2.6. Microbiological determination
For viable numbers of starter culture in the products, S.
thermophilus was enumerated using M17 agar acidified to
pH 6.8 by 1 MHCl (IDF, 1997) and subsequently incubated
at 37 ± 1 C for 48 h under aerobic condition. The number
of L. bulgaricus was determined using MRS agar acidified
to pH 5.4 with 100% glacial acetic acid then incubated at
37 ± 1 C for 72 h under anaerobic condition (IDF, 1997).