the impact of inoculation rate and order on physicochemical, microstructural and sensory attributes of probiotic doogh

effects of inoculation level (4 or 8-fold compared to standard inoculation) and order (standard inoculation before fermentation and 3-fold inoculation at the end of fermentation = 1+3, two-fold inoculation before fermentation and the same at the end of fermentation = 2+2, 2+6, 4-fold before fermentation = 4, 4+4, and 8) of culture inoculums containing probiotics on viscosity, phase separation, particle size analysis, microstructure and sensory attributes of probiotic doogh were studied. the probiotic microorganisms were lactobacillus acidophilus la-5 and bifidobacterium lactis bb-12. treatments with 2- and 4-fold inoculation before fermentation had the highest instrumental viscosity and surface tension at the end of fermentation. the size diameter of particles in the structure of treatment 8i was significantly (p < 0.05) smaller than i after stirring with a lab stirrer (1500 rpm), and even after homogenization with a homogenizer (150 bar). 8i was an un-uniform, disintegrated and clumped structure with limited junctions in its network that resulted in a weak structure with bigger particles after agitation and smaller particles after stirring and homogenization compared to other treatments. this treatment also had the lowest record in ranking sensory test among treatments with a mixed culture-like and vinegary-like taint. overall, treatments with 2- and 4-fold inoculation were realized as the best from the sum of physiochemical and sensory properties point of view.