A weak post-acidification UV mutant with improved textural properties.

To derive a mutant of SH2-1 with the capacity of weak postacidification and high texturing, first, taking frs4-1 and grx02 as the controls, H-ATPase activity was demonstrated to be highly related to the postacidification of SH2-1. Then, by detecting H-ATPase activity, the weak postacidify mutant of SH2-1 (renamed as sh2-5-66) was selected from 80 UV mutants. The pH and acidity of the milk fermented with sh2-5-66 were separately 0.57 pH units higher and 57.1 °T lower than that of SH2-1. The acidification of sh2-5-66 was further demonstrated to be genetically stable during 100 generations cultivation. Moreover, the milk fermented with sh2-5-66 showed improvement in textural and rheological properties and flavor during storage which could be further improved by coculture with the commercial starter st447.