Properties of Antioxidant Film Based on Protein Isolate and Seed Coat Extract from Bambara Groundnut

Bambara groundnut (BG)-based films containing seed coat extract at different concentrations were prepared and characterized. BG seed coat extract (BGSCE) had a total phenolic content of 708.38 mg GAE/g dry extract. BGSCE majorly consisted of quercetin 3-galactoside, rutin, and azaleatin 3-arabinoside. BGSCE exhibited ABTS and DPPH radical scavenging activities (ABTS-RSAs and DPPH-RSAs), a ferric reducing antioxidant power (FRAP), and an oxygen radical absorbance capacity (ORAC) of 66.44, 4.98, 4.42, and 0.91 mmol Trolox equivalent/g dry extract, respectively. When BGSCE at various concentrations (0-8%, w/w, protein content) was incorporated into the BG protein isolate (BG-PI)-based films, film containing 4% BGSCE exhibited higher thickness, tensile strength, elongation at break, water vapor and UV-light barrier properties, and a*-value (redness) than the control film (p < 0.05). Films containing BGSCE had greater ABTS-RSA, FRAP, and ORAC than the control film (p < 0.05). An FTIR analysis elucidated that the proteins interacted with phenolic compounds in BGSCE. Nonetheless, less thermal stability was attained in films added with BGSCE. Hence, the addition of BGSCE possessing antioxidant activity exhibited an important role in properties and characteristics of BG-PI-based film. The developed active film could be applied as packaging material possessing antioxidant property for food applications.