51B-8

G. O. I. EZEIKE, Y. C. Hung, R. E. Brackett, R. Stinchcomb, and S. Radhakrishnan. Center for Food Safety and Quality Enhancement, The University of Georgia, Department of Food Science and Technology, Griffin, GA 30223

Safety considerations necessitated evaluation of pasteurization protocols of liquid egg products that impart functionality to many food products. There is a need to evaluate the viscosity of liquid egg products after pasteurization.

The objective was to characterize the viscosity of pasteurized liquid egg products and evaluate the effect of pasteurization.

Liquid whole egg (LWE), egg white (LEW), egg yolk (LEY) and salted (5%) and sugared (5%) yolk (LEY-SS) were each pasteurized at 60^oC for 3.5 and 4.5 min; 56.7^oC for 3.5 and 8.75 min; 61.1^oC for 3.5 and 5.8 min; and 63.3^oC for 3.5 and 9.5 min; respectively. Viscosity of control (unpasteurized) and pasteurized samples was determined with a Brookfield viscometer at 4, 7 and 20^oC at shear rates of 0.3 to 37 sec^-1 using duplicate samples. Total dissolved solids (TDS) was measured using a Bausch and Lomb refractometer.

Viscosity characterization indicated that the products were non-Newtonian and pseudoplastic (shear thinning) and fitted the power law (R²=0.993 to 0.998). Flow behavior index of LEY-SS was less affected compared to other products, but LEY-SS showed a dramatic increase in the consistency coefficient indicating higher thermal tolerance than LWE or LEW. An Arrhenius relationship was found between viscosity and reciprocal absolute temperature. Compared to control, pasteurization of LWE reduced viscosity at 4, 7, and 20^oC, with percentage changes of 8.5%, 15%, and 17% respectively at a shear rate of 36.8 s^-1. Surface plots indicated that viscosity decreased with increasing shear rate and with increasing temperature both being important during whipping. Exponential models of viscosity gave high correlations (R²=0.94, LWE) with TDS, which could influence processing energy and flow behavior of the liquid egg products when pumped.

Results indicate that products pasteurized with these protocols maintained their flow characteristics.