Protecting from Oxygen (and from other gases)

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As mentioned in previous chapters, the benefits provided by innovation inthe paper and board business are connected with the possible chemicalmodification of fibres, with coupling with other materials (composites), aswell as with special surface treatments.Today paper and board can substitute polymers by virtue of their enhancedability to act as barriers to gases, while displaying an active, antimicrobial,photocatalytic, etc. behaviour. The desired barrier effect is primarily againstoxygen. Considerable interest was aroused in the past by substances likeartificial or natural antioxidant additives, capable to act as a barrier to oxygenby preventing its action, as well as by solutions that prevent oxygencontact with food, such as vacuum and modified atmosphere. One interestingoption today is nanocellulose, a strong barrier to oxygen and othergases that can truly compete with resins currently in use to produce compositematerials.A water barrier is also required for paper and board. Surface treatmentsare therefore available for paper, enhancing its resistance to water contactwithout affecting its recyclability and biodegradability properties.Also important is the grease barrier. Greaseproof paper can be obtainedthrough the enhanced disaggregation of the fibre mesh, which can beachieved either chemically or mechanically. Alongside mass treatment,surface coatings are also available. These act as a physical barrier to greaseby means of paraffin, fluorinated emulsions, or silicone-based composites.Coatings based on polymer solutions have a severe drawback – they prevent paper recyclability. Therefore latest research in the paper and boardpackaging pipeline is aimed at producing new grease-barrier coating options,to be used without jeopardizing the medium’s recyclability. In thesenatural coatings, the “active” part, i.e. the fraction responsible for the desiredbarrier properties, is made up of biodegradable substances, includingpolysaccharides, proteins, and fatty acids.Microbial proliferation is another important cause for food decay. Bacterialcontamination occurs, in particular, on the product’s surface, and incorporatingantimicrobial agents in packaging allows to reduce the amountof preservatives added to food and to modulate their release. At present,research is carried out based on a variety of approaches: these range froma release mechanism, where the antimicrobial agent is incorporated in thematerial and migration to food occurs through diffusion and distributionwith a decreasing effect in time, to a contact-based mechanism, where theantimicrobial agent is immobilized on the material and the antimicrobialaction is displayed at the interface, thus ensuring a long-lasting effect.Abundant research is carried out on chitosan, another natural substanceand a structural component of the shell of certain crustaceans. It is a biodegradablematerial with excellent antimicrobial properties. Lastly, severalstudies focus on titanium dioxide, which displays both an antibacterial anda photocatalytic action and is therefore applied in the paper and board sectoron food packaging, as well as on other products, such as air purificationdevices.
Lingua originaleEnglish
Numero di pagine28
Stato di pubblicazionePublished - 2016

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