Impact of magnetic assisted freezing in the physicochemical and functional properties of egg components. Part 2: Egg yolk

Effects of freezing assisted with magnetic fields (MFs) in a commercial Cell Alive System (CAS) unit at − 50 °C, with a static MF only (0% CAS) and with a static MF plus oscillating MF (10% CAS), on egg yolk (Y) was investigated. Y samples were obtained from commercial eggs laid by three hen strains (two of them in fortified cages and the third one free outdoors). The main goal was to study the thermal denaturation of protein involved in MF processing. Results showed that freezing treatment was the factor with the highest influence. Thermal denaturation enthalpy of Y was markedly affected (~ 45% total protein in comparison with Fresh sample), but similar for the two MF processes, where 0% CAS was taken as the Control freezing treatment. MF effects were predominantly thermal in nature and were the factor with the highest influence on the thermal behavior (which ran parallel to that of egg white, as described in Part 1), as well as on most of the functional properties exhibited by the MF samples. Rheology and free Sulfhydryl content were studied complementarily to Differential Scanning Calorimetry (DSC) data. Some important functional properties such as Emulsion Ability and Emulsion Stability were also determined. The hen strain feeding factor had practically no influence on the physical or functional behavior of both untreated and processed Y samples, except on their color parameters.