Nine commercial potato cultivars have been analyzed in order to detect differences in nutritional quality, considering the balance between nutrients and anti-nutrient compounds present in each. The most important nutrients studied in this paper were: water, starch, free sugars, such as glucose, fructose and sucrose, malic acid, citric acid, ascorbic acid and chlorogenic acid. The anti-nutrients measured included α-solanine, α-chaconine and asparagine. This last compound was added to the anti-nutrient compounds because it is involved in the formation of acrylamide during thermal food processes. From this study, by considering the nutritional quality of each cultivar, we can divide the potato cultivars into three groups, each being suitable for a different technological processes. 相似文献
The use of (3,3,4,4-2H4)PGE2 as internal standard for the quantitative measurement of PGE1 by gas chromatography-mass spectrometry is reported. A method for the simultaneous analysis of PGE1 and PGE2 is also described. The prostaglandins were analyzed by selected ion monitoring as the methyl ester-trimethylsilyl ether (ME-TMS)
derivatives of PGB1 and PGB2, respectively. In all cases, a linear response over the range 1 to 70 ng (2.8 to 198 pmoles) was demonstrated. The use of
this procedure is exemplified by its application to the PG analysis of sheep seminal vesicles.
Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department
of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable. 相似文献
Growth, substrates and end-product formation of the maltose and citrate co-metabolization byLactobacillus brevis subsp.lindneri CB1 citrate-negative strain were initially studied in synthetic medium. Compared to maltose (19 g/l) fermentation, the co-metabolization of maltose (10 g/l) plus citrate (9 g/l) caused faster cell growth, increased the concentrations of lactic acid and especially of acetic acid (from 0.7 g/l to 2.9 g/l), produced succinic acid (0.5 g/l) and reduced ethanol synthesis. Highest activities of acetate kinase, the same of lactate dehydrogenase and a reduced alcohol dehydrogenase activity were detected in cytoplasmic extracts of cells growing on maltose plus citrate. The breakdown of citrate depended upon the continuous presence of maltose in the growth medium. Upon depletion of citrate, the cells continued through the normal maltose fermentation, having a diauxic metabolic curve as shown by impedance measurements. Concentrations of citrate from 3 g/l to 15 g/l led to increases of acetic acid from 1.25 g/l to 5.55 g/l. Since maltose was naturally present during sourdough fermentation, the addition of 9 g citrate per kg wheat dough enabled the co-metabolization of maltose and citrate byL. brevis subsp.lindneri CB1. Compared with traditional sourdough fermentation, faster cell growth, a higher acetic acid concentration and a reduced quotient of fermentation were obtained by co-metabolism. 相似文献
Compounds of the system (AgI)x(Ag2B4O7)1?x can be thought of as a network made by an equal number of BO3 and BO4 groups containing silver iodide polyhedra. Partially crystalline compounds are obtained when the AgI molar fraction, x, is more than two times the Ag2B4O7 fraction. For the same iodine concentration, the ionic conductivities of the AgI : Ag2B4O7 glasses are comparable with those of other AgI : Ag-oxysalt glasses. However, their glass transition temperatures are substantially higher. With increasing silver iodine content, the physical properties which have been investigated approach smoothly the corresponding values expected for α-AgI. However, it is shown that Ag+ within the iodide polyhedra is not the unique current carrier and that a wide distribution of barrier heights exists in these glasses. 相似文献
Currently there is widespread use of ultrahigh molecular weight polyethylene (UHMWPE) acetabular components in total joint replacement prostheses. What has been most surprising about the wear of UHMWPE under such circumstances is the occurrence of brittle fracture. Such fracture had not been observed in the usual engineering tests done in the laboratory on UHMWPE. It was only when prosthese which had been removed from patients were examined or run in hip joint simulators with serum or synovial fluid as the lubricant, that brittle fracture was encountered. The problem of environment-enhanced brittle fracture in plastics dates back to 1946. Interestingly, the phenomenon was first described in polyethylene. The prime variables involved are polymer molecular weight, sensitizing environment, stress filed, and temperature. Other things being equal, brittle behavior in polyethylene is extremely sensitive to the amount of low molecular weight polymer present. In the light of the foregoing we have studied the molecular weight distribution in six commercially available UHMWPE components. These were obtained from six different manufacturers. The specimens were characterized both on their bearing (wear) surfaces and in their interior bulk. The results obtained indicate that:
1 The UHMWPE components contain substantial amounts of low molecular weight polymer.
2 The UHMWPE components differ significantly in molecular weight distribution.
3 The UHMWPE components contain substantial amounts of crosslinked polymer.
The preparation of new rubber based nanocomposites by using properly modified organophilic clays is described. A commercial organophilic montmorillonite containing a hydroxylated ammonium ion is reacted with LPBs. The reaction causes a decrease of the polarity of the clay and a great increase of the interlayer distance. The modified organoclays are successfully dispersed into rubber matrices (SBR or BR) by melt blending in an internal batch mixer. SAXS analyses and TEM micrographs revealed the formation of highly exfoliated nanocomposites containing intercalated stacks made of few lamellae.