Cold fire
FEW cooking processes have been as theatrical as induction. Since the early 1980s, chefs at catering shows have amused visitors with demonstrations akin to conjuring tricks, tucking five pound notes under simmering saucepans to retrieve them intact, and placing hands inches from intensely hot cooking.
It looks as if all that showmanship may at last be paying off. Induction's unique heating principle - where energy is transferred directly to the pan itself - has yet to make much impact in the kitchen, but it is leading a revolution in front of house cooking.
A growing number of large self-service restaurants are building induction hobs into their main serveries, with a chef cooking and pan-finishing individual dishes inches from the customer's tray.
Unlike other forms of display heating, induction tops stay cool so risks of customers burning their hands are minimised. At the same time, the smooth, one-piece glass-ceramic top looks smart and remains clean, while the front of house area stays a lot more comfortable for staff and customers.
"The power is there when you want it and the heat is in the right place," comments Athol Dipple, divisional manager at the BhS fashion retailing chain, which has now installed induction-based front of house cooking at three of its public restaurants and expects to convert more of its 88-strong chain.
The hobs, typically installed as four single units built flush with the front counter and with a further double hob on the back-bar, are used for pan-cooking jobs, from finish-cooking sauced dishes like beef in pizzaola sauce - in single and multi-portion quantities - to soup, pasta and vegetables.
Costs
Mr Dipple concedes that the hobs are relatively costly compared with conventional boiling tops; the list price of a two-ring Frialator Cuisine Induction of the type used by BhS is just under £3,300. "But you have to weigh that against the energy saving," he points out.
In this respect, induction wins hands down. Transfer of energy to the pan is all but instant, with none of the 20-minute wait for heat-up encountered on conventional, solid top ranges. At the same time, chefs cannot waste energy and fill the place with heat by leaving the hob on all day. Induction power switches off as soon as the pan is removed.
A study by the School of Food and Accommodation in Dundee confirms the savings potential. A meal for 10 was found to need 49% less energy when cooked by induction compared with a conventional electrical-resistance hob.
Caterers seem to be getting the induction message, at least in terms of installing hobs to add to front of house "theatre". The Pavilion motorway service chain uses induction for pasta and stir-fry dishes, while some Jarvis Hotels use hobs to cook hot breakfasts to order.
Yet this ingenious technique has yet to really break through where it counts most: in the kitchen. The first induction hobs predated the combi-steamer, which has since become a virtually standard kitchen fixture, with at least 20 makes competing for attention. By contrast, only a few companies are marketing induction hobs.
Why has it been such a struggle? Relatively low power ratings and prices as much as three times those of conventional boiling tops did not help in the early days, but availability in the past year of hobs offering 5-6kW per ring (which is thought to equate to 9-10kW on a conventional hob) has been accompanied by more competitive pricing (see panel, right).
improvements
There have also been design improvements, notably infinitely variable power control plus more convenient ways of displaying the level visually to the chef. Frialator hobs have a 0-9 illuminated scale visible through the glass, and the latest Moorwood Vulcan induction hobs have a circle of diode lights around each ring, which also help chefs position pans correctly on the stove.
The level of controllability has been particularly attractive for chefs dealing with delicate sauces, as Dorothy Wright, catering advisor at Nestlé UK in Croydon, Surrey, has found in the company's hospitality suite. "You can have it just on the simmer or, conversely, a very intense heat," she points out. The kitchen's two Moorwood Vulcan induction hobs serve both for cooking and bain-marie holding.
Safer
As well as keeping the cooking area cool, the minimal heat output also has safety implications. "One of our cooks slipped on the wet floor recently and burned his hand when he grabbed at the top of the stove," comments flight sergeant Jim Wright, senior chef at RAF Finningley air base near Doncaster. If he had fallen on one of the kitchen's two induction hobs, the injury would have been far less serious, Wright suggests.
However, chefs have to be alert when using induction because of its speed. "As my chef says, it does a three-minute egg in two minutes," Wright remarks. "Even with a pan which is bigger than the ring you can boil a gallon of water within eight minutes. You definitely won't do that on a solid top," he says
Induction's impact is not just affecting cooking speed. The notion of the range as an immovable cast-iron monument in the middle of the kitchen is beginning to change, too. The Bonnet Induc 3 single induction hob, for example, is portable. Weighing 14kg, it is sufficiently small and self-contained for a chef to use on counters, tables, trolleys or wherever else cooking is needed.
glass top
Undoubtedly, many chefs remain sceptical about the effects of banging pans around on a flat glass top.
Such concerns are not, of course, exclusive to induction; commercial ceramic hobs are now available with halogen, infra-red, high-speed metal elements and enclosed gas burners, and there is also a small but growing choice in glasstop griddles.
Commercial ceramic hobs have toughened glass to a depth of 5-6mm, compared with 2-3mm on a domestic ceramic hob, so they should be capable of withstanding most chefs' treatment.
But accidents can happen. The main kitchen at the National Theatre on London's South Bank has twice broken an induction hob top since installation in 1988. On one occasion a chef dropped a heavy pot on its edge on to the top, while on another, a large porter put his knee through a top when he climbed on to it to clean above it.
Such damage might sound pretty catastrophic but repair was not overly complicated or expensive, according to head chef Melvyn Schnable. A new sheet of toughened glass was sealed in place and the top was ready for use after a few hours.
Servicing
The main reservation expressed by longer-term users concerns the relatively sensitive electronics. Many problems which dogged early models of induction hobs appear to have been rectified, including spread of the energy field beyond the cooking ring, which led to electrical shorting between zones if a saucepan was wrongly placed on the top. But circuits, fuses and transformers can still blow unexpectedly.
Paul Smith, manager at the BT Tower in central London, which handles private lunches, dinners and buffets for up to 90 people, has had a small induction hob for more than five years and has experienced a number of problems since the three-year warranty ended.
Because it is totally electronic, the hob either works or it doesn't. Smith has found it both difficult and expensive to repair, with only one company in the London area - Enfield Technical Services - able to handle the work, with the hob typically having to go to its workshops rather than be fixed on site. Despite these problems a new hob of similar type and make - Bonnet - is on order.
Newcomer
"Reliability has been a real bugbear with this type of technology," comments Malcolm Snowball, an electronics engineer with years of experience with catering equipment as technical director of WM Still and operations director of the Viscount Group. He is now heading a new venture called Induced Energy which plans to launch a range of hobs and drop-in chassis this year. The chassis will be offered to cooker and counter makers, opening the door for mainstream appliance makers to introduce induction hob options.
Snowball claims that his designs gain from the rapid rate of electronic component development in terms of prices and reliability. He also claims to have cracked two specific problems associated with induction. First, there will be no need to buy special induction pans; any flat-based pan with a ferrous content will suffice and even copper and aluminium pans may be a possibility on a patented system which he is currently investigating.
This means units have an automatic power control which ensures that for any given setting the power absorbed by the pan remains constant irrespective of pan size or material. The hobs also detect if a pan boils dry and switch off automatically.
Second, the problem known as "hetrodyning" - an annoyingly high-pitched whine caused by mechanical vibration of two or more pans on an induction hob - is "completely eliminated", he claims. o
