Development of a novel curcumin loaded lysine modified alginate intelligent film reinforced by lignosulfonic acid with high color stability for monitoring shrimp freshness

Alginate-based film is an environmentally friendly food packaging material. However, poor mechanical properties and limited functionality restrict its application. To overcome these challenges, lysine was used as a multifunctional linker to conjugate with alginate to improve mechanical properties and curcumin was introduced to endow it with pH responsiveness. However, as a natural pigment, curcumin is prone to degradation in light and thermal environments. Therefore, a novel intelligent nanocomposite film was developed by incorporating lignosulfonate acid (LA) nanoparticles to furtherly enhance its mechanical properties and UV-blocking performance. The results showed the tensile strength (TS) and elongation at break (E%) of the fabricated alginate-based curcumin films had been increased by 8.3% and 1685.76%, respectively, by optimizing the content of lysine, LA, and curcumin. The incorporation of curcumin improved the thermal stability, UV-blocking, water resistance, antioxidant, and antibacterial properties of the alginate film. Moreover, the incorporation of LA enhanced the color stability of curcumin both with and without UV-light. Furthermore, the alginate-based curcumin film demonstrated great potential for visually monitoring shrimp freshness. In conclusion, this study presented an innovative and effective strategy to develop an intelligent film with excellent mechanical properties and high color stability.