Residual lipids naturally present in <i>Pouteria sapota</i> seed starch act as built‐in interfacial modifiers

Abstract BACKGROUND Under‐utilized tropical residues represent promising renewable resources for the development of biodegradable materials within a circular bioeconomy framework. Pouteria sapota (mamey) seeds, an agro‐industrial by‐product rich in starch, lipids and proteins, offer a novel feedstock for biopolymer films. RESULTS Starch was isolated from P. sapota seeds with and without prior defatting and used to prepare starch–polyvinyl alcohol (PVA)–glycerol films via a solvent‐free casting process. The influence of residual lipids on the interfacial, structural and thermal properties of the resulting films was evaluated systematically. Fourier transform infrared spectra revealed a characteristic CO band (≈1730 cm −1 ) attributed to lipid traces in non‐defatted samples, whereas defatted starch films exhibited a cleaner carbohydrate signature. Static water contact angle increased from 33.8° (defatted) to 69.8° (non‐defatted), confirming that native lipids enhance surface hydrophobicity. Differential scanning calorimetry thermograms showed a major endothermic transition at 171.7 °C (Δ H = 95.4 J g –1 ), indicating semicrystalline behavior and good thermal stability. Soil burial tests evidenced 10–20% weight loss after 30 days, suggesting partial biodegradability under aerobic and anaerobic conditions. CONCLUSIONS Residual lipids act as natural interfacial modifiers within starch–PVA matrices, tailoring wettability and thermal performance without external additives. P. sapota seed starch thus emerges as a viable, low‐cost biopolymer source for short‐life coatings and packaging films in sustainable materials engineering. © 2026 Society of Chemical Industry (SCI).