Discover three reasons your commercial fryer oil is changing colour. Plus, the limitations of relying on colour alone
(Visual Oil Checks) to determine oil quality.

In the following article, we will explore three reasons your commercial fryer oil is changing colour, highlighting the following questions:

  • What kind of fryer oil are you using?
  • What product(s) are you frying?
  • How are you maintaining your oil?

We will also offer a closer look at the limitations of relying on colour alone to determine oil quality, with an increasing number of Commercial Kitchens now moving away from Visual Checks in favour of Food Oil Monitors (Cooking Oil Testers).

Jump to the correct response to your fryer oil changing colour

1. What kind of oil are you using?

First, you need to consider the type of oil you are using on site. It is typical for Commercial Kitchens to fill their fryers with an oil that has a high smoke point, as this ensures the oil can be heated to a high temperature without smoking or producing a strong odour.

Over-heating oils with a low smoke point could impact the quality, taste, and safety of your fried product. For example, Extra Virgin Olive Oil produces a bitter taste when heated past its smoke point. Flaxseed and Walnut Oil also have low smoke points and produce unpleasant flavours when overheated.

Below are four types of oil that are suitable for use in Commercial Kitchen fryers:

Feature Peanut Oil (Refined) Sunflower Oil Soybean Oil Avocado Oil
Smoke Point (approx.)* 232°C 226°C 232°C 270°C
Cost Medium Medium Low High
Flavour Mild Mild Neutral Neutral
Additional Considerations Peanut Allergies Health Benefits Health Benefits

Heating oils past their smoke point is one of the main reasons they can change colour to a shade of dark brown or black.

In some instances, a colour-change could suggest the oil needs to be replaced. However, this isn’t always the case. This is why Visual Oil Checks are an unreliable approach. 

Jump to the correct response to your fryer oil changing colour
* The smoke point of your oil will be impacted by the way in which it is stored and handled. You will need to consider the environmental variables associated with the uncontrolled environment of a Commercial Kitchen.

2. What product(s) are you frying?

Next, you need to consider the type of product(s) being fried in your Commercial Kitchen. This is because certain food products can speed up the rate at which your fryer oil changes colour. 

Examples include items coated in breadcrumbs or batter which tend to darken oil more quickly – effectively staining it. You should also note that high levels of salt, along with saturated and unsaturated fats can contribute to the discolouration of oils. However, as mentioned above, colour alone isn’t a reliable indicator of degradation. In fact, so long as your oil is regularly filtered and food debris is skimmed throughout service, you can continue cooking with darker oil without compromising food quality (up to a point). The solution is to find a more accurate and reliable approach to monitoring your oil quality.

This will also help in kitchens faced with the opposite problem – working with food products, such as chips, that produce such a minimal amount of debris that the oil colour doesn’t change as quickly, even if it it is nearing the end of its usable life.

Jump to the correct response to your fryer oil changing colour

3. How are you maintaining your oil?

Another point to consider is how you are handling your fryer oil. Maintaining best practice could make all the difference, so you will need to pay close attention to the following measures:

  • Don’t overfill the baskets in your fryer
  • Ensure correct frying temperatures
  • Always use a timer
  • Skim the vat throughout the day
  • Top-up oil level throughout the day
  • Proactively filter the vats
  • Regularly test oil quality
  • Cover your fryers overnight

Finally, you need to make sure you are storing your fryer oil correctly. Exposure to heat, light, and air can speed up the discolouration process, not to mention oil degradation, so it’s important that you find a cool, dark storage area with suitable airtight containers.

The incorrect maintenance of your oil could be another reason that it is changing colour to a dark brown or black. However, a colour-change doesn’t always mean your oil needs to be changed
– a key point to remember if you want to save on the cost and hassle of unnecessary replacements.

Jump to the correct response to your fryer oil changing colour

4. Do you need to change your oil if you notice a colour-change?

As mentioned throughout this article, Visual Oil Checks are an unreliable approach to determining whether or not your fryer oil needs to be changed.

Firstly, Visual Checks are subjective, entirely dependent on the team member making the call. All it takes is a busy individual to decide they don’t have time to carry out an oil change and the safety, quality, and consistency of your product could be seriously compromised.

Equally, an inexperienced or overzealous team member could decide that the slightest change in colour requires a complete replacement – costing your business time and money.

Food Oil Monitors help to de-skill oil checks and eliminate guesswork. Operating under a traffic light system, the monitor flashes green if the oil quality is acceptable, amber if the oil will need to be changed soon, and red if the oil needs to be replaced immediately. The monitor also provides a digital measurement in thirty to sixty seconds and displays the oil temperature.

Hospitality and food preparation sites that previously relied on Visual Checks, before making the switch to Food Oil Monitors have reported a reduction in oil usage of up to 52%. This demonstrates just how difficult it is to judge oil quality from colour alone, along with the importance of finding an accurate and consistent approach to oil monitoring.

So there you have it, three reasons your commercial fryer oil is changing colour. We hope this article has helped to answer this important question, and has also highlighted the limitations of using colour alone to determine oil quality.

If you have any further questions about oil usage at your site, or about Food Oil Monitors (Cooking Oil Testers), our in-house team of experts are here to provide support.

You can contact them directly on 01473461800 or sales@klipspringer.com. Alternatively, you can fill out the contact form below and one of our friendly team members will be in touch.

If you have any questions relating to our products or services, the Klipspringer team would be happy to help. Share your details below to arrange a consultation.