Beer Bagasse as Filler for Starch-Based Biocomposite Films for Food Packaging Applications

Development of biodegradable packaging materials and valorization of agri-food waste are necessary to produce more sustainable materials while reducing the environmental impact. Starch-based biocomposite films reinforced with beer bagasse fractions with different purification degrees were developed and characterized in structural, mechanical, thermal and optical properties. To this aim, 5% and 10% (w/w) of either beer bagasse (BB) or its lignocellulosic-rich fibers (LF), obtained by subcritical water extraction at temperatures between 110 and 170 °C, were incorporated into starch matrices. Elastic modulus and tensile strength values increased by up to eight-fold and 2.5-fold, respectively, compared to the control film. The incorporation of BB or LF significantly enhanced the mechanical resistance of the films. In general, the increment in the filler:polymer ratio significantly increased the EM values (p < 0.05), while decreasing the stretchability of the films around 80–85%, regardless of the type of filler. This effect suggests a good interfacial adhesion between the fillers and the polymeric matrix, as observed by FESEM. The biocomposite films exhibited a dark reddish appearance, reduced transparency, light blocking barrier capacity and remarkable antioxidant activity due to the presence of phenolic compounds in the fibers. The water vapor and oxygen barrier properties were better preserved when using the more purified LF obtained at 170 °C. Overall, starch films reinforced with beer bagasse fractions showed strong potential for the development of biodegradable food packaging materials.