Today, we’ll talk about frying, since it is one of the most popular cooking methods worldwide. From French fries to tempura, frying enhances taste and appearance, and it’s also a quick and convenient cooking technique, making it a basic in home kitchens and small food businesses alike.
However, frying comes with certain risks. When not done correctly, it can lead to the formation of harmful compounds like acrylamide, a substance linked to health concerns, and acrolein, a toxic byproduct of degraded oils. Additionally, poor frying practices can result in unsafe oil reuse and cross-contamination.
With the right knowledge and habits, frying can be both safer and enjoyable. In this post, we’ll explore the key risks associated with frying and share tips for consumers and small businesses to fry foods more safely, ensuring better health.
Understanding the Risks
Now let’s talk about risks. There are many kinds of risks, such as fire hazards, burns, cross-contamination with allergens, and so forth. In this post however, our focus will be on harmful substances formed during the frying process.
1. Acrylamide
Acrylamide is a chemical that forms when starchy foods are cooked at high temperatures (above 120°C) as part of the Maillard reaction, a process between reducing sugars and the amino acid asparagine. This reaction is responsible for the desirable browning and flavour in fried foods, but it also produces acrylamide as a byproduct.
Health Concerns:
- Carcinogenic Potential: Acrylamide is classified as a probable human carcinogen, meaning it has been shown to increase cancer risk in animals and is likely to do so in humans.
- Other Risks: It has also been linked to neurotoxicity (damage to the nervous system), developmental toxicity (harmful effects on foetal and child growth), and reproductive toxicity (potential effects on fertility and reproductive health).
Sources: While this post focuses on frying, acrylamide is also formed in other high-temperature, dry cooking methods, such as baking, roasting, and toasting. Foods most associated with acrylamide include French fries, crisps, bread, breakfast cereals, coffee, and baby foods. The EU regulation (EU) 2017/2158, which remains part of UK law post-Brexit, sets measures to reduce acrylamide levels in these foods.
2. Acrolein
Acrolein is a volatile substance that forms when oils or fats are overheated or degraded. Unlike acrylamide, which comes from fried food, acrolein is produced directly from the breakdown of oils. This process accelerates when oils are reused or heated beyond their smoke point—the temperature at which oil begins to smoke visibly.
Health Concerns: Acrolein is harmful to the respiratory system and eyes. Short-term exposure can cause irritation of the eyes, nose, throat, and lungs, while long-term exposure may lead to more severe health issues. Acrolein is also a suspected carcinogen.
Oil Degradation Cycle:
- As frying oils degrade:
- Their smoke point lowers.
- Harmful byproducts, including acrolein, form more rapidly.
- This creates a vicious cycle where the longer oil is used, the faster it degrades, releasing acrolein.
Regulation: While there is no specific law targeting acrolein in food safety, international regulations address the overall Total Polar Compounds (TPC) in frying oils. TPC includes acrolein and other byproducts of oil degradation. When TPC levels exceed 25%, the oil is considered unsafe for frying.
Reducing Risks for Consumers
- Moderation. The first and most effective step to minimize health risks is to reduce the intake of fried foods. Instead, focus on incorporating more raw foods like fresh fruits and vegetables into your diet. When cooking is necessary, choose gentler methods such as steaming, boiling, or poaching, which preserve nutrients and minimize the formation of harmful compounds. Occasional indulgence in fried foods is fine, but prioritizing these healthier options can improve your overall diet.
- Choose the Right Oil. When selecting an oil for frying, it’s essential to consider both its smoke point and nutritional quality. While refined oils like canola, sunflower, and peanut oil are often recommended for their higher smoke points, they are not the only options. There is a common misconception among consumers and chefs that extra virgin olive oil (EVOO) should not be used for frying or cooking in general. However, EVOO is an excellent choice for cooking and frying at moderate heat (below 180°C). EVOO retains antioxidants and healthy monounsaturated fats, making it a stable and healthy choice.
- Prepare Foods Properly.
- For potatoes:
- Soak cut potatoes in cold water for at least 30 minutes to remove surface starch.
- Pre-cook potatoes by boiling or steaming for 3–5 minutes to reduce surface sugars, which lowers acrylamide formation.
- See also the tip shared in the business section.
- For potatoes:
- Control Frying Temperatures:
- Use a thermometer to maintain the oil temperature below 180°C.
- Avoid overfrying food.
- Avoid Moisture. Do not fry wet or moist foods, as water accelerates oil degradation.
- Limit Oil Reuse. Reuse oil minimally to reduce the buildup of harmful compounds
Reducing Risks for Food Businesses
- Establish Oil Management Practices:
- Regularly filter oil to remove food debris that accelerates degradation.
- Replace oil once Total Polar Compounds (TPC) exceed 25%. Use TPC testers for regular checks.
- Avoid mixing fresh oil with degraded oil, as this speeds up the breakdown of the new oil.
- Use Proper Equipment:
- Invest in fryers with built-in thermostats to maintain consistent frying temperatures below 180°C.
- Install a fryer hood to remove pollutants like acrolein, ensuring better air quality in the kitchen.
- Prepare Ingredients Safely:
- For potatoes: Follow the same preparation steps as recommended for consumers, such as soaking cut potatoes in water and pre-cooking them (e.g., by boiling or steaming).
- Avoid overfrying: This helps minimize the formation of harmful compounds like acrylamide.
- Storage tip: Do not store potatoes in the fridge at temperatures below 6°C, as this can increase sugar levels in the potatoes, leading to higher acrylamide formation during frying.
- Monitor Supplies:
- Inspect deliveries and reject food items that are overcooked or burnt.
- Maintain Cleanliness:
- Skim oil regularly to remove floating debris.
- Clean fryers and surrounding areas to prevent cross-contamination.
Scientialex Oil Testing Services
At Scientialex, we’re happy to assist food businesses in monitoring the quality of their frying oils, and we offer this service free of charge for one or two samples per company. Simply send us a sample of your frying oil by post, and we’ll analyse it and send the results back via email.
To gain the most accurate insights, we recommend sending a sample of oil that is considered exhausted, ideally taken from the container used to store discarded frying oil. This allows us to assess the level of degradation at the point where you replace the oil, providing valuable information to refine your oil management practices and ensure better safety and quality. Have more questions regarding the testing? Send us an email, and we’ll be happy to help
Conclusion
Frying can be a safe and efficient cooking method with the right practices. Understanding the risks and following these tips helps reduce harmful compounds for both consumers and businesses.
Feel free to leave a comment below if you have any questions or thoughts!
References
- European Union. (2017). Regulation (EU) 2017/2158 on Acrylamide Levels in Food. Retrieved from https://eur-lex.europa.eu/eli/reg/2017/2158/oj.
- UK Government. (2017). Regulation (EU) 2017/2158 as Retained in UK Law. Retrieved from https://www.legislation.gov.uk/eur/2017/2158/contents.
- Gertz, C. (2023). Formation of harmful compounds during frying processes. In G. Velisek (Ed.), Encyclopedia of Food Chemistry (2nd ed., pp. 325–330). Academic Press. Retrieved from https://www.sciencedirect.com/science/article/abs/pii/B9780128243152003250?via%3Dihub