Application and characterisation of industrial brewing by-products in biodegradable starch-based expanded composites

Concern headed under waste management promotes the development and application of biodegradable materials. Naturally occurring lignocellulosic fibres, such as malt bagasse (MB), are often low-cost industrial by-products with attractive properties. This work focused on extruding starch-based expanded composites, containing two different brewing residues, Pilsen malt bagasse (PMB) and Weiss malt bagasse (WMB). Their mechanical, thermal and structural properties were evaluated. The expansion index was higher in the WMB10 extruded composite (25.73 +/- 4.75), also evident in the SEM-FEG images which show more quantity and uniformity of pores. WMB5 and WMB10 resulted in a 50% decrease in composite water solubility relative to the Control. The hardness (N) of the samples was reduced by using MB fibres of both types, producing a less stiff and brittle material, which contributes to a potential application as alternative biodegradable packaging for non-biodegradable materials based on expanded polystyrene.