Submitted to: Meeting Abstract
Publication Type: Abstract only
Publication Acceptance Date: 3/8/2005
Publication Date: 7/29/2005
Citation: Datta, N., Tomasula, P.M., Call, J.E., Luchansky, J.B. 2005. Tangential microfiltration of skim milk for removal of bacillus anthracis spores. (abstract). American Dairy Science Assn. Mtg. Paper No. 153. Interpretive Summary: N/A
Technical Abstract: The objective of this study was to examine the use of cross-flow microfiltration as a step prior to high-temperature short-time (HTST) pasteurization to remove Bacillus anthracis (BA) spores that may have been intentionally added to raw milk. In experiments, 2500 mL of retail skim milk were inoculated with an average of 6.0 log10 spores/mL of the attenuated Sterne strain of Ba. The milk was then microfiltered in a Membralox TI-70 bench scale pilot unit at 50ºC using ceramic membranes with pore sizes of 0.5, 0.8, and 1.4 microns, respectively, to determine permeate flux, spore removal, and transmission of lactose, calcium, and milk proteins, at cross-flow velocities of 2, 4, and 6 m/s. The trials were conducted with or without backpulsing, a feature that prevents membrane fouling and concentration polarization effects. Samples of the permeate were collected over a period of 4.5 hrs and were direct plated onto BHI agar plates to enumerate surviving spores. Results indicated that the 0.5 micron membrane is unsuitable for microfiltration of milk because low permeate flux and severe pore plugging and fouling were observed after only 5 min of operation. The 0.8 micron membrane, at each cross-flow velocity studied, removed approximately 6.2 log10 spores of BA/mL milk that were recovered in the retentate, whereas, for the 1.4 micron membrane, the maximum number of spores, approximately 3.0 log10 spores of BA/mL, were removed at a cross-flow velocity of 6 m/s. Transmission of lactose, calcium and milk proteins through both membranes was 100%. Permeate flux decay was only about 4% at cross-flow velocity of 6 m/s regardless of the use of the backpulse feature. As confirmed in this study, microfiltration of milk prior to HTST pasteurization can remove >99.9999% (6 Log) of BA spores and thus, improve the safety and biosecurity of the milk supply.