<p>Citrus peel is an abundant food-processing by-product with strong potential as a food-grade bioactive ingredient. This study investigated the biophysical, biochemical, and molecular characteristics of <i>Citrus maxima</i> (Burm.) Merr. peel powder and its relationship to functional performance in food systems. The peel was processed into powder using four drying methods: low-temperature oven, microwave, infrared, and vacuum drying. The results demonstrated that the drying method significantly influenced the biophysical, chemical, and molecular properties of the resulting powders. Biophysically, microwave drying produced the smallest particle size (121.68 ± 48.61&#xa0;nm) with high crystallinity but exhibited relatively low colloidal stability. In contrast, vacuum drying provided the highest thermal and colloidal stability, with the highest main decomposition temperature (325.66&#xa0;°C). From a chemical and bioactive perspective, infrared drying was the most effective in preserving antioxidant activity (DPPH inhibition of 71.57 ± 2.11%) as well as phenolic and flavonoid contents, while vacuum drying offered greater protection of lipophilic components (TBARS inhibition of 76.32 ± 2.45%). Molecular characterization further supported these findings. FTIR analysis revealed that vacuum drying better preserved glycosidic (C–O–C) linkages and hydroxyl (–OH) groups associated with polysaccharide structures, whereas infrared drying intensified carbonyl (C=O) and carboxylate (–COO⁻) signals, indicating surface oxidation. XPS results corroborated these observations by showing a higher C–O ratio in vacuum-dried samples, while infrared-dried samples exhibited increased carbonyl and carboxylate groups. Overall, infrared and vacuum drying produced citrus peel powders with a balanced combination of structural integrity, molecular stability, and bioactive functionality, supporting their potential application as value-added functional food ingredients.</p> Graphical abstract <p></p>