Upcycling Coffee By-Products Into Functional Ingredients: A Review on Sustainable Processing, Health Benefits, and...

Coffee processing generates millions of tons of residues annually, including silverskin, spent grounds, and cascara. Previously regarded as waste materials, these by-products are increasingly recognized as valuable sources of bioactive compounds, particularly dietary fiber, polyphenols, and melanoidins. This review presents a comprehensive framework for valorizing these waste streams into high-value functional food ingredients. The valorization chain is examined holistically. It begins with detailed compositional and safety characterization of coffee residues, followed by implementation of environmentally sustainable extraction technologies. Green extraction methods, including supercritical CO₂ extraction, deep eutectic solvents, and enzyme-assisted approaches, demonstrate superior efficiency in recovering target bioactive compounds while minimizing environmental impact. Advanced preservation strategies, notably microencapsulation and controlled fermentation processes, significantly enhance both stability and bioavailability of extracted bioactives. Extensive research demonstrates multiple health-promoting mechanisms associated with these compounds, encompassing antioxidant activity, anti-inflammatory effects, prebiotic functionality, and metabolic regulation. Successful integration into various food matrices has been documented across bakery products, beverages, and processed meat applications, though formulation challenges persist regarding sensory optimization and regulatory compliance. Despite these promising applications, the translation from preclinical success to validated health claims requires further substantiation through robust human clinical trials. Additionally, emerging computational approaches show considerable promise for predictive modeling and process optimization in extraction and formulation development. The transformation of coffee residues from environmental burden to valuable functional ingredients represents a scientifically robust approach toward establishing more sustainable and circular food production systems globally.