Fabrication and characterization of novel sericin bigels for the co-encapsulation of bioactive ingredients and in vitro gastrointestinal release profile

Abstract

While sericin, a protein from silkworms, has been explored on biomaterials and pharmaceuticals, its integration into functional food systems remains underdeveloped. This study addresses the gap in utilizing the sericin in food processing by innovating the novel sericin bigel beads with a co-encapsulation function. Bigel beads were formulated using different ratios (1:1, 1:4, and 1:8) of oleogels and sericin hydrogels encapsulating β-carotene and L-ascorbic acid simultaneously. Their physical characteristics, stability, and release profile through in vitro gastrointestinal (GI) digestion were determined. Bigel beads with lower oleogel content had low hardness values. Bigel beads with equal contents of oleogel and hydrogel exhibited the highest water-holding capacity. On Fourier transform-infrared spectroscopy, no new peak formation or peak shifts were found, signifying the lack of interaction between oleogels and hydrogels. On differential scanning calorimetry analysis, bigel beads with higher sericin hydrogel contents exhibited a stronger and more stable gel network structure. The encapsulation efficiency (EE) of β-carotene in bigel beads with higher oleogel contents showed higher stability, whereas beads with higher hydrogel contents had a higher EE of L-ascorbic acid. Bigel beads stored at 4 °C and 25 °C exhibited similar stability, retaining approximately 40 % of bioactive compounds after 15 days of storage. In the simulated GI digestion of bigel beads, the release rate of encapsulated bioactive compounds was higher during the intestinal phase. This study offers a new perspective on the co-encapsulation of lipophilic and hydrophilic bioactive components in sericin bigel bead, showing promise for the creation of functional food with controlled nutrient delivery.