Encapsulation of probiotic Lactobacillus acidophilus by ionic gelation with electrostatic extrusion for enhancement of survival under simulated gastric conditions and during refrigerated storage

The probiotic Lactobacillus acidophilus was encapsulated in biodegradable and biocompatible capsules prepared by ionic gelation between phytic acid (PA) and chitosan (CS) with an electrostatic extrusion method. Calcium carbonate (CaCO₃) and starch were used as co-encapsulants for improvement of capsule stability. Capsules were characterised and evaluated for survival of encapsulated L. acidophilus cells in simulated gastric fluid (SGF) and during refrigerated storage. Loading capacity values of PA-CS capsules, PA-CS-starch capsules and PA-CS-CaCO₃ capsules were 8.20, 8.12 and 7.81 log CFU g⁻¹ of wet capsule, respectively. Capsules showed particle sizes of 1.3–1.5 mm and a uniform spherical shape. PA-CS-CaCO₃ capsules were the most stable vehicles for the protection of probiotic cells against acidic damage, particularly at pH 1.5 and pH 2. L. acidophilus cells from PA-CS-CaCO₃ capsules showed only a 0.64 log CFU reduction in numbers after 2 h in pH 1.5 SGF conditions. The numbers of L. acidophilus encapsulated in PA-CS-CaCO₃ capsules were decreased by only 0.69 log CFU g⁻¹, while PA-CS capsules and PA-CS-starch capsule numbers were reduced by more than 1.45 log CFU g⁻¹ after 4 weeks at 4 °C. Addition of calcium carbonate to PA-CS capsules provided protection against acid injury via antacid and buffering effects for encapsulation of L. acidophilus.