When to Change Deep Frying Oil

We have all heard about the dangers of frying oil in the kitchen and chefs have mostly been trained on identifying taste, smell and look of the oil.

However, do we know why we need to change oil in the deep fryer?

Do we need to filter/strain the oil daily?

The Facts

Frying oils undergo chemical changes during heating, exposure to light as well as storage. This is the chemical nature of oil products.

These changes lead oils breaking down into toxic chemical substances. Fortunately there are classic signs of this degradation.

  • Change or darkening of colour.
  • Rancid or ‘off’ smell
  • Rancid taste
  • Thickening of oil

The speed or rate at which this breakdown happens is dependent on the type of oil used.

In general the higher the amount of unsaturated fats in the oil the faster the oil breaks down.

Sunflower, Canola and Soy degrade a lot faster than Olive and Palm oils.

How do we Manage Oil Degradation?

The use of oil is a significant cost in the kitchen, however there is also a major food safety risk in incorrectly using frying oil.

Oil management is an important yet often overlooked risk in the kitchen.

Free Fatty Acids (FFA) is an effective way to measure and determine whether oil is still suitable or not. FFA depends on:

  • Time
  • Temperature
  • Moisture content

This means that the ‘shortening’ of oil cannot be easily measured if the above are unknown, such as how long the oil fryer was on for and at what temperature. Important the type of food that is fried also determines how long the oil will last. Considerations include foods with crumbs or batter, potato chips/fries.

An FFA of between 2 – 6 % is still usable and above 6% increases the potential toxicity. This can be measured by using two methods:

There are other products and equipment that help ensure the longevity of the oil.

Simply filtering the oil on a daily basis can help extend the life of the oil by removing solids that contribute to the degradation of the oil and will help minimize the water content.

However the main point here is that this risk can be managed and does not require you to discard oil after a single use, if cared for properly.

Keeping records of oil changes will also help you predict when oil changes are needed according the usage and time.

How to fill in an oil checklist 

  • Use oil shortening test strips / colour chart
  • Measure the quality of the oil according to the above
  • Has the oil been drained? (This should be done daily for cleaning of the fryer)
  • Has the oil been correctly strained? (This is to filter/clean the oil for reuse)
  • Is the oil still suitable for use? (Still yellow?)
  • If dark, then use a test strip to confirm replacement.
  • Was the oil discarded?

For more information on the food safety pillars check the ebook on Amazon.

If you would like to learn more about Hygiene Food Safety subscribe to the blog.

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