Carrageenan functions as a hydrocolloid with remarkable gelling, thickening, and stabilizing properties, making it indispensable in diverse food formulations. It is widely utilized in dairy, confectionery, and processed meat products to improve viscosity, texture, and structural stability. Owing to its strong water-binding capacity and synergistic interactions with proteins, carrageenan plays a vital role in developing low-fat and plant-based food systems.

A hybrid sulfated galactan composed of κ- and β-carrageenan motifs was isolated from Betaphycus gelatinus through hot (95 °C) alkaline extraction, followed by alkali treatment to convert residual precursor molecules into the predominant carrageenan form. Both native and alkali-modified Betaphycus galactans were characterized by high-performance size-exclusion chromatography (HPSEC), high-performance ion-exclusion chromatography (HPIEC), high-performance anion-exchange chromatography (HPAEC), FTIR, and NMR spectroscopy to elucidate their molecular weight distribution and structural architecture.

Enzymatic depolymerization using κ-carrageenase revealed distinct distributions of κ- and β-carrabiose units. The enzyme-resistant fraction was enriched in β-carrageenans, whereas the enzyme-sensitive portion contained abundant oligo-κ- or κ/β-carrageenans, indicating a blockwise arrangement of κ- and β-domains within the B. gelatinus polymer. The effects of alkali treatment and counterions (K⁺, Ca²⁺, and Ba²⁺) on the thermo-rheological properties of the hybrid galactan gels were evaluated by dynamic rheometry. K⁺ ions markedly enhanced gelation, demonstrating their specific role in network stabilization. Strong interactions between the hybrid carrageenan and casein were also observed, as evidenced by rheological analysis, X-ray diffraction, and differential scanning calorimetry (DSC), confirming its high binding affinity and compatibility with dairy proteins.

Caco-2 cell assays showed no cytotoxic effects upon treatment with the hybrid carrageenan. The gene and protein expression of tight junction markers (Claudin-1, Occludin, and ZO-1) remained comparable to control cells, confirming preservation of epithelial barrier integrity during polymer exposure. Furthermore, the hybrid carrageenan inhibited the adhesion of intestinal pathogenic bacteria.

In vivo administration of the hybrid carrageenan in mice showed no observable toxicity, confirming its safety for potential food applications. Overall, this study underscores the superior gel-forming capacity of Betaphycus polymers—particularly in the presence of K⁺ ions—their strong affinity toward milk proteins, and their favorable safety profile, supporting their potential use in functional and protein-enriched food formulations