Abstract: In this study,5 milk samples fermented respectively with 5 strains of Streptococcus salivarius subsp.thermophilus 9,17YA,1703CA, 1703D and 03 were assayed with SDE-GC-MS to assess the difference of the flavour compounds among them.This study identified 24,20,13,20,21 flavour compounds respectively,including 35 compounds in 6 categories: acids,esters, alcohol,carbonyls,aromatic compounds and heterocyclic compounds.The capability to produce 2,3-butanedione,the main flavor impact compound, was found in 5 strains: S.t-1703D> S.t-1703CA> S.t-17YA> S.t-03> S.t-9, but not much difference except theS .t-9.

Key words: fermented milk, flavor compounds, Streptococcus salivarius subsp.thermophilus, SDE-GC-MS (simultaneous distillation/extraction- gas chromatography- mass spectrometry)