Desenvolvimento de nanoemulsões de óleos essenciais incorporadas em filme de metilcelulose para uso em alimentos

• Autor(a) principal: Pontes, Silvania Farias Oliveira
• Data de Publicação: 2013
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/482
• topic: Embalagem ativa; Biopolimeros; Nanotecnologia; Active packaging; Biopolymers; Nanotechnology; CNPQ::CIENCIAS AGRARIAS::CIENCIA E TECNOLOGIA DE ALIMENTOS::TECNOLOGIA DE ALIMENTOS

Aiming minimize the environmental impact induced by conventional polymers, alternatives like biodegradable polymers use, as methylcellulose, has been proposed. In addition, film production incorporated with natural antimicrobials, as essentials oils, can promote an improvement in foods safety and shelf life. The purposes of this work was to develop essentials oils nanoemulsions, like oil/water, and incorporate themselves to methylcellulose films aiming to produce active packaging; evaluate the in vitro and in loaf bread antimicrobial effect and the mechanicals and barriers properties of this film. In addition to the optical properties characterization, Fourier transform spectroscopy and the obtained films structures observation through the Scanning Electron Microscopy and Atomic Force Microscopy were techniques applied in this work. For the in vivo study, slices of loaf breads were placed in films and had the microbiological, physico-chemical and sensory qualities evaluated. The conditions employed for the nanoemulsions production containing 1.5% of Tween 80 and 2.0% essential oil were: 400 W of potency and 20 kHz of frequency for 10 minutes in ultrasonic homogenizer. Under these conditions essential oils nanoemulsions were formed and exhibited diameter ranging from 120 to 230 nm, without presenting signs of macroscopic instability (visual). It was observed that the nanoemulsions incorporations in films allowed the antimicrobial activity for Aspergillus niger and Penicillium spp in vitro and were effective reducing yeast and mold counts in sliced loaf breads during 15 days storage. A 10 days prolongation of loaf breads shelf life was noted and no molds development was observed. Regarding the mechanical properties, the essentials oils nanoemulsions incorporation do not affected the resistor tensile but resulted in an elongation increasing. In addition it promoted changes in elasticity modulus by making them less rigid. The water vapor rate of permeability and the films surface hydrophilicity were not changed by the nanoemulsions incorporation. At a 210 nm wavelength, the films demonstrated excellent transparency characteristics and according to color parameters L*, a * and b* films exhibited clear yellow staining. Scanning Electron Microscopy and Atomic Force Microscopy pictures showed structures of the spherical droplets whose diameter ranged between 150 and 250 nm. Similar sizes were found in scattered light analysis. According to FTIR spectrum analysis it was observed that the interactions between the polymer and the nanoemulsions were very similar regardless of the presence or absence of the nanoemulsions formations but were different in each oil composition. The analyses of Physico-chemical and sensory qualities of packed breads, throughout the storage period, showed that the loaf breads hardened and theirs moisture content ranged directly correlated with the parameter texture variation. Breads samples pH, acidity, and color parameters were not affected by the essentials oils nanoemulsions incorporations. Focus group sessions revealed that antimicrobial packaging uses negatively interfered in loaf breads sensory characteristics resulting in their rejection. It was also observed that the expression "active packaging" is a breakthrough concept and unfamiliar for loaf breads consumers. Disclosures are necessary to improve this new concept understanding, besides elucidating possible doubts about this packaging system.