Growth response and metabolic activity of Bifidobacterium infantis ATCC 27920G in creams enriched with native phosphocaseinate retentate

Creams containing 14% milk fat were enriched to total protein content of 4. 4, 5.5 and 6.5% with native phosphocaseinate obtained by microfiltration of skim milk. Cream was inoculated with freeze-dried Bifidobacterium infantis culture at the concentration of 1x10(7), 5x10(7) and 1x10(8) cfu/g of crea m and fermentations were performed for 24 h. Unenriched cream (14% milk fat ) and skim milk were used as control and reference. The final bifidobacteri a counts were 1.5 x 10(9), 1.4 x 10(9) and 1.3 x 10(8) cfu/g Of cream far i noculum concentrations of 1x107, 5x107 and 1x10(8) cfu/g of cream, respecti vely. The final titratable acidities developed for the cream variable were 0.54, 0.58, 0.68, 0.82 and 0.98% for skim milk, unenriched cream, and enric hed beams with 4.4, 5.5 and 6.5% total protein, respectively. The lactose h ydrolysis reached 1.29, 2.00 and 2.72g/100 g of cream and the sum of acetic and lactic acid produced were 0.79, 0.60 and 0.35 g/100 g of cream with 1 x 10(7), 5 x 10(7) and 1 x 10(8) cfu/g inoculum concentrations, respectivel y. The high level of bifidobacteria inoculum resulted mainly in lactose hyd rolysis activity whereas the low level of bifidobacteria inoculum allowed t he increase of biomass by 2 log cycles.