THE CHANGE OF APPARENT VISCOSITY OF LIQUID WHOLE EGG DURING OHMIC AND CONVENTIONAL HEATING

Abstract

ABSTRACTElectrical heating of food products is a novel technique which provides rapid and uniform heating, resulting in less thermal damage to the product. Although the technology offers many advantages, the rheological behavior of liquid whole egg during ohmic heating has not been known yet in the literature. The objective of this research was to examine effects of conventional and electrical heating methods on the rheological behavior of liquid whole egg at a temperature range between 20 and 60C by using concentric rotational viscometer. The ohmic heating was applied at the voltage gradient of 20 V/cm at 50 Hz by matching the same heating curve with the conventional method. The liquid whole egg exhibited characteristics of non‐Newtonian shear thinning fluid. The flow behavior index (n) of liquid whole egg was in the range of 0.908–0.992 and 0.909–0.983 for ohmic and conventional heating, respectively. The consistency coefficient decreased as the temperature increased. The apparent viscosity of heated liquid egg was not statistically different for both heating methods (P > 0.05). The activation energy values for temperature dependency of predicted apparent viscosity were not statistically different for rheological models applied (P > 0.05), while they were significantly different according to heating method (P < 0.05). The liquid whole egg was more sensible to temperature changes during conventional heating. It was concluded that this difference could be either the result of the electrical effect on the apparent viscosity of the liquid whole egg or thermal effect during ohmic heating and fast homogeneous heating during ohmic treatment.PRACTICAL APPLICATIONSLiquid egg products are so sensible to heat treatments that it can result in many undesirable changes which would provide the occurrence of many undesirable changes. To avoid these undesirable changes, ohmic heating could be applied to liquid whole egg products as a faster and homogeneous alternative heating method. As the rheological behavior changes during heating must be characterized especially for the application of novel heating technologies. Although there were numerous researches on the determination of rheological properties of egg products, unfortunately, there has been no study ever done on explaining the rheological behavior of liquid whole egg during ohmic heating in open literature to the best of the authors' knowledge. Electrical effects of ohmic heating on food rheology rather than thermal effects are also still unclear. Results from this study will give important information to academic studies and industrial applications for the design of continuous ohmic heating systems for non‐Newtonian foods.