A large number of flavor components were identified in yoghurt with the major ones
being carbonyls such as acetaldehyde, acetone, and diacetyl. Several pathways were described
for acetaldehyde production, including decarboxylation of pyruvate, reduction of acetyl~CoA,
and cleavage of threonine to glycine and acetaldehyde. S. thermophilus was reported to
produce greater amounts of acetaldehyde compared to L. bulgaricus in the presence of
necessary stimulatory growth factors. In addition to carbonyl compounds, volatile fatty acids
and amino acids have also been shown to enhance yoghurt flavor.