Functional properties of sodium and calcium caseinate antimicrobial active films containing carvacrol

Active edible films were prepared by adding carvacrol into sodium caseinate (SC) and calcium caseinate (CC) matrices plasticized with two different glycerol concentrations (25 and 35 wt%) prepared by solvent casting. Functional characterisation of these bio-films was carried out by determination of some of their physico-chemical properties, such as colour, transparency, oxygen barrier, wettability, dye permeation properties and antibacterial effectiveness against Gram negative and Gram positive bacteria. All films exhibited good performance in terms of optical properties in the CIELab space showing high transparency. Carvacrol was able to reduce CC oxygen permeability and slightly increased the surface hydrophobicity. Dye diffusion experiments were performed to evaluate permeation properties. The diffusion of dye through films revealed that SC was more permeable than CC. The agar diffusion method was used for the evaluation of the films antimicrobial effectiveness against Escherichia coli and Staphylococcus aureus. Both SC and CC edible films with carvacrol showed inhibitory effects on both bacteria.

Ethylene vinyl acetate/nanoclay-based pigment composites: Morphology, rheology, and mechanical, thermal, and colorimetric properties

In this study, a new type of nanopigment, obtained from a nanoclay (NC) and a dye, was synthesized in the laboratory, and these nanopigments were used to color an ethylene vinyl acetate (EVA) copolymer. Several of these nanoclay-based pigments (NCPs) were obtained through variations in the cation exchange capacity (CEC) percentage of the NC exchanged with the dye and also including an ammonium salt. Composites of EVA and different amounts of the as-synthesized nanopigments were prepared in a melt-intercalation process. Then, the morphological, mechanical, thermal, rheological, and colorimetric properties of the samples were assessed. The EVA/NCP composites developed much better color properties than the samples containing only the dye, especially when both the dye and the ammonium salt were exchanged with NC. Their other properties were similar to those of more conventional EVA/NC composites.

Linear low-density polyethylene colored with a nanoclay-based pigment: Morphology and mechanical, thermal, and colorimetric properties

In this study, a novel kind of hybrid pigment based on nanoclays and dyes was synthesized and characterized. These nanoclay-based pigments (NCPs) were prepared at the laboratory with sodium montmorillonite nanoclay (NC) and methylene blue (MB). The cation-exchange capacity of NC exchanged with MB was varied to obtain a wide color gamut. The synthesized nanopigments were thoroughly characterized. The NCPs were melt-mixed with linear low-density polyethylene (PE) with an internal mixer. Furthermore, samples with conventional colorants were prepared in the same way. Then, the properties (mechanical, thermal, and colorimetric) of the mixtures were assessed. The PE–NCP samples developed better color properties than those containing conventional colorants and used as references, and their other properties were maintained or improved, even at lower contents of dye compared to that with the conventional colorants.