Culinary Biophysics: On the Nature of the 6X°C Egg

Shell-on eggs cooked by immersion in water at low and constant temperatures (~60-70 °C) yield yolks with very particular textures. Structure development in such unique cooking conditions is far from understood. The present study shows that egg yolk, despite its compositional complexity, follows typical gelation kinetics found in many globular proteins and that it can develop structure at temperatures as low as 56 °C. It follows that yolk texture is dictated by time/temperature combinations. Under isothermal, low temperature cooking conditions, the thickening and gelation kinetics of egg yolk follow Arrhenius-type kinetic relationships. The energy of activation of these processes was ~470 kJ mol ^-1, which agrees well with the values reported for the denaturation and gelation of the thermally labile chicken serum albumin and immunoglobulin Y. Results are related to common foodstuffs in order to allow chefs and home cooks to achieve a priori conceived textures in egg yolks.