Intrinsic tolerance of Bifidobacterium species to heat and oxygen and survival following spray drying and storage

Aims: This study examined the tolerance of various species of the genus Bifidobacterium to heat and oxygen and evaluated the survival of selected strains following spray drying and during storage. Methods and Results: Nine Bifidobacterium species were considered to be relatively tolerant to both heat and oxygen and mostly segregated into two clusters within the 16S rDNA phylogenetic tree. Four species were tolerant to oxygen and 12 species were considered sensitive to oxygen and heat. Using a skimmed milk-based carrier good survival following spray drying and storage at 4 degrees C correlated with tolerance to heat and oxygen. Viability was inversely related to storage temperature and at 15 degrees C and 25 degrees C, a significant decline was observed for all species. The inclusion of gum acacia had no significant affect on survival or viability. However, using a fluidized-bed spray dryer viability was greatly improved. Conclusions: A group of closely related species tolerant to heat and oxygen had high survival following spray drying and maintained viability during prolonged storage at 4 degrees C. Significance and Impact of the Study: Spray drying is a suitable method for the production of skimmed milk powder enriched with high numbers of viable bifidobacteria.