Survival and metabolic activity of microencapsulated Bifidobacterium longum in stirred yogurt

Live cells of Bifidobacterium longum, microericapsulated in kappa-carrageenan, were added to stirred yogurt after fermentation (pH 4.6) and stored at 4.4 degreesC for 30 d. Cell enumeration indicated no decline of encapsulated cell number in yogurt samples, while there was significant reduction in nonencapsulated cell population (89.3% for B. longum B6 and 91.8% for B. longum ATCC 15708). Ion-exchange high-performance liquid chromatography showed comparable amounts of lactic and acetic acids in all samples, indicating little metabolic activity by bifidobacteria in experimental yogurts. Consumer sensory analysis of blackberry-flavored yogurts revealed that samples containing encapsulated bifidobacteria had a grainy texture. Results suggested that microencapsulation protected bifidobacteria from the low pH of yogurt.