For a soft cooked egg, the white should be in the consistency of a soft quivery jelly and the yolk a thick liquid. This requires 3-5 minutes of cooking in boiling water. An addition of 2 minutes should be allowed if eggs are at refrigerator temperature. Or should be cooked at 85oC for 4-6 minutes and put in cold water.
Eggs hard cooked in a shell need to be cooked until the white changes to an opaque tender gel and the yolk become pale yellow and has a mealy rather than a pasty consistency. Eggs should be cooked at 85oC for 18 minutes or at 100oC for 8-10 minutes and put in cold water. Heat is transmitted from hot-water around the egg to the yolk through the coagulating white by conduction. To get the yolk hot enough to coagulate the surrounding white must be heated somewhat over cooked by the time yolk is fully cooked. The yolk can be hard cooked with minimum damage to the white if the water in which the egg is cooked is not above 85oC. If the temperature of the water is too low, cooking time is excessively long, the white is so tender that it is difficult to remove the shell without tearing the white and the yolk is waxy and has the colour of an uncooked egg.
In both the methods, eggs should be submerged in cold water for 5 minutes. Boiling for 20 minutes produces hard cooked eggs that are firm and exhibit strong egg odour and more off flavours.
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