The standard time to steam egg custard in an egg cooker is approximately 10 to 12 minutes. This duration is sufficient for the egg custard to set properly without overcooking or becoming rubbery. The precise timing can vary slightly depending on the specific model of the egg cooker and the desired consistency of the custard. Most egg cookers come with a built-in timer that automatically shuts off once the custard is ready, ensuring that it is cooked to perfection.

The reason for this timing is rooted in the science of heat transfer and the physical properties of eggs. When eggs are steamed, heat is transferred to the egg whites and yolks, causing them to coagulate and solidify. The process of coagulation is temperature-dependent, with the proteins in the eggs denaturing at around 158°F (70°C). The steam in an egg cooker provides a gentle and even heat, allowing the eggs to reach this temperature without becoming too dry or overcooked. The duration of 10 to 12 minutes is a balance between ensuring the eggs are fully cooked and maintaining a creamy texture.

Data from various kitchen appliances manufacturers and culinary experts support this timing. For instance, the Hamilton Beach Egg Cooker manual recommends steaming eggs for 12 minutes, while the Cuisinart Egg Cooker suggests 10 minutes. These recommendations are based on extensive testing and are designed to produce a custard that is both safe to eat and enjoyable to consume. Additionally, the USDA Food Safety and Inspection Service advises that eggs should be cooked to an internal temperature of 160°F (71°C) to ensure they are safe to eat, which aligns with the cooking time provided by most egg cooker manufacturers.