Exploring Pouteria lucuma seed starch: a novel non-conventional biopolymer for film production via casting and extrusion

The escalating consumption of plastics and their improper disposal have intensified global environmental concerns, driving the search for sustainable alternatives. In this context, non-conventional starches derived from agro-industrial residues have gained attention as renewable biopolymer sources, as they do not compete with food-grade starch and provide added value to underutilized by-products. This study examines the techno-functional properties of starch from lucuma seeds (Pouteria lucuma) and evaluates its performance in film production through solvent casting and flat-sheet extrusion. Lucuma seed starch (≈10 µm) exhibited pseudoplastic, non-Newtonian behavior (n = 0.54 ± 0.00), low amylose content (8.3 ± 0.3%), and a C-type diffraction pattern. Its hydration properties, defined by high swelling capacity, substantial water absorption at high temperatures, and low syneresis, revealed a thermo-functional behavior favorable for film development. The texture profile, characterized by cohesiveness (0.50) and elasticity (0.92), reflected a structural integrity compatible with processing by extrusion. Extruded films showed significantly lower water vapor permeability (0.82 × 10⁻⁹ ± 0.27 to 0.95 × 10⁻⁹ ± 0.31 g·m⁻¹·s⁻¹·Pa⁻¹) than solvent-cast films (2.16 × 10⁻⁹ ± 0.15 to 2.77 × 10⁻⁹ ± 0.28 g·m⁻¹·s⁻¹·Pa⁻¹). They also exhibited markedly improved mechanical performance, with higher tensile strength, greater Young’s modulus, and increased elongation at break, demonstrating the combined effect of extrusion and formulation in enhancing structural cohesion and toughness. Thermogravimetric analysis further revealed greater thermal stability for the extruded films. Additionally, these films displayed superior UV-blocking capacity compared with solvent-cast films, contributing to their functionality as biodegradable packaging materials. These findings highlight lucuma seed starch as a promising non-conventional biopolymer for developing biodegradable films, offering a sustainable alternative for packaging applications within a circular economy framework.