Encapsulation of walnut husk and pomegranate peel extracts by alginate and chitosan-coated nanoemulsions

Walnut husk extract (WHE) and pomegranate peel extract (PPE) were produced through ultrasound-assisted extraction. Total phenol, flavonoid and tannin contents (TPC, TFC and TTC), antioxidant and antimicrobial activities were determined. The best extracts were used for production of alginate (Alg) and chitosan (CS)-coated nanoemulsions containing WHE (NWHE) or PPE (NPPE). The encapsulation efficiency (EE%), loading capacity (LC%), particle size, zeta potential, and release trait were determined. The mixture of ethanol: water (80:20) resulted in the extraction yield of 10.97 and 11.87 % for WHE and PPE, respectively. PPE indicated higher TPC and antioxidant activity percentage than WHE. The main phenolic compound of WHE was luteolin (42.04 mg/ kg). Higher antimicrobial activities achieved for PPE than WHE. Minimum inhibition concentrations for WHE were 700 and 500 mu g/mL in terms of Staphylococcus aureus and Escherichia coli, respectively. The best NWHE3 and NPPE3 based on the Alg (1 %, w/w) and CS (3 %, w/w) exhibited EE of 87.75 and 89.07 % and LC of 9.85 and 9.74 %, respectively. The NWHE3 and NPPE3 had particle sizes of 182 and 218 nm and zeta potential values of +12.23 and + 10.67, respectively. Nanoemulsions provided a controlled release of WHE and PPE at the simulated gastric and intestinal fluids.