Active antimicrobial food packaging using biological potential from Malaysian medicinal plants

Despite extensive research on medicinal plants, many remain underexplored. Therefore, the aim of this study was to investigate the potential of underutilised Malaysian medicinal plants of Colubrina asiatica, Garcinia atroviridis, and Gnetum gnemon as antimicrobial agents in biobased and biodegradable zein film. The research focused on their application as wrapping film, utilising raw beef as a food sample to represent typical microbial risks in foods, such as food contamination by Escherichia coli, Listeria monocytogenes, and Salmonella. Electrospinning was used to produce zein-based films. A comparative assessment of biological activities of the plant extracts was first performed. The extraction of C. asiatica, G. atroviridis, and G. gnemon using ethanol-to-water ratios of 0:100, 25:75, 50:50, 75:25 and 100:0 and two extraction methods of solvent extraction (S) and microwave-assisted extraction (MAE) yielded C. asiatica extract (CAE), G. atroviridis extract (GATE), and G. gnemon extract (GGE). The findings highlighted that the ethanol ratio influenced extraction yield and bioactivities more significantly than the extraction method. GATE exhibited the highest yield but showed the lowest total phenolic content, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) activities. Antimicrobial testing at 50 mg/mL showed that GATE50-S/M had stronger antibacterial activity, while CAE50-M exhibited higher antifungal activity. A significant correlation was found between the total phenolic content of CAE and antioxidant activities (p < 0.05). Novel zein-based films, Ze-CAE, Ze-GATE, and Ze-GGE were successfully produced using electrospinning, utilising zein as the primary polymer and incorporating 5% (w/w) of the selected extracts. An evaluation of their properties showed that Ze-GGE films had significantly greater fibre diameter and thickness compared to the other films (p < 0.05). All films displayed a water contact angle between 20° and 35° (hydrophilic surface), with encapsulation efficiency exceeding 90%. The attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) spectra confirmed successful encapsulation of CAE, GATE, and GGE into zein films without structural modification and highlighted hydrogen bonding between zein and the plant extracts. Ze-GATE was the most thermally stable among all films. In a soil burial test, all films exhibited the indicator of a rapid biodegradation process. All the beef samples wrapped with the zein-based films, particularly Ze-GATE and Ze-GGE, exhibited reduced bacterial growth over a five-day storage period, indicating a higher antibacterial activity compared to the tested commercial film. However, the hydrophilic characteristics of films present a limitation for beef wrapping, highlighting the need for further research. The outcomes of this research contribute to the knowledge for the development of active antimicrobial films developed from biobased and biodegradable materials, aiming to reduce the reliance on plastic packaging and offering a sustainable alternative.