3.4. pH, microbiology, whey separation and rheology of yogurt
On each analysis day, the pH and growth of S. thermophilus and
L. bulgaricus in yogurts were unaffected (P N 0.05) by seaweed extract
type or concentration (Table 4). The pH of yogurts was significantly negative correlated (P b 0.001) with days 14, 21 and 28 of storage
(Table 5) reflecting minor decreases in pH as a function of storage
time.Whey separation was similar for all yogurt samples on each analysis
day and overall rates ranged from ~15–21% (Table 4). Similarly,
Brignac and Aryana (2012) reported that the addition of antioxidant
compounds (vitamin C, vitamin E and β-carotene) did not influence
whey separation in yogurt. In general, the modulus of yogurts varied
as a function of storage time (Table 4). On day 28 of storage, all yogurts,
with the exception of AN100 (0.5%) and AN80e (0.25%), had significantly
lowermodulus values compared to the control, indicating that seaweed extracts influenced the rheology of yogurt at the end of the storage period.
The modulus of yogurts was lower than that reported by Lee and
Lucey (2004) which may be attributed to lower starter culture inoculation
rates (0.1%) used in the present study.