How to Tell if Your Frying Oil Needs to Be Changed

How to Tell if Your Frying Oil Needs to Be Changed

How does one determine whether frying oil is still good or if it needs to be changed? Experts agree there are several key indicators of oil breakdown or bad oil. Let’s take a look at the most important ones:


The surest way to determine that oil has degraded to the point of discard is when food begins to have an “off” odor or taste. This may manifest itself as a bitter taste, especially a bitter aftertaste. The food may also taste soapy.

The German Society for Fat Research (DGF), one of the pre-eminent groups of oil researchers in the world, stated the following in 2000, “Sensory parameters of food are the prime quality index.”

Simply put into an equation:

Bad Oil = Bad Food = Unhappy Customers


Total Polar Materials, or TPM, are the standard adopted in Europe and elsewhere around the world as a regulatory index for determining frying oil quality and safety in restaurant frying oils. The simplest definition for total polar materials is all non-triglyceride materials soluble in, emulsified in, or suspended in oil.

Fresh oil typically contains two to four percent polar compounds, but may contain less. As oil is used, it breaks down, and the polar content of that oil increases. The rate of degradation depends upon the food being fried (coated products will damage oil more than French fries, for example). The temperatures at which foods are fried, the cleanliness of a fryer, and additional factors will also contribute.

Whether TPM will become a regulatory standard used in the U.S. in the coming years has yet to be decided. Regulatory officials in countries that regulate restaurant frying oils utilize different quick tests to test oil in the field. These include colorimetric tests and instruments that measure viscosity and other factors. If the TPM content is high, a sample will be collected and tested in a laboratory using an internationally recognized test for TPM established through the International Union of Pure and Applied Chemistry (IUPAC) or the Association of Official Analytical Chemists (AOAC).

A direct correlation has been found between soap content of the oil and the TPM content. High TPM equals high soap content. TPM measuring devices don’t measure soap content, but it is much cheaper to measure for soap content at a lab then it is to measure TPM.


Remember that oil is food. Each time a customer eats fried food, they eat the oil, as well. Extending the life of your oil will make them happier, and it will directly impact your bottom line.

To extend the life of your frying oil, it’s important to understand the best practices for maintaining your frying oil. Download our free Frying Oil Maintenance Tips, and find out how to enhance your fried food program.


By | 2018-04-26T18:29:47+00:00 July 27th, 2015|Categories: Fry Oil Tips, Frying Oil|Tags: , , , , , |Comments Off on How to Tell if Your Frying Oil Needs to Be Changed

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