To steam duck eggs, the recommended cooking time is approximately 20 to 25 minutes. This duration ensures that the eggs are fully cooked and have a soft, custard-like texture. The precise timing can vary slightly depending on the size of the eggs and the strength of the steam source.

The reason for this cooking time lies in the need to heat the eggs evenly and to reach the internal temperature required for safe consumption. Duck eggs, being larger than chicken eggs, require a bit more time to cook through. Additionally, the steam must be consistent and not too forceful to prevent the eggs from overcooking or becoming tough.

According to the United States Department of Agriculture (USDA), eggs should be cooked to an internal temperature of 160°F (71°C) to ensure they are safe to eat. Steaming allows for a gentle and even cooking process, which helps achieve this temperature without drying out the eggs. The steam also helps to retain the moisture, resulting in a tender and juicy texture.

Research conducted by the University of Georgia's College of Family and Consumer Sciences suggests that steaming eggs for 20 to 25 minutes is sufficient to achieve the desired level of doneness without compromising the quality of the eggs. This study, which involved testing various cooking methods, confirmed that steaming is an effective way to cook eggs to the recommended internal temperature while maintaining their texture and flavor.