Preserving functional properties of hen’s egg yolk during freeze-drying

A novel freeze-drying process for egg yolk was developed, including precrystallisation and full contact rapid freezing, which is able to reduce the freeze induced gelation to a minimum without ingredients. Conventional pasteurisation conditions (temperatures up to 68 °C) showed to be critical for the preservation of the functional properties of freeze-dried yolk. In combination with optimised pasteurisation conditions (64 °C, 2 min), the results in relative viscosity maximum (the rose of the egg yolk), heat induced gel strength and flow behaviour tally well with those of refrigerated liquid yolk. For the first time, a freeze-dried egg yolk with preserved functional properties and natural taste could be produced at standard costs without ingredients.