How To Correctly Use a Commercial Fryer

Although there are no verified data, surely 90% of bars and small restaurants do not use the fryers correctly.

The reasons that lead us to make this statement come from the type of fryers that the bar or small restaurant usually buys, more concerned with price than with the performance of the fryer. This statement leads us to the next question; does an inexpensive fryer work badly? The answer is no. There are excellent fryers for the hotel and catering industry that are very competitively priced, but the problem lies in the way they are used.

A cheap industrial deep fryer for the catering industry usually does not have enough power to maintain the temperature when the product is poured into it. This means that when the temperature drops below 150 degrees, the product is cooked instead of fried and the batter is not crispy.

The solution is easy; you have to put a small amount of product each time you fry it, however, what they usually do is always put the fryer at full power above 200º Centigrade, burning and degrading the oil and filling it with toxins.


Oil degradation and consequences:

The critical decomposition temperatures of oils commonly used for frying are:

Olive oil: 210º C
Sunflower oil and soybean oil: 170º C
Margarine: 150º C
Rapeseed and Corn Oil: 160º C
Butter 110º C

A misuse of a deep fryer for catering can cause serious illnesses to our customers, among them:

Development of gastritis.
Heart problems.
It accelerates the process of blood clotting.
It favours the development of neurodegenerative diseases such as Alzheimer’s, among others.
Digestive discomforts-increase the risk of suffering from stomach cancer among other types of tumors.

These illnesses are basically produced by the use of burned and overheated oils for frying. The oil used in hotel and catering fryers begins to degrade around 200 Cº, producing the following chemical processes in an accelerated manner:

Thermo-oxidation: Fatty acids are oxidized producing peroxides and free radicals, these in turn react with each other forming non-radical compounds, generally aldehydes or ketones that are quite toxic to humans, this process produces odors, undesirable flavors and darkening, as well as increased viscosity and foaming.

Hydrolysis: Moisture in the oil causes the breakdown of the fatty acid ester that decomposes, undesirable odors and flavors also appear, there may even be a taste of soap, and increases the acidity of the oil.

Polymerization: The presence of free radicals that combine with each other or with the fatty acids form linear (with different degree of length and branching) or cyclical (especially in the presence of double bonds) polymers. These compounds have greater size and molecular weight and therefore tend to increase the viscosity of the oil and the formation of foam and to form a layer of plastic consistency on the surface of the oil and in the container, which is very difficult to remove.

Properly frying food is a process that improves the texture, taste and appearance of food. Caramelisation and toasting reactions take place on the surface of the product, giving the food a pleasant color and flavor, a crisp exterior, while the interior remains juicy because moisture is not lost during frying.

Commercial deep fryer

How to correctly use an industrial fryer for catering?

It is very important not to go over 180º-185º in the temperature of the oil, so we need a fryer that maintains that temperature without problems when we put the product in it (that has good power).

The oil tank must be filled with the amount indicated in the manufacturer’s manual. Overfilling the fryer can cause overflows and will not heat the oil evenly.

Wet food should not be poured in, as water may collect at the bottom of the bucket and cause hot oil splashes.

Remember to change the oil when it degrades if you do not have a meter. It should be changed when it looks “dirty” or is a darker color.

Use an oil with a good price/quality ratio if this oil is good you will have to change it less time than a low quality one.

Frequent mistakes when buying and using a commercial fryer

Models with a small capacity of 4-6-8 litres and low power are usually chosen, so when trying to fry the product the following happens:

If the fryer is small and you pour a lot of product, the oil drops to 160º and the product is cooked instead of fried; the solution adopted by most bars is to put the oil at 250º (at full strength) so, as you know, the oil degrades.

If you buy a fryer with little power when you fry continuously will not be able to maintain the temperature of the oil so you accelerate the process of hydrolysis of oil and this will degrade quickly.

When choosing a small and cheap fryer, instead of adjusting to the real capacity of the fryer we will surely want to get more out of it, we will degrade the oil so we will have to change it daily or poison your customers with toxic oil; besides, your final product will not have the most desirable taste.

There are cooks who believe that the normal frying temperature is 220º, this is considered an excessive temperature, so they are consistently degrading the oil.

Fryer Cooking Guide

Raw to done 3506
Blanched, only 3503
Browned, only 3503
Commercially treated 3506
Frozen, fat blanched 3502
Potato chips  3503–4
Potato puffs36011⁄2
Frozen breaded shrimp 3504
Fresh breaded shrimp 3503
Frozen fish fillets 350 43504
Fresh fish fillets 350 33503
Fresh breaded scallops 350 43504
Breaded fried clams 350 13501
Breaded fried oysters 350 53505
Frozen fish sticks 350 43504
Raw to done 32512–15
Croquettes 350 3–4
Turnovers 3505–7
Precooked, breaded 350 3–4
Breaded veal cutlets 350 3–4
Breaded onion rings  35011⁄2–2
Precooked broccoli 3503
Precooked cauliflower 360 3–4
Precooked eggplant 360 3–4
Breaded tamale sticks 3603
French-toasted sandwiches 3751
Yeast-raised doughnuts 3751
Hand-cut cake doughnuts  37511⁄2
Doughnuts 3752–3
Glazed cinnamon apples 3003
Corn on the cob 3003
Turnovers 3754–5


(Source for table: Design and Equipment for Restaurants and Foodservice, Third Edition)

Which fryer should you choose?

It doesn’t matter if you work with a large fryer, just because it’s big doesn’t mean it uses more oil; on the contrary, you can work at a lower temperature, without spoiling the oil by enhancing the flavor of your products.

You should also choose a powerful fryer, it is a good practice to lower the temperature of the fryer (150-160º) if it is not being used, this will help to maintain the properties of the oil.

Never choose a water fryer; although it may seem to clean the oil better, hydrolysis processes occur more quickly, and are also very dangerous.