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  • 1
    ISSN: 1438-2385
    Keywords: Micrococcus strains ; Cheese ripening ; Organoleptic characteristics ; Arzúa cow's-milk cheese
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Ten batches of Arzúa, a soft cow's-milk cheese produced in northwest Spain, were prepared from pasteurized milk. Two (control) batches (CB) were made with a commercial starter containingLactococcus lactis subspecieslactis andcremoris. Another eight batches (MB) were made with the commercial starter plus one of eightMicrococcus spp. strains previously isolated from raw-milk Arzúa cheeses. In all MB, β-casein degradation over the 30-day ripening period was more pronounced (mean 31%) than in the CB (mean 12%). αS1-Casein degradation was highly variable in the MB, though mean degradation over the ripening period (75%) was similar to that observed in the CB (73%). Similarly, volatile fatty acid (VFA) content was highly variable in the MB, with the mean content at 30 days (3.8 mEq per 100 g) being higher than in the CB (1.6 mEq per 100 g). Rheological characterization of the cheeses (by uniaxial compression) revealed significant differences between batches, with some samples fracturing under the compression pressure applied and others not. Sensory evaluation also revealed significant differences. “Non-milk” aromas were more frequently detected in batches made with lipolytic micrococcal strains. Betweenbatch differences in tastes and texture were also detected. Multiple correlation analysis of the data obtained at day 15 of ripening revealed statistically significant positive correlations (r〉0.70) between αS1-casein content and dry matter content, between αS1-casein content and sensorially evaluated firmness, and between VFA content and sensorially evaluated rancidity. Statistically significant negative correlations between sensorially evaluated firmness and the ratio of αS1-I content to αS1-casein content were detected. The results of this study suggest a need for further studies aimed at selecting those strains which could be most suitable for the production of Arzüa cheeses; due to their effects on texture, αS1-caseinolytic strains seem to be more appropriate than β-caseinolytic ones.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 22 (1991), S. 111-117 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Visible excitation resonance Raman difference spectra, in resonance with the 605-nm absorption maximum of fully reduced and mixed-valence cyanide-bound cytochrome oxidase, were recorded. Under these conditions, the vibrations of ferrocytochrome a are markedly enhanced owing to its dominant contribution to the 605-nm α-band absorption of reduced cytochrome oxidase. The effect of H/D exchange in the Raman spectra of cytochrome a was also investigated as a way to establish formyl- and vinyl-peripheral substituent sensitive modes. Measurements of the depolarization ratio dependence of cytochrome a vibrational modes resulted in some isotope-sensitive modes with characteristic depolarized behavior; however, it was observed that the majority of the visible excitation vibrations exhibit polarized values. This is interpreted as being due to a significant lowering in the molecular symmetry of the heme a porphyrin macrocycle caused by the unusual peripheral substituent pattern of heme a and, presumably, by the strong cytochrome a-protein interactions. Both structural effects appear to result in a selective enhancement of cytochrome a Eu substituent-sensitive modes as detected by the low-frequency resonance Raman spectrum.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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