water. The IPW values demonstrated that soils with the greatest amount of IPW (Ships with IPW = 87.3%) exhibited the most rapid movement of pyrithiobac (peak concentration after 0.04 pore volume). The experimentally determined pyrithiobac breakthrough curves confirmed the high mobility of this herbicide in these alkaline and predominantly smectitic soils. These results indicate that pyrithiobac mobility was influenced by soil type and preferential flow processes when leached through intact soil columns.     

Mercury speciation in the Scheldt Estuary

Surface waters of the Scheldt Estuary were sampled on various occasions between 1991 and 1994. Longitudinal particulate Hg (PM) concentrations ranged from 0.4 – 1.7 μgHg/g and are essentially controlled by physical mixing of polluted fluvial particulates with relatively unpolluted marine particulates. Total dissolved mercury (TDM)concentrations ranged from 0.5 to 5.2 ng/L and are strongly influenced by removal and mobilization processes in the upper estuary, while in the lower estuary mixing processes cause a progressive decrease in TDM towards the mouth. Speciation studies showed that dissolved Hg is predominantly bound to strong complexing ligands (organic substances) in the upper estuary, but this fraction decreases with increasing salinity. In June 1993, however, the reactive mercury fraction was also high in the upper estuary. Model calculations showed that a conditional stability constant for Hg- humic acid interactions of 10¹⁹ was a good estimate for the Scheldt estuary. Dissolved methylmercury was analyzed on three occasions. Significant seasonal variations were observed with concentrations ranging from 11 to 120 pg/L in the winter and 80 to 400 pg/L in summer. Supersaturation of Hg° is observed throughout the whole estuary resulting in an estimated evasion flux of 140–1400 ng/m² day.     

A yield-independent, 15N-isotope dilution method to estimate legume symbiotic dependence without a non-N2-fixing reference plant

The proportional contribution of atmospheric N₂ to the N nutrition of lupin (P _atm) was estimated in a field experiment following addition of NH₄Cl of KNO₃ to unconfined microplots (1.5 m²) at 2.5 g N m^-2 (10 atom% ¹⁵N). The integrated ¹⁵N enrichment, or mean pool abundance, of nitrate extracted from 0- to 15-cm samples taken under the lupin crop on eight occasion between 28 and 190 days after sowing was used as the reference criterion to estimate P _atm by the ¹⁵N-isotope dilution technique. Estimates of P _atm were similar to those obtained using canola as a non-fixing reference plant, but were higher than estimates obtained using a yield-dependent model. Use of mean pool abundance obviates the need for a non-fixing reference plant, and the frequent sampling and isotope-ratio analysis of the legume biomass required with the yield-dependent model is unnecessary. However, further work is needed to validate a sampling strategy commensurate with the growth of the legume roots.     

Oxidation of methane in the rhizosphere of rice plants

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.     

Rapid sedimentological and biological assessment of hydrocarbon contaminated sediments

It is possible to rapidly detect the presence of high concentrations of sediment associated hydrocarbons using a sediment profile camera and simultaneously evaluate the general sedimentological and biological character of a contaminated area. In sediments that were heavily contaminated with hydrocarbons from spills and chronic long-term additions the presence of hydrocarbons was seen about 50% of the time in the sediment profile images as unique features, ‘H spots’. The presence of these features was related to the concentration of hydrocarbons in the sediment. In highly contaminated muddy sediments ‘H spots’ were found in images collected at stations that had from 270 to 610 ppt total hydrocarbons. Sedimentological and biological information obtained from the sediment profile images confirmed the impacted nature of Elizabeth River sediments. Sediment profile imaging provide a means of obtaining an overall evaluation of the quality of a habitat and impacts on that habitat from pollution related environmental disturbances. While qualitative, an advantage of sediment profile image data is that they can be evaluated in less than a day and used to quickly locate inclusions of hydrocarbons in the sediments for further quantitative chemical or biological sampling, or mapping of heavily contaminated areas.     

Hard-setting behaviour of some structurally weak tropical soils

Some soils set hard on drying and may limit crop productivity. The hard-setting behaviour is influenced by soil properties and management. The objective of this study was to relate physical properties of soils sampled from 3 sites in Nigeria to soil strength or degree of hard-setting and to management. Clearing the vegetation and tillage led to a decrease in organic matter content and wet aggregate stability and increased bulk density leading to an increase in soil strength. The soil strength increased as the water content decreased but the increase was much more marked for mechanized cleared or tilled soils than for the less disturbed treatments of forestry or no-till cropping.