3.3. Influence of different concentrations of casein hydrolysate on growth,
changes in pH and EPS production
In order to evaluate the possible effects of CH, a number of fermentations
(37 °C for 18 h) were carried out using milk supplemented
with different CH concentrations, and the growth behaviour and
EPS synthesis determined. Significant (Pb0.05) differences in the cell
counts were observed for both strains when grown in milk supplemented
with CH from 0.5% up to 1.5% (w/v); more specifically, the
cell counts increased as the CH concentration increased (Table 2).
However, no significant differences in the cell counts were observed
when CH ranged from 1.5% to 2.5%. Depending on the Bifidobacterium
strain and the level of CH supplementation, the pH of fermented milk
samples decreased from 6.7 to 5.3–3.9 after 18 h incubation
(Table 2). Overall, there was a good correlation between the final
cell concentration and the decrease in pH and the EPS levels with
the different CH concentrations used, for both strains (Fig. 2 and
Table 2). Small differences were observed in the amounts of EPS produced
by B. infantis NCIMB 702205 at different CH supplementation
levels, whereas distinct differences were observed for B. longum
subsp. infantis CCUG 52486. More specifically, there was three-fold
increase in the EPS levels produced by B. longum subsp. infantis
CCUG 52486 as the CH supplementation was increased from 0.5%