Preparation of alginate-gelatin capsules and its properties

Capsules based on alginate and gelatin prepared by extrusion method could increase the cell numbers of Lactobacillus casei ATCC 393 to be 10⁸ CFU·g⁻¹ in the wet state of the capsules. The capsules were spherical, smooth-surfaced and non-aggregated with a diameter of (4.0 ± 0.3) mm. The behavior of the samples were quite similar at low relative humidity (33%, 52%) and the ratio of weight change reached 93%. Four kinds of capsules in simulated gastric fluid (SGF) exhibited shrinkage while the beads eroded accompanied with slight swelling in simulated intestinal fluid (SIF). The pH values affected the stability of the capsules and with the increase in pH, the capsules changed from shrank then swelled and finally, broke into pieces. The capsules behaved differently under different ion intensities and the introduction of gelatin weakened the stability of capsules compared with the alginate ones. Cells of L. casei ATCC 393 could be continuously released from the capsules in the simulated gastrointestinal tract (GIT) and the release amounts and speeds in SIF were much higher and faster than those in SGF.