While at the Piedmont Natural Gas Test Kitchen, we conducted a GFEN test for a national QSR chain headquartered in the southeast. This QSR chain’s signature products are chicken and homemade buttermilk biscuits, which led us to perform fryer and oven tests. In keeping with tradition, we shall leave the operator anonymous.
In the case of the gas vs. electric fryer test, the client wanted information to make a substantiated and intelligent choice when it comes to selecting fryers for their foodservice operation. In the case of the oven test, the client elected to evaluate their current brand of convection oven against some of the other popular and well-respected brands available on the market today. Considering that their fuel choice for convection ovens has been electric, could a gas-fired alternative win this challenge to become their future oven of choice?
Fryer Challenge and Results
The fryer test featured four popular brands of 18- and 20-inch gas and electric fryers specified by the client, one of which might not have even been in the game had it not been for the results of the GFEN Annual Fryer Challenge that we conducted on behalf of the gas industry in May 2003. The cook process this time was for a single product: fresh fried chicken!
We ran a total of 74 tests to collect the data necessary to properly evaluate overall runtime energy consumption, cold start to cook temperature time and various load recoveries. Although these factors are all different, they all interact when evaluating which fryer will cook the most product in a given time period, with the lowest energy consumption and oil loss.
We also evaluated the hedonics of the finished product. From previous issues you will recall that by hedonics we mean the subjective qualities such as color, texture and taste of the product. In an effort to better diagnose these factors, we developed a chart that allowed for a quick appraisal in areas from the crust to the meat itself (see Figure 1).
An important part of the testing was the evaluation of the products’ internal temperatures (remember, poultry products must be cooked to a minimum of 165°F internal temperature for safety integrity) for all four pieces of chicken products: breast, wing, thigh and leg.
The gas fryers all had varying inputs, ranging from 72,000 BTU/h – 120,000 BTU/h for the 20-inch models and 65,000 BTU/h – 110,000 BTU/h for the 18-inch units, for a total of six gas fryers. There were only two electric models selected: a 20-inch unit at 20kW and an 18-inch unit at 22kW.
During the cold start-ups with both fuel sources, we noted some surprising results. The gas models got up to the 340º F cook temperature with times varying from Fryer B’s 14 minutes (the fastest) to Fryer D’s 58-minute snail’s pace (see Figure 2). The two electric models took from 14 minutes to over 50 minutes so cold start-ups were fairly comparable between the gas and electric units.
The dramatic difference was in terms of energy cost. Due to electricity’s demand factor, the electric fryers cost more to start up. Looking at it from a pure cost view, the fastest gas fryer cost 23 cents to get up to cook temperature versus 29 cents for the fastest electric unit. (Gas cost was calculated at 95 cents/therm, electric cost at 7.5 cents/kwh). This equates to a 26% savings with gas fryers (see Figure 3)!
The actual cook tests reflected similar variances. Protocols called for cooking light loads (20 pieces), medium (40 pieces) and heavy loads (60 pieces) of fresh breaded chicken at 340°F in a free float for 11 minutes. The product was then held under heat lamps for 30 minutes with hedonics recorded at various stages of the hold cycles.
After a one-hour cook cycle, we noted the energy consumption for the 20-inch models and compared them to the start-up times which showed that although Fryer B got up to cook temp first, it came in third place in the overall cook cycle energy consumption. Point being, the first horse out of the gate may not always be the first across the finish line. In this case, Fryer A, the fryer with the highest BTU input, did the most efficient job in the energy category (see Figure 4). Fryer A got the best energy use marks in the 18-inch category as well.
Hedonically, the chicken produced in all the gas fryers was similar as far as the crust and meat attributes were concerned, except in the heavy cooking loads. Here is where Fryer A really took the lead with its virtually instant recovery and steady cooking curve. It was obvious that this fryer could not only produce consistency in heavy load situations, but because of the steady cooking curve, produced a product that was still palatable and sellable (after the 30-minute hold) to the client’s customers. Similar results were noted with the competing electric fryers, but with higher energy costs. Of particular interest was a noted difference with chicken cooked in an electric fryer as being noticeably greasy after the 30-minute hold.
Oven Challenge and Results
The oven test protocol established a 6-minute bake at 375ºF in both the electric and gas units. The four gas ovens all had varying inputs, ranging from 25,000 BTUH – 60,000 BTUH. The four electric models varied as well, from 5.5 kW – 8.0 kW.
We ran a total of 115 tests to collect the data necessary to properly evaluate overall run time energy consumption, cold start to cook temperature time and various load recoveries. Although these factors are all different, they all interact when evaluating which oven will cook the most product in a given time period, with the lowest energy consumption and minimal sheet pan rotation. The more rotation steps one can eliminate, the lower your labor costs per pan. Food costs can also be reduced due to improved product consistency and reduced overcook waste.
Protocols called for cooking light loads (1 pan), medium loads (2 pans) and heavy loads (3 pans) of proofed buttermilk biscuits at 375ºF for 6 minutes. During the measured one hour cook tests with both fuel sources, we noted some surprising results. The gas models got up to the 375ºF cook temperature with times varying from Oven C’s 12 minutes (the fastest) to Oven D’s 27 minutes. The electric models took from 6 minutes (the fastest overall) to over 20 minutes. The primary difference was in the higher electric energy cost due to the electric demand charge factor.
Looking at it from a pure cost view, the gas oven costs during the one-hour test ranged from $0.15 – $0.43 cents per hour and the electric ovens ranged from $0.30 – $0.37 per hour. Simply put, this test showed that the most energy efficient gas convection oven cost 50% less to operate than the most energy efficient electric convection oven (based upon gas cost at $0.95/therm, electric cost at $.075/kWh).
Once pulled from the oven, the product was held under typical holding lamps for up to 30 minutes. Hedonics were recorded at various stages of the hold cycles. Hedonically, the biscuits produced in all the gas ovens were similar as far as the crust and texture attributes were concerned. Gas Oven D ultimately produced a true benchmark product but used nearly three times the energy of gas unit B (see Figure 5).
It was during the holding phase that a significant difference in the electric bake vs. the gas bake was noted. Biscuits baked in the electric ovens were internally drier and the external surfaces were somewhat hard. The gas-baked biscuits were significantly softer with a much higher internal moisture content.
This increased moisture enabled the biscuits to stay under the holding lamps for approximately 45 minutes instead of the standard 30 minutes. In other words, the gas convection ovens increased product shelf life by 50%. And overall, the gas oven biscuits held up to 50% longer under the holding lamps, affording the client to minimize food waste and labor costs. A significant factor to that ever-important bottom line!
Gas Combustion is the Secret
What is the secret to the success of the gas equipment? Well, there’s no real secret. It’s just that the by-products of gas combustion are carbon dioxide and water vapor. In most gas convection oven technologies, the by-products of combustion actually flow through the oven cavity prior to exiting the flue. This process gives gas baking a moister heat, contrary to the electric process that simply bombards the food products with a dry and direct heat that tends to produce a much drier product and, as this test proved, a product with a significantly reduced shelf life!
The end results of this challenge provided the client with the information needed to make a substantiated and intelligent choice when it comes to selecting fryers and ovens for their foodservice operation.
By making the switch to gas convection ovens, the client would be able to minimize food waste and cut the labor costs required to make the biscuits and most importantly, they will be able to serve a more consistent and superior product to the customer! In the case of choosing fryers, the challenge provided the client with the information needed to make a substantiated and intelligent choice for their foodservice operation. Once again, as this test proves, gas gives you more for less!
If you are interested in learning more about this particular test or how GFEN can assist you in evaluating your cooking equipment, log on to www.gfen.info and look for the test facility directory of participating natural gas companies.