Submitted to: International Journal of Food Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/16/2012
Publication Date: 12/23/2012
Publication URL: http://dx.doi.org/10.1016/j.ijfoodmicro.2012.12.005
Citation: Geveke, D.J., Torres, D. 2012. Liquid egg white pasteurization using a centrifugal UV irradiator. International Journal of Food Microbiology. 162(2013):43-47. Interpretive Summary: Thermal pasteurization damages the functional properties of liquid egg white (LEW). Research on nonthermal pasteurization of LEW is lacking and necessary. In this study, we used a UV irradiator that centrifugally formed a film of LEW on the inside of a rotating cylinder. The thinness of the film allowed the UV to penetrate all the way through the LEW. Escherichia coli in the LEW was reduced by 99.999% within 3.2 seconds using only a fraction of the energy of other pasteurization treatments. These results suggest that LEW may be pasteurized using a centrifugal UV irradiator. Such quick UV treatment could ensure food safety while maintaining quality.
Technical Abstract: Studies are lacking on UV nonthermal pasteurization of liquid egg white (LEW). The objective of this study was to inactivate Escherichia coli using a UV irradiator that centrifugally formed a thin film of LEW on the inside of a rotating cylinder. The LEW was inoculated with E. coli K12 to approximately 8 log cfu/ml and was processed at the following conditions: UV intensity 1.5 to 9.0 mW/cm2; cylinder rotational speed 450 to 750 RPM, cylinder inclination angle 15 to 45 degrees, and flow rate 300 to 900 ml/min, and treatment time 1.1 to 3.2 s. Appropriate dilutions of the samples were pour plated with tryptic soy agar (TSA). Sublethal injury was determined using TSA + 4% NaCl. The regrowth of surviving E. coli during refrigerated storage for 28 d was investigated. The electrical energy of the UV process was also determined. The results demonstrated that UV processing of LEW at a dose of 29 mJ/cm2 at 10 deg C reduced E. coli by 5 log cfu/ml. Inactivation significantly increased with increasing UV dose and decreasing flow rate. The results at cylinder inclination angles of 30 and 45 degrees were similar and were significantly better than those at 15 degrees. The cylinder rotational speed had no significant effect on inactivation. The occurrence of sublethal injury was detected. Storage of UV processed LEW at 4 and 10 deg C for 21 days further reduced the population of E. coli to approximately 1 log cfu/ml where it remained for an additional 7 days. The UV energy applied to the LEW to obtain a 5 log reduction of E. coli was 3.9 J/ml. These results suggest that LEW may be efficiently pasteurized, albeit at low flow rates, using a nonthermal UV device that centrifugally forms a thin film.