Effect of protein-carbohydrate wall systems on viability and stability of freeze-dried probiotic microcapsules

Probiotic applications are often limited by poor survival during processing and storage, highlighting the need for effective protective encapsulation systems. This study comparatively evaluated the influence of protein-carbohydrate wall material systems on the structural stability and viability of freeze-dried microcapsules. Microcapsules were designed using maltodextrin (MD), skim milk powder (SMP), and gum arabic (GA) in single, binary, and ternary combinations to individually encapsulate four probiotic strains (Lactiplantibacillus plantarum, Limosilactobacillus fermentum, Lactobacillus acidophilus, and Bifidobacterium breve). Encapsulation efficiency, cell viability, physicochemical properties (moisture content, water activity, bulk density, and color), and structural characteristics (scanning electron microscopy, dynamic light scattering, zeta potential, X-ray diffraction, thermogravimetric analysis, and Fourier-transform infrared spectroscopy) were evaluated. Compared with single- and binary-wall systems, the ternary MD:SMP:GA formulation demonstrated improved encapsulation efficiency and maintained post-lyophilization viability up to 9.25 log CFU/mL. Wall material composition largely influenced microcapsule structure and probiotic survival, with only minor strain-dependent variability observed. Structural analyses indicated that MD:SMP:GA promoted the formation of uniform amorphous microstructures stabilized through hydrogen-bonding interactions and electrostatic effects, creating a protective microenvironment that limited molecular mobility and preserved cellular integrity during freeze-drying. These findings provide mechanistic insight into protein-carbohydrate interactions influencing freeze-dried microencapsulation and demonstrate the potential of ternary MD:SMP:GA systems for improving probiotic stability in functional food and nutraceutical applications.