A weak post‐acidification Lactobacillus helveticus UV mutant with improved textural properties

To derive a mutant of L. helveticus SH2‐1 with the capacity of weak postacidification and high texturing, first, taking L. delbrueckii frs4‐1 and S. thermophilus grx02 as the controls, H(+)‐ATPase activity was demonstrated to be highly related to the postacidification of L. helveticus SH2‐1. Then, by detecting H(+)‐ATPase activity, the weak postacidify mutant of L. helveticus SH2‐1 (renamed as L. helveticus sh2‐5–66) was selected from 80 UV mutants. The pH and acidity of the milk fermented with L. helveticus sh2‐5–66 were separately 0.57 pH units higher and 57.1 °T lower than that of L. helveticus SH2‐1. The acidification of L. helveticus sh2‐5–66 was further demonstrated to be genetically stable during 100 generations cultivation. Moreover, the milk fermented with L. helveticus 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 S. thermophilus st447.