A ternary composite system of sunflower oil, myofibrillar protein, and alginate in microcapsules significantly affected the viability of L. acidophilus during gastrointestinal delivery.

L.acidophilus is prone to inactivation during gastrointestinal delivery. Therefore, this study constructed a ternary composite system of sunflower oil, myofibrillar protein (MP), and sodium alginate (SA) in microcapsules to improve the gastrointestinal viability of L. acidophilus. Two alginate types, high-mannuronate sodium alginate (HM-SA) and high-guluronate sodium alginate (HG-SA), and two sunflower oil forms, sunflower oil (SFO) and structured sunflower oil (SSFO), were compared. The physicochemical properties of the ternary composite microcapsules were characterized, and their protective efficacy was evaluated using the standardized INFOGEST 2.0 in vitro digestion protocol. The HM-SA + MP + GL + SFO microcapsules exhibited the highest encapsulation efficiency and the largest mean bead size. During digestion, the corresponding probiotic-free HM-SA + MP + SFO ternary composite system maintained a low Turbiscan Stability Index and high viscosity, indicating comparatively restricted particle movement and favorable physical stability. Intermolecular-force analysis showed that HM-SA + MP + SFO had the highest ionic-bond and hydrogen-bond values, while molecular docking gave the lowest binding energy for the linoleic acid+HM-SA combination with myosin. After gastric and intestinal digestion, the HM-SA + MP + GL + SFO microcapsules retained 6.41 and 6.04 Log CFU/mL viable cells, respectively, whereas no viable cells were detected in the non-encapsulated L. acidophilus group. These results demonstrate that the HM-SA- and SFO-containing ternary composite microcapsules provided the best overall physicochemical stability and preservation of L. acidophilus viability among the tested delivery systems.