A weak post‐acidification <i>Lactobacillus helveticus</i> UV mutant with improved textural properties

Abstract

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