Abstract:
The effect of freezing on the survival of Salmonella spp. was studied by freezing the sample of giant tiger shrimp added with Salmonella at 0.47, 0.79, 1.5 and 45 cm/hr. It was found that the detectable number of survival cells was lowest (0.21%) but highest in the number of injured cells (78.34%) when the samples were frozen at freezing rate of 45 cm/hr. The same affects show in the freezing of salmonella suspension, the percentage of the survival was 0.15 % and the injured cell was 81.09 % of the survival. The Salmonella suspension was stored at - 10, - 20 and - 75 ํC for 12 week, and found that the storage at -10 ํC caused the decreasing of survival of salmonella, healthy salmonella and injured salmonella faster than storage at the lower temperature. At -10 ํC, the reduction of total salmonella, healthy salmonella and injured salmonella cells were at the rate of 2.51, 2.34 and 2.56 weeks/log cfu, respectively. The Salmonella that added to the shrimp samples when stored with shrimp at - 10, - 20 and - 75 ํC for 12 week was found that at -10 ํC the reduction of total salmonella,healthy salmonella and injured salmonella was fastest, at the rate of 3.04, 3.10 and 2.94 weeks/log cfu, respectively. The suitable pre - enrichment for recovery the injured cell of S. derby was Tryptic soy broth supplemented with sodium pyruvate, yeast extract. This medium increased the healthy cells up to 88 % from 40% of Tryptic soy broth without yeast extract and sodium pyruvate, within 3 h at 42 ํC respectively