Antibacterial and biodegradable whey protein/gelatin composite films reinforced with lotus leaf powder and garlic oil for sustainable food packaging

Whey protein isolate (WPI) shows great potential for sustainable food packaging, thanks to its exceptional oxygen and oil barrier properties., but its moisture barrier and mechanical strength are limiting factors. The novelty of this study lies in incorporation of hydrophobic lotus leaf (L) particles in WPI-based bio-composites and comparing two binders: sodium alginate (S) and polyethylene-glycol-sorbitan-monooleate also known as Tween®80 (T) to enhance moisture barrier and mechanical strength. The lotus leaf powder reduced water vapor transmission rate (WVTR) by 64% to 445.86 ($g/m^2\cdot day$), and the binders further reduced WVTR by up to 46% while doubling tensile strength. Foldability was significantly improved, with T-based films retaining durability for over at least three months. Films with T exhibited higher thermal stability and surface hydrophobicity, with a contact angle above 90°. The optimal film, G20-T-L-GO, included T as the binder, 20 (w/w% WPI) of glycerol, and garlic oil (GO) for antibacterial properties. This formulation demonstrated antibacterial activity against “Staphylococcus aureus” with around 3 cm of inhibition zone but not “Escherichia coli”. It achieved a 76% WVTR reduction compared to the control sample with no lotus leaf and exhibited rapid biodegradation in soil within four days. Additionally, it dissolved entirely in salt water, deionized water, and tap water over the same period, confirming its biodegradable nature. These features make this bio-composite film a viable option for sustainable and functional primary and secondary food packaging due to all components being FDA approved.