Exploring the potentialities of using lignocellulosic fibres derived from three food by-products as constituents of biocomposites for food packaging

• Potential valorisation of fibres from agro-residues as fillers in biocomposites was studied.
• Composites’ mechanical properties were degraded in presence of the fibres.
• Composites’ water vapour permeability evolved differently as a function of fibre type.
• Properties were related to polymer molar weight, crystallinity and fibre/matrix adhesion.
• Developed composites could be used as food packaging materials.

Lignocellulosic fibres obtained by dry grinding of three different solid agro-residues, i.e. wheat straw, brewing spent grains and olive mills, were compared regarding their potential use as fillers in poly(3-hydroxybutyrate-co-valerate) (PHBV) for food packaging applications. Differences found in their composition might have influenced their grinding ability, as observed with the difference of sizes, i.e. 109 μm, 148 μm and 46 μm, respectively. Thereafter, composites structure was characterized regarding their morphology, fibre/matrix interaction, matrix molecular weight and crystallization behaviour. Poor fibre/matrix adhesion, degradation of PHBV polymer chains, and decrease of PHBV’s crystallinity were evidence. Consequently, mechanical properties were degraded in presence of the fibres. Water vapour transfer rate of composites was increased with wheat straw fibres introduction while it was decreased for olive mills-based materials. Regarding the food packaging applications, PHBV/wheat straw fibres composites appeared as promising materials to reach the requirements of respiring food products, whereas PHBV/olive mills composites would be more adapted for water sensitive products.