Incorporação do antioxidante natural a-tocoferol em filmes de carboximetilcelulose

Abstract

A incorporacao de antioxidantes em filmes e recobrimentos comestiveis auxilia na prolongacao da vida de prateleira dos alimentos retardando o processo de oxidacao desses produtos. A funcao da vitamina E como antioxidante e desacelerar as reacoes de oxidacao impedindo a propagacao das reacoes via radicais livres. O a-tocoferol (TC) e o antioxidante natural mais abundante, com maior bioatividade e biodisponibilidade. A carboximetilceluose (CMC) e um polissacarideo anionico, linear, insipido, inodoro, soluvel em agua, sendo amplamente utilizado em produtos alimenticios. O objetivo deste trabalho foi incorporar TC em filmes de CMC e avaliar a estabilidade quimica e as propriedades antioxidantes. Os filmes foram obtidos atraves da tecnica de casting. As emulsoes de CMC 2% (m/m) com o TC e os surfactantes, Tween 80 (TW) e lecitina com diferentes composicoes, foram preparadas em um Ultra-Turrax a 7500 rpm por 20 minutos. As emulsoes secaram em placas de Petri por aproximadamente 6 dias. Medidas de fluorescencia indicaram que o TC presente nos filmes permaneceu estavel por todo o periodo analisado, o qual foi de 8 semanas. Filmes contendo CMC e TC sem os surfactantes apresentaram separacao de fase na matriz. A analise morfologica demonstrou que os filmes contendo TW mostraram-se homogeneos, porem continham grandes cavidades, enquanto que nos filmes com TW e lecitina as a homogeneidade se manteve, entretanto com poros muito menores. Na analise de cor, os filmes apresentaram-se transparentes, sem grandes variacoes de cor. No que diz respeito a permeabilidade ao vapor de agua (PVA), os filmes contendo TW e lecitina apresentaram valores de permeabilidade proximos ao da CMC pura, demonstrando que nao houve rompimento da matriz polimerica. As propriedades mecanicas dos filmes tambem sofreram alteracoes com as adicoes, uma vez que com o aumento da concentracao dos surfactantes, houve um decrescimo nos valores do modulo de Young e tensao de ruptura, e consequentemente, ocorreu um aumento no alongamento maximo. Nas analises de perfil de liberacao e atividade antioxidante, os filmes apresentaram valores superiores para as amostras que continham lecitina em sua formulacao, o que pode ser explicado pela interacao entre a lecitina e o TC e sua afinidade com o etanol. Conclui-se que, os sistemas aqui estudados apresentam potencial aplicacao para embalagens biodegradaveis na industria de alimentos.<br>

Abstract : The incorporation of antioxidants into edible films and coatings helps to extend the product shelf-life by retarding oxidation processes in food products. Vitamin E functions as a chain-breaking antioxidant that prevents the propagation of free radical reactions. The most naturally abundant form is a-tocopherol (TC), which is also the most biologically active and most bio-available. Carboxymethyl cellulose (CMC) is a linear, long-chain, water-soluble, anionic polysaccharide, tasteless, odorless, free-flowing powder and has wide application in foods. The objective of this work was to incorporate TC in CMC films and assess its chemical stability and antioxidant properties. Films were obtained by casting technique. For each film, 2g of CMC were solubilized for 24 h at 60°C and 250 rpm. After that, TC and surfactants with differents compositions, were emulsified in an Ultra-Turrax at 7500rpm for 20min. The filmogenic solution was then casted in Petri dishes and dried during 6 days at ambient temperature. The surfactants used were Polysorbate 80 (TW) and Lecithin (LC). Fluorescence measurements were made to monitor the stability of a-tocopherol present in the films for 8 weeks, which showed good stability during the studied period. Films containing CMC and TC without surfactants showed a clear phase separation between TC and the CMC matrix. The morphological analysis showed that films containing TW were homogeneous, but contained large cavities, while in the films containing lecithin and TW, the homogeneity is maintained, although with much smaller pores. In colorimetric analysis, the films were transparent, without major variations in color. Regarding the water vapor permeability (PVA), films containing lecithin and TW showed PVA values close to that of pure CMC, indicating that no break of the polymer matrix has occurred. The mechanical properties of films have also changed with the compound addition, since an increasing concentration of the surfactants causes a decrease in the values of Young's modulus and tensile strength, and also increase in elongation, typically of plasticizers. In the analysis of the release profile and antioxidant activity of TC, the films showed higher values for both properties for samples containing lecithin in its formulation, which can be explained by the interaction between lecithin and TC and its affinity with ethanol. It is concluded that the systems studied here have potential application for edible coatings.