Effect of high-speed homogenisation on the morphological characteristics and survivability of Lactobacillus rhamnosus GG-coated microbeads

Xanthan gum can be utilised to overcome the structural defects in alginate microbeads and to improve the stability of microbeads under harsh conditions, that is, high acidic pH and homogenisation speeds. Present study was conducted to assess the survival of Lactobacillus rhamnosus GG using alginate (1.5% w/v) and xanthan gum (0.5% w/v) for encapsulation and structural modifications of microbeads. Homogenisation emulsion technique was used for encapsulation at various homogenisation speeds, that is, 3000 rpm (HS1), 6000 rpm (HS2), 9000 rpm (HS3) and 12 000 rpm (HS4). The resultant microbeads were characterised for diameter, beads yield, structural morphology using the scanning electron microscopy, probiotic count, bacterial survival, storage stability and homogenisation efficiency. Scanning electron microscopy images indicated that the beads produced at 12 000 rpm are more uniform, spherical in shape and have large surface area when compared with the other treatment groups. The diameter of microbeads was reduced from 323.1 to 238.2 mu m as the homogenisation speed increased from 3000 to 12 000 rpm. The highest bacterial count (i.e., 9.45 log CFU g(-1)), homogenisation efficiency (91.6%), beads yield (23.0%), survivability (86.5%) and storage stability (9.84 to 7.90 log CFU g(-1)) were recorded at 12 000 rpm (HS4). Conclusively, the homogenised encapsulated microbeads at 12 000 rpm significantly improved the beads surface and sphericity, and bacterial survivability.