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Griddles

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The griddle is the workhorse of the fast food industry. Nearly every commercial cooking operation uses some type of griddle.

A griddle is simply a flat metal plate that cooks food by conducting heat directly from the griddle surface to the food product. A thin layer of cooking oil or grease from the cooked item usually separates the food from the griddle surface to keep the food from sticking. Griddles are used to cook a variety of foods including: bacon, eggs, chicken, hamburgers and steak. Some also like to use the hot griddle surface to heat food in a small pan, like melting butter.

Some griddles are equipped with a platen placed a few inches above the griddle surface to provide additional cooking from above. This add-on cooks the top surface of the food by exposing it to radiant heat energy, cooking the food faster and sealing in the juices for improved taste and reduced shrinkage.

Griddle types

Two major types of griddles are available: single-sidedand double-sided. Single-sided griddles cook food on the bottom only. Double-sided griddles cook food on both sides simultaneously.

Single-sided griddles

A single-sided griddle can be installed as:

  • a built-in unit
  • part of a range or cooking center
  • a free-standing unit that sits on tubular steel legs
  • a portable unit mounted on a stainless steel mobile stand.
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Heavy duty griddles are usually free-standing. The cooking surface typically range from 30 to 36 inches deep and up to 72 inches wide. Often, two or more free-standing units are installed side-by-side, or back-to-back.

Counter-top griddles are small, free-standing units, normally located on a countertop or in a counter base. They range from 15 to 24 inches deep and from 15 to 72 inches wide.

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Double-sided griddles

Double-sided griddles heat food from both the top and bottom. They have a large bottom griddle plate and at least one platen on top. Platens press on the food, "sandwiching" it between two hot pieces of metal. This allows food to be cooked on both sides simultaneously. Stop devices on the platen keep the food from being crushed. A counter-balanced lift holds each platen in place when raised.

A double-sided, non-contact griddle has a plate on the bottom and at least one platen on top. However, a non-contact griddle's top platens do not actually contact the food. The "hood" stays about one inch above the food, heating like a broiler. The heat source may be a gas burner, conventional electric elements, quartz lights, or a ceramic infrared burner.

A double-sided griddle cooks food very quickly. For example, 8 to 12 hamburgers cook in roughly 3 minutes. The double-sided, non-contact design eliminates the need to turn food for uniform cooking, which can reduce labor costs.

Comparing electric vs. gas griddles

There are many factors to consider when selecting a griddle: initial cost, food preparation productivity, ease of operation, heat generation in the kitchen, and whether electricity or gas is used as the energy source. However, consider that energy only accounts for 3 to 5 percent of a typical food service establishment's total costs. Therefore, while one fuel may be less expensive in a BTU to BTU comparison, the best choice in cooking equipment is the one that minimizes total operating costs, not just energy costs. Features that reduce labor costs or result in higher food product yield will nearly always outweigh any energy considerations. Make sure that you include all of these factors in any equipment evaluation.

Therefore, when comparing gas an electric models, compare equipment that is similar in all ways except the energy source.

Advantages of electric griddles

In general, electric griddles offer these advantages :

  • More uniform temperature across the surface of the griddle, which makes electric griddles easier to operate and produces consistent food quality.
  • Thinner griddle plates that use less energy and about half the time to preheat.
  • More efficient operation with less heat loss into the kitchen, lowering kitchen cooling costs and reducing maintenance.

A recent new electric technology is the induction griddle on which the griddle surface is heated by a magnetic field inducing electric currents across the griddle plate. This produces a more uniform surface temperature and brings the griddle surface up to cooking temperature very quickly, saving money, rejecting less heat to the kitchen, and producing a more consistent food product.

Energy usage

Single-sided electric griddles normally consume 3 to 25 kW of power. The average preheat time can range from 7 to 20 minutes depending on the plate configuration and BTU input. Energy consumption for gas single-sided griddles normally approaches 20,000 to 30,000 BTUs per 12-inch section, with preheat times of 15 to 23 minutes. Again, these figures depend on plate configuration and BTU input.

A low energy input figure generally implies slow pre-heat and recovery time. Typical kW consumption for the electric double-sided griddle ranges from 21 to 35 kW, with a preheat interval of about 18 minutes. Typical ratings for gas powered double-sided griddles range from 90,000 to 140,000 BTUs, with preheat times of 18 to 23 minutes.

Energy and money saving tips

Here are a few common-sense operating tips that save money:

  • Heat only the griddle sections necessary for a task.
  • Pre-heat only until the griddle surface has achieved the correct cooking temperature.
  • Set the temperature for each section no higher than that required to cook the food.
  • Turn the griddle down or off during slow production times.
  • Use pre-cooked foods and avoid frozen products where possible.
  • Use a cover while cooking where it will not adversely affect the cooking process.
  • Scrape the cooking surface between production intervals. Cleaning some types of griddle surfaces requires special tools. Consult the manufacturer or owner's manual for details.
  • Clean the griddle frequently, and always re-season the griddle afterwards.
  • Inspect each section of the griddle periodically, searching for hot or cold spots.
  • On gas units, make sure each gas flame burns blue and adjust the gas-to-air ratio when necessary.
  • It takes 77 BTUs to heat a pound of ground beef from 40°F Fahrenheit to 140°F, but 196 BTUs are used to heat the same pound of beef from 0°F to 140°F. Therefore, simply thawing food before cooking can increase energy savings.

Heat loss issues

Griddles are among the largest energy users in food service, so energy efficient operation is an important way of reducing operating costs. Most of a griddle's operating costs arise from heat loss from the bottom, the top, and the four edges of the cooking surface. In addition, cooking surface losses are increased due to the relatively small quantities of food typically cooked on the large surface during most of the day.

Heat lost from a griddle warms the kitchen, which makes workers uncomfortable unless the cooling system removes the excess heat. These losses can therefore add greatly to overall cooling costs, which is an important factor favoring electric griddles over gas units. Even if a kitchens is not air-conditioned, so cooling costs are not an issue, worker productivity and morale suffer as room temperatures rises, increasing costs through lower worker performance and increased turnover.

Many higher quality griddles are designed for improved energy efficiency, partly through the use of newly developed griddle plate surfacing. These improved surfaces restrict the griddle's normally excessive radiation of energy. In full-load cooking tests, griddle efficiency ranges all the way from 31% to 71% depending on model. Griddle inefficiency is most evident in light-load cooking operations, where efficiency ranges from 13% to 50%.

Griddle components

Components

Griddles come in many sizes and may be freestanding or built into a range body with ovens below. Generally, the griddle surface is divided into 12-inch sections, each with its own heating unit and control mechanism. This design lets different sections operate at different temperatures, so the chef can cook different kinds of food at the same time.

All griddles have at least one thermostat dial that controls the cooking temperature. Some griddles also have surface temperature indicator lights that are typically located on the control panel. Gas griddles have slotted vents for each burner for the intake of combustion air.

Griddles normally have a metal splash guard surrounding all but the front of the cooking surface. The splash guard keeps food from sliding off and minimizes grease splatter. A grease trough, usually running along each side of the griddle plate, drains grease and residual food particles, depositing these wastes into a collecting pan. Grease troughs may also be located on the front or back of the griddle. Some griddles have a slightly tilted griddle plate that causes grease to run off. These units also usually produce less smoke while cooking.

The cooking surface of a single-sided griddle is called a plate and its design dictates the performance of the griddle. High quality plates distribute heat uniformly across the griddle. The most common griddle plate is made of flat steel or cast iron and ranges in thickness from one-half to one inch.

Griddle surfaces are usually smooth and flat, but some types of griddles have ribbed or grooved surfaces. Grooved surfaces are designed to emboss food with charred grid marks, similar to broiled and grilled foods.

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Ribbed surfaces cook somewhat slower than flat surfaces because only the parts of the food that touch the raised edges of the grooves are exposed to full heat. For this reason, manufacturers usually install a grooved surface on only a single section of the griddle, with remaining sections equipped with a flat plate for total direct-contact cooking.

Griddle operation tips and issues

General operation

Griddles can operate between 200° and 550°F, but cooking temperatures normally fall between 225° and 375°F. Most units preheat to their thermostatically controlled cooking temperature in 15 to 30 minutes.

Griddles are usually turned on at the beginning of the cooking day and left on all day. This arrangement wastes significant energy if the unit is only used occasionally. This practice is common because griddles take a relatively long time to preheat; it can be impractical to turn off the unit when its not being used. In addition, food service operators like to have the griddle cooking capacity in reserve and so they will rarely turn it off until the end of the cooking period.

Performance

Griddle surfaces often develop hot spots and cold spots. Hot spots usually occur near the heat source while cold zones occur in areas farthest from the heat source. Food cooks faster in hot zones and may be difficult to control because of the higher heat. Some griddles develop a cold zone around the perimeter, about two inches wide, which is not useful for cooking but can be used to keep cooked food warm.

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An experienced chef knows where hot and cold zones are and can adjust the cooking approach accordingly. However, most griddle operators, especially in fast food restaurants, are not this experienced. They fail to adjust cooking times to account for hot zones and cold zones, cooking everything for the same amount of time. This results in inconsistent quality, with some food under-cooked and some over-cooked.

Good griddle design can minimize changes in surface temperature across the griddle and help maintain consistent food quality. These units also reduce the amount of training needed for new griddle operators.

Maintenance

Griddle surfaces should be cleaned regularly. A clean griddle surface offers more uniform heat distribution and operates more efficiently. A clean griddle also prevents the bitter taste of charred food in the final food product.

Griddle operators should:

Scrape excess food and fat particles from the surface with a flexible spatula, grill brick, or other device after each cooking load.

Clean and wipe out grease troughs, remove any stuck-on food, and clean the surface with a soft cloth, rubbing with the grain of the metal while the surface is still warm. This should be done at least once a day and more frequently during heavy cooking loads.

The platen on a two-sided griddle can often be much harder to clean. Some models have stainless steel platens that make cleaning easy. Others have a special coating like Teflon to prevent food from sticking. A few models use disposable non-stick paper to prevent sticking.

For more information about the benefits of electric griddles vs. gas, please contact us for a copy of an EPRI performance or ventilation report.

Electric and gas griddle ventilation study

Ventilation study

As part of a larger study to identify optimal designs for commercial kitchen appliances, researchers tested one electric griddle and one gas griddle in operation with two hood types: an exhaust-only, wall-mounted canopy hood and a custom-engineered backshelf hood.

These tests revealed the following:

  • The cooking capture and containment (C&C) flow rate under a canopy hood for the electric griddle is 241 scfm/lf, 13% lower than for the gas griddle, 40% lower than the 400 scfm/lf building code value, and 7% lower than the 260 scfm/lf Underwriters Laboratories (UL) listing.
  • The cooking C&C flow rate under a custom-engineered backshelf hood for the electric griddle is 100 scfm/lf, 9% lower than for the gas griddle, 67% lower than the 304 scfm/lf building code value, and 26% lower than the 136 scfm/lf UL listing.
  • The idle C&C flow rate under a canopy hood was 26% and 32% less, respectively, than the cooking C&C flow rate for gas and electric griddles, and was 0.5% and 22% less, respectively, under the backshelf hood.
  • At the cooking C&C flow rate, the electric and gas griddles required about 60% lower flow under the backshelf hood than under the canopy hood. These results indicate that custom-engineered backshelf hoods can operate with exhaust flows about 65% below code values, and that electric griddles with both hood types require about 10% less exhaust than gas units. Designers should apply site-specific data when evaluating equipment options.

Background

To help electric utilities and the food service industry minimize commercial kitchen exhaust hood operating costs, EPRI is undertaking a series of tests to determine the exhaust requirement for a wide range of food service equipment and ventilation hoods. The exhaust requirement is the air flow needed to capture and contain cooking products and heat. Findings compare actual exhaust requirements with building code and UL levels. The ventilation tests described here examined electric and gas griddles operating under a wall-mounted canopy hood and under a custom-engineered backshelf hood using American Society for Testing of Materials (ASTM) standard method production conditions.

Test Equipment and Conditions

Both griddles measured 28 in by 3 ft. The electric griddle was rated at 17.1 kW and the gas griddle at 90,000 Btu/h.

The canopy hood, an exhaust-only, wall-mounted type, was 5-ft wide by 4-ft deep and UL listed at 260 scfm/lf for cooking operation. The backshelf hood, a custom-engineered, exhaust-only type, was 3.4- ft wide by 3.5-ft deep by 5-ft high and was UL listed at 136 scfm/lf for cooking operation. Both hoods had three nominal 20-in by 20-in standard baffle filters.

For each test, researchers positioned the griddle under the hood in accordance with ASTM F1275-95 and performed the tests using ASTM F1704-96. The temperature of the griddle was set to a calibrated 375°F.

The project team evaluated C&C with visualization techniques aided by a smoke generator. They ran each test a minimum of three times in a consecutive series to attain statistical certainty as prescribed in ASTM F1704-96.

Results

Figure 1 shows C&C flow rates for electric and gas griddles operating under both canopy and custom backshelf hoods, as well as flow requirements under two specification options. Operating under a canopy hood, the electric griddle's measured cooking C&C flow rate is 241 scfm/lf, 40% lower than the rate required by building codes and 7% lower than that listed by UL. The idle C&C flow rate is 165 scfm/lf, 32% lower than the cooking rate. The gas griddle's measured cooking C&C flow rate is 276 scfm/lf, 31% lower than the rate required by building codes and 6% higher than that listed by UL. The idle C&C flow rate is 203 scfm/lf, 27% lower than the cooking rate.

Operating under a custom-engineered backshelf hood, the electric griddle's measured cooking C&C flow rate is 100 scfm/lf, 67% lower than the rate required by building codes and 26% lower than that listed by UL. The idle C&C flow rate is 78 scfm/lf, 22% lower than the cooking rate.

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The gas griddle's measured cooking C&C flow rate is 110 scfm/lf, 64% lower than the rate required by building codes and 19% lower than that listed by UL. The idle C&C flow rate is 109 scfm/lf, 0.5% lower than the cooking rate.

References

  • Commercial Kitchen Ventilation Performance Report, Electric Griddle Under Canopy Hood, EPRI TR-106493-V4, July 1996.
  • Commercial Kitchen Ventilation Performance Report, Gas Griddle Under Canopy Hood, EPRI TR-106493- V3, July 1996.
  • Commercial Kitchen Ventilation Performance Report, Electric Griddle Under Custom Engineered Backshelf Hood, EPRI TR-106493-V6, July 1996.
  • Commercial Kitchen Ventilation Performance Report, Gas Griddle Under Custom Engineered Backshelf Hood, EPRI TR-106493- V5, July 1996.
  • Too Much Hot Air: Reexamining Commercial Kitchen Ventilation Systems, EPRI TB-105709, October 1995.
  • Minimum Energy Ventilation for Fast Food Restaurant Kitchens, EPRI TR-106671, July 1996.
  • Standard Test Method for Performance of Commercial Kitchen Ventilation Systems, ASTM F1704-96.
  • Standard Test Method for the Performance of Griddles, ASTM F1275-95.