Endogenous polysaccharide-protein composite nanoparticles prepared from spent coffee grounds as multi-flavor carriers

Spent coffee grounds (SCG), an abundant byproduct of coffee production, are rich in endogenous polysaccharides and proteins, offering considerable potential for the development of waste-derived functional materials. In this study, endogenous polysaccharide-protein composite nanoparticles (CPP NPs) were recovered from SCG through alkaline extraction and investigated as flavor carriers for cigarette-related thermal applications. The effects of extraction pH on the composition, physicochemical properties, structural characteristics, and flavor encapsulation performance of the resulting nanoparticles were systematically evaluated. CPP NPs prepared at pH 11 exhibited the most favorable physicochemical properties and were therefore selected for the preparation of a freeze-dried multi-flavor powder (CPP-D5) with both original coffee-derived and extraneous cocoa-related flavors. Major cocoa-related volatile compounds remained detectable in the resulting powder after storage, while their normalized relative proportions varied with storage temperature. Py-GC-MS analysis showed that cocoa-related volatile compounds persisted under moderate thermal conditions, while additional volatile compounds were generated at higher temperatures, increasing the complexity of the volatile profile. These findings suggest that CPP NPs function not only as efficient flavor delivery vehicles but also as active contributors to aroma development during heating. This work demonstrates a high-value utilization strategy for spent coffee grounds and highlights their potential as multifunctional flavor delivery systems for food applications.