As illustrated in Figs. 1 and 2, the firmness of co-cultures was
remarkably improved compared to pure cultures, ranging from
0.33 N (St–Lb in M) to 0.49 N (St–Lr in SM) after D1 and from
0.37 N (St–Lb in M) to 0.55 N (St–Lr in SM) after D7, as the likely
result of interactions between microorganisms. Such an interaction,
probably characterized by a synergistic effect, could be explained
with the discovery that S. thermophilus produces little
amounts of formic acid and CO2