Top of the range

It would not be the ideal situation, but it's hard to think of anything on a restaurant menu that could not be produced from a six-burner cooking range with an oven underneath - unless it's ice-cream.

In basic design and appearance the cooking range with oven underneath has not fundamentally changed in 100 years. Gas or electricity has replaced coal as the fuel of choice, but the principle is the same: direct heat to pans on top or surrounding heat in the oven.

Although the fundamentals of cooking ranges have not changed, the technology has. It might be one of the longest-lasting items of prime cooking equipment in a professional kitchen, but the cooking ranges available today are hugely different from even just 20 years ago. The changes are not always obvious to the chef, but in the competitive area of manufacturing and design, performance development and adapting to changing market needs is how to gain a sales advantage.

Chris Syder, product manager for Electrolux in the UK, says the development work done on the Molteni cooking range, an Electrolux brand, shows just how hard manufacturers are thinking about design and performance.

Show cookery

Says Syder: "Traditionally designed one-piece island suites like the Molteni are always going to be wanted for their solid build, performance and - let's be honest - their status among chefs. But even such an icon of tradition as the Molteni has to move on. That's why we have developed a podium version of the Molteni for show cookery in restaurants or demonstration work in colleges.

"Putting an induction wok area in a Molteni might be seen by some chefs as criminal damage to a kitchen style icon, but as a manufacturer of cooking ranges, we have to keep moving forward. But the traditionalists can rest easy as regards the stove - the classic Molteni cooking range is still available."

While electricity tends to be the main energy source in mainland Europe because of the lack of natural gas, when choosing a range in the UK there is a choice between the two fuels. The popularity of gas for cooking ranges in the UK is because there is currently an availability of cheap natural gas. This is a finite energy source, and as supplies begin to dwindle over the next 20 years there will be a switch to electricity. In that countdown time the energy efficiency of the gas burner is going to become increasingly important.

Basic physics implies that all the gas consumed is converted into heat, but that's not true. Gas burner efficiency is about mixing the right amount of oxygen with the gas to provide the maximum heat during combustion.

The easiest way to illustrate this is with the classic classroom Bunsen burner: when the air valve is closed the flame burns soft and yellow with a low heat; when the air valve is opened the flame becomes fierce and blue. The same amount of gas is being consumed by the burner, but the heat output between the blue flame and the yellow flame is hugely different. So technical is gas burner design that many manufacturers of cooking ranges buy in the gas burner as a specialist component.

The spread of the flames is also important in burner efficiency. The most energy-efficient heat transfer from burner to cooking pan is through the base, not the sides, of the pan. Flame should not creep outside the base area. Fitting the right size of pan to the right size of heat source contributes to energy efficiency on both gas and electric hobs.

The CE standard - the manufacturing benchmark for catering equipment to be sold within the European Union - stipulates a minimum performance rating for gas burners; but, as Neil Roseweir, development chef for Falcon Foodservice Equipment, points out, the minimum standard on burner efficiency is a meagre 50%.

Falcon is about to launch completely redesigned high-efficiency burners. "Performance with energy efficiency is the route Falcon are going," says Roseweir.

Any explanation of energy efficiency on a cooking range will be more about science than cooking, but everyone using a cooking range, either gas or electric, should understand the simple science of heat production.

Until a few years ago the heat output in cooking ranges sold in the UK was rated in British Thermal Units (abbreviated to Btu). Metric creep has now seen the Btu replaced by the kilowatt, though some range manufacturers rate power output in both kilowatts and Btu. The other unit of measurement to understand is the joule.

So what does it mean when a gas burner or electric hob is rated in kilowatts, and how can a chef tell from such a figure how fast it is going to cook?

Nick McDonald, marketing and export director for Lincat, explains: "To take a practical example, a 5kW burner will deliver more power than a 3kW burner, in the same way that a 100W light bulb is brighter than a 60W bulb. Similarly, a hob burner operating at 5kW for one hour will consume more gas than a 3kW burner over the same period. A 5kW burner might alternatively be rated as 17,065 Btu/hour [1kW is equivalent to 3,412.8 Btu/hour]."

It's also important to spare a thought for the power of the oven. It's a mistake to assume that provided a low-rated oven is sufficiently powerful to reach the required temperature it will perform in a similar way to an oven with a higher power rating. The more powerful oven will provide a faster return to the target cooking temperature after the door has been opened.

Glossary
The physics that defines the heat output of cooking ranges is complex, but these are the scientific units a chef needs to understand:

• Joule - an internationally recognised unit of energy (or heat).
• Watt - an internationally recognised unit of power. Equivalent to one joule per second.
• British Thermal Unit (Btu) - a measure of the quantity of heat. Since 1956, defined as approximately 1,055 joules.
• Kilowatt - a unit of power equal to 1,000 watts. Equivalent to 3412.8 Btu/hour.

A kilowatt is a measure of power, not energy (which is measured in joules). The mathematical equation says energy = power x time (eg, one joule = one watt for one second).

Contacts

Suppliers of cooking ranges who can advise on energy efficiency include:

Lincat, www.lincat.co.uk
Euro Catering Equipment, www.eurocateringequipment.co.uk Electrolux and Zanussi Professional, www.foodservice.electrolux.com Falcon, www.falconfoodservice.com
Parry, www.parry.co.uk

CESA, the Catering Equipment Suppliers Association, has an explanation of what cooking ranges are and the choices available as part of its free, comprehensive guide to understanding catering equipment. The information is available via e-mail from enquiries@cesa.org.uk.

Types of cooking range

Open-top, four-burner and six-burner

These are either open gas burners or electric radiants with an oven underneath. The most common configuration is for either four or six burners or radiants, but ranges with a greater number of burners or radiants are available for busy kitchens. Their big advantage is fuel efficiency, since almost all of the heat is directed at the cooking pan and not into the kitchen environment to be lost in the air. Direct contact with the heat source also means pans can be heated quickly.

Key points to look for

At least one burner or radiant should be more powerful than the others for fast boiling or heating large pans.

Ease of cleaning, as ranges get very dirty.

Solid top

These have a solid cast-iron top heated underneath either by strategically placed gas jets or electric elements. They will have an oven underneath, the same as an open burner range. Their advantage is that, size for size, they can accommodate more pans than an open-burner range and pans can be moved around from fierce, direct heat to a cooler part of the top. Can be wasteful on energy when areas of the top are left unused.

Key points to look for

Can just part of the top be switched on when just a few pans are cooking, to save energy?

Has the stove got a rapid-heat point for fast boiling?

Boiling table

The top is exactly the same as a standard cooking range, but with a boiling table there is no oven below. This is useful for reducing purchase cost when there is already sufficient oven capacity in the kitchen. The space below is also a convenient storage area for pans.

Island suite

These combine a cooking range with other prime cooking units. Their reputation is for withstanding the most punishing of cooking demands in busy kitchens. Many of the prime cooking functions are brought together in this one unit, which saves on space and allows chefs to control several cooking functions close to hand. There are two types of island suite:

Modular

This system is usually bespoke in construction, with the individual cooking units that a kitchen needs bonded together for a seamless unit. There is a wide range of options, which can include a burner range, a solid top, fryers, pasta cookers, griddles, ovens, griddles, grills, chargrills or induction hobs - in fact, any type of prime cooking process.

One-piece

These are usually built in the factory as a solid cooking suite and, as well as off-the-shelf configurations, bespoke units can be built to order. Since these are modelled in the grand tradition of island suites, they tend to stay with dry heat as a cooking medium rather than offering fryers and water-based cooking options.