Determination of aflatoxin concentrations in peanut butter by enzyme-linked immunosorbent assay (ELISA): study of three commercial ELISA kits

Sixteen United Kingdom analytical laboratories participated in an evaluation of 3 commercially available enzyme-linked immunosorbent assay (ELISA) kits for analysis of aflatoxin in peanut butter. Each laboratory was sent 3 sets of 10 randomly numbered samples of peanut butter. Each set consisted of 5 pairs of undisclosed duplicates. Four of the sets of duplicates were naturally contaminated butters with "target" aflatoxin values (estimated by liquid chromatography) between 8 and 81 micrograms/kg. The fifth pair was a blank peanut butter containing approximately 3 micrograms/kg of total aflatoxins. A statistical treatment of the results of the study is presented, together with discussion of the relative merits of the different kits.     

The Potted-Plant Microcosm Substantially Reduces Indoor Air VOC Pollution: I. Office Field-Study

Volatile organic compounds (VOCs) are major contaminants of indoor air, with concentrations often several times higher than outdoors. They are recognized as causative agents of “building-related illness” or “sick-building syndrome”. Our previous laboratory test-chamber studies have shown that the potted-plant/root-zone microorganism microcosm can eliminate high concentrations of air-borne VOCs within 24 hours, once the removal response has been induced by an initial dose. However, the effectiveness of the potted-plant microcosm in ‘real-world’ indoor spaces has never previously been tested experimentally. This paper reports the results of a field-study on the effects of potted-plant presence on total VOC (TVOC) levels, measured in 60 offices (12 per treatment), over two 5–9 week periods, using three planting regimes, with two ‘international indoor-plant’ species. Fourteen VOCs were identified in the office air. When TVOC loads in reference offices rose above 100 ppb, large reductions, of from 50 to 75% (to <100 ppb), were found in planted offices, under all planting regimes The results indicate that air-borne TVOC levels above a threshold of about 100 ppb stimulate the graded induction of an efficient metabolic VOC-removal mechanism in the microcosm. Follow-up laboratory dose-response experiments, reported in the following paper, confirm the graded induction response, over a wide range of VOC concentrations. The findings together demonstrate that potted-plants can provide an efficient, self-regulating, low-cost, sustainable, bioremediation system for indoor air pollution, which can effectively complement engineering measures to reduce indoor air pollution, and hence improve human wellbeing and productivity.     

Aluminium toxicity and multiplication of Rhizobium trifolii in a defined growth medium

The responses of six strains of R. trifolii to pH, Ca, Al and phosphate were studied in the defined medium of Munns and Keyser (1981) supplemented with vitamins. Wild-type strains responded in the same way as rifampicin-resistant mutant strains. Multiplication was inhibited by acidity alone at pH4.3, and by 50 μM Al at pH 5.5 (despite the precipitation of Al). This inhibitory effect of Al was overcome by increasing the pH above 6.0, or by increasing the phosphate concentration from 10 to 100 μm. Ca concentration had no effect, nor did holding the medium at 22°C for 36 weeks before inoculation. There was variation between strains in their responses to concentrations of A1 < 50 μM. These responses indicate that the defined medium is a satisfactory model for the white clover rhizosphere.Results from these studies and from chemical analyses indicate that the inhibitory effect of Al under partially-neutralized conditions is not due to a direct effect of monomeric A1, nor to an indirect effect of polymeric A1 in reducing the concentration of phosphate, but is due to a direct effect of polymeric A1.     

Gram-negative identification card for identification of Salmonella, Escherichia coli, and other Enterobacteriaceae isolated from foods: collaborative study

Twelve laboratories evaluated the Gram-Negative Identification (GNI) Card to identify members of the Enterobacteriaceae. Eighty-four isolates, previously isolated from foods, were used in the collaborative study; the isolates represented 12 genera within the Enterobacteriaceae group. Each collaborator streaked each isolate on tryptic soy agar plates for purity. In the method, plates are incubated 18-24 h at 35 degrees C. Isolated colonies are then subcultured to tryptic soy agar slants and incubated 18-24 h at 35 degrees C. An emulsion is made from the growth on the slant in 1.8 mL 0.45% sodium chloride solution. The GNI Card is filled and placed in a reader/incubator. Isolates are identified and an identification is printed. The Vitek System correctly identified 96.7% of Salmonella sp., 97.0% of Escherichia coli, and an average of 93.8% of the other enteric genera. The method using the Vitek System and GNI Card has been approved interim official first action by AOAC as a screening method for the presumptive identification of Salmonella sp., E. coli, and other Enterobacteriaceae isolated from foods.     

Longitudinal growth strain as a log and wood quality predictor for plantation-grown <Emphasis Type="Italic">Eucalyptus nitens</Emphasis> sawlogs

Peripheral longitudinal growth strain (LGS) was measured on a total of 81, 22-year-old pruned Eucalyptus nitens trees from five thinning treatments in a plantation thinning trial in Tasmania. Growth strain data were gathered at breast height on each tree using the CIRAD-Forêt method. The effects of thinning treatment and tree diameter on LGS and its relationships to solid-wood traits determined in a processing trial were examined. LGS was significantly higher in the direction of the prevailing wind and was not significantly affected by either thinning treatment or tree diameter. An index of log end splitting was positively related to tree diameter, sawlog position (upper/lower), and LGS, which explained up to an additional 20% of the variance after tree diameter and log position were accounted for in a linear regression model. High LGS and log end splitting were significant indicators of increased board end splitting.     

Histological structures of cooked rice grain

Raw and cooked whole grain sections of milled, medium grain California rice were compared for gross histological and morphological features using fluorescence and scanning electron microscopy (SEM). Cooked and raw grains were compared and the differences were assessed by autofluorescence of the cell walls and correlating fluorescence to SEM images. Milled, raw grains contain fine cracks throughout the endosperm. Cooked grains have wider, more defined cracks, suggesting that they serve as channels for water migration into the grain during cooking. Water penetrates unequally into the grain during cooking: low water penetration produces dense regions with minimal starch gelatinization, and high water penetration produces large voided areas. The voids occur in the transverse orientation of the grain and are the main of cause grain expansion during cooking.     

Sorption and vapor transmission properties of uncompressed and compressed microcellular starch foam

Microcellular starch foams (MCFs) are made by a solvent-exchange process and consist of a porous matrix with pores generally ranging from approximately 2 microm to submicrometer size. MCF may potentially be useful as a slow-release agent for volatile compounds because of its ability to sorb chemicals from the atmosphere and to absorb liquids into its porous structure, and because it can be compressed to form a starch plastic. MCF made of high-amylose corn and wheat starches was prepared with or without 2% (w/w) silicone oil (SO) or palmitic acid (PA). The MCF was loaded with 1% of various volatile compounds with vapor pressures ranging from 0.02 to 28 mm. The MCF depressed the vapor pressure from 0.37 to 37% compared to a control containing no MCF. Incorporating SO or PA in the matrix of the MCF had little effect on sorption of volatiles. Compressing MCF at 1.4, 6.9, and 69 MPa made a starch plastic with varying porosity. The vapor transmission rate of various volatile compounds through MCF was positively correlated to the vapor pressure of the test compound but was inversely proportional to the compression force used to form the starch plastic. The results indicate that uncompressed and compressed MCFs could be effective slow-release agents for a variety of volatile compounds, especially if used together.     

染色单板光变色的规律和影响因子的研究

该文以染色杨木和染色樟子松单板为试材,利用氙光衰减仪进行辐射试验,使用色彩色差计测定光辐射前后和光辐射过程中的试件表面材色,并以国际照明委员会颁布的CIE(1976)L*a*b*表色系统进行颜色表征.分析其光变色规律和试验因子对染色单板光变色的影响,并进行耐光性能评价.     

Western pine beetle: field response to its sex pheromone and a synergistic host terpene, myrcene

In the field, both sexes of the western pine beetle, Dendroctonus brevicomis, are attracted by the female-produced bicyclic ketal exo-brevicomin; this response is enhanced by myrcene (a constituent of the beetle's host, ponderosapine), which is not an attractant by itself. This synergism may be part of the phenomenon of the mass attack on its host. Temnochila virescens chlorodia, one of the principal insectan predators of this beetle, is attracted by exo-brevicomin alone.     

Crystal structure analysis of deamino-oxytocin: conformational flexibility and receptor binding

Two crystal structures of deamino-oxytocin have been determined at better than 1.1A resolution from isomorphous replacement and anomalous scattering x-ray measurements. In each of two crystal forms there are two closely related conformers with disulfide bridges of different chirality, which may be important in receptor recognition and activation.