What Is a Steam-Jacketed Kettle?

Norma Jean Howland
Norma Jean Howland
Industrial kitchens and restaurants may feature steam-jacketed kettles.
Industrial kitchens and restaurants may feature steam-jacketed kettles.

A steam-jacketed kettle is similar to a double boiler and cooks large quantities of food by using steam heat. It is designed with both an inner and outer steel wall that cooks the contents inside by releasing steam into the space between the walls. These devices are often used to cook foods like stock, gravy, sauce, or soup, and may be powered by electricity or gas. They come in various sizes, for installation on the floor, countertop, or wall. Steam-jacketed kettles are often used in restaurants and industrial kitchens, where very large amounts of food are prepared daily.

Steam-jacketed kettles may be used in military ships.
Steam-jacketed kettles may be used in military ships.

All the different styles and sizes of steam-jacketed kettle use steam to cook the contents inside. Most are made from stainless steel, and usually, the steam jacket is permanently filled with treated, distilled water. Since steam encapsulates most of the kettle, it may cook more evenly than a traditional stock pot because it offers a more uniform cooking surface. It also tends to warm contents more quickly than a traditional pan, heated primarily from the bottom.

Electricity, gas, or both may supply power to the kettle. A gas fired kettle requires a gas hook up source to operate and may also require electricity if it has automatic ignition. Gas kettles also require a kitchen ventilation system for safety.

A steam-jacketed kettle can be tilting or stationary. A kettle that is meant for floor use is usually stationary and may have legs that can be adjusted to different heights so that cooks can reach the pot. There are also smaller sized kettles, wall-mounted or for countertop use, that can be manually tilted to make it easier and safer to remove the contents. Most kettles also have a draw off valve.

Often, a steam-jacketed kettle is used for industrial cooking purposes. They are found in hotels, and schools and on military ships and bases. This kind of kettle can cook large amounts of stew, pasta, or chili and can also be used to braise meat, cook dessert, or reheat various foods. Steam-jacketed kettles tend to be popular for institutional use because they require less stirring, can simmer longer-cooking recipes, and are less apt to burn food.

How Are Steam Jacketed Kettles Heated?

As their name implies, steam-jacketed kettles harness steam energy to heat food. Conduction heat transfer allows the heat to move from the kettle's metal structure to its contents. Molecules begin moving more rapidly and bump into each other, continuously shifting their energy to neighboring particles.

Most steam-jacketed kettle models consist of an inner kettle, an outer jacket and the heating element connecting to an exterior power source. The jacket covers about two-thirds of the kettle, with some space in between the kettle and jacket. Inside that sealed space, steam can flow and heat the kettle evenly on all sides.

Kettle Heating Methods

You may notice several types of steam-jacketed kettles available. Electric freestanding units simply require a power cord and an outlet. Gas-operated versions require professional installation to a gas line. Direct-steam versions may require an IPS connection hooked up by a professional plumber. Some models already contain treated water so you don't have to vent and refill them.

How To Clean a Steam Jacketed Kettle

When cleaning your steam-jacketed kettle, you should take some sensible precautions. First, switch its thermostat dial to the OFF position. If your kettle is electric, disconnect it from the power source. Allow the kettle to cool before you begin. Next, you should always use non-caustic cleaners when cleaning and sanitizing the kettle. Avoid using harsh tools such as wire brushes, scrapers and steel pads. Finally, do not use chloride detergents when cleaning and sanitizing. Your cleaning process requires a few simple steps:

  • With a nylon brush, scrape out any remaining food residue inside the kettle.
  • Mix a solution of hot water with your preferred non-caustic alkaline detergent.
  • Clean the inside of the kettle first. You can use a cloth dampened with your cleaning solution for the exterior controls and housing. 
  • Do not spray water onto any gas or electrical components while cleaning. 

Cleaning after each use is preferred. If your steam-jacketed kettle is constantly in use, you should clean it once every twelve hours.

Steam-Jacketed Kettle Maintenance

To ensure a long service life from your steam-jacketed kettle, proper care is essential. Besides cleaning your kettle, you must perform other steps. Before each use, inspect its compound gauge. It should be in the green zone and not in the vent air zone. If your kettle is equipped with a marine latch, check to ensure it works correctly and isn't clogged with food. Also, inspect your unit for any missing screws and replace them right away.

Other periodic maintenance is needed for your kettle. Lubricate its trunnion bearing and test its pressure relief valve once every six months. Be sure to replenish and change out any water as required. Finally, be sure to replace steam seals on direct-steam kettles at least once a year.

Replacing a Steam-Jacketed Kettle

Steam-jacketed kettles last a fairly long time, but they may eventually need replacement. You'll want to watch out for some signs that you should shop for a new kettle:

  • Leaking: Check for leaks if its compound gauge does not stay in the green zone. Remember to look for visible leaks in the jacket area. 
  • Excessive repair costs: If you're forced to make frequent repairs, you may want to replace your kettle. 
  • Slower cook times: Deviations from normal cook times may result from leaks or heating element failure. 
  • Breakdown in materials: External stress fractures and pitting inside the kettle's inner lining may occur due to heavy use or exposure to acidic substances. 

What Is a Steam Jacketed Kettle Used For?

Steam-jacketed kettles can cook a wide range of foods. They're popular appliances for cooking soups, stews, pasta and other kinds of large-quantity dishes that contain significant amounts of liquid. These kettles are also useful for preparing portions of dishes, not just the final product. They're useful for cooking large quantities of sauce, broth and stock. Even dishes that you wouldn't think to cook in a steam-jacketed kettle do surprisingly well: rice, jams, jellies, puddings and other creamy deserts.

Quality and Consistency

Besides the capacity to cook foods in big batches, steam-jacketed kettles offer other advantages. Heat remains at consistent levels. Also, heat surrounds the entire contents of the kettle for more even heat distribution. Steam-jacketed kettles can achieve your desired temperature faster than traditional stovetop pots.

With many kettle models equipped with advanced controls, you can confidently cook a large batch of one dish while prepping another without worrying about scorching or boilovers. Food cooked in these kettles also maintains the same flavor and quality, regardless of who's the chef in the kitchen.

What Are the Uses of Steam Jacketed Kettle?

As mentioned earlier, steam-jacketed kettles are very useful for institutional and big-batch cooking. But these appliances have virtually limitless uses. They serve as a sort of "pot without the stove." So unless a dish requires different cooking methods — think stir-frying or deep frying — you can probably cook it in a steam-jacketed kettle. The copious amount of liquid in soups, stews, sauces and similar dishes means that solid chunks of food won't get stuck and scorched.

Steam-Jacketed Kettles and Creamy Foods

Creamy soups and sauces can be tricky to cook via traditional stovetop methods. Most professional chefs and cooks are adept enough to prevent scorching and burning. But the thicker liquid can stick to the bottom of a regular pot and scorch. But this won't happen in a steam-jacketed kettle. The uniformly distributed heat supplied by the kettle is key, which is perfect for many kinds of heat-sensitive dishes:

  • Cream sauces and soups
  • Cheese sauces
  • Chocolate and fudge
  • Fruit fillings and syrups
  • Cream fillings and icings
  • Pudding and pie fillings
  • Roux

Reheating Food in a Steam-Jacketed Kettle

Thanks to its uniform heat distribution, you can also use a steam-jacketed kettle to reheat food. This is a rather simple process — just add the food to the kettle, choose the proper temperature setting and heat for the specified time.

Tilting Steam-Jacketed Kettles

Some steam-jacketed kettles also tilt to pour out their contents more easily. This also allows for simpler cleaning of the kettle's interior. You use an attached handle to gradually and carefully tip the kettle toward the container you wish to pour the contents into. Go slow to avoid splashing hot liquid onto yourself and others.

How Do Steam Kettles Work?

As you know, steam-jacketed kettles use pressured steam to deliver even heating all over the inner kettle. Depending on the model of kettle you have, about two-thirds of the inner kettle will be contained within the outer metal jacket.

Due to the steam involved, heating times are must faster than with conventional stovetop pots. Steam pressure is another key factor that impacts heating times. Let's say, for example, you have a 40-gallon kettle. Setting the operating pressure higher makes the content cook faster. The reason for this is simple: Higher pressures result in higher water boiling points and higher cooking temperatures. By setting your 40-gallon kettle to 30 PSI, it will take around 15 seconds to heat. But adjusting it to 45 PSI decreases heating time to about 13 minutes.

How Altitude Affects Boiling Points

Unless you live in a high-altitude location, you're probably not familiar with how it impacts cooking. That's because water reaches a lower boiling point the higher up you go. At sea level, water boils at 212 degrees Fahrenheit. But at 2,000 feet above sea level, its boiling point is 208 degrees Fahrenheit. Go up to 3,000 feet and the boiling point lowers to 206 degrees.

So, why does this happen? Air pressures are slightly lower at higher altitudes. With lower air pressure, there's less pushing down on the water. For every 1,000 feet you go up, boiling points lower by about 1.8 degrees. There can even be subtle differences between cities in the same state. For example, Columbus, Ohio, is at 900 feet above sea level. Cincinnati, located about 110 miles away, is at 480 feet above sea level. That difference translates to water's boiling point at 210 degrees in Columbus but 211 degrees in Cincinnati.

Because of lower air pressures at higher altitudes, water requires less energy to boil. But here's the caveat: Just because water boils faster doesn't mean your food will cook faster. The lower boiling point temperature is just that — a lower temperature. If you have two pans of soup both at 202 degrees Fahrenheit but in different cities, they're still at the same temperature. It doesn't matter if pot A in Denver is already boiling while pot B in New Orleans is not.

Steam-Jacketed Kettles and High-Altitude Cooking

Thanks to high-altitude trickery, food takes longer to cook. Liquids never exceed their boiling points no matter how high you crank up the heat. How does this affect your cooking in a steam-jacketed kettle? Food will just take a little longer to get done. You can still the kettle's steam pressure to higher levels. You still get uniform heat all over the kettle's surface. The speed and efficiency that steam-jacketed kettles offer makes up a little for the longer cook times at higher altitudes.

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Discussion Comments

Phaedrus

The nice thing about a steam-jacketed kettle is that the food at the top is usually the same temperature as the food at the bottom. Our church used to use these cast iron pots with gas burners to make their chicken stew, but then we found a used steam-jacketed kettle at a restaurant supply store. It's made all the difference in the world. We sell the stew to raise some money for the church, and we used to have to stir the cast iron pots constantly to prevent burning. Now we can pour everything into the kettle, stir it around and let the steam heat do all the work.

Buster29

When I worked for a commercial kitchen that supplied food for senior centers, I used three huge steam-jacketed kettles to prepare all of the hot items in bulk. We made vats of Jello and dipped them into steel pans to let them set up. I also boiled shrimp in a steam-jacketed kettled filled with seasoned water. It was really the only way to do hundreds of pounds of food in a short amount of time.

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