Novel multifunctional collagen-based food packaging film incorporating with bilberry anthocyanin for freshness monitoring

Abstract

A multifunctional film was developed using collagen and phenolic acid-grafted chitosan as the film-forming framework with bilberry anthocyanin extract (BE) as an indicator. All the prepared films presented compact cross-sectional structures. Compared with CC/BE (collagen/chitosan/BE) film, the CCC/BE (grafted of caffeic acid) and CCP/BE (grafted of protocatechuic acid) films exhibited significantly enhanced physical properties including UV resistance, water resistance (water vapor permeability value reducing from 2.30 to 1.74 × 10⁻¹⁴g·m⁻¹·Pa⁻¹·s⁻¹) and mechanical property (tensile strength value increasing by 23 %). Besides, the DPPH free radical scavenging rate of CCP/BE and CCC/BE film was 58.05 % and 81.87 %, respectively, much higher than that of CC/BE film (5.46 %). The grafted films showed obvious color changes in different pH solutions: CCP/BE film changed from red to light purple to blue-gray and CCC/BE film changed from red to purple-gray to blue-gray, exhibiting good pH-sensitivities. CCP/BE and CCC/BE films also had ammonia-sensitive discoloration characteristics. CCC/BE film effectively provided on-going visual evaluation of shrimp freshness through color changes, and the film showed the highest S_RGB values (the sensitivity value of the change in film color to TVB-N) throughout the monitoring process, which suggested that the combination of BE and CA made the color changes of anthocyanin more noticeable.