Mechanical and water vapor permeability properties of biodegradables films based on methylcellulose, glucomannan, pectin and gelatin

Abstract

Mechanical and water vapor permeability properties of biodegradables films based on methylcellulose, glucomannan, pectin and gelatin Propriedades mecânicas e de permeabilidade ao vapor de água de filmes biodegradáveis à base de metilcelulose, glucomanana, pectina e gelatinaHulda Noemi Mamani CHAMBI 1 *, Carlos Raimundo Ferreira GROSSO 1 IntroductionInterest in edible films is connected with the development of easily degradable packaging, non-aggressive to the environment (CHEN, 1995;KOELSCH, 1994). Natural polymers such as proteins and polysaccharides, offer great opportunities, since their biodegradability and environmental compatibility are assured (KROCHTA; DE MULDER-JOHNSON, 1997). However, films produced with these materials have low water vapor barrier property and low mechanical resistance in comparison with films produced from synthetic polymers.Several studies have been carried out to improve film performance such as the cross-linking of the polymeric chains (CARVALHO; GROSSO, 2004;HERNÁNDEZ-MUÑOZ;VILLALOBOS;CHIRALT, 2004;CHAMBI;GROSSO, 2006), the addition of hydrophobic compounds (TANADA-PALMU; GROSSO, 2002;BERTAN et al., 2005) and blended polysaccharides and/or proteins (XIAO et al., 2001a,b;CIEŚLA;SALMIERI;LACROIX, 2006;WANG et al., 2007).Another alternative to obtain films with good performance would be through mimic biological structures such as the cell wall composed of a three-dimensional network of cellulose, pectin, hemicelluloses (xylan, mannans, xyloglucans) and structural proteins (CHANLIAUD et al., 2002;KERSTIENS, 1996). This network should be able to bear high-strain strength allowing reversible deformation, in reply to the osmotic pressure caused by the cell turgescence (CHANLIAUD et al., 2002).Cellulose, the most abundant organic polymer in the world, is a linear homopolymer constituted by glucose molecules linked by highly polar and hydrophilic glycosidic bonds β (1-4); however, it is insoluble in water (JUNQUEIRA, 1997). In order to provide solubility, cellulose is esterified ResumoMimetizar estruturas biológicas como a parede celular dos tecidos vegetais pode ser uma alternativa para obter filmes biodegradáveis com propriedades mecânicas e de barreira ao vapor de água melhoradas. O objetivo do presente trabalho foi avaliar as propriedades mecânicas e de permeabilidade ao vapor de água (PVA) de filmes produzidos pelo método de evaporação do solvente (casting) a partir de misturas de metilcelulose, glucomanana, pectina e gelatina. Inicialmente, foram produzidos filmes a partir dos polissacarídeos em pH 4. O filme com melhor desempenho mecânico (tensão na ruptura = 72,64 MPa; elongação = 9,85%) foi obtido a partir de metilcelulose-glucomanana-pectina na proporção 1:4:1, respectivamente. Posteriormente, adicionou-se gelatina a esta mistura de polissacarídeos, e o pH foi ajustado para 4, 5 e 6. Os resultados mostraram melhoras significativas na PVA quando os filmes foram produzidos em pH 5 e com as proporções polissacarídeos/gelatina de 90/10 e 10/90, atingindo-se valores de 0,094 e 0,118 ...

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