As expected, the quality parameters of the yogurts were depen-
dent on the exposure time of the samples dependent on the expo-
sure time in which they were subjected to a refrigeration
temperature. The pH value of samples ranged from 4.58 for control
sample (0 days/10 C) to 4.12 for the sample that remained for
84 days at 10 C (p < 0.05) suggesting the occurrence of post-acid-
ification, which is a relevant parameter that influences the viability
of the probiotic bacteria in fermented dairy products, like yogurt.
‘Post-production acidification’ is defined as a decrease in pH values
after fermentation and during storage under refrigerated tempera-
tures, mainly due to the uncontrolled growth of Lactobacillus del-
brueckii ssp. bulgaricus under these conditions (Lourens-Hattingh
& Viljoen, 2001). Additionally, the results reinforce which the tol-
erance of Bifidobacterium spp. towards pH values is strain-depen-
dent. Indeed, recent research reported B. animalis ssp. lactis
showed significantly better (p < 0.0001) survival than B. longum
in stressed environmental conditions as acidity environments
(Jayamanne & Adams, 2009).