Biodegradable Starch-based Films Incorporating Starch Isolated from Spoiled Chestnuts ( Castanea sativa Mill.): A Sustainable Valorization Strategy for the Food Packaging Industry

1. IntroductionThe durability, versatility, and low production cost of conventional plastics have made them indispensable across numerous global industries. However, most of these plastics are derived from fossil fuels, contributing to a growing environmental crisis that includes resource depletion and extensive pollution [1,2]. This challenge is intensifying rapidly, with global plastic production now exceeding 460 million tons annually and projected to potentially triple by 2050 [3]. Consequently, plastic pollution has become a priority concern for major international organizations, including the United Nations, the World Economic Forum, the World Health Organization, and the European Union [2].Most monomers used to produce plastics, such as ethylene and propylene, are derived from fossil hydrocarbons, and the majority of commonly used plastics are not biodegradable. As a result, instead of decomposing, they accumulate in landfills and natural environments, including oceans basins, freshwater systems, and terrestrial habitats [3,4]. Currently, the only permanent methods for eliminating plastic waste involve destructive thermal treatments, such as combustion or pyrolysis. Yet, the lifecycle of most plastic remains linear: approximately 79% of all plastics produced have been landfilled or released into the environment, 12% incinerated and only 9% recycled [3].Packaging accounts for the largest source of global plastic waste and typically has the shortest useful lifespan among industrial plastic applications [2]. Within a circular economy framework, plastics would be manufactured from renewable or recycled materials. Biodegradable plastics have emerged as a promising alternative, designed to break down more readily through natural processes and mitigate long-term environmental accumulation. Among these, starch-based materials have attracted significant interest due to their low cost, renewability, excellent film-forming properties, biocompatibility, and inherent biodegradability [5]. Starch-based bioplastics are already employed in disposable tableware, edible coatings, packaging materials, and other industrial applications [6]. Continued development of starch-based blends and composites is therefore considered a key strategy for reducing global dependence on petrochemical plastics.The circular economy also emphasizes retaining biological materials in use for as long as possible and recovering valuable compounds from agricultural residues, thereby reducing reliance on virgin resources and minimizing pollution [7]. Valorization of byproducts, which involves transforming materials previously regarded waste into valuable secondary raw materials, is central to this approach [8]. By valorizing agricultural and food processing residues, it is possible to reduce disposal costs, decrease environmental impacts, and create new revenue streams [7,9].In this context, biodegradable starch-based films were produced using starch recovered from spoiled chestnuts. Previous research has shown that this starch possesses functional properties suitable for use in the food industry [10]. Building upon this foundation, the present study investigates the suitability of chestnut byproduct starch for developing biodegradable films for packaging applications. The main objective of this study was to produce starch-based films from chestnut-derived starch and evaluate their structural characteristics, mechanical performance, and hydrophobic properties. This assessment aimed to determine the potential of chestnut starch as a sustainable and functional raw material for biodegradable packaging solutions.