Product Knowledge Guide: Steam-Jacketed Kettles

Steam-jacketed kettles can be energy savers in commercial kitchens, since these units heat up faster and at lower temperatures than stock pots on range burners. This results in a more efficient method of cooking soup, stocks and sauces, with less chance of scorching the product.

iStock 000051423750XXLargeFoodservice operators use these units in a variety of applications, including boiling water for cooking pasta and other foods. Today’s Mexican chains find that this equipment is ideal for cooking beans in large batches. It not only is more efficient but is also safer than having to work with full stockpots on ranges.

Unlike food cooked in a stockpot on a burner, product produced in steam-jacketed kettles typically doesn’t need to be constantly monitored or stirred. Most units have temperature control knobs that can be set for a simmer up to a rapid boil. This keeps temperatures at more accurate levels, typically within 5 degrees F.

Along with providing faster cook times at lower temperatures, kettles can produce greater volumes of product with increased consistency. These units also provide reduced labor for prep work and cleaning.

Both countertop and floor model kettles are available. Stationary floor models are typically 20 gallons and up in capacity, while tilting floor models generally range from 20 to 200 gallons. Countertop size units also are available in 1-quart to 12-gallon capacities. Although electric heating is most popular with this type, gas versions are available. Smaller sizes are more commonly used in independent restaurants and operations with less volume.

While countertop kettles offer a manual tilt feature where operators grab a handle to pull the kettle down for dispensing, stationary floor models provide either a mechanical handle or a switch with a motor for tilting.

There are three types of power options with this equipment. Self-contained electric kettles have water sealed inside a jacket and simply need to be plugged in to an outlet. Self-contained gas kettles have basically the same construction, but utilize a gas burner. The third type of kettle is direct steam, which provides the highest efficiency by cooking high volumes quickly.

Kettles can be fully jacketed with a bowl in a bowl design or two-thirds jacketed with a larger inner bowl, depending on the model. The fully-jacketed type provides heat transfer all the way to the top of the kettle. When product is filled to the brim, heating occurs all the way up the sides.

Two-thirds jacketed units are the most popular type, since the heat energy is transferred not only from the bottom of the kettle similar to a stockpot on a range, but also its sides. This substantially increases the surface area for energy absorption into the product. These units also provide a cool zone at the top where the jacket stops and the inner liner continues. As a result, there is less skimming than with full-jacketed types, which can be hard to work around due to the hot rim. In addition, two-thirds jacketed kettles cost less, since there is not as much metal used in construction.

Because capacities are measured to the kettle brim, the actual volume that can be accommodated in the kettle will be 20 percent less than the unit’s designated size.

Most kettles have between a 45 and 50 psi (pounds per square inch) steam jacket rating, which produces an even temperature from the entire jacketed surface of 267 degrees F to 338 degrees F. In addition, some European models offer 15 psi or 25 psi. In terms of steam’s physics, the higher the pressure, the hotter the temperature that kettle can achieve. For example, if there is pressure of 50 pounds, it’s possible to hit steam temperature of almost 300 degrees F. This provides faster cooking capabilities.

When kettles are used with covers, heat up time can decrease by almost 50 percent, which keeps energy use to a minimum. While typically standard on stationary kettles, covers tend to be optional for tilting floor kettles. Covers can be hinged, which only stay up with assistance, or spring-assisted, which stay up after lifting.

Generally an option on most tilting kettles, tangent draw-off valves are recommended for easier dispensing of the unit’s hot contents. Operators need to specify this feature upon ordering, since valves cannot be added in the field.

Other options available with kettles include LED controls, which offer increased accuracy and reliability. Also, for products with high acid content, manufacturers recommend specifying 316 stainless rather than 304. The higher grade metal has more nickel content and provides greater durability. Gallon markings are standard on some kettles and options on others. A heat deflector shield is available to help protect staff from burns. Operators may also want to consider purchasing a specialized brush for easier cleaning, long-handled paddles or whips for stirring and baskets for storage.

Hot and cold water faucets can be specified on the kettle to simplify filling larger capacity units. Pan carriers for tilting kettles hook on the front lip of the units to hold pans level when tilting, minimizing spillage. Baskets for cooking pasta and rice also are available in 6- and 12-gallon sizes. These drop directly into the kettle’s boiling water for cooking.

There have been few new developments with these units, although one manufacturer offers a line of two-thirds jacketed kettles with an improved bottom, which allows for a shallower design. Some newer steam-jacketed kettles feature solid-state temperature control with self-diagnostic capabilities.

 Consider This When Specifying Kettles

While everyone’s familiar with steam-jacketed kettles, there’s more to specifying them than meets the eye. Consultant William Taunton, general manager at Gastrotec Foodservice Design and M.A.S. Consultants, Santiago, Chile, shares a few key considerations to weigh when purchasing a steam kettle.

FE&S: What are the new options or innovations with these units that operators should be aware of?

WT: High-pressure kettles made in Europe are really effective and safe to use. These have very soft tilting mechanisms and high energy efficiencies.

FE&S: What are the specific applications that best suit steam kettles?

WT: We recommend this type of equipment be used for stews, sauces, creams, soups and in general food products that have a high humidity content and will flow. Kettles are available in a variety of sizes and operators can purchase larger units for special projects. In general, we recommend high-production facilities have large-batch productions.

FE&S: What are the common issues or problems to avoid when choosing and installing steam kettles?

WT: The most common issues I see include wrong specification in terms of the stainless steel quality and sizing and capacity miscalculations.

FE&S: What should operators consider when purchasing a steam kettle?

WT: There are several considerations. For example, understand the capacity requirements and the type of products staff will cook in these units in order to select the right type of stainless steel interior liner. It’s also important to know what type of energy source is available. Will the operation require a mixer? If so, then determine whether a horizontal, vertical or diagonal mixer will be the most appropriate. Service and parts availability also represent another key consideration.

 Steam Kettle Care and Maintenance

Although one of the simpler pieces of equipment in commercial kitchens, steam kettles are regularly subjected to acidic foods, hot water and high temperatures. Collectively, these factors can wreak havoc on units if operators fail to properly maintain them. Below, Rick Sher, director of service at Day & Nite/All Service in New Hyde Park, N.Y., provides tips on cleaning and maintaining kettles.

  • Maintenance should include daily cleaning, such as wiping out the kettle interior and rinsing it with soap and water, then rinsing it again. Clean draw valves on a regular basis, too.
  • Whether gas, steam or electric, it’s important to make sure the kettle’s burner is clean. Periodically blow out the burner or clean it with a wire brush.
  • Keep the regulator that powers it clean and free from debris. And adjust the regulator to ensure proper flow.
  • With tilting kettles, properly lubricate the draw valve. The stopper can sometimes get beat up, but that is replaceable.
  • Use only distilled water within the jacket, or run the risk of rust, which can clog the kettle’s burners.
  • Perform quarterly planned maintenance. It should include checking the pressure and electrical connections, depending on the type of unit, and greasing trunnions on tilting kettles.
  • Signs that indicate a kettle needs replacing include rust buildup, pin hole leaks or signs of rotting on older units.
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