Structural characterisation and cell viability of a spray dried probiotic yoghurt produced with goats' milk and Bifidobacterium animalis subsp. lactis (BI-07)

The aim of this study was to obtain and characterise probiotic yoghurt powders with respect to their physico-chemical properties and also to evaluate the viability of probiotic microorganisms. The yoghurts were prepared by using goat milk inoculated by yoghurt cultures and the probiotic strain Bifidobacterium animalis subsp. lactis (BI-07). In the spray drying process, the temperature of inlet air (130, 150 and 170 °C) and the concentration of maltodextrin (10 and 20%) were varied. The dried goat yoghurts with added probiotics had low moisture and aw values, solubility between 68.2 and 81.1% and were highly hygroscopic. The yoghurt powder particles showed an average size from 12.7 ± 5.50 μm to 23.4 ± 0.84 μm, amorphous state, round shape and glass transition temperature varying from 42 to 45 °C. The use of drying temperature 130 °C and addition of 10% (w/w) maltodextrin produced the best probiotic viability during storage.