Deep-fat fryers are a feature of just about every professional kitchen. They are one of the most basic items of prime cooking equipment, but are badly in need of a public relations makeover. There's a widespread perception that they produce unhealthy food and are responsible for most of mankind's health problems, from acne to obesity.
True, a diet based on deep-fried food could contribute to health problems, but so could too much sugar, too few vitamins or, in the case of King Henry I, a surfeit of lampreys.
Deep-fat frying is one of the ancient methods of cooking, alongside baking, boiling and the barbecue. While water will raise the cooking environment to only 100°C, oil can successfully cook food up to 180°C, the temperature at which most frying is done. This transfers heat to thin or porous food items much faster than boiling water. An additional effect of this high heat is to cause the surface of food to blister and shrink, forming a crisp seal that inhibits the penetration of an excess of oil.
The high temperature of deep-fat frying has one big disadvantage - the outside of the product can be cooked before the inside. This brings obvious health hazards with both cooked and uncooked products.
While a lot of chilled and frozen foods are cooked at the optimum crisping temperature of 180°C, more dense foods such as chicken Kiev or fresh battered fish may need a lower temperature to achieve full cooking on the inside and crispness on the outside without burning.
Split cooking temperatures may be needed for thicker products, one temperature to cook the product through and a second to crisp and seal the outside. The best example of this process is with freshly cooked potato chips, which can be blanched at about 130°C, then drained and fried to crispness later at 180°C.
With frozen products the initial cooking process has already been done. The deep-fat fryer has just to raise the core temperature to 65°C or higher to eliminate harmful bacteria that may be in the food and to crisp the outside. Recommended frying temperature and cooking period is usually contained in the packaging.
Timings of deep-fat frying are so crucial to a consistent and properly cooked product that in deskilled kitchens the timings and temperatures for all food should be laid down by kitchen management and displayed close to the fryer. A skilled chef can sense and see from the colour whether deep-fried food is cooked, but the semiskilled line cook may not.
Consistency of deep-fried product is why many fast-food outlets needing a high output of chips choose deep-fat fryers with computer-controlled auto-lift fry baskets. The baskets are loaded with frozen chips and a preset control button is pressed, which lowers them into the oil. The basket automatically lifts out of the oil when the chips are cooked.
What size fryer do I need?
All food floats in hot oil, cooking in the top two inches of the fryer. This can lead to the choice of a fryer which is too big and heating up more oil than is needed. Where there's a high daily demand, typically at lunchtime and in the evening, choice of fryer should be based on peak-demand needs. Basing fryer needs on the output of chips over 24 hours doesn't reflect what the kitchen actually has to produce in a much shorter period.
The industry-wide performance measure of a deep-fat fryer is usually given in weight of chips per hour the fryer can handle. But this assumes an even demand throughout the day, which seldom happens.
Another point to consider when looking at chips-per-hour rates between different fryers is to ensure the same type of chip is being rated by each manufacturer. Frying times will vary considerably between frozen chips, chilled chips, blanched chips and, most importantly, size of chips.
The best way to find out the size and power of a fryer is to ask an equipment distributor or manufacturer to calculate the capacity based on the weekly throughput of all fried foods. The result of this may well be to have two fryers, with one solely for chips. To have just one deep-fat fryer could result in a huge slowdown as different products compete for time in the single fryer.
Heat-recovery time is a crucial feature of any deep-fat fryer. This is the time it takes the heating elements to recover the desired frying temperature when chilled or frozen food is lowered into the hot oil. Busy fast-food operations need a short heat-recovery time to keep churning out products such as chips. If demand on the fryer is lower, such as in a hotel kitchen, then the power of the fryer can be less.
The heat-recovery power of a deep-fat fryer is usually reflected in the price. Fry tanks are often similar in size of basket, but the difference is in the ability to heat the cooking oil rapidly.
Gas or electric power? There's no clear answer to whether gas or electric power is better, as both have their good points. Electric fryers are cheaper to buy and suitable for low- to medium-volume needs. If the kitchen is churning out high volumes of fried food, particularly chips, then gas-powered fryers may be dearer to buy, but cheaper to run. However, there have been advances in the technology of electric fryers and the operation cost and performance between gas and electric can be negligible. Within the next two years comparative energy costs will influence buying decisions. Servicing costs for gas fryers will be slightly higher because of the need to check the gas system.
If the inclination is towards gas-fired fryers, there are three heating systems with no clear choice on which is the best option. Tube burners have wide tubes running across the lower inside of the fry tank. Inside the tubes are gas jets which transfer the heat into the oil through the tube wall.
The second system uses a big bank of gas jets concentrated on the exterior of the fry tank, while the third uses high-output infrared heaters.
Features to look for A fryer is a simple piece of catering equipment compared with, say, a combi-oven, and the controls tend to be few and simple to use. Features that could sway a buying decision include the means of emptying the oil for filtration or disposal. Any deep-fat fryer without an oil-draining system poses a potential health and safety hazard as the fry tank will need to be lifted manually and the oil poured into another vessel.
Simple systems include a tap which drains the oil into a collection pan underneath. Where simple filtration is being done, this allows for warm oil to be drained off, which aids the filtration. A safety feature to look for is a drain tap which cannot be accidentally turned on while the fryer is in 180¡C frying mode. Some high-speed fryers offer a more advanced self-filtration feature.
Another potential hazard arises if the temperature controls are at the back of the fry pan, which means a chef has to stretch across the frying area to adjust them. Choose a fryer with temperature controls on the front.
For more information on all catering equipment:
The Catering Equipment Suppliers Association (CESA) 020 7233 7724
The Catering Equipment Distributors Association (CEDA) 01274 826056