XVIII European Symposium on The Quality of Eggs and Egg Products, İzmir, Türkiye, 23 - 26 Haziran 2019, ss.75-78
Eggs are all-natural and inexpensive sources of high-quality protein and well-balanced basic nutrients. Eggs are processed into liquid for uses in food service industry or ingredients in baking industry due to its excellent functional properties such as whipping, emulsifying and gelling properties. Thus, processed egg products are widely used in industrial food industry as functional ingredients in preparation of food service. Egg white is more sensitive to high temperature than whole egg or egg yolk due to the coagulation of protein and adverse effect on functional properties such as foaming properties. Because of the limitation in industry, there is an increasing interest to alternative methods. Nowadays, along with the new practice, processing aids are used.
Enzyme-modified liquid egg products are one of the fastest growing products in the egg processing industry due to changing consumer lifestyles that seek out more convenient, quick-to-prepare solutions. Enzyme fermentation has been used in egg products for improving or recovering the technological and functional properties. Lipase enzyme used as processing aids in egg processing to improve functional properties of liquid egg white (LEW). In this research, the rheological behaviours of LEW treated with lipase enzyme at different concentrations (0.01%; 0.02% and 0.03%) were investigated. Rheological characterisation of the enzyme treated and non-treated (control) LEW samples were examined using rheometer. Shear rate ramp test, in the linear viscoelastic region, frequency sweep test, amplitude sweep test and oscillation time tests at 60°C were conducted. In the study, it was determined that with increasing frequency loss modulus (G’’) was higher than storage modulus (G’), and therefore the treated LEW samples exhibits liquid-like nature. In enzyme concentration of 0.01% in the low-frequency value (G''> G') shows viscoelastic property, at the increasing frequency (G' <G'') the protein system exhibits liquid behaviour. In fact, at high frequency with the interclusion of G 'and G'' curves it happened that G’>G’’ and system will act as a viscoelastic solid.
In conclusion, the rheological properties of enzyme modified LEW were determined and this information can be used in egg processing industry. This study showed that lipase enzyme modified LEW exhibited a gel like rheological characteristics with a G'' much higher than the G' and, the Herschel-Bulkley model fit the shear stress and shear rate data.