UNDER PRESSURE
For many years, low- and high-pressure pressure cookers could only be found in the spaciousness of institutional, hotel and country club kitchens. These units required a great deal of expense, space, and a skilled operator. Barriers such as these made it difficult--if not impossible--to broaden market use of this time-saving and health-oriented equipment.
Labor and time savings became very obvious when compared to the older tradition of cooking simple vegetables in a large pot of boiling water on the range top. The loss of the aesthetic sharp colors and of vital nutrients in the food product are difficult to avoid.
For these reasons, the best pressure cooker and best pressure cooker recipes were introduced. Physicists have known for years that there is more heat produced for cooking in one pound of steam at zero pressure than there is in one pound of steam at 15 pounds of pressure. Air in the steam environment had proved to be a major barrier to obtaining efficient heat transfer. A blanket of air and condensate would buffer the pressurized steam from the product, causing uneven cooking and a loss in heat transfer of more than 50 percent.
HEAT TRANSFER
A system had to be designed to purge the air from the cooking cavity. This was achieved by a continuous, turbulent flow of pure steam. The result is a radical increase in the efficiency of heat transfer to the product.
This increase in an environment of 100 percent in a pressure cooker, compared to a pressurized cavity with 90 percent steam and 10 percent air, combine to produce as much as a 300 percent more efficient heat transfer.
The transfer of heat in the pressure cooker and the latent heat of fusion given up by the steam's condensing on the food, cause the cooking process. This allows speedy penetration of certain foods (especially frozen products), thereby decreasing cooking times significantly. The cooking temperature resulting in the process is 212[deg.] F. This may not seem like a very high temperature, but the BTUs and heat transfer to the product is actually much higher.
An example may best illustrate this point. You could put your hand in an oven set at 350[deg.] F. without being burned or uncomfortable; however, if you were to try to place your hand over a tea spout of boiling water, and the temperature of the steam was the same, you would be in definite pain. Steam carries more heat at lower temperatures.
COOKING WITH STEAM
Pressure cookers with multiple pan capacities can cook many different foods at the same time without transfer of flavors. One of the greatest advantages of the pressure cookers is that the door can be opened at any time during the cooking process. Because of this fact, cooking progress can be checked, other menu items can be added or removed, and the cooking process can continue without interruption.
More Reading: http://en.wikipedia.org/wiki/Pressure_cooking
Some other benefits of cooking with pressure cooker may be noted:
1. Foods retain their natural, bright color, and are tastier while retaining their nutritional value.
2. Shrinkage is minimal, reducing waste and food cannot burn or dry out.
3. Minimal space is required for the preparation of a large variety of food products, as compared with less efficient methods.
4. Less heat is generated in the kitchen, so the kitchen becomes a more comfortable working environment.
5. These benefits, as well as others, speak well for the pressure cooker; it is with menu items such as seafood and vegetables where its advantages may best be seen.
These benefits, as well as others, speak well for the pressure cooker; it is with menu items such as seafood and vegetables where its advantages may best be seen.