Spray drying temperatures determine Lacticaseibacillus rhamnosus GG cell integrity, and microstructure and physicochemical properties of wood hemicellulose-based microcapsules

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Abstract

Spray-dried microencapsulation enhances probiotic viability and stability during food processing and digestion, but process evaluation typically measures only cultivable cells, which overlooks sublethal cellular damage. Accurate assessment of probiotic survival and functionality requires integrating structural, physiological, and viability analyses, particularly when optimizing processes or using new protective materials. This study addresses this knowledge gap by using galactoglucomannans (GGM) and glucuronoxylans (GX), emerging polysaccharide-based materials derived from forest industry side-streams with multicomponent and heterogeneous molecular structures, as protective matrices for the well-characterized, dehydration-sensitive probiotic Lacticaseibacillus rhamnosus GG (LGG) during spray drying at low (140/50 °C) and high (170/70 °C) inlet/outlet temperatures, with gum Arabic (GA) serving as a reference. The effects of these materials and processing conditions on probiotic survival and cell integrity, as well as on the physicochemical and microstructural properties of the resulting powders, were investigated. The results showed that elevated drying temperatures markedly decreased LGG viability and compromised cell integrity, especially in GGM-based powders, as indicated by greater salt sensitivity, lower ζ-potential, and surface damage observed via atomic force microscopy. Conversely, higher temperatures improved yield, lowered water activity and moisture content, and had minimal effects on particle size, amorphous structure, and water sorption isotherms, including monolayer moisture content. Although all microcapsules remained spherical, elevated drying temperatures produced thinner, less uniform protective layers, especially in GX- and GGM-based microcapsules. These findings highlight the importance of carefully controlling probiotic spray drying conditions when using wood-based hemicellulose matrices to balance structural integrity and viability with desirable powder properties. • Wood hemicelluloses were used as sustainable carriers for probiotic encapsulation. • Elevated drying temperatures significantly reduced probiotic viability. • Structural damage to cells during spray drying adversely affected probiotic survival. • Higher drying temperatures enhanced process yield but reduced moisture content. • High-temperature drying produced thinner and less uniform protective layers.

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