Steam-jacketed kettles can produce greater volumes with increased consistency, while reducing labor for both preparation and cleaning. Here is a quick overview of this type of foodservice equipment. 

Steam-Jacketed Kettles: An Overview

Steam-jacketed kettles utilize steam energy to transfer heat via conduction to the food product inside.

The energy source — electric, gas and direct steam — that operates the unit helps define the categories of kettles available to operators. Direct steam kettles offer greater efficiency, cooking the fastest with the highest capacity as compared with electric and gas models. Kettle sizes range from 5 to 200 gallons, although 40 gallons represent the most common size commercial foodservice operators tend to use.

Stationary floor models typically start with a 20-gallon capacity and go up from there. In contrast, the capacity for tilting floor-type kettles ranges from 20 to 200 gallons. Tabletop kettles accommodate between 1 quart and 12 gallons of product.

While some tilting kettles have a handle, larger models utilize a crank. Stationary kettles include a tangent draw off valve that opens to drain product from the vessel.

The operating pressures of these kettles range from 45 PSI to 50 PSI, which produces an even temperature from the entire jacketed surface of 267 degrees to 338 degrees F.

These units feature either 304 or 316 stainless steel construction. While 304 is designed for general purpose use, such as boiling pasta, the more durable 316 can be a better option if the foodservice operator will prepare highly acidic foods, like pasta sauce, in the kettle.

The majority of kettles are two-thirds jacketed, which means that the unit transfers heat energy not only from the bottom of the kettle, like in a stock pot on a range, but also from the sides. This dramatically increases the surface area for energy absorption into the product. Operators can also purchase fully-jacketed kettles.

Most kettles come with optional accessories as well as features that enhance the operation for specific applications, such as mixers, draw off valves, pan carriers and mixing faucets.

New steam-jacketed kettle features include solid state temperature control with self-diagnostic capabilities. A heat deflector shield can help protect staff from burns.

One manufacturer introduced a new line of two-third jacketed kettles with an improved bottom, which allows for a shallower design.

   How to Know When to Replace a Steam-Jacketed Kettle

Steam-jacketed kettles can last as long as 20 years, depending on usage and care. But here are a four signs that it may be time to replace a kettle.

Leaking: If the kettle's compound gauge does not reside in the "green zone" when cool, this could indicate a leak in the unit. Also, look for visible leaking from the kettle's jacket area.

High repair costs: If an older kettle's repair costs start getting too high, it may be time to consider retiring it and purchasing a new one.

Slower cooking: If the unit takes longer to cook, this could be a main indicator that the kettle either has a leak or a failure of the heating element. Both instances indicate a new kettle might be necessary.

Material breakdown: Inner liner pitting and/or external stress fissures, which may occur from heavy use or acidic foods, may indicate the end of a kettle's service life.

   Steam-Jacketed Kettle Applications

Depending on the size and application, steam-jacketed kettles can be used in both the front and back of house for a wide range of tasks. Here are a few of the many ways foodservice operators use steam-jacketed kettles.

The types of foods operators commonly prepare in these units include soup, sauces, stocks, pasta, gravy, stew, meat, beans, rice and desserts.

Although operators typically use steam-jacketed kettles to slow boil and simmer food, these units can be effective in reducing liquid in stocks, beans and soups.

Operators can also incorporate kettles in a cook-chill line for rethermalizing or chilling food, the latter with use of a cold water line connection.

Large governmental, institutional and commissary facilities often use large kettles with pumps, vacuum bagging and a variety of different chilling methods to produce thousands of prepackaged product that can be shipped to satellite facilities for use.

Mixer arms also are available as an attachment for some units to stir product in the kettle during large batch cooking. 

   Maintaining a Steam-Jacketed Kettle

Proper cleaning and regular maintenance can help extend a kettle's service life. Here are nine maintenance tips to help foodservice operators get the biggest return on their investments in steam-jacketed kettles.

  • Use non-caustic cleaners when washing and sanitizing these units each day. Refrain from using such items as chloride detergents, steel pads, wire brushes and scrapers.
  • Regularly lubricate the trunion bearing and test the pressure relief valve every six months to ensure proper operation.
  • Promptly replace missing screws in the control cover to ensure water tight seals and reduce the chance of water infiltrating the control box.
  • For kettles with a marine latch, make sure it works properly and is not clogged with starch or other sticky food products.
  • The compound gauge should be checked before use to make sure it is in the "green zone" and not in the "vent air zone".
  • Replenish internal hemi water with distilled water and liqua-phase rust inhibitor or equivalent product when required.
  • Change any steam seals on direct-steam kettles once a year or as required by use.
  • Periodically check for any pitting or stress fissures as well as any possible leakage.
  • Refrain from spraying water directly or indirectly on electrical or gas components during cleaning.

   Energy Efficiency and Steam-Jacketed Kettles

Newer kettle technologies are more energy efficient and can save operators money over the long term.

Kettles are more energy efficient than alternate cooking methods, due to the transfer of steam energy via conduction and the increased surface area gained by the lined jacketed construction.

Additional options are available per individual manufacturers specifications for digital temperature read outs as well as food cooling in some instances.

Kettles also are available with better ergonomic designs for easier use.