Steam Vs High Pressure: What's The Real Difference?

Pressure cooking and steaming are two different methods of cooking food. Pressure cookers are sealed vessels that use high-pressure steam and water or water-based liquids to cook food. The steam is trapped inside the cooker, which raises the pressure and cooking temperature, allowing food to cook faster than at normal pressure. On the other hand, steaming is when you cook food with steam, and it can be done in a pressure cooker or a dedicated steamer. While pressure cooking can be used for a wide range of ingredients, steaming is primarily used for cooking vegetables.

Pressure cooking uses steam and water to cook food

Pressure cooking is a cooking method that uses steam and water to cook food. It is a sealed chamber that traps the steam generated as its contents are heated. As steam builds, 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.

In a conventional pot, as the pot is heated, the temperature inside increases until the water starts to boil. At that point, all the heat energy goes into boiling the water, and the temperature doesn't increase unless all the water boils away. Water in liquid form cannot be heated to a higher temperature than its boiling point.

The same thing happens in a pressure cooker, but the temperature inside is much higher. The temperature at which a liquid boils is dependent on the surrounding pressure. When you cook in a regular pot at atmospheric pressure (14.7 pounds per square inch [psi]), water boils at 100°C (212°F). Inside a pressure cooker, the pressure can increase by an additional 15 psi, to almost 30 psi. At that pressure, water boils at 121°C (250°F). That means food can cook at a much higher temperature than it ever could at atmospheric pressure. And since cooking reactions speed up at higher temperatures, your food cooks faster. It also doesn’t dry out, since the water stays in liquid form.

The pressure cooker can be best explained by the “ideal gas law” (or “general gas equation”), which describes the behaviour of most gases under most conditions. It is commonly given as: PV = nRT. P stands for pressure; V stands for volume; T stands for temperature; n represents the amount of a given gas; and R represents a constant (the ideal gas constant).

In the closed chamber of a pressure cooker, we can assume that the volume (V) of the chamber doesn’t change, and that R (being a constant) doesn’t change either. There is a maximum pressure that the chamber can reach, regulated by a valve system. As the pressure cooker heats food up (i.e., heats water in the food), T goes up. And as T increases, something else must increase to balance the equation. Since we assume that V is constant, it is more than likely that pressure (P) increases as well.

We can explain this increase in pressure another way, too: As the system heats up, there is more energy supplied to molecules of water vapour, which causes them to bounce around and collide randomly both with each other and against the walls of the container. The force of these collisions against the walls is one definition of pressure, based on the “kinetic model of gases.”

The higher cooking temperature in a sealed pressure cooker means, in general, faster cooking without burning food. And, because the vessel is sealed, it also limits evaporation of critical volatile flavour and aroma compounds. An added plus: the contents of a pressure cooker go relatively undisturbed, since the liquid never effectively boils.

Steam carries more energy than liquid water

Steam and pressure cookers are not the same thing, but you can use a pressure cooker to steam food. Pressure cookers are much faster and more efficient than steaming, as they cook at a higher pressure, exceeding the normal boiling point of water.

The extra energy in steam is released when it condenses back into liquid water. This is why steam burns are more severe than boiling water burns. The energy in steam is also harnessed for practical uses, such as turning turbines to generate electricity in power plants, and for heating and cooking in various industries.

The science behind steaming food is simple. The trapped steam and lower quantity of water allow food to be cooked at a higher temperature than the normal boiling point of water. This is why pressure cookers are so effective and time-efficient.

Steam cooking is faster and more efficient

Steam cooking involves cooking food with steam, which can be achieved using a pressure cooker or a steamer. Pressure cookers use high-pressure steam and water or a water-based liquid inside a sealed vessel to cook food. The high pressure limits boiling and creates higher temperatures, allowing food to cook much faster than at normal pressure. The trapped steam and lower quantity of water make this possible, and the results are impressive.

The science behind it is simple: cooking at a higher pressure means food can be cooked at temperatures above the normal boiling point of water. The higher cooking temperature in a sealed pressure cooker means food cooks faster without burning. Additionally, the sealed environment limits the evaporation of critical volatile flavour and aroma compounds, preserving the food's flavour and texture.

Steamers, on the other hand, are primarily designed for cooking vegetables. They are extremely effective in this regard and provide health benefits over boiling. However, pressure cookers offer superior versatility as they can be used with a wider range of ingredients and types of food, including soups, rice, meat, and pulses.

When it comes to speed and efficiency, pressure cooking is the clear winner. Pressure cookers are often around ten times more efficient and faster than other cooking methods. They also save energy, as less water or liquid is heated, and food reaches its cooking temperature faster.

In summary, steam cooking with a pressure cooker is faster and more efficient than traditional stovetop cooking methods due to its ability to create higher temperatures, its versatility in handling various types of food, and its energy-saving benefits.

Steam can be used to sanitise kitchen equipment

Steam is an effective way to sanitise kitchen equipment. Steam cleaning is one of the oldest and most effective ways to kill viruses, bacteria, mites, germs, and fleas. The high temperatures reached by steam (above 100°C) are what make it such a good disinfectant.

Steam can be used to sanitise a wide range of kitchen equipment, including:

• Exhaust fans
• Tile backsplashes
• Countertops and cutting boards
• Ovens
• Trash cans, compost bins, and recycling containers
• Stainless-steel surfaces
• Grills
• Baseboards and cabinet ledges
• Ice and water dispensers
• Grout
• Glass

Steam is also useful for removing hardened gunk from microwaves, as well as disinfecting them.

However, it's important to note that steam cleaning is not suitable for all materials. For example, it should not be used on materials that could melt or be damaged by moisture.

Steam cooking is ideal for vegetables

Steaming is also a healthy way to cook vegetables. Unlike boiling, where vitamins and minerals can leech into the water, steaming helps retain these important nutrients. Additionally, steaming does not require the use of oils or fats, promoting a lower-calorie and more nutritious meal.

Another benefit of steam cooking vegetables is the versatility it offers. You can steam a wide variety of vegetables, from leafy greens to firmer options like carrots and squash. You can also easily adjust the cooking time based on the thickness of your vegetable slices, allowing you to control the texture and doneness of your vegetables.

Furthermore, steamed vegetables provide a blank canvas for flavour customisation. You can dress them up with various toppings, sauces, or seasonings to suit your taste and create diverse meals. For example, you can add olive oil, tamari, sauerkraut, hemp seeds, scallions, toasted seeds, or tahini. You can also steam vegetables in flavoured liquids like vegetable or chicken broth to enhance their taste.

Lastly, steam cooking is a gentle method that helps preserve the texture and colour of vegetables. This makes it ideal for preparing dishes where you want to maintain the integrity of the ingredients, such as salads or side dishes. Overall, steam cooking is a convenient, nutritious, and versatile way to prepare vegetables, making it a popular choice for home cooks.

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