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How Does a Pressure Cooker Work?

December 21, 2023

Once notorious for their risky design, pressure cookers have an interesting history. During World War II, Americans were encouraged to can their food, leading to a surge in the use of pressure canners. This trend continued after the war, creating a high demand for pressure cookers. However, the rapid production during this period often compromised quality and safety. A typical 1950s model, for example, had a single valve prone to clogging. This could cause the cooker's gasket to burst under extreme pressure, sometimes even ejecting the lid.


Thankfully, modern pressure cookers are far safer. Advances in manufacturing and design have included multiple safety features, such as various valves, improved pressure regulators, and secure lid locks. These enhancements have transformed stainless steel pressure cookers from dubious kitchen gadgets to reliable cooking tools.

M-type Stainless Steel Pressure Cooker

Understanding How Pressure Cooker Work

A pressure cooker is simply a container that retains steam for this purpose, generating very high internal pressures. The boiling point of water is raised, making it possible to fry and roast food at temperatures higher than the normal 212°F. Additionally, evaporation is minimal; thus, this technique provides high heat-up rates and improved flavor extraction from foodstuffs.


Let's quickly get into high school chemistry to understand this process better. From the ideal gas law equation (PV = NRT), where P is pressure, V is volume, T is temperature, n is gas quantity, and R is a constant, a pressure cooker works. R and volume remain the same in a pressure cooker. To maintain equation balance, the cooker warms up, increasing temperature (T) and pressure (P).

This pressure increase can also be understood through the kinetic theory of gases, where heating the cooker adds energy to the water molecules, causing them to move more rapidly. These molecules collide with the walls of the cooker, and these collisions are what we measure as pressure.


But what happens when the cooker reaches its maximum pressure? Consider a pressure cooker making chicken stock. When it hits maximum pressure, the temperature levels out. If you continue heating, the cooker adds energy, causing more collisions. To prevent an endless increase in pressure, steam is released. This is seen in traditional stovetop models where the valve rattles as it releases steam. Modern electronic models have a regulating cooker that automatically sets the heat level while controlling the steam/pressure/temperature, making the procedure easier and safest.


Under an average American stainless steel pressure cooker the pressure could go up to nearly fifteen pounds per square inch beyond the standard atmospheric pressure. Such generates a total pressure, or "absolute," pressure of just about 30 psi within the steamer, pushing up to the range of about 250oF (121oC) about the boiling point of water.


Here's a quick note on pressure readings: Likewise, most pressure cookers calculate their pressures exceeding that of the air condition level. The atmospheric pressure at sea level is approximately 15 psi; thus, when a gauge on a cooker reads 15 psi, an extra 15 psi will be inside the cooker, giving a total pressure of 30 psi.


This high-pressure and high-temperature cooking makes the process fast; as they say, the juice stays in. In addition, because the liquid does not boil conventionally, it cooks food more uniformly.

Pressure Cooking at Higher Elevations

Let's consider pressure cooking in high-altitude areas like Denver or the Andes Mountains. This happens naturally because of altitude and the atmospheric pressure being low. For example, the ambient pressure in Denver is approximately 12.2 pounds per square inch (psi).


A pressure cooker's total pressure is lower at greater altitudes than at sea level due to lower air pressure. If one cooked at 5280 feet above sea level in Denver, the total pressure inside the cooker would be 27.2psi (12.2psi air pressure and the other boiling point drops to 244.8°F due to decreasing pressure.


How will it impact your cooking? In short, cooking time has to be slightly longer at higher elevations. Approximately five percent cook time should be added with each elevation of 1000 feet over 2000 feet. The adjustment also balances for the low pressure and temperature so that your food remains well done.

hot sale stainless steel high pressure cooker- ZHENNENG

Your Pressure Cooker Options: Electric vs. Stovetop

In selecting pressure cookers in America, one must choose between electric or stovetop units. There are their respective merits and demerits. However, the most notable disparity between them is the running pressure. Both have pros and cons, but a key difference lies in the operating pressure. Electric pressure cooker work at a lower pressure of about 12 psi, while stovetop models operate around 15 psi. This variance in pressure affects cooking times; food cooked in an electric stainless steel pressure cooker generally takes longer due to the lower temperature.


So, why opt for a lower pressure and longer cooking time? The answer is convenience and safety. Electric models offer ease of use – they can reach a pressure of 15 psi. However, they keep it lower when cooking, eliminating the need to monitor the heat constantly. With an electric pressure cooker, you can set it up and then focus on other tasks, akin to the "set it and forget it" approach.

stovetop pressure cooker

stovetop pressure cooker

Cooling Down Your Pressure Cooker: Three Effective Methods

When your cooking is done, there are three main ways to bring the pressure down in your cooker: natural venting, rapid venting, and cold water injection.


● Natural Release: It is the most straightforward, whereby you remove the cooker from the heat, and as it happens for the rest of the time, it cools itself down. The pressure decreases gradually, releasing the spring-loaded lock. Remember that the food inside continues cooking during this process, especially if there's a lot in the cooker.


● Quick Release: This method is more immediate. It involves removing the weight from the vent or pressing a button to release steam quickly. This stops the cooking process immediately but can cause the contents to boil vigorously. It's a great technique if you're looking to blend ingredients further, like in a split pea soup, without using a blender.


● Cold Water Release: The third method involves running the cooker under cold water. This quickly lowers the pressure inside, allowing you to access the contents immediately. Unlike the quick release, this method doesn't cause the contents to boil. Nevertheless, it should be noted that this method is not appropriate for electric pressure cookers.


Each method has its strengths; it is sometimes best to choose them depending on a recipe or our taste. The quality of the stainless steel pressure cooker also matters, so It’s recommended that you get it from reliable sellers. One of the best in the market is Zheneng. We’re a stainless steel kitchenware manufacturer with a stellar reputation. Check out our products and let’s make your kitchen safe!

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