Emulsion-loaded konjac glucomannan/oat β-glucan/alginate hydrogel beads enhance the gastrointestinal and thermal tolerance of Bifidobacterium animalis subsp. lactis BL99.
Abstract
In this study, emulsion-loaded hydrogel beads were developed using konjac glucomannan (KGM), oat β-glucan (Glu), and sodium alginate (SA) as composite wall materials, with a shortening-based water-in-oil (W/O) emulsion incorporated for the protective delivery of Bifidobacterium animalis subsp. lactis BL99. Rheological analysis showed that the KGM/Glu system at a ratio of 6:4 exhibited enhanced viscoelasticity. FTIR analysis indicated changes in the hydrogen-bonding environment and polysaccharide fingerprint region, while dual-channel CLSM observation of separately labeled KGM and Glu revealed partial spatial overlap and interpenetrating distribution, supporting favorable compatibility and chain association between the two polysaccharides. Contact angle and ζ-potential analyses were used as auxiliary indicators of apparent surface wettability and charge characteristics. DSC results showed that shortening exhibited a broad melting range of 12-52 °C, suggesting its potential as a thermally responsive phase. CLSM and SEM showed that oil droplets were embedded within the KGM/Glu/SA gel network, forming a multiphase structure with dispersed oil domains and probiotic-entrapping regions. Compared with KGM/Glu/SA hydrogel beads without emulsion (KSG), emulsion-loaded KGM/Glu/SA hydrogel beads (E-KSG) showed improved morphology, denser cross-sectional structure, and better stability in simulated intestinal fluid. After 360 min of simulated gastrointestinal digestion, BL99 counts in KSG and E-KSG were 4.81 and 5.05 log CFU/g, respectively. E-KSG maintained 8.35 and 4.98 log CFU/g after treatment at 63 °C for 30 min and 95 °C for 120 s, respectively, and improved BL99 viability during storage in peach juice, milk, and yogurt. These results demonstrate that the KGM/Glu/SA network combined with shortening-based W/O emulsion enhanced gastrointestinal protection, thermal tolerance, and storage stability of BL99.