Metal-Ion Coordinated Spent Coffee Grounds-Based Films Achieve Multifunctional Food Preservation

Recently, the Tropical Crop Origin Processing Team of the Institute of Processing, Chinese Academy of Tropical Agricultural Sciences (CATAS) systematically elucidated the regulatory mechanism of metal ions on the structure, properties and food preservation functions of spent coffee grounds-based films, providing new ideas for the high-value utilization of spent coffee grounds and the development of degradable food packaging materials. As the main by-product of the coffee industry, spent coffee grounds are produced in huge quantities globally each year, but most are landfilled as waste, which easily causes environmental problems such as water pollution and methane emissions. It is worth noting that spent coffee grounds contain components such as carbohydrates, lignin, proteins and lipids, making them an as-yet underdeveloped biomass resource. In this study, using spent coffee grounds as raw material, multifunctional food packaging films with good water stability, antibacterial properties, UV barrier properties and flame retardancy were successfully prepared through ionic liquid dissolution and metal ion solution regeneration. Furthermore, the study revealed the regulatory mechanism of metal ion coordination on the film structure, mechanical properties and functional characteristics. The results showed that the stable coordination crosslinking structure formed by metal ions and polysaccharide hydroxyl groups replaced the hydrogen bond network that was originally easily destroyed by water, significantly enhancing the surface hydrophobicity of the films, markedly improving the wet-state mechanical properties, and achieving water vapor barrier performance comparable to that of low-density polyethylene. In addition, specific metal ions also endowed the films with functions such as UV shielding, antibacterial and self-extinguishing flame retardant properties. All metal-ion coordinated films could completely biodegrade within 40 days in natural soil. In strawberry preservation experiments, compared with traditional plastic cling film, strawberries packaged with zinc-ion coordinated films had the lowest rot rate, with significantly reduced weight loss rate and degree of softening, and a markedly extended shelf life. The research results were published in Food Chemistry: X under the title “Sustainable and multifunctional metal-ion coordinated spent coffee grounds films for food preservation”. Zhang Shaokai, assistant researcher at the Institute of Processing, CATAS, is the first author of the paper, and Sheng Zhanwu, Lin Lijing and Liu Yijun, researchers, are co-corresponding authors. The research was funded by projects such as the National Key R&D Program, the Basic Research Operating Expenses for Central Public Welfare Research Institutes, and the Science and Technology Innovation Team of the National Tropical Agricultural Science Center of the Chinese Academy of Tropical Agricultural Sciences. Paper link: https://doi.org/10.1016/j.fochx.2026.103737