National Chain's Oven Challenge II
GFEN Tests Convection Ovens for QSR Chain
by Tom Stroozas - CFSP, RCGC, CFE
Manager - Commercial Marketing Piedmont Natural Gas

---

Figure 1 Biscuits were held for 30 minutes.

As promised last month, we will now move into the final installment of this three part series and discuss the recent findings from a GFEN test conducted at the Piedmont Natural Gas Test Kitchen for a national QSR chain headquartered in the southeast. Our focus this month is on the latest gas vs. electric convection oven tests.

Since one of this client's signature products is produced by baking, they 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?

The convection oven evaluation was conducted using a single product, yet one that the operator deemed essential to the chain's continued success as a leader in their market sector - homemade buttermilk biscuits. The challenge involved four popular brands of half-size convection ovens. The client chose to test both electric and gas units. The end results came as a surprise when their convection oven fuel of choice for over twenty years was proven to be a poor choice with a significant detriment to that most important bottom line!

Gas Ovens Improve Product Quality

The 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. (see figure 1) Hedonics were recorded at various stages of the hold cycles. From previous issues you will recall that by hedonics we mean the subjective quality of the product itself. In an effort to better diagnose these factors, we developed a chart that allowed for a quick appraisal in areas of the exterior color to internal moisture, texture and most importantly, taste. (see figure 2)

Figure 2

Hedonically, the biscuits produced in all of the gas ovens were similar as far as the crust and texture attributes were concerned. Gas oven D ultimately produced a true benchmark product (see figure 3) but used nearly three times the energy of gas unit B. (see figure 4)

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. (see figure 5) 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!

Figure 3 Benchmark Biscuits

Gas Combustion is the Secret

What is the secret to the success of the gas equipment? No 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 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! 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.

Figure 4 Energy Consumption

Figure 5 Gas-baked biscuits were softer with a higher internal moisture content.

Reprinted with permission from Cooking For Profit May 2004