Reverse spherification of alginate gel beads as carriers for broccoli sprout juice and the application in milk tea

Broccoli sprout juice is rich in sulforaphane (SF), a bioactive compound with diverse therapeutic properties, but its instability under environmental stresses limits its application. In this study, reverse spherification was employed to fabricate broccoli sprout juice alginate beads (BSJAB) for SF encapsulation, which were subsequently incorporated into milk tea. Four polysaccharides-pectin, κ-carrageenan, gum arabic, and konjac glucomannan-were incorporated into alginate matrices to produce composite beads. Results showed that the incorporation of polysaccharides significantly enhanced the structural compactness and mechanical stability of the beads. The composite beads achieved higher SF loading efficiency (up to 61.93%) and effectively reduced contraction under gastric conditions, thereby improving SF retention. Moreover, all polysaccharide-alginate beads modulated SF release kinetics by limiting release in simulated gastric fluid (SGF; <40% cumulative) and accelerating release in simulated intestinal fluid (SIF; >80% cumulative), with gum arabic-based beads exhibiting the highest release (85.53 ± 1.03%). When applied in milk tea, beads pretreated with 18% sucrose showed the lowest shrinkage (13.88 ± 0.10%), the highest SF loading efficiency (57.22 ± 1.43%), superior SF retention after 2 h of immersion (38.23 ± 2.66%), and the highest sensory acceptability. These findings highlighted the strong potential of polysaccharide-alginate composite beads as an effective encapsulation system for labile bioactive compounds.