How Pressure Cookers Work: Steam, Sealed, Cooking

Pressure cookers are designed to trap steam, which raises the internal pressure and cooking temperature, reducing cooking times. However, some steam release is normal during the pressurization process, and some older models release steam continuously while cooking. If your pressure cooker is releasing a lot of steam, it may be due to a faulty seal or valve, or because the heat is set too high.

Why does steam escape from a pressure cooker?

A pressure cooker works by using steam to build pressure. As the pressure builds up inside the pot, it produces high temperatures to quickly heat and cook the food inside. The pressure cooker raises the boiling point of water beyond the usual 212 degrees Fahrenheit. The temperature can go up as high as 250 degrees Fahrenheit.

The pressure cooker is designed to release steam to maintain a safe level of pressure. When the pressure builds up, safety valves open just enough to release excess pressure, resulting in a hissing sound and a rattle of the wobbler on the lid. This is perfectly normal.

However, if there is too much steam escaping from the pressure cooker, something may be wrong. It could be that the cooker is not sealed properly, or a valve was accidentally left open. The pressure within the pot needs to be maintained at a certain level to ensure the food cooks thoroughly, so this issue needs to be corrected.

Another reason for excessive steam could be that the pressure is too high. In this case, the heat needs to be reduced. If using a stovetop, this can be done by turning down the heat with the stove-top knob. For an electric stove top, the process is more complicated as the heating element will take time to reduce the temperature.

What is the ideal gas law?

While using a pressure cooker, it is normal to see a small amount of steam being released as the pot is warming up. However, if a lot of steam is escaping, it could indicate an issue with the sealing valve, sealing ring, or the lid not being properly closed.

Now, the ideal gas law, also known as the general or perfect gas law, describes the relation between the pressure (P), volume (V), and temperature (T) of a gas under conditions of low pressure and high temperature. The law is expressed as PV = nRT, where n is the number of moles of the gas, and R is the universal gas constant (8.31446261815324 joules per kelvin per mole).

This law is a generalization that encompasses Boyle's Law and Charles's Law as special cases. It is derived from the kinetic theory of gases and is based on three key assumptions:

• The gas consists of a large number of molecules in random motion, obeying Newton's laws of motion.
• The volume of the molecules is negligible compared to the volume occupied by the gas.
• The only forces acting on the molecules are during elastic collisions of negligible duration.

The ideal gas law is a useful tool for understanding and predicting the behaviour of gases, even though no gas exhibits these exact properties.

What is the history of the pressure cooker?

The history of the pressure cooker dates back to the 17th century when French physicist Denis Papin invented the "Steam Digester" in 1679. Papin, known for his work on steam power, created this airtight cooking vessel to increase water's boiling point using internal steam pressure, reducing cooking time. In 1681, Papin presented his invention to the Royal Society of London, and he was later elected as a member.

However, it wasn't until the 20th century that the term "pressure cooker" became commonly used. In 1910, inventor Zeno E. Crook founded "The Pressure Cooker Company" in Denver, Colorado, introducing a practical aluminium cooker for home use. Despite this, the pressure cooker's popularity in the US didn't peak until the 1930s and 40s. In 1938, German inventor Alfred Vischler introduced the "Flex-Seal Speed Cooker" at a New York trade show. However, it was the "Presto" pressure cooker, unveiled at the 1939 New York World's Fair, that captured the attention of homemakers due to its easy-to-close interlocking cover. During World War II, the production of pressure cookers was halted as aluminium was needed for the war effort, but their popularity surged again post-war.

In the 1950s, the pressure cooker business evolved with the introduction of stamped aluminium models and advancements in stainless steel fabrication, creating long-lasting designs. However, by the late 1950s, the industry faced challenges due to inferior products and improper use by consumers, leading to a decline in the pressure cooker's reputation and popularity. It wasn't until the 1970s that additional safety features and contemporary styling revived interest in pressure cookers. The development of an interlocking cover that prevented opening until pressure was safely reduced, along with secondary overpressure devices, eased consumer resistance.

Today, pressure cookers continue to evolve, with the introduction of electric pressure cookers and smart programming that includes preset cooking times and settings based on heating intensity, temperature, pressure, and duration. The popularity of pressure cookers persists, particularly in Europe and Asia, with foreign manufacturers introducing new styles and features, many in the "luxury model" category.

How do you cool a pressure cooker?

When it comes to cooling a pressure cooker, it is important to exercise caution and follow the correct procedures to ensure safety and maintain food quality. Here are some detailed instructions on how to safely cool a pressure cooker:

Allow Natural Cooling:

The safest method is to let the pressure cooker cool down naturally. After cooking, turn off the heat source and simply let the cooker sit undisturbed. Avoid the temptation to rush the cooling process by jiggling the pressure valve or using cold water. Compromising the natural cool-down process can be unsafe and may affect the quality of your food.

Check the Sealing Valve:

Before starting the cooking process, ensure that the sealing valve and sealing ring are properly secured. Over time, screws and fasteners can loosen, so it's important to check them periodically. A loose sealing mechanism can cause steam to escape, preventing the cooker from building and maintaining pressure.

Adjust the Heat:

If your pressure cooker is releasing too much steam, it may be due to excessive heat. In this case, reduce the heat to the lowest setting once steam is produced. By maintaining a steady, low level of steam, you can effectively cook your food without increasing the pressure too much.

Inspect the Pressure Weight:

If you notice steam escaping from the pressure release nozzle, inspect the pressure weight mechanism. Ensure that it is properly seated and functioning correctly. The pressure weight should be able to move freely and sit securely on the vent.

Clean the Valve:

In some cases, the steam release may be due to a clogged valve. Over time, food particles or residue can accumulate and prevent the valve from sealing properly. Disassemble the valve, if possible, and clean it thoroughly. This can help ensure a proper seal and prevent steam from escaping.

Replace the Sealing Ring:

If you notice steam escaping after the cooker has come to pressure, the sealing ring may be missing or not seated correctly. Check the silicone seal inside the edge of the lid and ensure it is properly positioned. If necessary, replace the sealing ring with a new one.

It is important to follow these steps to ensure the pressure cooker functions optimally and safely. By allowing natural cooling, maintaining the sealing mechanisms, and adjusting the heat as needed, you can effectively cool a pressure cooker while preserving the quality and safety of your cooked food.

What are the different types of pressure cookers?

Pressure cookers are available in different types and varieties, and can be classified based on their generation, origin, or features.

First Generation Pressure Cookers

Also known as the "old type", these pressure cookers operate with a weight-modified or "jiggler" valve that releases pressure during operation. They are considered loud because the valve rattles as excess steam is released. Older pressure cookers typically offered only one pressure level, but newer models allow users to modify the weight of the valve and change the pressure.

Second Generation Pressure Cookers

These pressure cookers use spring-loaded valves that are often hidden from view in a proprietary mechanism. They offer two or more pressure settings and allow users to choose between multiple pressure options. Some second-generation pressure cookers do not release any steam during operation and instead use a rising indicator to show the pressure level. Others use a dial that releases pressure when turned.

Third Generation Pressure Cookers (Electric Pressure Cookers)

Electric pressure cookers include an electric heat source that automatically regulates the temperature and pressure. Like the second generation, they also feature a spring-loaded valve and provide dual pressure settings. They typically have a timer and the ability to keep food warm. However, they cannot be immersed in cold water to release the lid quickly and require caution when handling due to the release of steam through tiny valves.

Single-Purpose Pressure Cookers

Single-purpose pressure cookers are designed to handle a single pressure setting and can be used for various dishes, but the outcome cannot be controlled. They may be electric or valve-based stovetops. Many canning pressure cookers fall into this category and often lack extra features. Newer models may include pressure indicators or gauges to alert users to any issues.

Multi-Purpose Pressure Cookers

Multi-purpose pressure cookers are designed to multitask and can cook, steam, and sear. They come with multiple inserts, various temperature and pressure settings, and the option to convert them into slow cookers or rice cookers. They are a good investment for those looking to multitask in the kitchen.

Frequently asked questions