عنوان مقاله [English]
The effects of pH (5, 5.75, 6.5,7.4), K-sorbate(KS, 0.0,0.15, 0.3%), NaC1(0.5, 1.5, 3.0%), temperature (T, 15, 25, 35C), time (D, up to 43 days) and inoculum (10-2105) on the log probability percentage (LP%) of one cell of S. typhimunum to initiate growth in brain heart infusion broth were evaluated in a factorial design study. At 0% KS with £ 3% NaCl, pH level ³ 5 and T of ³ 15CC did not affect the growth of organism and 1-7 cells of Salmonella inoculum could initiate growth in 1-13d (LP% 1.9 to 2). When 0.15% KS was added to the combination, pH levels of ³ 6.5 also did not affect the growth of organism, but reduction of pH value to 5.75, only at T £ 25 C the growth of organism was inhibited (LP% -1.15 to -4.15). At pH level of 5.0 with combination of T ³ 15CC and 0.15% KS, the growth of the all of inoculated cells were innibited after 43d (LP% -4.51). When the concentration of KS was increased to 0.3%, pH levels of ³ 6.5 and T of ³ 15CC, could not affect the growth of the organism except for 3% NaCI at 15 C, which the growth was strongly diminished (LP% - 3.51). Whereas by reduction of pH to 5.75 at T levels of ³ 15C, the range of LP% reached to -1.51 to -4.51 (strong inhibitory action). At pH level of 5.0 and T of ³ 15C with concentration of £ 3% NaCl and 0.3% KS, the growth of the organism was completely inhibited after 43d. Overall the LP% of Salmonella was affected significantly (P<0.003) by pH, T, KS and D but not by NaCI concentration used in this study. Regression equation was derived relating LP% to KS, NaCl, pH, T and D. From the equation the number of cells needed to initiate growth can be calculated.