Fabrication of high-viability spray-dried probiotic powders using plant-based composite soy peptides as carriers

Maintaining probiotic viability during spray drying remains a major challenge in probiotic powder production. In this study, soluble soy peptides (SSP) and ultrasonically dispersed insoluble soy peptides (NISP), prepared from soy protein isolate were evaluated as plant-based carriers for protecting Lacticaseibacillus rhamnosus GG (LGG) during spray drying. The effects of carrier composition on LGG viability, membrane integrity, gastrointestinal tolerance, storage stability, regrowth capacity, adhesion ability, and powder physicochemical properties were systematically investigated. The results demonstrated that all powders maintained high LGG viability (> 9 log CFU/g), and NISP-containing formulations showed improved viability retention compared with SSP alone under the investigated drying conditions. In particular, the 2% NISP–SSP formulation achieved a high viable cell count (11.16 log CFU/g), improved flowability, and maintained LGG viability during storage. After spray drying, LGG in the 2% NISP–SSP formulation retained regrowth capacity and adhesion capacity under the tested conditions. After storage at 25 °C for 8 weeks (in sealed packages), viable counts remained above the minimum effective level after storage. These results highlight the potential of soy peptide–based carriers for developing spray-dried probiotic powders with improved viability and favorable physicochemical properties.