The surface wetting of five biopolymers, used as coating materials for a plastic film, was monitored over a span of 8 min by means of the optical contact angle technique. Because most of the total variation was observed to occur during the first 60 s, we decided to focus on this curtailed temporal window. Initial contact angle values (θ(0)) ranged from ∼91° for chitosan to ∼30° for pullulan. However, the water drop profile began to change immediately following drop deposition for all biocoatings, confirming that the concept of water contact angle equilibrium is not applicable to most biopolymers. First, a three-parameter decay equation [θ(t) = θ(0) exp(kt(n))] was fit to the experimental contact angle data to describe the kinetics of the contact angle change for each biocoating. Interestingly, the k constant correlated well with the contact angle evolution rate and the n exponent seemed to be somehow linked to the physicochemical phenomena underlying the overall kinetics process. Second, to achieve a reliable description of droplet evolution, the contact angle (CA) analysis was coupled with image analysis (IA) through a combined geometric/trigonometric approach. Absorption and spreading were the key factors governing the overall mechanism of surface wetting during the 60 s analysis, although the individual quantification of both phenomena demonstrated that spreading provided the largest contribution for all biopolymers, with the only exception of gelatin, which showed two quasi-equivalent and counterbalancing effects. The possible correlation between these two phenomena and the topography of the biopolymer surfaces are then discussed on the basis of atomic force microscopy analyses.

Development of packaging materials from renewable resources has for a long time been desirable for sustainability reasons, but with recent explosions in prices of petroleum products, this now becomes also more economically viable. This paper shows how fundamental chemistry underlying three forms of hydrogelsphysical hydrogels, chemical hydrogels, and interpenetrating polymer networks (IPN)can be integrated to produce a new family of food packaging materials from biopolymers, illustrated here using gelatin and low-methoxyl pectin as examples. Application of this technique to create hydrogels from bio-based materials offers the potential for developing novel, biodegradable packaging applications, particularly for foods, that meet the ever-increasing demands for natural and environmentally compatible materials.

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Nanocellulose has potential applications across several industrial sectors and allows the development of innovative materials, as well as the enhancement of conventional materials properties. The nanocellulose particles can be utilized as fillers, in composites manufacture, as coating and as self‐standing thin films, achieving always very interesting and promising properties. Very few of the several reviews that recently appeared on this topic in the scientific literature, however, summarized the potential of cellulose in nanoform specifically for the packaging field rather focusing on different aspects, ranging from the chemistry and the morphology of nanocellulose particles to the preparation methods, the industrial applications and the patents released. In the present review, the remarkable chemical and physical properties of nanocellulose are introduced and discussed with specific reference to the packaging needs. First, the cellulose resources and structure are introduced, then the process methods to reach the nanoscale, the corresponding morphologies and nomenclatures are summarized, mentioning also the possible chemical modifications of nanocellulose and, finally, its practical and potential applications for packaging materials, especially food packaging materials, are tentatively proposed and discussed. Although the review might not cover every aspect on nanocellulose, yet the key points, particularly those related to safety and biodegradability issues, are regarded and considered. Copyright © 2015 John Wiley & Sons, Ltd.

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