Submitted to: Meeting Abstract
Publication Type: Proceedings
Publication Acceptance Date: 1/11/2007
Publication Date: 8/28/2007
Citation: Bari, L., Mori, M., Ukuku, D.O., Kawamoto, S., Yamamoto, K. 2007. Efficiency of high pressure treatment on the inactivation of Escherichia coli O157:H7 in tomato juice and Salmonella in liquid whole egg. In: Proceedings of the 4th International Conference on High Pressure Bioscience and Biotechnology. September 27, 2006, Tsukuba, Japan. p.272-279.
Technical Abstract: Liquid foods have been implicated in numerous food-borne outbreaks and recalls. Tomato juice and phosphate buffer saline inoculated with Escherichia coli O157:H7 at 8 log CFU/ml was exposed to continuous or repeated cycles of high-pressure (300 MPa to 600 MPa) treatment at 25C. Treatment using moderate pressure at 300 MPa, 350 MPa and 400 MPa for up to 60 min reduced the population of inoculated E. coli O157:H7 by approximately, 3, 3 and 5 log cycles, respectively in tomato juice. Population of E. coli O157:H7 in all samples tested was decreased when temperature was increased from 30-40C. However, increase in temperature and a 600 MPa pressure resulted in more sub-lethal injury on cells inoculated in phosphate buffer than tomato juice. It appeared that the acidity of the tomato juice killed and prevented recovery of the injured bacteria. Treatment of 350 MPa and 400 MPa pressure at 25C for 40 min reduced the population of S. Enteritidis by approximately 4.8 and 6 log CFU/ml in liquid whole egg, respectively. Liquid whole egg treated at 350 MPa pressure 10 min at 50C showed the highest inactivation of Salmonella. However, pressure treatment at 400 MPa for 10 min at the same temperature (50C) caused coagulation of protein in liquid egg. When treatment pressure (350 MPA at 50C) was repeated every two (2 min) for a total of 8 min at 4cycles, a significant (P<0.05) bacteria inactivation occurred. No Salmonella was recovered in liquid egg after post pressurization (2 min x 4 cycles) storage at 4, 25 and 37C for 24h. The results of this study suggest that repeating 350 MPa hydrostatic-pressure treatments at least 4 times for a total of 8 min would lead to high inactivation of Salmonella in liquid whole egg than continuous pressure treatment.