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The effect of polymer/plasticiser ratio in film forming solutions on the properties of chitosan films

Publication . Fundo, Joana; Galvis-Sanchez, Andrea C.; Delgadillo, Ivonne; Silva, Cristina L. M.; Quintas, Mafalda A. C.

In this work physical-chemical properties of chitosan/ glycerol film forming solutions (FFS) and the resulting films were analysed. Solutions were prepared using different concentrations of plasticising agent (glycerol) and chitosan. Films were produced by solvent casting and equilibrated in a controlled atmosphere. FFS water activity and rheological behaviour were determined. Films water content, solubility, water vapour and oxygen permeabilities, thickness, and mechanical and thermal properties were determined. Fourier transform infrared (FTIR) spectroscopy was also used to study the chitosan/glycerol interactions. Results demonstrate that FFS chitosan concentration influenced solutions consistency coefficient and this was related with differences in films water retention and structure. Plasticiser addition led to an increase in films moisture content, solubility and water vapour permeability, water affinity and structural changes. Films thermo-mechanical properties are significantly affected by both chitosan and glycerol addition. FTIR experiments confirm these results.

2015Journal article

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Relationship between molecular mobility, microstructure and functional properties in chitosan/glycerol films

Publication . Fundo, Joana; Carvalho, Alexandra; Feio, Gabriel; Silva, Cristina L. M.; Quintas, Mafalda A.C.

Foods are partially crystalline partially amorphous systems. Edible films are considered good models for food systems due to their interesting physical properties, quite straightforward matrices, and easy reproduction. Chitosan is a semicrystalline biopolymer, biocompatible, biodegradable, with antimicrobial activity and filmogenic properties, thoroughly used in edible films' studies. This work aims to investigate the relationship between chitosan films' molecular relaxation time, their microstructure (crystallinity) and functional properties. Analyses were carried out using data on chitosan/glycerol films prepared with different polymer/plasticisant concentrations. Results demonstrate that there is a relationship between macroscopic properties and water and glycerol relaxation times. Moreover, results show that while water is free in the matrix, glycerol is linked to the chitosan polymeric chains, decreasing intermolecular attractions and increasing free volume, thus facilitating molecular migration. Also the data analysis reveals the usefulness of NMR and molecular mobility studies in the matrix for characterisation and development of polymeric structures. Industrial relevance: NMR spectroscopy is currently one of the key methods for food characterisation. Foodstuff is a complex matrix including many different compounds with different chemical structures, concentrations, solubility, properties and nutritional values. From a fundamental perspective, foods are mainly edible and digestible biopolymers that are partially crystalline/partially amorphous and thus edible films, specifically chitosan/glycerol films can be very interesting food model systems for mobility and microstructure studies. Studies on water and solids' mobility and thermo-mechanical properties in food systems (real or model systems),are fundamental to fully attain food physical properties and stability. These studies may be extremely useful for food product and process design, safety and sensorial attributes and also for better understanding and predicting, for example, food storage stability conditions.

2015Journal article

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Κ-carrageenan/chitosan nanolayered coating for controlled release of a model bioactive compound

Publication . Pinheiro, Ana C.; Bourbon, Ana I.; Quintas, Mafalda A.C.; Coimbra, Manuel A.; Vicente, António A.

Multilayer nanocoatings composed of κ-carrageenan, a sulphated anionic polysaccharide, and chitosan, a cationic polysaccharide, were produced by layer-by-layer deposition. The model cationic compound Methylene Blue (MB) was incorporated in different positions of the nanolayered coating and its loading and release behavior was evaluated. UV–VIS spectroscopy and quartz crystal microbalance analysis showed that the amount of MB loaded increased with the distance from the first layer, suggesting that the MB was able to diffuse into the κ-carrageenan/chitosan nanolayered coating and not only adhered to the surface of the layer immediately below it. For most of the tested conditions, the MB release from the κ-carrageenan/chitosan nanolayered coatings was successfully described by the linear superimposition model, which allowed concluding that MB transport is due to both concentration gradient and the polymer relaxation of the nanolayers. However, depending on temperature and pH of the medium and on the position of MB incorporated on the nanolayered coatings, different mechanisms prevail. Industrial relevance: The development of novel edible coatings with improved functionality and performance for e.g. fresh and minimally processed fruits is one of the challenges of the post-harvest industry. This work contributes to the understanding of the loading and release phenomena involved in structures at the nanoscale, which is useful for the development of bioactive compounds release systems for application in food industry. Moreover, the κ-carrageenan/chitosan nanolayered coatings represent a promising platform from which the controlled release of different bioactive compounds may be explored.

2012Journal article

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Sucrose in the concentrated solution or the supercooled “State”: A review of caramelisation reactions and physical behaviour

Publication . Quintas, M. A. C.; Fundo, J. F.; Silva, C. L. M.

Sucrose is probably one of the most studied molecules by food scientists, since it plays an important role as an ingredient or preserving agent in many formulations and technological processes. When sucrose is present in a product with a concentration near or greater than the saturation point—i.e. in the supercooled state—it possesses high potentialities for the food industry in areas as different as pastry industry, dairy and frozen desserts or films and coatings production. This paper presents a review on critical issues and research on highly concentrated sucrose solutions—mainly, on sucrose thermal degradation and relaxation behaviour in such solutions. The reviewed works allow identifying several issues with great potential for contributing to significant advances in Food Science and Technology.

2010Journal article

Open access

Molecular mobility, composition and structure analysis in glycerol plasticised chitosan films

Publication . Fundo, Joana; Fernandes, Rui; Almeida, Pedro M.; Carvalho, Alexandra; Feio, Gabriel; Silva, Cristina L. M.; Quintas, Mafalda

This study was developed with the purpose to investigate the effect of polysaccharide/plasticiser concentration on the microstructure and molecular dynamics of polymeric film systems, using transmission electron microscope imaging (TEM) and nuclear magnetic resonance (NMR) techniques. Experiments were carried out in chitosan/glycerol films prepared with solutions of different composition. The films obtained after drying and equilibration were characterised in terms of composition, thickness and water activity. Results show that glycerol quantities used in film forming solutions were responsible for films composition; while polymer/total plasticiser ratio in the solution determined the thickness (and thus structure) of the films. These results were confirmed by TEM. NMR allowed understanding the films molecular rearrangement. Two different behaviours for the two components analysed, water and glycerol were observed: the first is predominantly moving free in the matrix, while glycerol is mainly bounded to the chitosan chain.

2014Journal article

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