According to Klaver et al. (1993), one of the most
constraining drawbacks associated with the use of
dietary cultures in fermented milk products is the lack
of acid tolerance of some species and strains. When the
lactic acid content increases, pH levels correspondingly
decrease during fermentation. ‘Over-acidification’ or
‘post-production acidification’ is due to the decrease in
pH after fermentation and during storage at refrigerated
temperature. Excessive acidification is mainly due to the
uncontrollable growth of strains of L. bulgaricus at low
pH values and refrigerated temperatures. The ‘overacidification’
can be prevented to a limited extent by
applying ‘good manufacturing practice’ and by using
cultures with reduced ‘over-acidification’ behaviour
(Kneifel et al., 1993).