This study was aimed at gaining further insight on the role of hydration in adsorption processes of biopolymer/adsorbate systems using complementary methods (electromagnetic interference (EMI) shielding, calorimetry, and solvent/vapour adsorption isotherms). Cellulose and starch-based materials were used as the adsorbents, whereas water (liquid and vapour), ethanol and p-nitrophenol (PNP) in aqueous solution were the adsorbate systems. The biopolymer/water systems had higher uptake capacity overall, where starch materials showed higher uptake capacity than cellulose among the various solvents. The secondary and tertiary structure of the biopolymers was a key factor affecting their uptake capacity, as evidenced by the enhanced adsorption properties of starch over cellulose, along with higher uptake of amylose (AM) versus amylopectin (AP) in starch biopolymers. EMI results also confirmed that AM starch had higher adsorption toward water than ethanol. The textural properties and surface chemistry of the biopolymers were probed using dye adsorption (PNP at pH 8.5) in aqueous solution that showed parallel trends with water vapour adsorption isotherms. Isothermal Titration Calorimetry (ITC) revealed that the heat of adsorption in AP differed from that of AM since the biopolymer tertiary structure governs the accessibility of biopolymer adsorption sites. The role of branching in AP and amorphous domains in AM/AP composites are inferred to play a key role in hydration-driven allosterism known for such biopolymer/water vapour adsorption processes.