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Combi-ovens: Meeting the banqueting challenge

18 August 2005
Combi-ovens: Meeting the banqueting challenge

Banqueting presents extraordinary challenges. Where normal service periods have intensely busy peaks, your kitchen is built to deal with restaurant capacity and diners do not arrive all at once. In banqueting scenarios, they do. And you have to get food on to the tables of eight or more diners in a large room without it going cold.

Increasingly, combi-ovens are seen as the answer, as they have the ability to take chilled, pre-prepared food and heat it quickly. The term "combi" is derived from "combination", an adjective used because these ovens combine dry heat, which is either still or fan-driven, and steam, which is injected into the oven when needed.

Convection heat and steam are found in all combi-ovens, though some makers add other means of heating.

Leventi's Booster units add microwave power to steam and convection, and are claimed to reduce the already impressive cooking times of traditional combination ovens by a further 50%. For example, the company claims its five-grid Booster will cook 20 1kg chickens in 12 minutes or 70 jacket potatoes in 22 minutes.

The combination of dry heat and steam can bring great results for many types of food items because the steam tends to reduce moisture loss - when cooking meat, for example, or vegetables. But it is the combi's ability to regenerate precooked food quickly just prior to service that makes this class of oven such a good choice for banqueting situations.

Hobart UK product development manager Terry Ashmore believes that technology has outpaced tradition when it comes to banqueting. "In the past," he says, "the larger establishments needed plenty of space, an extensive range of equipment and a large brigade of staff. Now, it's much easier, and banqueting systems revolve around a variety of combis and trolleys."

Nick Bates, research and development chef with combi maker Angelo Po, says: "In a banqueting situation, combis are ideal - they're flexible, save time and energy, and cut down on person-hours. You're able to do large numbers of plated, regenerated meals with fewer staff. Banqueting has often meant either badly done silver-service or plated service that has taken resources from other areas. With combis, you need fewer staff, and preparation can be done when it suits you."

But a combi is not a piece of equipment you can simply plug in and use straight away, says Bates. "Suppliers should provide development staff to go through the fundamentals of using a combi with you," he says.

Combis often offer further refinements which can help in busy banqueting situations. Lincat's new range of Opus SelfCooking Centers, for example, features a new finishing mode. This automatically adjusts temperature, humidity, time and air speed to suit the particular food, ensuring that it doesn't dry out or leave pools of water on the plate.

Nick McDonald, marketing and export director of Lincat, says: "With just minutes to go, as the first course is served, the Opus OSC61 is capable of finishing 20 plated meals in just seven minutes. A special thermal hood can then be placed over the rack of 20 meals to maintain food at perfect serving temperature for as long as 20 minutes, while finishing a further two batches. A total of 60 plated meals can be prepared and served at one time."

The combi-oven is one of the most versatile items of cooking equipment any kitchen can have. But because it is versatile - capable of steaming, baking, roasting and dry-frying, for example - it is also relatively complex for a piece of kitchen equipment, so there are a few things it is worthwhile to know.

Because they are able to deal with so many different types of foods, there is a danger of flavour contamination. Everything cooked will deposit its own residual taste in the oven, so a key task in looking after a combi is to keep it clean to avoid flavour transfer.

Many combi-ovens have a pushbutton-operated cleaning function which will wash the oven cavity and take away food residue between cooking cycles. Where you have a number of combis, it is also possible to get mobile cleaning systems which can be wheeled to each oven in turn - and the most important cleaning cycle is the one at the end of each cooking shift.

While they are in use, a kitchen manager should listen for combi-oven doors being slammed - and train staff to close doors firmly instead. Door gaskets will withstand high heat and heavy use, but the flexible material of these seals means that, while they keep the cooking atmosphere in, they do need to be treated with care to avoid unnecessary damage.

Door seals can also get food debris stuck in their folds. An oven's clean cycle will deal with the main oven cavity, but door seals need specially cleaning to ensure food residues don't build up and impair the oven seal.

High-fat foods will deposit large amounts of fat in the oven. Different combis deal with this using various methods. Some channel the fat out of the oven through drains while others have internal collection points. Whichever your combi has, make sure all channels and reservoirs are cleaned out after every shift.

Finally, make sure you have a regular service contract. By their very nature, combis bring together water, heat, electricity and computer circuitry in one box and, if one of these begins to affect another, you could be in for a breakdown at a crucial time. Preventive maintenance can spot problems before they become expensive.

Combi-oven: Do's and don'ts

Do

  • Fit a water treatment system.
  • Check door seals weekly.
  • Clean daily.
  • Close doors carefully.

Don't

  • Trap probes in doors.
  • Cook strongly flavoured foods with delicate foods.
  • Allow fats to carbonise in the cavity.
  • Overload.
  • Leave food debris trapped in door seals.
  • Neglect to clean fat drains.

Source: CESA

Case study: Refusing to chill at Ross Priory
Ross Priory, on the banks of Loch Lomond, is hugely popular for traditional Scottish wedding receptions, with weekends booked two years ahead and midweek weddings becoming increasingly popular with couples.

Owned by Glasgow's Strathclyde University, the venue is also used by the university for entertaining VIP visitors and benefactors with banquets of a standard as high as anything else in the West of Scotland.

With this level of banqueting and function work, the route most chefs would take to delivering consistency and volume of meals would be cook-chill, but the head chef at Ross Priory for the past 10 years, Nicky Shillan, refuses to go down that road and insists on cook-serve and silver service for banqueting work.

Ross Priory has only electricity and no mains gas to cook by. At the heart of banqueting food production are two six-grid Falcon TMS combi-ovens. Shillan says they're capable of cooking virtually everything on the banqueting menu. He has no deep-fat fryer and no salamander, and the only range equipment he has are two electric solid-top hobs.

The way Shillan uses and configures his two combi-ovens is critical to the production of high quality cook-serve banqueting menus.

They are stacked on top of each other and, for most of the time, one is permanently in steam convection cycle and the other in dry heat.

This allows him to roast, bake, steam and gratinée simultaneously. According to Shillan, the evenness of cooking in the Falcon combi-ovens means that even delicate items such as salmon portions are as evenly cooked on the top shelf as on the bottom.

Producing cook-serve banqueting despite the constraints of the kitchen is all about good timing and preparation, says Shillan. "We get everything trayed up beforehand and don't put anything into the ovens until we are close to service," he says.

"I'd rather the food went out a bit late, and was perfectly freshly cooked, than do cook-chill," he adds. "When you have a function like a wedding, the guests don't notice if the main course is 10 minutes behind schedule, but they do notice the high quality of the food we're serving."

Case Study: Converts to cook-chill at Portsmouth Guildhall
Portsmouth Guildhall is a banqueting venue that is steeped in tradition, so switching from cook-serve and silver service to a cook-chill plated service was not a step taken lightly, according to catering manager Clive Marshall.

"We were very nervous about going to cook-chill and plated service," he says. "We do a few big-number banquets in a year, but most of our function work is for local businesses and organisations, where the numbers may be no more than 100 and customers take notice of the food. It's a good banqueting team at the Guildhall, but between us there was limited experience of cook-chill."

The problem the Guildhall was faced with was a familiar one to medium-sized banqueting operations. Despite the best efforts of kitchen and restaurant staff, food temperature on reaching customers was an issue, and getting trained staff to do silver service was becoming increasingly difficult.

So the Guildhall took the decision to switch to cook-chill banqueting and structured the system around a Rational SelfCooking Center.

The Rational SCC 202 has a 40-grid capacity and a door that allows trolleys loaded with plated meals to be wheeled in.

Marshall says the SelfCooking Center delivers great results in cooking and regeneration. "We usually cook the food in the Rational the day before and blast-chill," he says. "The chefs do the plate assembly in a chill room, usually in the afternoon before a function, then wheel in the trolleys for finishing when the starter has been set down.

"Regeneration time is unbelievably fast. It can take 120 chilled plated meals to service temperature in eight minutes. We then put thermal jackets around the trolleys to keep food hot, and service is one table at a time. Food temperature is no longer an issue."

Case study: Complex dishes in a combi, Newcastle Gateshead Hilton
Mike Wilkinson, executive chef at the new Hilton Newcastle Gateshead, is a huge fan of combination ovens. "The concept of these ovens has revolutionised plated functions," he says.

The hotel opened in April 2004 with three Electrolux combi-ovens installed in the kitchens, and Wilkinson cannot sing their praises too highly. "They are so easy to use and operate," he says. "We can prepare the food well in advance, and any alteration of function time can be accommodated - it only takes eight minutes to regenerate 104 plates. Using all three of our ovens, we can easily regenerate a whole function for 500 within 20 minutes."

Such a slick operation in the kitchen obviously has a beneficial knock-on effect in the dining room. "Service is very smooth, with the minimum of hassle," confirms Wilkinson.

On functions for up to 30, just one chef will use the ovens; for up to 200, it's two chefs; and for up to 500, there will be four chefs - two to empty the trolleys and two to sauce the plates.

Wilkinson is quick to point out that, as the ovens are multi-purpose, not only can they regenerate almost all items, but they are used for roasting, steaming or a combination, and are ideal for slow-cooking joints overnight to reduce shrinkage.

The hotel regularly caters for functions for up to 500 people and the menu may be straightforward or more complex, with the challenges facing the brigade - and their use of the combi-ovens - varying from day to day.

A particularly challenging function was a recent Entrepreneurs Forum dinner, where 190 covers were served with roast lamb rump with a rosemary-scented crust.

"The main course was quite complicated, involving a number of stages," says Wilkinson. "We had to make a rosemary mousse around the lamb, and wrap each portion in clingfilm. These were then steamed so that the lamb remained rare and moist. Next, they were pan-fried to crisp the mousse, and then finally regenerated."

Case study: Chilling and cooking in the same device at the Royal Armouries, Leeds
Head chef Gary Calder runs the banqueting operation at the Royal Armouries in Leeds and is a keen convert to cook-chill - in particular, to the nine Moffat Chillogen banqueting trolleys the Armouries have invested in. He wasn't instantly won over, though. "Never seen them. Didn't want them," was Calder's attitude on first sight.

But he has changed his tune. The museum has a number of rooms serving from 10 to 800 covers, and the whole museum can be hired. "Even in a quiet week, we serve around 1,400 meals," says Calder, "but last Christmas we produced over 15,000 in just four weeks."

The Chillogen combines chilled holding and regeneration in the same cavity. Food is blast-chilled then held at a temperature between 2°C and 5°C, then switched automatically to regeneration at a preset time.

"Meals are cooked in our central production kitchen and blast-chilled," says Calder. "On the day of service, we load them into the trolleys' refrigerated compartments and wheel them to the location."

Calder caters for nearly 700 covers at a time in the existing complex with his Chillogen ovens. Investment in 12 more is planned to service the museum's new 1,500-seat banqueting complex, which has its own purpose-built kitchen.

It's important to get to know your machines - to know what they can cook and how long it will take, says Calder. "When we took delivery of our own trolleys," he recalls, "we took a week out to experiment with different cuts of meat, and have designed our banqueting menus around those findings."

An added bonus is that the Chillogens have cut in half the Royal Armouries' need for serving staff, which it has had difficulty in recruiting.
The Chillogen works like a mobile satellite kitchen that caterers can take to their customers. The chef can load the trolleys in the kitchen, rapid-chill the plated food and then move it to the point of service at the function room. Here, at a specified time, it will regenerate its contents, fully automatically and at the place where it is needed for service.

If speeches overrun or guests are delayed, it will keep the food hot and in perfect condition until they are ready.

Technical questions to ask when buying a combi-oven

  • Does the oven have a water-filtration system to remove dissolved salts in the water and prevent scaling?
  • Is there a high pre-heat function to enable fast heat recovery when cold food is put into the oven?
  • How easy are the oven cavity and the door seals to clean, and what self-cleaning features does the oven have?
  • What are the programming features, how easy are they for staff to understand, and do they meet my kitchen needs?
  • Is there a self-diagnostic facility to warn me should something go wrong?
  • Is there a food core temperature probe, rapid cool-down feature or a reversible fan for even heat distribution?

Source: CESA

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