Harmful Fumes from Frying — Chromatography Investigates

One of the most popular methods of cooking is to fry food in oil — it is used the world over to produce food like stir-fries, steak and doughnuts. Many people would agree that fried food tastes good — whether it’s a stir-fry, tempura or a good burger.

Some researchers believe that evolution could be behind our love of fried food. When food was harder to find and man survived by hunting and collecting berries — finding a good calorie source was rewarded by our brains sending out a positive message. Fried food is relatively high in calories — and our brains reward us with good emotions for consuming those calories — hence we like the food.

The health benefits — or harms — of eating too much fried food are regularly discussed by governments, food experts and the media; but what about cooking fried food? Can standing over a pan of hot oil cause us any harm? Let’s take a look.

Depends on the oil

There have been several studies carried out to look at the fumes released when food is fried and what effect those fumes might have. In a study carried out at the University of Dayton Research Institute and reported in the Journal of Agricultural and Food Chemistry, the effects of different oil temperatures and different oils were investigated.

The scientists compared canola oil, olive oil and extra virgin olive oil. Extra virgin olive oil is unrefined olive oil, it is classed as the purest olive oil and is generally the highest quality oil, whereas olive oil has been processed which removes some of the colour and flavours. Canola oil is made from rapeseed and is a widely used relatively inexpensive vegetable oil.

Carcinogenic fumes?

The researchers were interested in finding out what was released when the oils were heated — particularly the substances acrolein and acetaldehyde. Acrolein is considered to be toxic to lungs and acetaldehyde is carcinogenic to humans — therefore they are not really substances you want to be inhaling. The oils were heated at 180 degrees Celsius (for 15 hours) and 240 degree Celsius (7hours) with the oil fumes collected and then analysed.

Gas chromatography in tandem with mass spectrometry (GC-MS) was used to analyse the volatiles that were collected from the oil fumes. GC-MS is one of the key techniques used to analyse volatiles released from oils as discussed in the article, Determination of Biomarkers in Petroleum by Multidimensional Gas Chromatography: Fundamentals, Applications, and Future Perspectives.

It was found that at both temperatures, the quantities of acetaldehyde and acrolein released from canola oil was much higher than that released from the olive oils. Based on the research, the researchers recommend that olive oil is used for frying, and that the recommended frying temperature of 180 degrees Celsius is used.

Fish and chip supper anyone?

Image by Takeaway via Wikimedia Commons