Abstract
In this study, ultrasound-assisted extraction (UAE) was utilized to isolate bioactive anthocyanins from purple sweet potato peel (PSPP), a major agricultural byproduct. The extracted anthocyanins were characterized and subsequently incorporated into chitosan matrices to develop active and intelligent food packaging films. UAE parameters, including solvent composition, extraction time, and ultrasonic power, were optimized, yielding a high total monomeric anthocyanin content of 112.4 mg/100g dry weight under optimal conditions (50% acidified ethanol, 25 min, and 250 W). The obtained PSPP extract (PSPPE) was integrated into chitosan (CS) films at varying concentrations (1%, 2%, and 3% w/v). The composite films exhibited a significant reduction in UV-vis light transmittance, with the 3% PSPPE film blocking over 98.5% of harmful UV light. Mechanical testing revealed that the incorporation of PSPPE increased the tensile strength of the films from 22.5 MPa to 28.1 MPa, while slightly reducing elongation at break. Furthermore, the active films demonstrated exceptional DPPH radical scavenging activity (up to 84.7%) and exhibited highly sensitive, visible color changes from red/pink in acidic environments (pH 2.0–4.0) to purple/blue under neutral conditions (pH 6.0–8.0) and green/yellow in alkaline media (pH 10.0–12.0). These findings indicate that CS-PSPPE composite films have outstanding potential as eco-friendly, active, and smart packaging systems capable of monitoring food freshness in real-time.
