A Comprative Study of Antimicrobial and Antioxidant Properties of Walnut Green Husk Aqueous Extract before and after Microencapsulation

Walnut green husk is one of agricultural residues that can be considered as natural compound with biological properties because of its phenolic compounds. In the present work, the goal is extraction of aqueous extract of green walnut skin and studying the effect of extraction temperature on the phenolic compounds and antioxidant and antimicrobial properties of extract. Meanwhile, the effects of spray dried encapsulation process of extract in maltodextrin on the biological activity of extract are investigated.
In this study, walnut green husk (Sozani variety) was extracted in two temperatures of 25 and 80 °C. Then it was encapsulated in 10% maltodextrin in three different concentrations of extract (0.5, 1 & 2 mg/ml) using spray drying method. Total phenol of the extract was evaluated before and after encapsulation. In addition, the antioxidant activity of the aqueous extract of walnut green husk was determined before and after microencapsulation by the scavenging effect on DPPH (2,2-diphenyl-1-picrylhydrazyl) radicals. Antimicrobial activity of the extract was determined by Agar well Diffusion Method against gram positive (Bacillus cereus, staphylococcus aureus) and Gram negative bacteria (Escherichia coli, Salmonella Typhimurium).
It was revealed that the effect of extraction temperature on total phenolic compounds was significant (p Sozani walnut green husk can be used as a cheap source of antioxidant and antimicrobial compounds due to having high amount of phenolic compounds. Therefore, microencapsulation can be used as an efficient method for increasing the stability of walnut green husk extract against the environmental conditions.