The first step in utilizing appropriate microorganisms to produce probiotic milk products is to recognize their growth conditions in milk and the factors influencing them. In this research, the effect of dextrose, valine, glycine, thiamine and differ
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The first step in utilizing appropriate microorganisms to produce probiotic milk products is to recognize their growth conditions in milk and the factors influencing them. In this research, the effect of dextrose, valine, glycine, thiamine and different temperatures on growth rate of Bifidobacterium bifidum in milk has been studied and for this purpose, fermented milk by B. bifidum has been used as stock culture in order to inoculate the milk samples. First 28, 35, 42, 49 and then 35, 38, 41 and 44°C incubators were used to choose the suitable incubation temperature for growth of the microorganisms and the acidity of milk samples were measured as a growth index of the microorganisms prior to and during incubation. Concentrations of 0 (control), 5, 10 and 15 ppm of thiamine; 0(control), 0.4, 0.6, 0.8 and 1% of dextrose; 0(control), 30, 60, 90 and 120 ppm of glycine and valine were used to evaluate their effects on the growth rate of B. bifidum and acidity of milk samples were measured before incubation and after 2, 4, 6 and 8 hours of incubation at 42°C. The rate of increase of acidity at 44°C and 41°C was significantly higher than the other temperatures (p<0.05). The addition of different concentrations of dextrose, valine and glycine had no significant effect on the rate of increase of acidity of the milk samples. The addition of thiamine also had no significant effect on the acidity although it reinforced the ability of B. bifidum in the production of proteolytic enzymes and gas.
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