The impact of microbial transglutaminase modification on fish gelatin-maltodextrin gels loaded with calcium citrate and vitamin D3.

Protecting vitamin D3 (VD3) bioactivity and calcium ion solubility in the upper gastrointestinal tract remains challenging. In this study, a microbial transglutaminase (MTGase)-crosslinked fish gelatin-maltodextrin (FG-MD) matrix was developed to co-encapsulate calcium citrate and VD3, and its protective effects during simulated upper gastrointestinal exposure were subsequently evaluated. Our results demonstrated that MTGase cross-linking (0.00-0.30%) significantly enhanced FG-MD functionality via ε-(γ-glutamyl)lysine bonds, attaining a maximum cross-linking efficiency of 75.16%. Thermo-irreversible gels (formed with ≥0.20% MTGase) exhibited remarkable thermal stability and optimized encapsulation efficiency, with encapsulation efficiencies reaching 93% for VD3 and 87% for calcium citrate. These crosslinked matrices effectively prevented acid-induced degradation of VD3 and calcium precipitation, which was also confirmed by FTIR analysis and microscopy examination. Furthermore, in vitro transport studies using Caco-2 cell monolayers showed higher calcium transport efficacy in the hydrolysates compared to free Ca2+ ions. This study offers a promising approach for developing more effective calcium and VD3 supplementation strategies.