Films containing antibacterial compounds could be used for packaging perishable foods such as fresh fish and meat for sea freighting over long distances. However, existing commercialised options (films with nanosilver zeolites or wasabi extract) are only permitted for food contact in certain regions and films containing alternative antibacterial ingredients are required e.g. for exports to Europe. Certain non-volatile phenolic plant extracts have shown promising antibacterial activity against a wide range of foodborne bacteria in in vitro assays and when integrated in coatings for perishable foods such as fish and meat. Extracts rich in gallotannins tend to show stronger antibacterial effects than other phenols such as flavonoids. Such extracts could be coated onto commercial barrier films by means of flexographic printing-a more industrially feasible option than rod coating or solvent casting typically used in antibacterial coating research. The goal of the present work was to investigate the antibacterial effect of printed latex coatings containing extracts rich in gallotannins and other types of phenolic compounds against 16 common spoilage and pathogenic bacteria of fish and meat. The largest zones of inhibition in disk diffusion assays were obtained with plastic films with coatings containing tannic acid alone, followed by tannic acid with phenolic-rich extracts of feijoa skin or mango seed. Significant inhibition was seen for all bacteria. This study shows that coatings with gallotannins as the main active ingredient can be printed onto commercial barrier films to control the bacteria that limit the shelf-life of fresh fish and meat.

The decrease in the corona treatment effect with time and its influence on the flexographic printability of low-density polyethylene-coated paperboard were studied. After corona treatment, sheets were stored in different ways. Some sheets were stored in a laboratory atmosphere, while others were protected from exposure to light, air, moisture and dust in polyethylene bags. The tendency for ink to spread on the surfaces was studied using contact angle measurements. Printability was evaluated as print density, dot gain, uncovered (white) and mottling. The results obtained show that the surface energy of the protected sheets decreased with time, but not as much and not as quickly as that of the unprotected sheets. In the case of the protected sheets, the percentage uncovered areas and mottling remained constant, but for the unprotected sheets they increased with increasing time after the corona treatment. No significant differences were seen in the other print quality measures.

One of the purposes of thermoplastic composites films and barrier dispersion coatings is to minimize the permeation of gases. In both cases, fillers and other additives are added during the film preparation to improve barrier properties. A high level of understanding has resulted from the study of the interaction between filler and polymer phases of thermoplastic composites, and a number of models have been developed to predict the relative permeability of these materials. However, barrier dispersion coatings have not been modelled in this way. The aim of this review was to discuss similarities and differences of thermoplastic composites and barrier dispersion coatings that may influence the applicability of the models for barrier dispersion coatings applied to paper-based materials. The models were developed as a function of the amount of fillers added in thermoplastic composites films and geometrical characteristics of the fillers such as size, thickness, shape and the distribution of fillers in the film. Two-and three-dimensional models with oriented and random arrangement of fillers were presented. Due to the parallel orientation and the similar length and width of fillers used in barrier dispersion coatings, three-dimensional models were more suitable to predict relative permeability. These models assumed plate-or circular-shaped fillers with parallel orientation. In order to prove the models, experimental information was required. Very limited data for barrier dispersion coatings with varying the amount of fillers have been reported in the literature. For this reason, further experiments are required under varied combinations of aspect ratio and the volume fraction of fillers.

Hydrophobic clay fillers have not been widely used in dispersion coatings for linerboard because of the difficulty of dispersing them in water. This work investigated whether hydrophobic clay can be used as filler in barrier dispersion coatings. Hydrophobic clay was compared with conventional clay in terms of coating consolidation, structure, wetting, and barrier performance. All coatings were applied to linerboard sheets made using a laboratory dynamic sheet former. The coated linerboards were examined using scanning electron microscopy and Raman spectroscopy, and were characterized with respect to water absorption, vapor transmission rate, and contact angles. The results show that a coating containing hydrophobic clay provides a superhydrophobic character to paper; i.e., a high water contact angle (150°) and relatively low water absorption. Raman mapping of cross-sections revealed that the latex distribution is uniform in the presence of either conventional clay or hydrophobic clay, and that the distribution of hydrophobic clay tends to be more uniform than conventional clay, which might reflect good mixing and consolidation of hydrophobic clay.

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