Fig. 2.

Viability of S. thermophilus cells after freezing at −20 °C for 24 h and 2 freeze–thaw cycles with various cryoprotectants. (a) Survival rate and culture pH of S. thermophilus after incubation for 7 h; (b) growth curve of S. thermophilus; (c) acidification ability of S. thermophilus; (d) S. thermophilus metabolic activity with various cryoprotectants; (e) effects of various cryoprotectants on the activity of lactic dehydrogenase (LDH), β-galactosidase, pyruvate kinase (PK) and hexokinase (HK); (f) effects of cryoprotectants on ATPase in S. thermophilus under cold stress. Different letters on columns indicate significant different values (P < 0.05).