Rheological and surface properties of edible coating solution prepared from vasa plant (Justicia Adhatoda L.) leaf extract

Incorporation of plant extract into edible coating solution (ECS) enhances the antimicrobial and antioxidant property of the coating solution. Vasa plant (Justicia adhatoda) was selected and tested for total antioxidant capacity using phosphomolybdate method. Ethanolic extract of Vasa plant was found to contain 94.47 mg.ml^-1 in equivalence of ascorbic acid for 24 hours of maceration. ECS suspension using ethanolic extract of vasa plant (3%, 6%, 9%) was prepared with starch (4%), sucrose (1%, 1.25%, 5%) and glycerol (10%, 15%, 20%) as base material at different proportions; and the rheological and physico-chemical properties of the ECS were determined. Prepared ECS followed Herschel-Bulkley fow curve having yield stress of 2.37-4.74 Pa and n-value in the range of 0.26-0.95. Further, the pH (6.2-6.9) and surface tension (58.10- 81.90 m. N.m^-1) of the ECS significantly (p<0.05) decreased by the increase in Justicia adhatoda extract. Electrical conductivity and total soluble solid of the formulated ECS ranged from 0.17-0.36 dS.m^-1 and 1.7-3.9 °Brix. respectively, and both of them significantly (p<0.05) increased with increase in sucrose and Justicia adhatoda extract. Optimized ECS contained 1.04 % sucrose, 18.44 % glycerol and 9.00% Justicia adhatoda extract.