The Making of Tarts and The Science Behind a True Delicacy
Tarts can be either sweet or savory; most tarts fall into the “sweet” category, and this is especially true in the case of seasonal confections such as holiday tarts. The problem with sweet tarts is that they often fail to live up to the expectations of those eating them. However, a little scientific investigation can help solve the problem of making sub-par tarts once and for all.
There are two major components to any tart – the crust and the filling. For a sweet tart, the dough used for the crust is called pâte sucrée, which is French for “sweet dough.” This dough, commonly referred to as tart dough, is different from a pie crust in that it is designed to stand on its own without support from a pie plate or other dish. This characteristic is achieved by adding egg yolks and a large amount of sugar to the dough. With a pie crust, the goal is to stop gluten from forming to allow for a flaky texture. In pâte sucrée, the same effect is achieved by the addition of egg yolks which contain proteins that have different properties than gluten. These proteins give the crust stability, but stop short of making it chewy. The additional sugar works to make the crust slightly crispy and crunchy as opposed to flaky, so that the crust has enough structure and stability to stand on its own. As with other crusts, the butter and flour should remain as cold as possible so that the butter is “cut” into the flour to achieve a fine texture, and work must continue quickly once the egg yolks are added because they contain water, which triggers the formation of gluten.
One of the most common and classic sweet tarts is a fresh fruit tart. Fruit tarts are almost always beautiful to look at, but not always so great to eat. Aside from soggy crusts, the problem is often rubbery, lumpy filling. This is because pastry cream, the filling of choice, uses both eggs and cornstarch as thickeners. However, eggs yolks begin to coagulate at 175 degrees Fahrenheit and cornstarch at 185 degrees Fahrenheit, so adding heated cream or milk to these components can make for disastrous results. The key to avoiding the coagulation is to make sure that the liquid is hot enough (preferably at a rolling boil) when added to coagulate both the egg yolks and the cornstarch at the same time. The result is a smooth, lump-free cream.
Holiday tarts (and other seasonal confections) are a true delicacy. And with the help of science, they can be a sure bet every time.