The hen's egg: Effect of a hole in the shell on the incidence of splitting during cooking

Abstract

Two experiments, involving nearly 1000 eggs, were designed to show whether or not piercing the shell at the broad pole prevents it splitting when an egg is soft‐boiled. With eggs stored in the laboratory the incidence of splitting was low after storage for 1 d and there was no indication that the presence of a hole affected it; after 5 d splitting was reduced; after 28 d it was prevented. This may be because at 1 d the shell is still permeable, so even if there is no hole the build‐up of internal pressure as the egg contents expand is limited; at 5 d, when shell permeability has fallen, pressure build‐up is prevented initially by the presence of a hole, though it can occur in the later stages of cooking because the hole becomes sealed by congealed albumen; at 28 d the hole remains patent and the air space can accommodate all the expansion of the egg contents. The nature of the hole, whether made by piercing with a needle or by drilling to 1·5 mm diameter with a dental drill, did not significantly affect the response of eggs of any age. Housewives should pierce eggs before boiling them, since if they are fresh it will do no harm and if they are stale it will prevent splitting.