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- Mathematical modeling of gallic acid release from chitosan films with grape seed extract and carvacrolPublication . Rubilar, Javiera F.; Cruz, Rui; Zuñiga, Rommy N.; Khmelinskii, Igor; Vieira, M. M. C.Controlled release of antimicrobial and antioxidant compounds from packaging films is of utmost importance for extending the shelf-life of perishable foods. This study focused on the mathematical modeling of gallic acid release into an aqueous medium from three chitosan films, formulated with grape seed extract (GSE) and carvacrol. We quantified the release by HPLC technique during 30days at three temperatures (5, 25 and 45°C). The diffusion coefficients, varying with temperature according to an Arrhenius-type relationship, and the respective activation energies for Film-1 and Film-2 were, respectively [Formula: see text] m2s-1 and [Formula: see text] m2s-1, Ea1=58kJmol-1 and Ea2=60kJmol-1 as obtained from the Fickian fit. The low concentrations of gallic acid released by Film-3 could not be detected by HPLC, therefore the respective diffusion coefficient was not estimated. This study will help with the development and optimization of active packaging (AP) films aiming at improved food preservation and shelf-life extension.
- Development of poly(lactic acid) films with propolis as a source of active compounds: biodegradability, physical, and functional propertiesPublication . Ulloa, P. A.; Vidal, J.; Lopez de Dicastillo, C.; Rodriguez, F.; Guarda, A.; Cruz, Rui; Galotto, M. J.Active films (AFs) using poly(lactic acid) (PLA) as a polymeric matrix containing various propolis concentrations (5, 8.5, and 13%) as the active agent (AA) were developed using a casting method. The purpose was to determine the effects of the incorporation of AA on the physical properties of the films and to evaluate the antioxidant and antimicrobial activities. Tensile strength and elastic modulus of the AFs decreased relative to the control (PLA without AA). Introducing the active substances from propolis into the PLA also affected its thermal properties (glass transition). Adding AAs to the polymer generated more opacity with a green-yellowish color compared to the control. In addition, AFs exhibited reduced water vapor permeability as the AA concentration increased. Biodegradation assay showed that the AFs degraded faster than the control. AFs exhibited antioxidant activity, which was measured as the ability to scavenge free radicals (2,2-diphenyl-1-picrylhydrazyl and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonate)), due to the presence of bioactive compounds (phenolics). Antimicrobial activity was evaluated against Escherichia coli and showed a reduction over 4-log cycles. Therefore, incorporation of propolis is a useful strategy for the development of active packaging with antioxidant and antimicrobial effects, which increase the shelf life of food products. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47090.
- Preparation and characterization of a chitosan film with grape seed extract-carvacrol microcapsules and its effect on the shelf-life of refrigerated Salmon (Salmo salar)Publication . Alves, Vera Lúcia da Conceição Duarte; Rico, Bruna P. M.; Cruz, Rui; Vicente, António A.; Khmelinskii, Igor; Vieira, MargaridaChitosan films with grape seed extract and carvacrol microcapsules (CMF) were prepared and their physico-chemical properties and effect on physico-chemical and microbiological parameters in refrigerated salmon were tested. CMF showed higher values of thickness (0.41 ± 0.04 mm), moisture content (13 ± 1 g water/100 g film), a (11 ± 3), b (12 ± 3), opacity (20 ± 1%), water vapor permeability (WVP) (4.4 ± 0.4) × 10−10 gPa−1s−1m−1, oxygen permeability (O2P) (1.3 ± 0.3) × 10−12 gPa−1s−1m−1 and carbon dioxide permeability (CO2P) (1.3 ± 0.3) × 10−12 gPa−1s−1m−1 as compared to those of the chitosan control film (CCF). CMF showed lower values of L (66 ± 5) and water solubility (17 ± 1%). The salmon packed into CMF presented on the 7th day of storage a lower value of TVB-N (37 ± 4 mg N/100 g fish) as compared to the CCF (42 ± 3 mg N/100 g fish) and control samples (CS; 66 ± 7 mg N/100 g fish). The CMF showed lower values of pH and lightness after 7 days of storage as compared to CS and CCF. The CMF showed also lower values of mesophilic and psychrophilic bacteria and Pseudomonas spp, reaching the maximum limit allowed for the first two only on the 7th day of storage. CMF increases the shelf-life of refrigerated salmon to 4–7 days of storage due to the antimicrobial effect of the natural agents.