Pastry cream, also known as crème pâtissière, is a fundamental component in the world of pastry. Its creamy texture and rich flavor make it the perfect filling for a variety of desserts, from éclairs and cream puffs to tarts and cakes. Understanding the science behind pastry cream and its variations provides a deeper appreciation for its role in creating delicious, well-balanced desserts.
What is Pastry Cream?
Pastry cream is a smooth, custard-like mixture made from a combination of milk, sugar, eggs, cornstarch, butter, and vanilla. It serves as the base for many classic French desserts and is praised for its rich texture, versatility, and ability to complement a wide range of other ingredients.
The key to pastry cream’s structure lies in the process of thickening. When heated, the starch molecules in the cornstarch absorb liquid and swell, causing the mixture to thicken. The eggs also contribute to the thickening process, with the proteins in the egg yolks coagulating as the mixture reaches a certain temperature, helping the pastry cream to set properly.
The Science Behind Pastry Cream
The creation of pastry cream is a delicate balancing act between ingredients and technique. The key scientific principles that govern the making of pastry cream are heat, protein coagulation, and starch gelatinization.
1. Heat and Protein Coagulation
Egg yolks are the primary source of protein in pastry cream. When eggs are added to the milk and sugar mixture, the proteins in the egg yolks (mainly albumin and globulin) begin to denature, or unravel, as they are exposed to heat. As they cool, they re-bind together to form a gel-like structure, which thickens the custard. However, if the custard is heated too quickly or too much, the proteins will over-coagulate and create a scrambled egg texture, ruining the smoothness of the cream.
To prevent this, the mixture should be cooked over medium heat, and it’s important to continuously stir to ensure even heat distribution. Using a double boiler can help regulate the temperature and prevent overheating.
2. Starch Gelatinization
Starch, typically cornstarch, is the thickening agent in pastry cream. When the cornstarch is heated with the liquid (milk or a combination of milk and cream), the starch granules begin to absorb the liquid and swell. As the granules expand, they release amylose, a substance that thickens the liquid around it. This process, known as gelatinization, gives pastry cream its signature consistency.
Cornstarch is preferred because it thickens at a lower temperature compared to other starches, such as flour. It also yields a smoother texture, which is essential for a velvety pastry cream.
3. Fat and Emulsification
Butter, often added at the end of cooking, contributes to the smooth, glossy finish of pastry cream. The fat in butter helps stabilize the mixture and gives it a rich mouthfeel. Emulsifiers in the egg yolks and butter work together to create a stable mixture by helping fat and water-based ingredients combine without separating.
The emulsification process is crucial in preventing the butter from breaking down or forming an oily film on the surface of the cream. Butter also enhances the flavor of the pastry cream, making it rich and indulgent.
Making Pastry Cream: The Basic Method
To make a traditional pastry cream, the following ingredients are commonly used:
- Milk
- Sugar
- Egg yolks
- Cornstarch
- Butter
- Vanilla extract or vanilla bean
Step-by-Step Process:
-
Combine milk and sugar: Heat the milk and half of the sugar together until just boiling. This helps dissolve the sugar and brings the milk to the right temperature for cooking the eggs.
-
Whisk egg yolks and cornstarch: In a separate bowl, whisk together the egg yolks, the remaining sugar, and cornstarch until smooth.
-
Temper the eggs: Slowly pour a small amount of the hot milk mixture into the egg yolk mixture while whisking continuously. This gradual addition helps prevent the eggs from cooking too quickly and forming curds.
-
Combine and cook: Once the eggs are tempered, pour the egg mixture back into the pot with the remaining hot milk. Continue to cook over medium heat, whisking constantly, until the mixture thickens and reaches a custard-like consistency.
-
Finish with butter and vanilla: Remove from heat and whisk in the butter and vanilla extract for flavor and a silky texture.
-
Cool the pastry cream: To avoid the formation of a skin on top of the cream, place a piece of plastic wrap directly on the surface of the cream while it cools. Once cooled to room temperature, refrigerate until ready to use.
Variations of Pastry Cream
Pastry cream is highly adaptable, and many variations can be created by altering or adding ingredients. Below are some popular variations:
1. Crème Diplomate (Diplomat Cream)
Crème diplomate is a lighter, fluffier version of pastry cream. It is made by folding whipped cream into cooled pastry cream, resulting in a mousse-like texture. This variation is often used to fill delicate pastries like puff pastries or fruit tarts, as the lighter texture complements the flakiness of the dough.
2. Crème Chantilly (Whipped Cream Pastry Cream)
This variation combines pastry cream with whipped cream, creating a smooth, airy texture. The whipped cream is added to the pastry cream after it has cooled, giving it a lighter, more delicate mouthfeel. Crème chantilly is often used as a filling for layered cakes or as a topping for fruit-based desserts.
3. Crème Pâtissière au Chocolat (Chocolate Pastry Cream)
Adding melted chocolate to pastry cream results in a rich, decadent chocolate pastry cream. The chocolate can be added after the pastry cream has thickened and cooled slightly. This variation is commonly used in chocolate éclairs, tarts, or as a filling for cakes.
4. Lemon Pastry Cream
For a zesty twist, lemon pastry cream adds fresh lemon juice and zest to the base. The citrus flavor complements the richness of the custard and is often used as a filling for lemon tarts or as a topping for shortcakes. The acidity of the lemon also helps to balance out the sweetness of the cream.
5. Pastry Cream with Liqueur
Adding a small amount of liqueur, such as Grand Marnier or Chambord, can give pastry cream an extra layer of flavor. The alcohol evaporates during the cooking process, leaving behind only the subtle taste of the liqueur, which pairs well with certain desserts like fruit tarts or chocolate-based pastries.
Troubleshooting Pastry Cream
While pastry cream is a relatively simple recipe, there are a few common issues that can arise:
- Curdling: If the eggs are cooked too quickly, they may curdle. This can be avoided by slowly tempering the eggs and stirring constantly.
- Lumpy texture: If the cornstarch isn’t dissolved properly or the mixture isn’t whisked enough during cooking, lumps can form. Whisking continuously while cooking helps prevent this issue.
- Too runny: If the pastry cream doesn’t thicken enough, it may need to be cooked a little longer. Alternatively, a bit more cornstarch can be added to the mixture at the beginning to ensure a thicker consistency.
Conclusion
Pastry cream is an essential component in the world of desserts. Its smooth, creamy texture and rich flavor make it the perfect filling for a variety of pastries and cakes. The science behind pastry cream is rooted in understanding the role of heat, starch gelatinization, and protein coagulation, which together create the velvety consistency that pastry cream is known for. By exploring different variations, pastry chefs and home bakers alike can experiment with flavors and textures to create unique and delicious desserts. Whether you are making a classic pastry cream or a flavored variation, mastering this recipe is key to creating perfect, indulgent pastries.