Title: Inactivation of E. coli O157:H7 and nonpathogenic E. coli in strawberry juice by pulsed electric field, sodium benzoate, potassium sorbate, and citric acid Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 15, 2009
Publication Date: July 12, 2009
Citation: Gurtler,J.,Geveke,D.,Zhang,H. 2009. Inactivation of E.coli O157:H7 and Nonpathogenic E.coli in Strawberry juice by pulsed electric field, sodium benzoate, potassium sorbate, and citric acid [abstract]. International Association for Food Protection, 96th Annual Meeting.Grapevine,TX.p.1. Technical Abstract: Introduction: Current regulations require that juice processors effect a 5 log CFU/ml reduction of a target pathogen prior to distributing products. Whereas thermal pasteurization reduces the sensory characteristics of juice by altering flavor components, pulsed electric field (PEF) treatment may be conducted at lower temperatures, thus preserving sensory characteristics. Purpose: This study was performed to determine the inactivation of E. coli O157:H7 and a nonpathogenic E. coli in strawberry juice by PEF with or without sodium benzoate, potassium sorbate, and citric acid. Methods: E. coli O157:H7 (ATCC 43895) and a nonpathogenic E. coli (ATCC 35218) were inoculated at 7 log CFU/ml into single strength strawberry juice with or without 750 ppm sodium benzoate, 350 ppm potassium sorbate, and 2.7% citric acid. Juice was treated at 45, 50 and 55C and 18.6 kV/cm for 150us with a prototype PEF unit in a biosafety level 2 laboratory. Results: Inactivation of surrogate E. coli at 45, 50, and 55C were 2.87, 3.11, and 3.55 log CFU/ml, respectively, in plain juice (pH 3.4), and 2.64, 3.24, and 5.05 with the addition of benzoic and sorbic acids (pH 3.5). Inactivation of E. coli O157:H7 under the same conditions were 3.03, 3.87, and 5.20 log CFU/ml, respectively, and 2.70, 3.63, and 5.70 with antimicrobials. E. coli O157:H7 in juice with antimicrobials and 2.7% citric acid (pH 2.6) treated with PEF was reduced by 3.88, 6.11 and >6.11 log CFU/ml at 45, 50 and 55C while the surrogate E. coli decreased by 4.31, 4.93, and >6.21 log under the same conditions. Significance: Slightly greater inactivation of E. coli O157:H7 than of the surrogate bacterium indicates that E. coli ATCC 35218 provides a margin of safety when used as a surrogate for O157:H7 in strawberry juice treated with PEF. Further studies will be performed on scaled-up PEF equipment in a pilot plant.