Title: Effects of pH and Temperature on Inactivation of Salmonella Tyhimurium DT104 in Liquid Whole Egg by Pulsed Electric Fields Authors
Submitted to: Journal of Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 16, 2008
Publication Date: January 28, 2009
Citation: Jin, Z.T., Zhang, H.Q., Hermawan, N., Dantzer, W. 2009. Effects of pH and Temperature on Inactivation of Salmonella Tyhimurium DT104 in Liquid Whole Egg by Pulsed Electric Fields. Journal of Food Science and Technology. 44:367-372. Interpretive Summary: Liquid egg may contain harmful bacteria such as species of Salmonella. Processing technologies are needed to inactivate these pathogens while maintaining the quality of the food. Liquid egg is pasteurized and stored frozen or refrigerated prior to use. Heating processes above 60 degree Celsius necessary to kill many of the pathogens denature the proteins and reduce the quality of egg products. Laboratory scale studies showed that combining pulsed electric fields and mild heat at 55 degree Celsius inactivated Salmonella typhimurium while maintaining the quality and functionality of the product. This method may be an alternative to high temperature heat pasteurization.
Technical Abstract: Pulsed electric fields (PEF) applies very short (microseconds) pulses of very high intensity (10 to 50 kV/cm) to foods to inactivate microorganisms by rupturing their lipid membranes. PEF process may be conducted at ambient temperature. The efficacy of PEF processing for pasteurization of liquid eggs, however, may be a function of processing temperature. In this study, effects of PEF treatment, treatment temperature, pH and combination of PEF with mild heat (PEF+heat) on the inactivation of Salmonella Typhimurium in liquid whole egg (LWE) were investigated. S. Typhimurium was inoculated in LWE, the pH of LWE was adjusted to 6.6, 7.2 or 8.2 prior to treatment, and treatment temperatures were controlled to 15, 25, 30 and 40C. PEF process conditions were 25 kV/cm field strength, 2.1 microseconds pulse duration and 250 µs total treatment time. S. Typhimurium in LWE at pH 7.2 was reduced by 2.1 log at 40C and 1.8 log at 30C. PEF inactivation of S. Typhimurium at 15 or 25C depended on the pH of LWE. Heat treatment at 55C for 3.5 minutes or PEF treatment at 20C resulted in approximately 1 log reduction of S. Typhimurium. Combination of PEF + 55C achieved 3 log reduction of S. Typhimurium and was comparable to the inactivation by the heat treatment at 60C for 3.5 min. This combinational process may be an alternative to high temperature heat pasteurization for liquid eggs with further development.