Abstract:
Black tiger prawn obtained from Samut Sakhon province shrimp market during March 2003 to February 2004 was assessed for the amount of total bacteria, psychrotrophs, coliform and Esherichia coli. It was found that the amount of total bacteria were 1.9x10[subscript 5] 4.1x10[subscript 5] CFU/g. The total bacteria detected from each season was not significantly different (P>0.05). During October to January, it was found that the amount of psychrotrophs was higher than the other. The coliform and E. coli detected during this period was 45.0 and 6.7% which less than 10 and less than 3 MPN/g, respectively. No Salmonella spp., Vibrio cholerae and V. parahaemolyticus was detected in all samples. Ozonated water of 548.53 mg/l TOC (0.13 mg/l ROC) could effectively reduce 5, 6 and 9 log of initial bacteria suspension to 2, 4 and 7 log respectively of total bacteria, psychrotrophs, coliform, E. coli, S. anatum and V. parahaemolyticus after contacting for 1 minute. The ratio between the amount of death bacteria and initial bacteria was increased when the concentration of ozone was in the range of 217.60 1132.27 mg/l TOC (less than 0.1 0.32 mg/l ROC). In addition, ozonated water could reduced all tested bacteria on black tiger prawn. The black tiger prawn that treated with ozonated water at the concentration of 217.60 1132.27 mg/l TOC for 1 minute could prolong the shelf-life to 6 and 8 days respectively, while the prawn that was not treated with ozonated could be kept for 4 days at 4 degree celcius before the TVB number of the prawn went over 30 mgN/100g. The ozonated water treated prawn had a better odor score than the untreated ones, but the texture and color score showed no significantly difference (P>0.05).