Development of a novel gelatin membrane containing curcumin-encapsulated chitosan–oleic acid complex particles for targeted nutrient delivery to the small and large intestine

• Edible composite membranes containing a water-insoluble compound were formulated • Chitosan-oleic acid particles enhanced curcumin incorporation into gelatin membrane • Physical properties of the membrane can be tuned by controlling its composition. • Stability of curcumin under ultraviolet irradiation improved after encapsulation • Controlled curcumin release was achieved in a simulated small intestinal environment Edible membranes containing water-insoluble bioactive compounds are used not only as preservation materials for dietary supplements but also as delivery carriers for beneficial food ingredients. In this study, we demonstrate that chitosan–oleic acid (CHI–OA) complex particles can function as stable delivery units when incorporated into a gelatin (GL)-based edible membrane. In the CHI–OA–GL composite membrane, scanning electron microscopy and confocal laser scanning microscopy observations revealed that the CHI–OA complex particles were well dispersed and entrapped within the GL membrane matrix without exposure on the membrane surface. Fourier-transform infrared spectrometry and small-angle X-ray scattering analyses revealed that the CHI–OA complex particle microstructure was maintained after membrane formulation. Tensile tests showed that Young’s modulus varied by approximately 4.5-fold in the mass-based CHI fraction of the membrane from 0 to 0.20 [g/g]. Moreover, up to 5.4 µmol/g curcumin could be incorporated into the composite membrane. Over 80% of the curcumin was retained in the composite membrane after 24 h of ultraviolet irradiation, whereas approximately 90% of the curcumin dissolved in methanol was degraded within 6 h. In an in vitro digestion test, the pH-responsive nature of the CHI–OA complex particles allowed curcumin to remain encapsulated in the gastric phase (pH 3). In contrast, during the intestinal phase (pH 7), curcumin exhibited a gradual release while maintaining a controlled-release behavior. Overall, this study highlights the potential of the CHI–OA–GL composite membranes as a solid-state delivery platform for value-added food materials containing water-insoluble bioactive ingredients.