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Title: EFFCT OF HIGH-PRESSURE TREATMENT ON SURVIVAL OF ESCHERICHIA COLI 0157:H7 POPULATION IN TOMATO JUICE

Author
item BARI, M - NFRI
item MORI, M - NFRI
item Ukuku, Dike
item KAWAMOTO, S - NFRI
item KAWAMOTO, K - NFRI

Submitted to: International Journal of Food, Agriculture, and the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2006
Publication Date: 5/1/2007
Citation: Bari, M.L., Mori, M., Ukuku, D.O., Kawamoto, S., Kawamoto, K. 2007. Effct of high-pressure treatment on survival of escherichia coli 0157:h7 population in tomato juice. International Journal of Food, Agriculture, and the Environment. 5(1):111-115.

Interpretive Summary: Liquid foods and beverages have been implicated in numerous food-borne outbreaks and recalls. In this study, we tested the efficacy of a non-thermal high-pressure treatment at moderate temperature in preserving the fresh-like attributes and reducing the population of E. coli 0157:H7 inoculated in tomato Juice and liquid whole egg. After processing treatment, survival and viability loss of the E. coli 0157:H7 in phosphate buffer, tomato Juice and liquid whole egg was monitored. Treatments of tomato juice using moderate pressure from 300 to 350MPa for up to 60 min reduced the population of E. coli O157:H7 by approximately 3000 CFU/ml, at 400 MPa for up to 60 min, population reduction for E. coli was 5000 CFU/ml. In liquid whole egg, a population reduction of E. coli O157:H7 by 4000 CFU/ml was achieved at 400 MPa for 40 min. Increase in temperature from 30 to 50oC enhanced treatment effect in reducing the population of E. coli O157:H7 in all samples tested. However, increase in temperature with a 600MPa pressure resulted to coagulation of the liquid eggs, and more injury to cells recovered in tomato juice than liquid egg. Repeating the pressure 4 times at 300 MPa for a total of 40 min at room temperature caused extra reduction of E. coli population by 100 CFU/ml. The results of this study suggests that repeating high-pressure treatment at least 4 times at 300 MPa for a total of 40 min would kill more E. coli O157:H7 strains in liquid whole egg and tomato juice than using continuous pressure for the same amount of time.

Technical Abstract: Liquid foods and beverages have been implicated in numerous food-borne outbreaks and recalls. In order to preserve and reduce E. coli 0157:H7 population of tomato Juice and liquid whole egg, the efficacy of a non-thermal high-pressure treatment at moderate temperature was investigated. Also, survival and viability loss of the E. coli 0157:H7 in 10 nM phosphate buffer (pH 7.0), tomato Juice and liquid whole egg was investigated. Phosphate buffer, tomato Juice and liquid whole egg were individually inoculated with E. coli 0157:H7 at 108 cfu/ml and then exposed to continuous or repeated cycles of high-pressure treatment at a moderate temperature. Pressure treatments at 300MPa, 350MPa and 400 MPa for up to 60 min reduced the population of inoculated E. coli O157:H7 by approximately 3.0, 3.0 and 5.0 log cycles, respectively in tomato juice. Population of E. coli O157:H7 in all samples tested was decreased when temperature was increased from 30-50oC. However, increases in temperature and a 600MPa pressure resulted in coagulation of liquid eggs. Also, higher numbers of injured cells were recovered in treated tomato juice than in PBS and whole liquid egg. Repeating (4 times) the pressure at 300 MPa for a total of 10 min at room temperature was significant (p<0.05) in reducing E. coli population by extra 1 log. The results of this study suggests that repeating high-pressure treatment at least 4 times at 300 MPa for a total of 10 min would inactivate more E. coli O157:H7 strains in liquid whole egg, tomato juice and than using continuous pressure for the same amount of time.