Spray Drying Yogurt Incorporating Hydrocolloids: Structural Analysis, Acetaldehyde Content, Viable Bacteria, and Rheological Properties

Hydrocolloids and some of their mixtures were used to prepare spray-dried yogurt. Acetaldehyde retention and microbial viability were evaluated. Morphology was examined by scanning electron microscopy and the yield stress was evaluated, to assess the damage to the microstructure by the drying process. The yield stress displayed a significant irreversible decrease after spray drying and micrographs indicate that the microstructure of the yogurt was severely damaged by the drying process. Micrographs indicated that κ-carrageenan and κ-carrageenan-locust bean gum gave more protection to the casein matrix, leading to greater acetaldehyde retention (92% and 89%, respectively). Microbial viability was improved when pectin was used as the encapsulating agent.