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1.
J W White I Kushnir L W Doner 《Journal of the Association of Official Analytical Chemists》1979,62(4):921-927
A new spectrophotometric method is described for determining hydroxymethylfurfural in honey in which interfering background absorption of honey is corrected for by use of a bisulfite-treated sample as blank. Two procedures for detecting high-fructose corn sirup (HFCS) in honey were also tested. In one, charcoal column pretreatment is used to concentrate trace oligosaccharides, followed by thin layer chromatography to differentiate those of HFCS from those of honey. The other method depends on measurement of the isomaltose/maltose ratio by gas-liquid chromatography. The charcoal/thin layer chromatographic method for HFCS has been adopted official first action. The bisulfite method for hydroxymethylfurfural has been adopted interim first action. 相似文献
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Small columns, 2.5 cm dia and of different lengths, were filled with an air-dried. Hanford sandy loam and leached with CaCl2 (0.001 n) and nitrate (10–100 μg/ml N) for 3 weeks. The average NO3 N concentration of the leachate during the last 12 days of the experiment was used to calculate denitrification rates. The net reaction of NO3? appeared to be zero order with the 50 and 100 μg/ml NO3 N applications with a rate constant of 0.27 μg/ml/h N residence time for columns 5–50 cm long. Nitrate was not completely lost with the lower NO3? N applications; this implies that greater than zero order reactions can also occur. Although N2 gas evolution was not measured, most N was doubtless volatilized since analysis of selected soil samples at the end of the experiment indicated no net assimilation of the NO3 N. 相似文献
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An iron-sulfur compound (Fe3S2) was synthesized at pressures greater than 14 gigapascals in the system Fe-FeS. The formation of Fe3S2 changed the melting relations from a simple binary eutectic system to a binary system with an intermediate compound that melted incongruently. The eutectic temperature in the system at 14 gigapascals was about 400°C lower than that extrapolated from Usselman's data, implying that previous thermal models of Fe-rich planetary cores could overestimate core temperature. If it is found in a meteorite, the Fe3S2 phase could also be used to infer the minimum size of a parent body. 相似文献
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White, fluffy cellulose/arabinoxylan mixtures (CAX) were generated from the solid residues remaining after corn fiber gum (CFG) production. Most CAX were produced using variations of a process in which a single alkaline hydrogen peroxide (AHP) step was used for delignification and for CFG (arabinoxylan) extraction. The optimal ratio of H2O2 to corn fiber to water was 0.1:1:20. Holding this ratio constant, time and temperature conditions were systematically varied, and yields of CAX and CFG determined. Parallel processes were conducted without H2O2 to determine its effect on CAX and CFG yield. CAX prepared under identical conditions but without H2O2 retained nearly twice the levels of CFG sugars, as revealed from L‐arabinose, D‐xylose, and D,L‐galactose levels. Even the CAX prepared under extreme AHP conditions (1 hr, 100°C), however, contained 32.9% of these CFG sugars. This CAX was obtained in a 25.1% yield, whereas those produced under less vigorous conditions were obtained in higher yields, because they retained more CFG. CAX prepared in the presence of H2O2 hydrated very effectively, as indicated by their high swollen volumes and water absorbance values. This suggests potential food applications for CAX as a bulking agent. In addition, the open structure of the CAX matrix would render these residues suitable for chemical derivatization and enzymatic saccharification. 相似文献
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Sequential alkaline extraction and alkaline hydrogen peroxide (AHP) bleaching have been used to prepare corn fiber gum in yields ranging from 21 to 40%, depending on the pH of the extraction medium. The pH was adjusted by using different ratios of NaOH and Ca(OH)2 The whitest product was obtained after AHP bleaching of the extract obtained using the lowest pH value. In order for the product gum to give its characteristic clear and low viscosity solutions, it was necessary to remove starch from the corn fiber substrate using α-amylase. The water-insoluble hemicellulose A fraction, a minor component, was removed by neutralizing AHP-treated extracts before ethanol precipitation of the useful hemicellulose B (corn fiber gum) fraction. At ambient temperature, AHP bleaching was near optimal after ≈2 hr under the processing conditions used. High ratios of arabinose (39%) to xylose (50%) were present in the corn fiber gum extracted under various alkaline conditions, and the H2O2 processing step did not significantly alter these ratios. The same low levels of galactose (7%) and glucuronic acid (4%) were present regardless of the extraction conditions. Molecular mass of the corn fiber gum preparations ranged from 2.78 × 105 for the material extracted with Ca(OH)2 to 3.94 × 105 for the material extracted with NaOH. Molecular mass was unaffected by the H2O2 present in the second processing step. As expected for a carbohydrate polymer with a rather low uronic acid content, solution viscosities were unaffected by the presence of salt. 相似文献
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Analysis and properties of arabinoxylans from discrete corn wet-milling fiber fractions 总被引：1，自引：0，他引：1
Three fibrous corn wet-milling fractions, coarse fiber, fine fiber, and spent flake, were isolated. More highly valued uses are sought for these milling products, which are generally directed into the corn gluten feed product stream. Coarse fiber was further dissected into pericarp and aleurone layers. An alkaline hydrogen peroxide process was used to efficiently extract corn fiber gum (CFG) from each of the materials. CFG is a hemicellulose B arabinoxylan which also contains low levels of D,L-galactose and D-glucuronic acid. CFG yield information was obtained from each source, as well as structural information in terms of degrees of branching of the beta-D-xylopyranose backbone with alpha-L-arabinofuranosyl moieties. There were significant differences in degree of branching among the CFGs from the various fractions. A novel capillary electrophoresis procedure was developed to measure these differences. Solution viscosity differences among the CFGs were also observed. 相似文献
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Recent syntheses of high-pressure alkali and alkaline earth silicates reveal a class of framework structures with corner-linked 4- and 6-coordinated silicon. These compounds possess the structural formula (A4-2x1+Bx2+)SimVI(SinIVO2(m+n)+2), where x, m, and n specify the amounts of alkaline earth, 6-coordinated silicon, and 4-coordinated silicon, respectively. Appropriate values of m and n yield a range of high-pressure structures, from fully 4-coordinated to fully 6-coordinated silicate frameworks. Recognition of this class of framework silicates leads to predictions of high-pressure structures as well as room-pressure isomorphs of high-pressure silicates. 相似文献
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The variability of the carbon-13/carbon-12 ratio in honeys was evaluated preliminary to use of the ratio to detect the addition of high-fructose corn syrup to honey. Eighty-four honey samples representing 34 states and including 37 floral types from 17 plant families were analyzed. The mean value of the per mil increment in carbon-13 (delta13C) for all samples is -25.2 per mil, and the coefficient of variation is 3.7 percent. This is the smallest variation yet encountered for a honey constituent or physical property. The range and magnitude of the values suggest that the floral sources are C(3) plants. 相似文献
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Benzene formed a stable coinplex through its pi electrons to the copper ion in copper(II)montmorillonite. Copper(II)was the only exchangeable metal cation in montmorillonite to form a complex with benzene. Only those clay minerals whose charge arises in the octahedral layer produced the complex. 相似文献