Browsing by Author "Peeva L."

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    Antioxidant activity of membrane-fractionated coffee extracts in dependence of the storage conditions
    (2016-11-15) Mitev D.; Peshev D.; Peev G.; Peeva L.
    Present paper aims at one of the important aspects of the application of products with antioxidant activity: namely the preservation and change of their properties during the storage in different conditions, as well as their reliable characterisation. The tests of antioxidant properties were conducted with membrane-separated coffee extracts, isolated using a ``Microdyn Nadir NP030P`` type of commercial nanofiltration membrane (30% retention of NaCl; MWCO∼400). Prepared coffee permeates and retentates were stored 0/10 days in cool/warm conditions, with/without air access and at different illumination conditions. The kinetics of content changes was evaluated according to Folin-Ciocalteu method of total phenolic/reducing content determination.
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    Antioxidant activity of membrane-fractionated coffee extracts in dependence of the storage conditions
    (2016-11-15) Mitev D.; Peshev D.; Peev G.; Peeva L.
    Present paper aims at one of the important aspects of the application of products with antioxidant activity: namely the preservation and change of their properties during the storage in different conditions, as well as their reliable characterisation. The tests of antioxidant properties were conducted with membrane-separated coffee extracts, isolated using a ``Microdyn Nadir NP030P`` type of commercial nanofiltration membrane (30% retention of NaCl; MWCO∼400). Prepared coffee permeates and retentates were stored 0/10 days in cool/warm conditions, with/without air access and at different illumination conditions. The kinetics of content changes was evaluated according to Folin-Ciocalteu method of total phenolic/reducing content determination.
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    Depot effect of bioactive components in experimental membrane filtrations
    (2017-02-06) Mitev D.; Peshev D.; Peev G.; Peeva L.
    Depot effects were found to be accompanying phenomena of membrane separation processes. Accumulation of target species in the membrane matrix during feasibility tests can hamper proper conclusions or compromise the filtration results. Therefore, we investigated the effects of delayed membrane release of chlorogenic acid and caffeine, considered as key compounds of interest in spent coffee products' recovery treatment. Permeate fluxes and key components release were studied in course of 24 hours via nanofiltration of pure solvent, both immediately after the mock solution filtration and after idle stay. Conclusions are drawn and recommendations advised for proper analysis of experimental data on membrane screening.
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    Depot effect of bioactive components in experimental membrane filtrations
    (2017-02-06) Mitev D.; Peshev D.; Peev G.; Peeva L.
    Depot effects were found to be accompanying phenomena of membrane separation processes. Accumulation of target species in the membrane matrix during feasibility tests can hamper proper conclusions or compromise the filtration results. Therefore, we investigated the effects of delayed membrane release of chlorogenic acid and caffeine, considered as key compounds of interest in spent coffee products' recovery treatment. Permeate fluxes and key components release were studied in course of 24 hours via nanofiltration of pure solvent, both immediately after the mock solution filtration and after idle stay. Conclusions are drawn and recommendations advised for proper analysis of experimental data on membrane screening.
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    PECVD polymerised coatings on thermo-sensitive plastic support
    (2016-02-09) Mitev D.; Radeva E.; Peshev D.; Cook M.; Peeva L.
    With this paper we describe several alternative approaches aimed at polymer-on- polymer coatings, produced by Plasma Enhanced Chemical Vapour Deposition (PECVD) technique. In our case three types of input compounds were applied for varied ``cold plasma`` PECVD deposition of nano-thick functional layers: namely hexamethyldisiloxane (HMDSO), pentane and toluene onto plastic substrates. The output characterisations through SEM imaging, ATR-FTIR, EDX, AFM and contact angle measurements, proved the methods' feasibility and properties of the plasma-polymerised coatings.