To simmer lamb in a pressure cooker, the general guideline is to cook it for about 30 to 40 minutes at high pressure. This cooking time can vary depending on the cut of lamb and the desired level of tenderness. For instance, a tougher cut like shoulder or leg of lamb may require a longer cooking time, whereas a tender cut like loin or ribeye might need less time. It's important to note that the cooking time also depends on the pressure setting and the initial preparation of the meat, such as whether it has been seared or not.

The reason for this cooking time is rooted in the principles of pressure cooking. Pressure cookers work by increasing the internal pressure, which raises the boiling point of water. This results in a higher temperature inside the cooker, which in turn speeds up the cooking process. The increased temperature allows the collagen in the lamb to break down more quickly, leading to a tender and juicy result. According to a study published in the Journal of Food Science, pressure cooking can reduce the cooking time for meat by up to 70% compared to traditional cooking methods, such as simmering on the stovetop.

Moreover, the pressure cooking process also helps to retain more of the meat's natural flavors and nutrients. This is because the sealed environment of the pressure cooker prevents moisture loss, which can occur during prolonged cooking times. A study by the University of Guelph found that pressure cooking can preserve up to 90% of the nutrients in vegetables, and a similar effect can be observed with lamb. By cooking lamb in a pressure cooker, you can achieve a tender and flavorful dish with minimal nutrient loss.

In summary, simmering lamb in a pressure cooker typically takes 30 to 40 minutes, depending on the cut and preparation. This method is efficient due to the increased temperature and pressure, which accelerate the cooking process while preserving the meat's natural flavors and nutrients.