Tracking transformations of polymeric carbohydrates from green coffee beans to spent coffee grounds: Mannan-dominant structures and valorization implications

C NMR indicated increasing structural order and higher thermal resistance in the spent residue, consistent with selective retention of recalcitrant mannan-rich domains and partial reorganization of cellulose and mannan. These results show that SCGs should not be viewed as a generic cellulose-rich feedstock. Instead, their process-dependent, mannan-dominant polymer structure should guide valorization strategies in food, fiber, and composite applications.