Truxillic calcium supramolecular skeleton fortified pH responsive and biodegradable alginate hydrogel films promoting fruit preservation.

This work presented a unique alginate hydrogel film fortified by truxillic calcium skeleton with notable physicochemical and mechanical properties, as well as the promising application in fruit preservation. A series of truxillic‑calcium-alginate (CBDA-Ca/SA) films were prepared. It was found that CBDA-10-Ca/SA can block over 50 % of UV-visible light. The maximum breaking strengths of (6 % CBDA-1-Ca)/SA and (2 % CBDA-10-Ca)/SA are 82 MPa and 79 MPa, about twice that of Ca/SA. CBDA-11-Ca/SA showed the highest WVP of 2.18 × 10 g ∙ m ∙ s ∙ Pa and CBDA-10-Ca showed the best performance in reducing the OTR of the films by 4.1× 10 cm ⸱cm ⸱ m ⸱ 24 h ⸱ Pa. With water absorption ranging from 3480 % in an acidic environment to 9520 % in an alkaline environment, the CBDA-10-Ca/SA film demonstrated exceptional pH responsiveness. The degradation rate of all films was around 70 % after four weeks of burial under the soil. The above studies indicate that polyphenols can not only act as "hooks" to grasp Ca to form supramolecular skeleton structure improving the mechanical strength of SA-based films, but also act as active components to endure the functional properties of SA-based films with antibacterial and antioxidant properties.