How to choose a deep frying oil for a restaurant

Start from cost per frying day

Most kitchens compare frying oils on the invoice: price per litre or per jerry can. The more useful number is what the oil costs per day of frying. That depends on how long the oil lasts before it has to be thrown away, how much fresh oil you add to top up, and how much staff time goes into changing and cleaning fryers.

An oil that lasts four days instead of three cuts the number of full changes by a quarter. Over a year, in a kitchen with several fryers, that usually matters more than a small difference in purchase price. So the first question is not "what is the price" but "how stable is this oil at frying temperature". A one month trial with daily TPM readings answers it better than any data sheet.

The second question is taste. Guests notice when fries taste of yesterday's fish or when a doughnut has a heavy, oily finish. The third is practical: pack size, storage, shelf life and the supplier's ability to deliver on time. This guide goes through all three.

What happens to oil in a fryer

At around 170 to 180 °C, three processes wear frying oil down. Water from the food splits the fat into free fatty acids, which lowers the smoke point and adds a soapy note. Oxygen from the air attacks the unsaturated fatty acids and creates off flavours. Over time, broken-down molecules join into polymers that make the oil thick, dark and prone to foaming.

The speed of oxidation depends mostly on the fatty acid profile. Oils rich in oleic acid, with one double bond, resist it best. Oils with a lot of linoleic acid, with two double bonds, break down faster, and linolenic acid, with three, breaks down fastest. That is the science behind most frying oil choices.

Professional kitchens track this with a total polar materials (TPM) meter. Many European countries treat 24 to 27% polar materials as the point where oil must be discarded.

Common frying oils compared

Typical characteristics of refined oils. Stability ratings are relative and assume the same fryer routine.

Smoke point: useful, but not the whole story

Smoke point is the temperature at which oil starts to give off visible smoke. Fresh refined sunflower, rapeseed and soybean oils typically smoke somewhere around 210 to 240 °C, well above normal frying temperatures. Unrefined oils smoke much earlier, often below 170 °C, which is why they are not used for deep frying.

The catch is that smoke point falls as oil breaks down, because free fatty acids smoke at lower temperatures. Two oils with the same smoke point when fresh can behave very differently on day three. Stability, not the starting smoke point, decides how long the oil stays usable. For that reason, a fresh oil with a high smoke point is a minimum requirement, not a reason to buy.

Smoke at normal frying temperature is therefore a useful warning. If a fryer set to 175 °C starts to smoke, the oil has broken down far enough that it should be changed, whatever the calendar says. Smoke also means acrolein and other irritants in the kitchen air, which staff will notice before any meter does.

Match the oil to the menu

A burger and fries restaurant runs its fryers all day with a narrow menu. High turnover means plenty of fresh oil is added through topping up, and taste consistency matters. A stable oil such as high oleic sunflower or a high oleic blend usually pays off here.

Breaded and battered products, such as schnitzel, chicken and fish, shed crumbs that burn and shorten oil life. Fish also passes its flavour into the oil, so most kitchens keep a separate fryer for it. In these fryers, regular filtering matters as much as the type of oil. Doughnuts and pastry need a clean, neutral taste and an oil that does not leave a greasy film; refined sunflower or high oleic sunflower oil are common choices.

Hotels and catering kitchens often fry in batches with long idle periods. Hot oil sitting in air oxidises even when nothing is being fried, so stability counts for more than in a fast-moving fryer, and a lid or a lower standby temperature helps.

Questions to ask a frying oil supplier

Packaging that works in a busy kitchen

Frying oil reaches restaurants in PET bottles, HDPE jerry cans and bag-in-box. PET bottles of 1 to 5 L suit small kitchens and pan frying. Jerry cans of 10 and 20 L are sturdy, stack well and pour easily into a floor fryer. Bag-in-box packs have a tap, take less storage space and collapse as they empty, so less air reaches the oil and the empty box is easy to dispose of.

Store oil cool, dry and away from light and the cooking line, and use the oldest stock first. Light and warmth start oxidation even before the pack is opened. If staff top up fryers from an open container, close it between uses.

Think about the people handling the oil, too. A full 20 L jerry can weighs close to 20 kg, and pouring it into a hot fryer is one of the more common causes of burns in kitchens. Packs with a good handle or a tap, and a routine of filling fryers when they are cold, make the job safer. For multi-site operators, one pack format across all outlets also simplifies ordering and training.

When to change the oil, and what to do with it

Change oil when the TPM reading reaches your limit, or when you see the warning signs: dark colour, persistent foam, smoke at normal temperature, a sharp smell or off flavours in the food. Never add fresh oil to oil that is already past its limit to stretch it: the spent oil speeds up the breakdown of the fresh oil.

Used frying oil must not go down the drain. It blocks pipes and pollutes water, and in many countries there are strict rules on its disposal. Collected oil is a valued raw material for biodiesel, so used vegetable oil recycling is both the legal route and the simplest one.

What we supply for professional kitchens

Our professional deep-frying solutions were developed by our R&D department for HoReCa use. The SUNFRY Chef's Choice line covers frying and deep frying sunflower oil, with RAPESEED FRY, SOYFRY and SUNRAP Chef's Choice for rapeseed, soybean and sunflower and rapeseed blends. For the heaviest use there is SUNFRY High Oleic Prime C4, a deep frying high oleic sunflower oil, and a high oleic blend, C2.

Packs run from 1 to 20 L, including PET bottles, bag-in-box and HDPE jerry cans, and all of them can carry your own label. Shelf life is up to 24 months at a recommended 6 to 30 °C. We deliver in trucks with 32 or 33 pallets or in 40'HC containers, under FCA, CFR, CIF, DAP or DDP.

Food manufacturers and distributors who need oil in bulk can choose refined sunflower oil, refined rapeseed oil or refined soybean oil by tank truck or in flexi bags.