Influence of the helical cavity diameter on the loading capacity and sustained release potential of V-amylose–α-linolenic acid complexes

V-amylose, a single-helical form of amylose, provides an enzyme-responsive platform for encapsulating bioactive compounds. However, the influence of its cavity diameter on α-linolenic acid (ALA) delivery remains poorly understood. This study investigated how cavity diameter affects the loading capacity and sustained release potential of V -amylose–ALA complexes. V6-, V7-, and V8-amylose were prepared and loaded with ALA in acetone. XRD, FTIR, and solid-state NMR confirmed the preservation of the single-helical structure after loading and the formation of V -amylose–ALA inclusion helices. V7–ALA complexes showed the greatest ALA loading capacity (29 mg/g) and favorable thermal stability. In vitro digestion showed that the V7–ALA complexes contained the highest proportion of slowly digestible starch (45.2%), providing an indirect indication of their superior sustained release potential. Molecular dynamics simulations showed that V7–ALA exhibited the smallest binding-induced cavity distortion with intermediate host–guest interaction and solvation, whereas V6 required greater cavity expansion and V8 showed weaker host–guest interactions and stronger solvation. Together, the experimental and simulation results identify cavity diameter as an important structural parameter for tuning molecular-level interactions and the macroscopic performance of V -amylose–ALA complexes. These findings provide a rational basis for designing advanced V -amylose-based delivery systems.