Commercial deep fryers and oil filters

Here's a step-by-step explanation of how an electric deep fryer or gas deep fryer works, from start to finish:

1. Preparation: The oil reservoir is checked to ensure it has the appropriate amount of cooking oil for frying.
2. Preheating: The fryer is turned on and preheated to the desired cooking temperature (as shown on the  fryer's thermostat or digital controls).
3. Immersion: The food is carefully lowered into the hot oil using a fryer basket or long tongs or a slotted spoon.
4. Cooking: The high temperature of the oil quickly cooks the submerged food, creating a crispy exterior while retaining moisture inside.
5. Monitoring: While the food is cooking, the operator occasionally flips or stirs the food for even cooking and to prevent sticking.
6. Completion: When the food is done, it’s carefully lifted out of the oil using the fryer basket or a slotted spoon.
7. Oil maintenance:
   After the frying process, the oil is periodically filtered or skimmed to remove debris and maintain the quality of the oil.
8. Cool down and cleaning: After the fryer has been turned off and the oil allowed to cool, the oil is drained and the surfaces are wiped down.

Open-pot deep fryer

Features a large fryer pot that, because the heating elements are on the outside of the pot, is completely open and unobstructed.

• suitable for unbreaded or lightly breaded foods (e.g. French fries, chicken wings)
• more space for high-volume frying
• absence of tubes or obstructions simplifies cleaning.
• narrow cold zone can quickly overfill with sediment and particles from heavily coated foods
• the external heating elements make the pot less energy-efficient
• requires more oil compared to other types.

Tube-type deep fryer

Features multiple heating tubes or pipes permanently affixed to the bottom of the fryer pot.

• submerged tubes distribute heat evenly
• wider cold zone traps more sediment and food particles and extends oil life
• suitable for heavily breaded items (e.g. fish, battered onion rings).
• tube design makes cleaning more challenging
• less capacity than other types (about 20% of the oil rests in cold zone)
• tubes may require maintenance and repair.

Ribbon deep fryer

Features a long, ribbon-like heating element connected to the bottom of the fryer pot.

• efficiently transfers heat from the element to the oil
• quick preheat and fast recovery times
• add less heat to your kitchen.
• ribbon-like elements are difficult to clean
• foods that touch elements may be scorched or burnt
• exclusive to electric deep fryers — more expensive to operate than gas.

Flat-bottom deep fryer

Features a shallow, open, flat bottom in which the heating element is embedded.

• best for delicate items that float near the surface (e.g. tempura prawns, doughnuts, funnel cakes)
• allows products to float freely for even cooking
• easier to clean, since the heating element doesn’t obstruct the bottom of the fryer pot.
• doesn’t have a cold, or sediment, zone — so unsuitable for high-volume tasks
• takes longer to heat up than other types
• lack of cold zone can create a burnt-sediment taste and reduces oil life.

Pressure deep fryers

Features a lid that locks in place to create a sealed frying chamber, enabling pressure to build up in the fryer.

• food retains more moisture and absorbs less oil
• shorter cook times at lower temperatures
• fast recovery time — a matter of seconds, load after load.
• deep cleaning between the elements can be tricky
• the food can’t be modified while it’s frying in the sealed pot.

Aside from the fact that electric deep fryers and gas deep fryers use different heat sources, the main differences between the two are:

Heating and recovery speed: Electric fryers use a heating element that’s immersed in the oil, so they heat the oil faster than an equivalent gas fryer. In contrast, gas fryers heat up the fry pot first, which then heats the oil, and so take longer to reach the desired temperature. For the same reasons, electric fryers recover faster, allowing operators to cook more items in quicker succession.

Capacity: Gas fryers typically have higher capacities than electric ones, so are more suitable for high-volume establishments.

Installation: Whereas gas fryers need to connected to a gas line by a qualified professional, electric fryers can simply be plugged into an electrical outlet, making them faster, easier and cheaper to install.

Control: Electric fryers usually allow for more user control. For example, they feature adjustable thermostats that allow you to set the temperature of your oil quickly and easily.

Ventilation: Electric and gas fryers both require an adequate ventilation system, but electric models don’t need a gas interlock system to be fitted and maintained.

Maintenance and repairs: Gas fryers are more complicated than electric ones and typically require more frequent maintenance, increasing the operating costs.

When selecting a fryer size, you’ll need to consider the volume of food you intend to fry plus the amount of space you have available in your kitchen.

Benchtop deep fryers typically range in width from 254mm to 508mm, making them suitable for establishments with limited space. They typically hold 4–6 litres of oil.

Single-basket floorstanding deep fryers are usually 381mm to 610mm wide, while multi-basket models range in width from 762mm to 1219mm or more. Floorstanding fryers can hold up to 45 litres of oil.

You also have the option of ordering a set of fryers that you can bank together to form a fryer battery.

If you’re filtering small batches of commercial fryer oil, follow these steps:

1. Allow the oil to cool.
2. Place a chinois (a conical-shaped, fine-mesh strainer) over a suitable oil-storage container.
3. Line the chinois with cheesecloth, to trap any larger debris or particles in the oil.
4. Pour the oil through the cheesecloth-lined chinois, allowing it to strain completely.
5. Dispose of the trapped debris and, when ready, return the filtered oil to the deep fryer.

If you’re using large batches of oil and want to avoid lengthy periods of downtime manually filtering your oil, you may want to consider investing in a fryer oil filtration system, or deep fry filter.

These systems typically consist of a separate filtering machine connected to the fryer via hoses or pipes. The machine electronically pumps oil out of the fryer, filters it, and returns it to the fryer.

The deep fry filter can filter the oil while it’s still hot; you don’t have to wait for the oil to cool.

Some high-end commercial deep fryers have built-in filtration systems.

How long you can keep oil in your commercial fryer will depend on the types of food you’ve been frying, the volume of frying, and the quality of the oil, including your filtration schedule.

Though there is no set time limit for oil changes, there are several signs that indicate it’s time to change the oil in a commercial deep fryer.

You should change the oil when it:

• becomes darker (e.g. brown) — a sign of degradation
• develops a rancid or off-putting smell
• transfers unpleasant flavours to the food being fried
• smokes or foams excessively during the frying process.