Effects of adding resistant and waxy starches on cell density and survival of encapsulated biofilm of Lactobacillus rhamnosus GG probiotics

• Prebiotic resistant starch had negligible impact on probiotic capsule cell density.
• Waxy starch improved freeze-drying, storage, and thermal tolerances, but not acid.
• Waxy starch increased surface roughness resulting in compromised chitosan coating.
• The best improvement in stress tolerance was obtained at 0.6% (w/v) waxy starch.
• Probiotic capsule was readily incorporated in soy milk with or without waxy starch.

Herein we investigated the effects of adding resistant and waxy maize starches on the initial cell density and stress tolerance of alginate-gum microcapsules containing high-density biofilm colonies of Lactobacillus rhamnosus GG probiotics. The stress tolerance was evaluated for (1) freeze drying, (2) 30-min heating at 100 °C, (3) two-week storage at 4 °C, and (4) exposure to simulated gastric juice. The addition of resistant starch, which was postulated to stimulate biofilm growth owed to its prebiotic properties, had minimal impacts on the initial cell density and stress tolerance of the encapsulated probiotics, signifying that co-encapsulation of probiotics with prebiotics did not necessarily lead to capsule improvement. In contrast, the addition of modified waxy starch at 0.6% (w/v) enhanced the freeze-drying (2×), thermal (25×), and storage (6×) tolerances of the probiotic microcapsules, while the initial cell density remained unaffected. The waxy starch addition, however, compromised the microcapsules' chitosan coating, resulting in lower acid tolerance. Lastly, the microcapsules were able to maintain the viability of the probiotics upon their incorporation into soy milk.