What Happens to Oil When You Fry Chips Over and Over?
<i>Trans</i>-Hydroxy, <i>Trans</i>-Epoxy, and <i>Erythro</i>-dihydroxy Fatty Acids Increase during Deep-Frying
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Trans-epoxy-FA increased more than cis-epoxy-FA, and surpassed them by day two — despite cis forms being more common in fresh oil.
People assume oxidation creates random byproducts, but this shows a strong, predictable bias toward the more harmful trans configuration.
Practical Takeaways
Replace frying oil after 2 days of repeated use (4x5 cycles) — even if it looks clean.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Trans-epoxy-FA increased more than cis-epoxy-FA, and surpassed them by day two — despite cis forms being more common in fresh oil.
People assume oxidation creates random byproducts, but this shows a strong, predictable bias toward the more harmful trans configuration.
Practical Takeaways
Replace frying oil after 2 days of repeated use (4x5 cycles) — even if it looks clean.
Publication
Journal
Journal of Agricultural and Food Chemistry
Year
2023
Authors
Elisabeth Koch, Ariane Löwen, Sharline Nikolay, Ina Willenberg, Nils Helge Schebb
Related Content
Claims (6)
As oil is reused for frying, a specific type of oxidized fat called E,E-hydroxy-LA becomes more common.
Scientists think that looking at the balance between different types of broken-down fats might help tell how much oil has been used for frying.
When you fry potato chips over and over, a specific type of fat called trans-epoxy fatty acid builds up more than other similar fats.
When oil is reused for frying, one kind of breakdown product (erythro-dihydroxy) builds up more than another (threo-dihydroxy), because it comes from a different type of fat that forms more during heating.
When oil is reused for frying, some unstable fat breakdown products disappear, but the stable ones they turn into don’t change much in amount.