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  • Theoretical, Physical and Computational Chemistry  (2)
  • Flavour development  (1)
  • Komplexe mit Schwefelliganden  (1)
  • 1
    ISSN: 1438-2385
    Keywords: Lactococci ; Proteolysis ; Flavour development ; Cheese-curd slurries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract This study describes the accelerating effect exerted on proteolysis and flavour development in cheese-curd slurries by combined application ofLactococcus lactis subsp.lactis IFPL359 and high concentrations of its Lac− Prt− derivative, (i.e. that which has reduced capacity to metabolize lactose and reduced proteolytic activity, strain T1). Cells of strain T1 partially lysed by either sonication or incubation with lysozyme, were also used to ascertain how proteolysis was affected by release of intracellular enzymes in the initial stage of incubation of the strains in cheese-curd slurries. The presence of strain T1 produced higher levels of non-protein nitrogen (NPN) and amine nitrogen (AN) during the first weeks of incubation when partially lysed cells had been added. Addition of whole cells of strain T1 produced higher values of NPN and AN at the end of incubation of slurries, accelerating proteolysis by about 2 weeks with respect to the control, which only contained the parental strain IFPL359. At the end of the experimental period higher amino acid levels were detected by HPLC in the slurry containing whole T1 cells. Volatile fractions of the different cheese-curd slurries were also analysed. The higher level of proteolysis produced by addition of high levels of strain T1 appeared to be related to release of intracellular enzymes by this strain owing to its greater capacity for autolysis.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 11 (1998), S. 407-410 
    ISSN: 0894-3230
    Keywords: gas-phase thermolysis ; N-methyl-N-phenyl-tert-butylsulfenamide ; morpholinyl-tert-butylsulfenamide ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: N-Methyl-N-phenyl-tert-butylsulfenamide (MPSA) and morpholinyl-tert-butylsulfenamide (MOSA) were thermolyzed in a stirred-flow reactor at temperatures of 340-390 °C and pressures of 7-13 Torr, using toluene as carrier gas, at residence times of 0.3-1.3 s. Isobutene was formed in 99% yield through first-order reactions having the following Arrhenius parameters (A,s-1, Ea, kJ mol-1): MPSA, log A  =  12.41 ± 0.02, Ea  =  158.8 ± 0.2; MOSA, log A  =  12.91 ± 0.22, Ea  =  159 ± 3. It is proposed that the elimination of isobutene takes place by unimolecular reaction mechanisms involving polar, four-center cyclic transition states, forming S-unsubstituted thiohydroxylamines as co-products. Thermochemical parameters, estimated by semiempirical AM1 calculations, are reported for the latter and for the parent molecules. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 10 (1997), S. 49-54 
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: ---Various diallyl- and allylpropargylamines were pyrolyzed in a stirred-flow reactor at temperatures in the range of 330-500°C, pressures of 8-16 Torr and residence times of 0·4-2·4 s using toluene as carrier gas. The reaction products were propene, allene and aldimines. The allene to propene ratio changed considerably with the third substituent on the N atom. At conversions in the range 13-55%, the consumption of the amines showed first-order kinetics. The following Arrhenius parameters [A (s-1) and Ea (kJ mol-1)] were obtained from the rate coefficients: diallyl-tert-butylamine, log  A = 10·32 ± 0·12, Ea = 139 ± 2; diallylneopentylamine, log A = 12·87 ± 0·26, Ea = 168 ± 3; allylpropargyl-tert-butylamine, log A = 10·23 ± 0·18, Ea = 126 ± 2; allylpropargyltosylamine, log A = 13·05 ± 0.36, Ea = 197 ± 5; and allylpropargylphenylamine, log A = 12·10 ± 0·35, Ea = 162 ± 4. Polar, six-center cyclic transition states are suggested for the elimination of propene and allene, via non-concerted bond breaking-bond forming mechanisms. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0044-8249
    Keywords: Komplexe mit Schwefelliganden ; ortho-Metallierung ; Palladiumverbindungen ; Sulfoxide ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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