• Bifidobacterium animalis;
  • Bifidobacterium bifidum;
  • Doogh;
  • Probiotic;
  • Inoculation;
  • Viability

The combined effects of probiotic sequential inoculation (before or after fermentation), type of native Bifidobacterium strain (Bifidobacterium animalis spp. lactis PTCC 1631 and Bifidobacterium bifidum PTCC 1644) and final pH of fermentation (4.5 or 4.2) on qualitative aspects of typical Iranian fermented milk drink (Doogh) were investigated. The blends inoculated with yoghurt bacteria only and with final fermentation pH of 4.5 had the shortest fermentation time. The highest viability of bifidobacteria in all treatments at the end of fermentation and throughout the refrigerated storage was observed for BlY-40-4.5 (B. lactis co-cultured with yoghurt starter bacteria and incubated at 40 °C until final pH of 4.5) and then for BbY-40-4.5 (containing B. bifidum). The most acceptable organoleptic properties were observed for treatments BlY-40-4.2 and BbY-40-4.2, and then for BbY-40-4.5.