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 −10  g ∙ m −1 ∙ s −1 ∙ Pa −1 and CBDA-10-Ca showed the best performance in reducing the OTR of the films by 4.1× 10 −5  cm 3 ⸱cm ⸱ m −2 ⸱ 24 h −1 ⸱ Pa −1 . 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 2+ 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.