Functional Materials for Intelligent Food Packaging

• Autor(a) principal: Dias, Bárbara Beatriz Caldas
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10362/156036
• topic: Food packaging; carboxymethylcellulose; cellulose acetate; ethyl cellulose; anthocyanins; curcumin; Domínio/Área Científica::Engenharia e Tecnologia::Nanotecnologia

Nowadays, plastic has been used as a common packaging material owing to its transparency, durabil-ity, and softness. Nevertheless, in the food packaging field, the increased plastic consumption has caused, not only severe environmental problems, due to their non-biodegradability, but also health threats, as a conse-quence of the plastic’s toxic additives migration. Generally, cellulose derivatives, namely carboxymethylcellulose (CMC), cellulose acetate (CA) and ethyl cellulose (EC), can be used to develop food packaging films as an alternative to plastics, because of their compatibility, non-toxicity, and higher stability. Additionally, the latest research, for the development of col-orimetric pH films to monitor the food freshness, has focused on adding safe and natural pigments, such as, anthocyanins (ANT), curcumin (CUR) and betalains (BE), owing to their pH sensing capabilities. The main focus of this thesis relies on the development of functional inks that can act as an indicator for food packaging applications. Therefore, ANT, CUR and BE were explored, as well as, CMC, CA and EC were tested for the development and stabilization of indicators. After their development, the films were char-acterized in terms of their pH sensing characteristics, morphology, chemical interactions, colour and its opac-ity, mechanical properties, moisture content, and lastly, a food model (salmon) was used for the evaluation of the indicators' capacity. Initially, a brown colour was observed in CMC, CA and EC-based films, which was associated with the presence of ANT, an orange colour was corelated with the presence of CUR and a pink colour to the addition of BE. When immersed in different pH buffer solutions, it was demonstrated different colour ranges, accordingly to the natural dye used in the CMC and CA-based films. However, for the EC-based films with the incorporation of different pigments, it was verified the maintenance on their colour. Morphological characteristics suggested a good compatibility between lower concentrations of pig-ments and the polymers matrix. For higher concentrations, the observation of small aggregates distributed in the films resulted in a low compatibility between the natural dyes and the polymers matrix. These observations were corelated with the films mechanical properties and the Fourier transform infrared spectroscopy analysis. The results suggest that the intelligent films reported here (CMC and AC-based films) show good capability to be used as indicators and, thus, act as a way to alert food spoilage.