Edible coatings based on chitosan-beeswax emulsions

Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica

The use of edible biopolymer-based films and coatings is an environmentally friendly technology that offers substantial advantages for increase of shelf-life of many food products including fruits and vegetables. The development of this kind of films and coatings is a technological challenge for the industry and a very active research field worldwide. In this work biodegradable edible films of chitosan with different contents of beeswax were prepared and characterized. Their hygroscopic properties and water vapour permeability, as well as their CO2 and O2 permeability, mechanical, optical and superficial properties were determined. All the obtained films are transparent with a slightly yellowish colour. They are homogeneous and dense, despite the films with beeswax presented some cracks and depressions in their structure. The incorporation of beeswax increases the films hydrophobicity, higher contact angle values, but still prevails their hydrophilic nature. Regarding the mechanical properties, these films are flexible and elastic, but the increase of beeswax content increases their brittleness. The films showed decreased water vapour permeability as well as decreased hydrophilic properties, with the increase of beeswax content. The sorption and diffusion coefficients were evaluated for water vapour transport. The permeability decrease was mainly due to the reduction of the diffusion coefficient. A reduction of the water vapour permeability and a significant reduction in oxygen permeability were achieved with the inclusion of beeswax in the polymeric matrix. Comparing to the films without beeswax, the water vapour permeability decreased 32% and the oxygen permeability 90% for the films with 10% beeswax. Regarding the carbon dioxide permeability, it increased about 240% for the films with 10% beeswax. From the results, it is thought that these films are promising to be used in food packaging mainly for fruits and vegetable coating, mainly due to their barrier properties that allow the products to breathe and inhibit the oxidation process.