Production of Active Biodegradable Antioxidant and Antibacterial Films Based on Salep Powder, Turmeric Powder, and Selenium Powder: A Novel Approach to Sustainable Packaging

IntroductionThe widespread use of synthetic plastics in packaging is a major global environmental problem, contributing to greenhouse gas emissions and pollution. Most plastics are non-biodegradable, accumulated in the environment, fragmented into ecosystems, and eventually give rise to harmful microplastics. Incineration of plastics also releases toxic gases, further polluting the air. Developing biodegradable alternatives from natural sources like proteins and polysaccharides is crucial for sustainable packaging. These biopolymer films, like those made from salep and enhanced with natural additives such as turmeric and selenium, offer improved functionality including antioxidant and antibacterial properties. Materials and MethodsSalep and turmeric powders were obtained from medicinal plant stores in Urmia, West Azerbaijan, Iran, while glycerol (99% purity) and selenium powder were purchased from Merck, Germany, and used without further purification. For film preparation, predetermined amounts of turmeric powder were dispersed in 100 mL of distilled water and stirred at 40–50°C and 500 rpm for 15 min, then filtered through a cloth filter to remove coarse particles. The required amount of selenium powder was added to the filtrate and stirred for another 15 min under the same conditions. Next, 2 g of salep powder were gradually added through a fine sieve to obtain a homogeneous mixture, followed by glycerol addition at 30% w/w relative to salep. Finally, 25 mL of the prepared solution was cast into 10-cm Petri dishes and dried at room temperature for 24 h. In total, 13 film formulations were prepared according to the statistical design. Results and DiscussionThe results demonstrated that increasing the turmeric concentration enhanced the yellowness (b*) and decreased the lightness (L*) of the films, while the addition of selenium shifted the color toward the green/blue spectrum (a*). Regarding functional properties, turmeric exhibited antibacterial activity, particularly against Gram-positive bacteria, whereas selenium alone showed no effect; however, their combination revealed a strong synergistic antibacterial effect. A similar synergy was observed in antioxidant activity, where selenium stabilized and enhanced the effect driven by turmeric. Optical analysis indicated that turmeric increased light absorption and reduced transparency. Interestingly, the combination of turmeric and selenium reduced transparency less than individual components, suggesting its potential for protective packaging. FESEM imaging revealed that turmeric created a smooth, homogeneous surface, whereas selenium alone formed rough clusters; notably, their combination resulted in a more uniform surface by counteracting selenium aggregation. Finally, the UV–Vis spectrum of the turmeric extract confirmed the presence of three main absorption peaks at 342 nm (isomers), 380 nm (curcumin tautomers), and 457 nm (curcumin), with the latter shift attributed to the polarity and hydrogen bonding effects of the water solvent. ConclusionThis study, focusing on the development of biodegradable films based on salep powder reinforced with turmeric and selenium powders, demonstrated the potential of exploiting the synergy between them. Active biodegradable films using salep, turmeric, and selenium were developed in this study. Turmeric enhanced properties, while selenium boosted performance synergistically, improving antibacterial activity and structural stability. Tailoring film features offers protective packaging, reducing plastic waste and enabling intelligent packaging.