Ionically crosslinked pectin films incorporated with Rosa roxburghii Tratt polyphenol: influence of gluconate and chloride ions

This research aimed to fabricate and characterize low-methoxyl citrus pectin films crosslinked respectively with Ca 2+ , Mg 2+ and Zn 2+ in chloride or gluconate salt, and optionally incorporated with polyphenol from Rosa roxburghii Tratt (RRT) leaves (RTLP) for potential in active food packaging, through the solution casting method. Although RRT has been proven with health benefits due to the renowned abundance of polyphenols, there remains a research paucity on RRT leaf-derived polyphenol for the biological functionalities in vitro to achieve an economic added value . Specifically, it has been determined that two-step method of cellulose hydrolysis and ultrasonication, as compared to the single step and their simultaneous combination, was observed with the remarkable capability of scavenging free radicals and suppressing carbohydrate digestion as evidenced by α-glucosidase/α-amylase inhibitory activities in a dose-dependent manner, which was accordingly incorporated into pectin film. Generally, the ionic cross-linker observably increased the tensile strength especially for 18.49 MPa of P-Mg(Cl) as compared to 1.34 MPa of P-water. Interestingly, both cation and anion are responsible for ionic cross-linking performance, for example the altered anionic group of Mg 2+ from chloride to gluconate decreased the tensile strength by ∼73 %. On another hand, the RTLP incorporation could not only contribute to the packaging performance of films with excellent antioxidant capability, but also significantly alter their physico-chemical properties assessed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, X-ray diffraction and thermo-gravimetric analysis etc. These results showed a promising venue to prepare pectin-based film with great potential in food packaging industry.