Desenvolvimento de sistemas biopoliméricos ativos incorporando óleo essencial de cravo para preservação de alimentos

Abstract

The search for safer, natural, and sustainable foods has driven the advancement of technologies aimed at food preservation and the replacement of conventional packaging. In this context, this thesis aimed to develop two distinct active packaging systems using clove essential oil (CEO) as the active compound combined with biodegradable polymers, in order to evaluate their ability to inhibit different bacterial species. The thesis was organized into three chapters: the first dedicated to a literature review, and the following two chapters presented in the form of scientific articles. In Chapter 2, a bioactive chitosan film containing 1% chitosan and clove essential oil at concentrations of 1% and 1.5% was developed. Successful entrapment of CEO within the chitosan polymer matrix was observed. The film containing 1% CEO exhibited a uniform microstructure, improved flexibility, and adequate thermal stability. The film containing 1.5% CEO showed microphase separation. Both films were able to inhibit the growth of Escherichia coli, Salmonella Enteritidis, and Staphylococcus aureus. Refrigerated strawberries, cherry tomatoes, and Fuji apples were coated using the dipping technique, and the formulation containing 1% CEO was able to extend the shelf life of refrigerated strawberries by 8 days. The developed film proposes a simpler clean-label packaging approach, highlighting its potential application as active packaging. In Chapter 3, CEO was encapsulated using cellulose nanocrystals (CNC), producing a Pickering emulsion (PE-CEO) for incorporation into hydroxypropyl methylcellulose (HPMC). Stable emulsions were produced and maintained for at least 90 days using 1.5% CNC. The emulsions demonstrated antibacterial activity against E. coli ATCC 25922, S. Enteritidis 13076, K. pneumoniae, and S. aureus 25923, as well as multidrug-resistant and ESBL-producing strains, including E. coli ESBL, S. diarizonae ESBL, K. pneumoniae, and S. aureus. HPMC films containing different concentrations of PE-CEO (1.5, 3.0, 6.25, and 12.5%) were then produced. These films exhibited a homogeneous microstructure, transparency of up to 59.2%, appropriate viscoelastic behavior, and a significant reduction in bacterial counts after 24 hours for all tested strains, particularly at the higher concentrations (6.25 and 12.5%). Overall, the results demonstrate that the developed films represent a promising and sustainable approach, aligned with the clean-label concept for the development of active packaging.