Removal of Bacillus anthracis sterne spore from commercial unpasteurized liquid egg white using crossflow microfiltration

Authors: Mukhopadhyay, Sudarsan; Tomasula, Peggy; Luchansky, John; Porto-Fett, Anna; Call, Jeffrey

Submitted to: Journal of Food Processing and Preservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/11/2011
Publication Date: 8/1/2011
Citation: Mukhopadhyay, S., Tomasula, P.M., Luchansky, J.B., Porto Fett, A.C., Call, J.E. 2011. Removal of Bacillus anthracis sterne spore from commercial unpasteurized liquid egg white using crossflow microfiltration. Journal of Food Processing and Preservation. 35:550-562.

Interpretive Summary: In the post 9/11 world, methods are needed to protect the food supply in the event of intentional contamination. The egg industry currently uses heat pasteurization to destroy and control the level of potentially harmful bacteria, such as Salmonella, which is in a vegetative form. Heat pasteurization is ineffective for destruction of spore-forming bacteria, such as Bacillus anthracis (BA). There is an urgent need to develop an effective process technology to protect value-added foods such as liquid eggs from potential threat agents. We report the development of a new filtration process, called microfiltration, which is capable of removing almost 99.9999% of BA spores from liquid egg white without affecting its ability to foam or gel. This study indicates that this newly developed microfiltration step, used prior to pasteurization of liquid eggs, can improve the safety, biosecurity and wholesomeness of the Nation’s liquid egg supply.

Technical Abstract: Current pasteurization technology used by the egg industry is ineffective for destruction of spores such as those of Bacillus anthracis (BA). The validity of a cross-flow microfiltration (MF) process for separation of the attenuated strain of BA (Sterne) spores from commercial unpasteurized liquid egg white (LEW) was examined. Unpasteurized LEW from a local egg breaking plant was inoculated with BA to a level of approximately 10-6 spores/mL of LEW and microfiltered using a 1.4 micron ceramic membrane. LEW was screened, homogenized and diluted (1:2 w/w) with water containing 0.085 M sodium chloride to aid the membrane permeation. The MF process parameters, pH and temperature, were optimized to facilitate maximum spore removal. On average, the permeate flux increased at a rate of 50 l/h.m2 per unit pH decrease, which is almost 30 times greater compared to the rate of increase in flux due to unit 4 deg C raise in temperature. Spore removal efficiency was at least 6.14 log-10 spores /ml. Storage stability of MF processed LEW showed no out growth of spores for 21 days at 4 deg C. Egg white protein permeation and hence the functional properties were unaffected during MF. The data reported in this investigation shows that crossflow microfiltration of LEW prior to pasteurization can remove at least 99.9999% of BA spores without affecting the functional properties of LEW thus providing a strategy for safety, biosecurity and wholesomeness of value-added fluid foods such as LEW.