Enhanced viability of encapsulated probiotics using whey protein isolate-dextran conjugates: Effect of dextran molar mass

Abstract

Encapsulation is an effective strategy to protect labile compounds and maintain the viability of beneficial microorganismsduring food processing and storage. This study investigated the use of Maillard reaction conjugatesof whey proteins isolate (WPI) and dextran (DX) as wall materials for encapsulation of lactic acid bacteriaconsidered as potential probiotics: Bifidobacterium animalis subsp. lactis INL1 (INL1) and Lactobacillus plantarum73a (L73a). WPI/DX conjugates were prepared by controlled heating of WPI with dextrans of 6 and 100 kDa,referred to as WPI/DX6 and WPI/DX100. The bacterial cells were suspended in canola oil, used as oil phase of asolid-in-oil-in-water emulsion where the conjugates served as encapsulating agents. The emulsions were spraydriedto produce powdered microcapsules. Compared to native WPI, both conjugates formed more stableemulsions, characterized by smaller droplet sizes, lower creaming indices, and higher interfacial activity. Theseimprovements were attributed to different mechanisms: in WPI/DX6, conjugation with low-molar-mass dextranaltered the native protein structure, promoting better interfacial adsorption and more stable emulsions, whereasin WPI/DX100, the protein structure was considerably preserved and the high-molar-mass dextran enhanced theamphiphilic behavior of the conjugate and provided stronger steric stabilization.The emulsification process did not affect bacterial viability; however, spray drying led to a reduction in cellcounts across all formulations. Despite this, both WPI/DX conjugates provided superior protection during storagecompared to native WPI. Viability was better preserved at lower temperatures (􀀀 18 ◦C > 4 ◦C > 21 ◦C), with thehighest survival observed in WPI/DX100-L73a microcapsules stored at 4 ◦C.