Physicochemical and mechanical properties of edible films based on WPI and a novel hydrocolloid: Persian gum

In this study, the effect of Persian gum (PG) as a novel gum to be used in edible films was examined. Sorbitol-plasticized whey protein isolate (WPI) films with incorporation of PG in different ratios (100:0, 80:20, 60:40, 50:50, 40:60 and 20:80 WPI: PG) were prepared. The effects of PG concentration on the physicochemical properties; water vapour permeability (WVP), moisture sorption isotherms and mechanical properties; tensile strength (σ_max) and elongation at break (%EB) were observed. Incorporation of PG in the film matrix significantly increased WVP (p<0.05) when added in ratios 60:40, 50:50, 40:60 and further increased in the ratio of 20:80 (WPI: PG). The moisture uptake of the films was not greatly influenced by the increment of PG. Addition of PG in the lowest concentration of 80:20 (WPI: PG) highly decreased the tensile strength of the films; however further addition of PG did not cause any great decrement. A significantly higher elongation was observed especially when PG was present in ratios 40:60 and 20:80 (WPI: PG). Overall, incorporation of PG in sorbitol-plasticized WPI films affected positively the elongation characteristics. However, improvement is needed for WVP to retain more stable values. This study suggests further examination of the soluble and insoluble fractions of PG using different polymers and plasticizers. A study on the antimicrobial properties of PG in edible films could also be examined since PG is traditionally used as a remedy.