 A soft-boiled egg served in the half shell | |||||||
| Alternative names | Dippy egg[1] | ||||||
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| Main ingredients | Eggs (typically chicken) | ||||||
| Variations | Baked eggs, starting temperature, preparation | ||||||
| 136 kcal (570 kJ) | |||||||
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Boiled eggs are typically from achicken, and are cooked with their shells unbroken, usually by immersion in boiling water. Hard-boiled or hard-cooked eggs are cooked so that theegg white andegg yolk both solidify, while soft-boiled eggs may leave the yolk, and sometimes the white, at least partially liquid and raw. Boiledeggs are a popularbreakfast food around the world.
Besides a boiling water immersion, there are a few different methods to make boiled eggs. Eggs can also be cooked below the boiling temperature, i.e.coddling, or they can be steamed. Theegg timer was named for commonly being used to time the boiling of eggs.
Eggs have a long history of use as a food source, following the history of thedomestic Chicken, and recipes that include boiled eggs have been recorded since the first known cookbook,De re coquinaria,[2] in which at least one recipe calls for the use of preserved boiled eggs.[3]Alexander Pope is recorded as having recommended the method of cooking eggs over the embers or ashes of an open fire.[4]
The process of cooking an egg causes theproteins within the yolk and albumin todenature and solidify, resulting in a solid egg white and yolk.[5] Coagulation (denaturing) of egg white proteins begins in the 55–60 °C (131–140 °F) temperature range, and egg yolks thicken at the slightly higher temperature of 65 °C (149 °F), solidifying at 70 °C (158 °F). As such, the yolk of an egg will never solidify before the white, though in a boiled egg heat will take longer to reach the yolk through the albumin (compared to afried egg), making this doubly true.[4] The process may be reversed through breaking the connections between the proteins, which has been demonstrated through the application of eithersodium borohydride orvitamin C.[6]
There are variations both in degree of cooking and in the method of how eggs are boiled, and a variety ofkitchen gadgets for eggs exist. These variations include:
Hard-boiled or hard-cooked[7] eggs are boiled long enough for the yolk to solidify (about 10 minutes).[8] They can be eaten warm or cold. Hard-boiled eggs are the basis for many dishes, such asegg salad,cobb salad andScotch eggs, and may be further prepared asdeviled eggs.[citation needed]
There are several techniques for hard-boiling an egg.[9] One method is to bring water to a boil and cook for ten minutes.[10] Another method is to bring the water to a boil, but then remove the pan from the heat and allow eggs to cook in the gradually cooling water.[8] Over-cooking eggs will typically result in a thin greeniron(II) sulfide coating on the yolk,[11] though the coating has been reported as having little effect on flavor.[6] This reaction occurs more rapidly in older eggs as the whites are more alkaline.[12] Rinsing[4] or immersing the egg in cold water after boiling is a common method of halting the cooking process to prevent this effect,[5] and in commercial operations the discoloration is removed by immersing peeled eggs in a bath oforganic acid after cooking.[13]
Hard-boiled eggs are recommended by the United States Department of Agricultural Food Safety and Inspection Service to be used within two hours if kept at room temperature, or within a week if kept refrigerated and in the shell.[14][15][16] Shelled hard-boiled eggs sold in bulk are pickled or sealed in an atmosphere of carbon dioxide and nitrogen for preservation.[2]
Hard-boiled eggs are commonly sliced, particularly for use in sandwiches. For this purpose specializedegg slicers exist, to ease slicing and yield even slices.For consistent slice sizes in food service, several eggs may have their yolk and white separated and poured into a cylindrical mold for stepwise hard-boiling, to produce what is known as a "long egg" or an "egg loaf". Commercial long eggs are produced in Denmark by its inventorDanæg [da] and in Japan byKENKO Mayonnaise [ja]. The machine for producing long eggs was first introduced in 1974.[17] In addition to being sliced, long eggs can also be used in their entirety ingala pies.[18]
Haminados, braised eggs slowly cooked overnight, is a traditionalSephardic Jewish dish first documented in medieval Spain and now part ofIsraeli cuisine, where they are typically served on their own or as part of theShabbat stewchamin and other dishes.[19][20]
While the traditionalegg timer counts to 3 minutes for cooking a soft-boiled egg,[21] some how-to guides recommend longer cooking times ranging from five[8] to six minutes.[22] ChefHeston Blumenthal, after "relentless trials", published a recipe for "the perfect boiled egg", suggesting cooking the egg in water that starts cold and covers the egg by no more than a millimeter, removing the pan from the heat as soon as the water starts to bubble. After six minutes, the egg will be ready.[23]
Soft-boiled eggs are not recommended by theFood and Drug Administration for people who may be susceptible tosalmonella, such as very young children, the elderly, and those with weakened immune systems.[24] To avoid the issue of salmonella,eggs can be pasteurised in shell at 57 °C for an hour and 15 minutes. The eggs can then be soft-boiled as normal.[25]
Soft-boiled eggs are commonly served inegg cups, where the top of the egg is cut off with a knife, spoon, spring-loaded egg topper, or egg scissors, using anegg spoon to scoop the egg out. Other methods include breaking theeggshell by tapping gently around the top of the shell with a spoon.[26] Soft-boiled eggs can be eaten withtoast cut into strips, which are then dipped into the runny yolk. In the United Kingdom and Australia, these strips of toast are known as "soldiers".[27]
In Southeast Asia, a variation of soft-boiled eggs known as half-boiled eggs are commonly eaten for breakfast.[28][29] The major difference is that, instead of the egg being served in an egg cup, it is cracked into a bowl to which dark or light soy sauce or pepper are added. The egg is also cooked for 7 minutes, resulting in a runnier egg instead of the usual gelatin state and is commonly eaten withkaya toast andkopi.[30][31]
Boiled eggs are also an ingredient in variousPhilippine dishes, such asembutido[32] andchicken galantina.[33] Boiled or steamed duck eggs that have been incubated for several days are also eaten in the Philippines, Vietnam, Laos, Cambodia, and Thailand as the food known asbalut.[34]
In Japan,marinated soft-boiled eggs (味付け玉子,ajitsuke tamago) are commonly served alongsideramen. The eggs are typically steeped in a mixture of soy sauce,mirin, and water after being boiled and peeled. This provides the egg a brownish color that would otherwise be absent from boiling and peeling the eggs alone. Once the eggs have finished steeping, they are usually served on top of the soup.[35][36] A similar method of cooking soft-boiled eggs popular in Japan is that of the hot spring boiled egg (温泉玉子,onsen tamago), which is cooked at a constant temperature of 70 °C (158 °F) as is present in the volcanichot springs of Japan, producing an egg with solid yolk andsol-like white.[2]
Boiled eggs often form part of larger, more elaborate dishes. For example, a boiled egg may garnish a bowl oframen (often first marinated insoy sauce), be baked into a pie such as atorta pasqualina [it],[44] or be encased inaspic (similar to the French dish œufs en gelée, which features poached eggs[45]). They may also be chopped and mixed with mayonnaise to formegg salad, or be deep-fried and then baked within a serving oflamprais.[46]
Boiled eggs can vary widely in how easy it is to peel away the shells. In general, the fresher an egg before boiling, the more difficult it is to separate the shell cleanly from the egg white.[22] As a fresh egg ages, it gradually loses both moisture and carbon dioxide through pores in the shell; as a consequence, the contents of the egg shrink, it loses protein, and thepH of thealbumen becomes morebasic.[4] Albumen with higher pH (more basic) is less likely to stick to the egg shell, while pockets of air develop in eggs that have lost significant amounts of moisture, also making eggs easier to peel.[47]
Keeping the cooked eggs soaked in water helps keep the membrane under the shell moist for easy peeling. Peeling the egg under cold running water is an effective method of removing the shell. Starting the cooking in hot water also makes the egg easier to peel.[22]
It is often claimed that steaming eggs in apressure cooker makes them easier to peel.[48]Double blind testing has failed to show any advantage of pressure cooking over steaming, and has further shown that starting boiling in cold water is counterproductive. Shocking the eggs by rapidly cooling them helped, and cooling them in ice water for 15 minutes or longer gave more successful peeling. Shocking was also found to remove the dimple in the base of the egg caused by the air space.[22]
There are severalfoodborne illnesses associated with eggs,[49] most if not all of which are caused bypathogenic bacteria.[50] The harmful bacteria associated with eggs are mostly of thegenusSalmonella,[51] but other harmful bacteria that can grow at refrigerated temperatures have been found in retail egg products, such asBacillus cereus andStaphylococcus aureus.[50] Previous studies indicated that "the complete coagulation of [the] whole egg" was sufficient to destroySalmonella bacteria,[52] but it is now known that the only factor in the inactivation or destruction of pathogenic bacteria in eggs istemperature.[51] Boiling eggs at a temperature of at least 62 °C (144 °F) for 30 minutes has been shown to inactivateSalmonella bacteria,[51] though theFood and Drug Administration recommends cooking at the higher temperature of 74 °C (165 °F).[49]
Bulk hard-boiled eggs have been linked to disease outbreaks such as listeria[53] andS. aureus infections, mainly from contamination and when eggs are not washed in the supply chain.[50]
When shell eggs are hard cooked, the protective coating is washed away, leaving bare the pores in the shell for bacteria to enter and contaminate it. Hard-cooked eggs should be refrigerated within 2 hours of cooking and used within a week.
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