Fractionation of liquid egg yolk: Influence of chemical and structural characteristics of egg yolk granular and plasma fraction on the continuous centrifugal separation process
نویسندگان
چکیده
Egg yolk is an essential ingredient for the preparation of a large variety of food emulsions. Thereby the emulsifying properties of egg yolk depend mainly on the physiological status of the two egg yolk fractions, granules (HDL) and plasma (LDL), which can be influenced by environmental conditions. Recent studies substantiate that a separate use of each fraction in innovative food products will offer new ways in emulsification technology. It became evident that the granula fraction represents no homogeneous component, but consists of different subclasses with different size, density and structure. This inhomogeneity leads to a subclass depending sedimentation behaviour of the whole granula fraction in egg yolk. A variation within the egg yolk pH to acidic milieu conditions results in changes of each subclass constitution. Especially sub fractions with small particle size and high protein content incorporate a higher amount of granular LDL. Therefore, the particle density is decreased, which leads to a much lower sedimentation velocity. Based on these findings, the impact of variable rheological properties on the sedimentation behaviour of polydisperse colloidal suspensions with high particle concentrations is discussed. It was detected that if a limiting particle concentration is reached all particles within the polydisperse particle collective are sedimenting with the same velocity. At the so called zone-sedimentation the high fluid viscosity as well as strong particle-particle interactions are resulting in constrained separation effects. The results allow a deeper insight in the structural complexity of the LDL and HDL egg yolk fraction and offer therefore new information for the technofunctional properties of egg yolk fractions.
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