PROTEIN PROCESSING USING HIGH-PRESSURE GASES AND SUPERCRITICAL FLUIDS
Location: Eastern Regional Research Center
Title: EFFECTIVENESS OF CROSS-FLOW MICROFILTRATION FOR REMOVAL OF MICROORGANISMS ASSOCIATED WITH UNPASTEURIZED LIQUID EGG WHITE FROM PROCESS PLANT
Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 16, 2008
Publication Date: August 1, 2009
Citation: Mukhopadhyay, S., Tomasula, P.M., Van Hekken, D.L., Luchansky, J.B., Call, J.E., Porto Fett, A.C. 2009. EFFECTIVENESS OF CROSS-FLOW MICROFILTRATION FOR REMOVAL OF MICROORGANISMS ASSOCIATED WITH UNPASTEURIZED LIQUID EGG WHITE FROM PROCESS PLANT. Journal of Food Science. 74(6):M319-M327.
Interpretive Summary: Liquid Egg White (LEW) is an important part of our food supply because it has high protein content and is essentially cholesterol-free. The functional properties of egg white, in particular foam formation and heat coagulation, are also exploited in a large number of food preparations. Improper washing, temperature abuse, and prolonged storage in the plant may result in microbial invasion of the interior of the egg. Thermal pasteurization is the most popular preservation technique used by the egg industry to reduce the levels of most of the microorganisms; however, it does not eliminate all microorganisms. Also, heat from the pasteurization process impairs some of the delicate functional properties of egg white. In this study, a novel intervention technology based on a membrane separation technique called microfiltration was developed to remove all microorganisms which are naturally present in LEW. This new technology significantly reduced the number of microorganisms that were present in the feed LEW, yet all of the nutritional and functional qualities of LEW were retained.
A pilot-scale cross-flow microfiltration (MF) process was evaluated for its efficiency in removing the natural microflora present in commercial liquid egg white (LEW), obtained from a local egg breaking plant, while maintaining the nutritional and functional properties of the LEW. LEW, containing approximately 106 +/- 1.7 colony forming units (cfu) per mL of total aerobic bacteria, was microfiltered using a ceramic membrane with a nominal pore size of 1.4 'm, at a crossflow velocity of 6 m/s. To facilitate MF, LEW was screened, homogenized and then diluted (1:2 w/w) with distilled water containing 0.5% sodium chloride. Homogenized LEW was found to have a 3 - fold lower viscosity than unhomogenized LEW. Influence of MF temperature (25 deg C and 40 deg C) and pH (6 and 9) on permeate flux, transmission of egg white nutrients across the membrane, and microbial removal efficiency were evaluated. The pH had a significantly greater influence on permeate flux than temperature. Permeate flux increased by almost 148% when pH of LEW was adjusted from pH 9 to pH 6 at 40 deg C. Influence of temperature on permeate flux, at a constant pH, however, was found to be inconclusive. Microbial removal efficiency was at least 5 Log10 cfu/mL, with a limit of detection < 1 Log10 cfu/mL. Total protein and SDS–PAGE analysis indicated that this novel MF process did not alter the protein composition of the feed LEW and that the foaming properties of LEW were retained in the post-filtered samples.