The art of frying

There was a time when the only things that really mattered when buying a deep-fat fryer were how fast it could fry chips and what it cost to buy. Speed of cooking chips is still important, and manufacturers commonly rate the performance of a fryer in "chips per hour" as well as kilowatts of heat input into the cooking oil.

Purchase price is always going to be a buying factor but, as with other items of kitchen equipment, the whole-life cost of a deep-fat fryer is increasingly important. The chips-per-hour rating goes into the buying equation, but so do the costs of the energy and the cooking oil.

Logic says that those with most to gain from better energy and cooking efficiency are the big operators that produce vast amounts of chips across a nationwide chain of units. But according to Nick McDonald, marketing and export director for manufacturer Lincat, while chain restaurants can make huge savings with greater efficiency in frying, smaller operators can also benefit.

"Energy and oil efficiency are just as important to small operators as they are to big ones - in fact, probably more so," McDonald says. In smaller kitchens, operating budgets tend to be tighter and economies of scale harder to find. Fryers may not be in constant use, so minimising heat-up and temperature recovery times, and maximising output, are key issues."

With a product range of 27 deep-fat fryers, running from light- to heavy-duty, Lincat has been looking closely into energy and oil efficiency for the past 18 months. Among the design tweaks it has taken on board is making fry baskets fit more snugly to the fry tank so that energy is not wasted heating oil that cannot be used for cooking.

Thermostats are now designed to react much more sensitively to temperature drops, so energy is not wasted pulling back the frying temperature. The thermostat on a Lincat fryer now kicks in after a mere 2% variation from the setting. On the more powerful fryers, the fry tanks are insulated to reduce heat loss and maximise energy efficiency.

Parry Group commercial director Peter Eglin claims his company's fryers have an exceptional oil-to-tank ratio for a traditional fryer, which means fast heat-up and recovery times and reduced oil usage.

But McDonald says that operators also have a role to play in improving energy efficiency by frying the optimum basket load - neither putting in too little product, which wastes energy, nor overloading, which affects hourly production as well as delivering a poorer product to the customer's plate.

Cooking oil is a large and ever-present cost in deep-fat frying, and it can have a very short fry-tank life. Constant heating would break it down gradually in any case, but frying items such as breaded or battered foods accelerates this process. And when there is salt in the fried item, such as sausages, then the breakdown is very rapid. The tell-tale signs of this are a darkening of the oil, an acrid smell, and a lessening of the oil's ability to crisp fried food quickly.

Another unwelcome feature of frying in oil past its use-by time is that foods being fried will absorb more of the oil.

With so much of the cooking in the professional kitchen now controlled by computers and subject to rigid operational guidelines, rather than being monitored by the expert eye of an experienced chef, there are sometimes few ways of gauging when cooking oil needs to be changed.

While the quality of cooking oil might seem to be the concern not of those who make deep-fat fryers but of those who use them, Valentine has addressed the problem by agreeing a distribution deal for the German-built Testo 265 oil monitor. Looking like a digital thermometer with a probe, this device gives an indication of the effects of oxidation and thus of how "used" the oil has become.

Valentine national accounts manager Malcolm Morris says that oil quality and cost control has, in the past, been very hit-and-miss. "One site I visited had a policy of changing the oil every week, regardless of how busy they had been - they were often discarding oil which was still in good condition," he says. "By properly testing the cooking oil before it was changed, we probably saved that caterer £80 a week."

All well and good, but what has really turned heads in the areas of oil and energy efficiency in deep-fat fryers has been the development of the Infinity fryer by Falcon, the prime cooking division of Aga Foodservice Equipment. Depending on who you listen to, this new fryer either has stood conventional wisdom concerning gas-fired fryer design on its head, or is trading short-term savings for greater oil costs in the medium term.

Falcon is pitting the Infinity against the two world-leading high-performance gas fryers, Frymaster and Pitco, which between them dominate the global fast-food chains. Few doubt the performance levels of Frymaster and Pitco but the Infinity boasts two features that Falcon claims its rivals do not have - first, the way the Infinity mixes gas with air before it goes into the burner jets underneath the fry tank; and second, the absence of a cool zone in the fry tank.

Gas needs oxygen from the atmosphere to combust. There are several ways in which this gas-air mix can be created before it goes into the burners, but most of these have an element of randomness in the mixing, resulting in varying degrees of heat efficiency from the gas consumed. What Falcon says it has done with Infinity fryers is to pre-mix the gas and air in a controlled fashion before it hits the under-tank burners. The optimum gas-air mix is said to produce the optimum heat from the gas.

Gas heating is very intense with a concentrated heat source, while electric heating elements tend to spread the heat evenly. This is broadly accepted, but where the discussion over energy and oil efficiency becomes more contentious is Falcon's claim that the cool zone in gas-powered deep-fat fryers is "dodo" technology.

A cool zone is a feature of most heavy-duty fryers powered by gas. It is a depression in the bottom of the fry tank, usually V-shaped, which is below the heat source. So while it is hot, oil here is below the temperature of the main body of the cooking oil.

With coated food products, there is always a degree of fall-off of coating debris, and current design thinking on high-performance gas fryers says that this will carbonise and destroy the oil more quickly. However, if the food debris is allowed to fall into the cool zone, carbonisation will be much slower and the oil will last longer with good filtration practice.

Falcon's view of the cool zone is that, if you have one, it requires more oil to fill the tank and uses more energy to heat the extra oil. So the company has designed Infinity fryers to have a flat-bottomed tank that needs less oil, and with an internal filtration system which drops hot oil through a filter underneath the fry tank and then pumps it back in a cycle lasting just a few minutes. By regular automatic filtration throughout a busy frying day, less oil and less energy are used, Falcon says, resulting in substantial cost savings.

Not surprisingly, some of the other fryer manufacturers are sceptical of some of the energy and oil efficiencies Falcon is claiming.

David Daniels, European regional sales and marketing director for Frymaster, says that the cool zone concept in deep-fat fryers is tried, proven and trusted technology. Used with suction filtration, he says, it extends the life-cost of cooking oil in a deep-fat fryer.

Daniels adds that even increased frequency of filtration in a flat-bottomed fryer may not be fast enough to stop carbonisation in the cooking oil. "Sediment falling from food products requires just a few minutes to convert the sugars in the food into concentrated carbon at 170¼C, or the even higher bottom-plate temperature of a flat-bottomed fryer," he says. "This carbon is bitter in taste but, more importantly, becomes the catalyst for chemical changes which will degrade the oil."

The gloves are off in the cost-efficiency battle in the deep-fat frying business, but there can be no doubt that the real winner will be the operator.

Contacts
Falcon
01786 455200
Fri-Fri
01246 450255

Frymaster
www.enodis.com

Henny Penny
020 8686 8855

Parry
01332 875544

Valentine
0118 957 1344