Steam Power: Pressure Cooker's Secret Weapon

Pressure cookers are a sealed chamber that traps steam generated from boiling water at extreme temperatures, which helps build pressure and heat up food quickly. The steam generated inside a pressure cooker helps cook food faster and more efficiently. The steam also helps retain moisture in food, making it tender in a short amount of time.

Steam is trapped in the cooker, raising the pressure and cooking temperature

The pressure cooker was invented in the 17th century by French physicist Denis Papin, who called it the "steam digester". Papin's invention works by expelling air from the vessel and trapping steam produced by boiling liquid. This trapped steam raises the internal pressure, increasing the temperature inside the cooker to between 100–121 °C (212–250 °F).

The pressure cooker is a sealed vessel that traps steam generated by heating its contents. As steam builds, the pressure increases, driving the boiling point of water past 212°F (100°C). This higher temperature shortens cooking times and, due to a lack of evaporation, extracts flavour more efficiently from foods.

The science behind the pressure cooker can be explained by the ideal gas law, which states that: PV = nRT. In a sealed pressure cooker, the volume (V) of the chamber doesn't change, and neither does R (the ideal gas constant). There is a maximum pressure that the chamber can reach, which is regulated by a valve system. As the pressure cooker heats up, T (temperature) increases, and so something else must increase to balance the equation. This is usually pressure (P).

The increase in pressure can also be explained by the kinetic model of gases. As the system heats up, there is more energy supplied to the molecules of water vapour, which bounce around and collide randomly with each other and the walls of the container. The force of these collisions against the walls is one definition of pressure.

The higher cooking temperature in a sealed pressure cooker means, in general, faster cooking without burning food. The sealed nature of the cooker also limits the evaporation of critical volatile flavour and aroma compounds.

This higher temperature cooks food faster than at normal pressure

The pressure cooker works by trapping steam generated from the boiling liquid inside a sealed vessel. This raises the internal pressure, which in turn raises the boiling point of water past 212°F (100°C). This higher temperature cooks food faster than at normal pressure.

The pressure cooker can be explained by the ideal gas law, which states that pressure multiplied by volume equals the number of particles in a gas multiplied by the ideal gas constant, multiplied by temperature. In a sealed pressure cooker, the volume and amount of steam are fixed, so the temperature can be controlled by setting the pressure.

The higher cooking temperature in a sealed pressure cooker means faster cooking without burning food. The contents of a pressure cooker are also left relatively undisturbed as the liquid never effectively boils.

The science behind pressure cooking is simple: cooking at a higher pressure means food can be cooked at a temperature that exceeds the normal boiling point of water. The trapped steam and much lower quantity of water make this possible.

Steam is expelled from the vessel, preventing overcooking

Pressure cookers are designed to hold steam inside while cooking. However, if a large amount of steam is escaping, something might be wrong with the pressure cooker. This could be due to issues with the sealing valve, sealing ring, or the lid not being properly closed.

The escape of steam from a pressure cooker can be a safety mechanism to prevent excessive pressure build-up, which could otherwise lead to an explosion. The steam release/venting handle or the pressure release nozzle is designed to release excess pressure and maintain a safe operating pressure. This safety feature ensures that the pressure in the pot does not get too high, addressing the concerns of those who are wary of using pressure cookers due to the risk of explosions.

The amount of steam released should be minimal and may not even be visible. If a significant amount of steam is escaping, it could indicate an issue with the sealing mechanisms, such as the gasket, or with the heat being too high.

To troubleshoot, users can check the sealing valve, sealing ring, and gasket for any damage, missing parts, or dirt that might prevent proper sealing. Ensuring that the lid is correctly closed and secured is also crucial. Additionally, it is important to adjust the heat settings, as excessive heat can cause an excessive release of steam.

Steam is a healthy and gentle way to cook food

Steam cooking is a healthy and gentle way to prepare food. The pressure cooker encloses steam for optimal cooking results. Here are some of the benefits of steam cooking with a pressure cooker:

Preservation of Nutrients

Steaming is a gentle cooking method that helps preserve vitamins and minerals. The food is cooked in a closed container with steam, which prevents the leaching of nutrients into the cooking water. This is especially beneficial for cooking vegetables, as it ensures that important vitamins and minerals are retained in the food.

Reduced Cooking Time

Pressure cookers significantly reduce cooking time compared to traditional methods. The high pressure and temperature achieved in a pressure cooker allow food to cook much faster. This not only saves time but also energy, making it a more efficient way to cook.

Ease of Use and Control

Pressure cookers are easy to use and provide precise control over cooking time. The steam regulator allows you to adjust the cooking time according to your needs. Additionally, the pressure cooker can be opened at any time without prior steaming, making it convenient to check on the food.

Versatility

Steam cooking in a pressure cooker is suitable for a wide range of foods, including meat, fish, vegetables, and even desserts. You can also cook multiple foods at the same time, as long as they have similar cooking times. This versatility makes the pressure cooker a valuable tool in the kitchen, as it can take on the role of several other appliances.

Safety

Modern pressure cookers have numerous safety features to prevent accidents. They are designed with multiple valves, pressure regulators, and safety locks to ensure safe operation. The risk of explosion, though once a concern, is now extremely rare with today's pressure cookers.

Steam cooking preserves vitamins and minerals

Steam cooking is a gentle method of preparing food that uses hot water vapour to cook ingredients. It is one of the healthiest ways to prepare food because it retains vitamins, minerals and other important nutrients.

Steaming is particularly good for cooking vegetables as they retain more of their nutritional value than when prepared in other ways. For example, vitamin C and folate, two water-soluble vitamins, are retained in greater quantities when steamed compared to other cooking methods. The heat distribution in steam cooking is also more even, preventing hot spots from developing in dishes and cooking food more evenly.

Steaming is also a good way to prepare fish, as it does not dry it out or overcook it. Meat can also be steamed, although it may need to be browned first to create the flavour of roasted meat.

Steaming is a faster and more energy-efficient way of cooking than boiling or broiling. This is because steam transfers energy more efficiently than water, resulting in quicker cooking times and lower energy usage.

Steam cooking also helps to preserve the natural raw properties of food, such as texture, taste, colour, flavour and overall freshness. Other methods of cooking vegetables can result in a complete loss of their firmness and crispiness, leaving them overcooked and unappetising.

Steaming is also a healthy way to cook meat, as it helps to lower cholesterol levels. Steam cooking removes fat from meats like pork or lamb, which can then be easily removed after cooking. In contrast, cooking methods like frying and grilling tend to cook excess fat into the meat itself, increasing the total fat content.

Steam cooking also increases the yield of cooked food, producing a significantly larger amount of cooked food from either meat or vegetables than other forms of cooking.

Frequently asked questions