Fortification of soluble soybean polysaccharide edible films with licorice root extract for nut preservation

In order to improve the poor mechanical properties and strong hydrophilicity of soluble soybean polysaccharide (SSPS) based films, licorice residue extract (LE) was introduced into the film-forming matrix. In this study, the effect of the amount of LE on the microstructure, physical and functional performances of the SSPS-based films, and its antioxidant activity and practical application in delaying the oxidation of oil-fried peanuts were investigated. The results showed that the compounding of LE increased the tensile strength (TS) by 4.39 times, decreased the WVP to 62 %, and increased the contact angle by 17.77 %, respectively. FTIR and SEM analyses verified the formation of intermolecular hydrogen bonds among LE, glycerol and SSPS. Furthermore, radical scavenging activity experiments proved that the films possessed a superior capacity to scavenge DPPH and ABTS^•+ radicals up to 63.51 % and 93.10 % respectively, when the LE dosage was at 10 %. It is worth noting the shelf life of oil-fried peanut was extended by about 3.25 d at 60 °C (~65 d at 20 °C) with the packaging of SSS-LE8 film. The preparation of SSPS-LEx film could promote the development of biomass-based packaging materials and their preservation applications in nuts and other products.