Antioxidant and antibacterial activities of cassava starch and whey protein blend films containing rambutan peel extract and cinnamon oil for active packaging

Blending of cassava starch and whey protein isolate (WPI) films containing plant extracts showed modified properties and release behaviors. Effects of native starch (NS) and acetylated starch (AS) on film properties, antioxidant and antibacterial activities were investigated. WPI and WPI-starch films contained ethanolic fractions of rambutan peel extract (RPE) and cinnamon oil (CO). Mechanical, physical and water barrier properties of blend films depended on starch type and contents. Corilagin and (E)-cinnamaldehyde were the highest active components in RPE and CO, respectively. FTIR revealed hydrophobic interaction and hydrogen bonding between starch-protein-polyphenols. Protein conformation was altered giving modified amide I and amide II bands. Active compounds reduced water vapor permeability depending on starch types that governed CO dispersion. Starch, particularly AS, enhanced release of polyphenols and DPPH. scavenging activity in water and 50% ethanol. Antibacterial activity of the blend films differed between in vitro (disc diffusion method) and real food (salami) and was governed by the phenolic release and food components, respectively. WPI films showed the lowest in vitro antibacterial activity but the highest efficacy to delay microbial growth in salami. Release mechanism controlled the antioxidant capacity of active protein-starch films, whereas antibacterial capacity in foods strongly depended on food matrix components.