Custard

Custardis a variety of culinary preparations based on sweetenedmilk,cheese, orcreamcooked witheggoregg yolkto thicken it, and sometimes alsoflour,corn starch, orgelatin. Depending on the recipe, custard may vary in consistency from a thin pouring sauce (crème anglaise) to the thick pastry cream (crème pâtissière) used to filléclairs. The most common custards are used incustard dessertsordessert saucesand typically include sugar and vanilla; however,savorycustards are also found, e.g., inquiche.
Custard is usually cooked in a double boiler (bain-marie), or heated very gently in asaucepanon a stove, though custard can also be steamed, baked in the oven with or without awater bath, or even cooked in apressure cooker. Custard preparation is a delicate operation because atemperatureincrease of 3–6 °C (5.4–10.8 °F) leads to overcooking andcurdling. Generally, a fully cooked custard should not exceed 80 °C (176 °F); it begins setting at 70 °C (158 °F).Abain mariewater bath slows heat transfer and makes it easier to remove the custard from the oven before it curdles.Adding a small amount of cornflour (U.S.corn starch) to the egg-sugar mixture stabilises the resulting custard, allowing it to be cooked in a single pan as well as in a double-boiler. Asous-videwater bath may be used to precisely control temperature.
While custard may refer to a wide variety of thickened dishes, technically (and inFrench cookery) the wordcustard(crèmeor more preciselycrème moulée,[kʁɛmmule]) refers only to an egg-thickened custard.
Whenstarchis added, the result is called 'pastry cream' (French:crème pâtissière,pronounced[kʁɛmpɑtisjɛːʁ]) or confectioners' custard, made with a combination of milk or cream, egg yolks, fine sugar, flour or some other starch, and usually a flavoring such as vanilla, chocolate, or lemon.Crème pâtissièreis a key ingredient in many French desserts, includingmille-feuille(or Napoleons) and filled tarts. It is also used in Italian pastry and sometimes inBoston cream pie. The thickening of the custard is caused by the combination of egg and starch.Corn flouror flour thickens at 100 °C (212 °F) and as such many recipes instruct the pastry cream to be boiled. In a traditional custard such as acrème anglaise, where eggs are used alone as a thickener, boiling results in the over-cooking and subsequent curdling of the custard; however, in a pastry cream, starch prevents this. Once cooled, the amount of starch in pastry cream sets the cream and requires it to be beaten or whipped before use.
Whengelatinis added, it is known ascrème anglaise collée([kʁɛmɑ̃ɡlɛzkɔle]). When gelatin is added andwhipped creamis folded in, and it sets in a mold, it isbavarois. When starch is used alone as a thickener (without eggs), the result is ablancmange.
In the United Kingdom, custard has various traditional recipes some thickened principally with cornflour (cornstarch) rather than the egg component, others involving regular flour; seecustard powder.
After the custard has thickened, it may be mixed with other ingredients: mixed with stiffly beaten egg whites and gelatin, it ischiboust cream; mixed with whipped cream, it iscrème légère,[kʁɛmleʒɛːʁ]. Beating in softened butter producesGerman buttercreamorcrème mousseline.
A quiche is a savoury custard tart. Some kinds oftimbaleor vegetable loaf are made of a custard base mixed with chopped savoury ingredients.Custard royaleis a thick custard cut into decorative shapes and used to garnishsoup,steworbroth. In German, it is known asEierstichand is used as a garnish in German Wedding Soup (Hochzeitssuppe).Chawanmushiis aJapanesesavoury custard, steamed and served in a small bowl or on a saucer.Chinese steamed eggis a similar but larger savoury egg dish.Bougatsais a Greek breakfastpastrywhose sweet version consists ofsemolinacustard filling between layers ofphyllo.
Custard may also be used as a top layer ingratins, such as theSouth Africanbobotieand manyBalkanversions ofmoussaka.
In Peru,leche asada("baked milk") is custard baked in individual molds.It is considered a restaurant dish.
French cuisine has several named variations on custard:
Recipes involving sweet custard are listed in thecustard dessert category, and include:
Custards baked in pastry (custard tarts) were very popular in theMiddle Ages, and are the origin of the English word 'custard': the French termcroustadeoriginally referred to the crust of a tart,and is derived from the Italian wordcrostata, and ultimately the Latincrustāre.
Examples includeCrustardes of flesshandCrustade, in the 14th century English collectionThe Forme of Cury. These recipes include solid ingredients such as meat, fish, and fruit bound by the custard.Stirred custards cooked in pots are also found under the namesCreme BoyledeandCreme boiled.Some custards especially in theElizabethanera usedmarigold(calendula) to give the custard color.
In modern times, the name 'custard' is sometimes applied to starch-thickened preparations likeblancmangeandBird's Custardpowder.
Stirred custard is thickened bycoagulationof egg protein, while the same gives baked custard its gel structure. The type of milk used also impacts the result. Most important to a successfully stirred custard is to avoid excessive heat that will cause over-coagulation andsyneresisthat will result in acurdledcustard.
Eggs contain the proteins necessary for the gel structure to form, and emulsifiers to maintain the structure. Egg yolk also contains enzymes like amylase, which can break down added starch.This enzyme activity contributes to the overall thinning of custard in the mouth. Egg yolk lecithin also helps to maintain the milk-egg interface. The proteins in egg whites are set at 60–80 °C (140–176 °F).
Starch is sometimes added to custard to prevent premature curdling. The starch acts as a heat buffer in the mixture: as they hydrate, they absorb heat and help maintain a constant rate of heat transfer. Starches also make for a smoother texture and thicker mouth feel.
If the mixture pH is 9 or higher, the gel is too hard; if it is below 5, the gel structure has difficulty forming becauseprotonationprevents the formation ofcovalent bonds.
Cooked (set) custard is a weakgel, viscous, andthixotropic; while it does become easier to stir the more it is manipulated, it does not, unlike many other thixotropic liquids, recover its lost viscosity over time.On the other hand, asuspensionof uncooked imitation custard powder (starch) in water, with the proper proportions, has the oppositerheologicalproperty: it is negative thixotropic, ordilatant, allowing the demonstration of "walking on custard".