d. abedi

The objectives of this paper were production of probiotic yoghurt using L. paracasei ssp. tolerans, and evaluation of pH changes, viable counts, and organoleptic properties of the produced yoghurt. It was observed that the pH decrease during the fermentation period was faster in the milk inoculated with L. paracasei ssp. tolerans plus starter culture. There was a gradual decrease in pH in both of the fermented milks during the first 120 min, followed by a sharp drop between 180-210 min, and a steady reduction later until the desired pH was achieved. The viable count of the probiotic bacterium (L. paracasei) decreased almost linearly during the storage time, but remained higher than the standard limit for probiotic products. Incorporation of L. paracasei ssp. tolerans in yoghurt neither affected the viability of the starter cultures during 21 days of cold storage, nor the organoleptic properties of the yoghurt. There was no significant difference between organoleptic properties of the control and the probiotic yoghurts.