BACKGROUND: Riboflavin, a water-soluble vitamin, is not synthesized in the human body. Hence, developing riboflavin carriers that can be retained in the gastrointestinal system for longer periods can facilitate riboflavin supplementation. RESULTS: The present study aimed to prepare a soy protein isolate (SPI)-κ-carrageenan composite gel-mediated riboflavin delivery model. Additionally, the effects of different concentrations of κ-carrageenan on the micromorphology, gel strength and rheological properties of SPI gels were investigated. The results showed that incorporating high- concentration of κ-carrageenan (0.4 g kg CONCLUSION: Altogether, the findings of the present study provide insights into SPI-κ-carrageenan composite gels regarding gel properties and interaction mechanisms, as well as a strategy for the slow release of riboflavin in the gastrointestinal tract. © 2025 Society of Chemical Industry.