Effect of ultrasound on the physical, morphological, and mechanical properties of bioplastic obtained from lucuma seed starch (Pouteria lucuma)

Abstract

Pouteria lucuma seeds are a byproduct that is a valuable starch source for potential food and non-food applications. This study investigated the impact of ultrasound treatment on native lucuma seed starch (NS) to develop bioplastics and evaluate their physical, morphological, mechanical, and biodegradability properties. Extracted starch (5 % w/v) in distilled water was sonicated at 300 W for 5, 10, and 15 min. Subsequently, physical, chemical, and morphological features were analyzed via SEM. Bioplastics were formulated using NS and ultrasound-treated starch (US) at 4, 5, and 6 % (w/v) with glycerol and 5 M acetic acid, followed by heating to gelation and casting. A completely random design was employed for the experiment. NS and US starches observed significant differences (p<0.05) in physicochemical properties, amylose content, color, and swelling power. Ultrasound treatment caused native starch degradation and increased swelling power, with US starch granules reaching 11.44 µm versus 9.36 µm for NS. DSC analysis revealed changes in gelatinization enthalpy (ΔH) from 2.47 ± 0.06 to 2.18 ± 0.02 J/g. Bioplastics from treated starch showed good tensile strength, with the 5 % US15 (T2US) exhibiting superior resistance and elongation. SEM images indicated crack-free morphology, and biodegradability exceeded 60 % in five days. In conclusion, ultrasound treatment enhances the chemical and thermal properties of the lucuma seed starch for bioplastic production. The T2US treatment positively influenced the resulting bioplastics' physical, mechanical, and biodegradability characteristics.

Keywords

• Biodegradable
• Brightness
• Gelatinization
• Seeds
• Starch