Over the years, health professionals are constantly hammering us about the harmful effects of trans fats and why we should stay clear of them. The food industry is not oblivious to this, and they eventually follow the trend. By now, many big name companies are proudly selling no-trans fat products. Of course, these products do not automatically make them healthy, but they are nevertheless healthier than they once were.
While trans fat can be naturally found in animal food sources, they can also be artificially created thanks to manufacturing techniques. Processed foods are often loaded with artificial trans fat, mainly deriving from partially hydrogenated oils. But get this: cooking can create trans fat as well.
A team of researchers from India sought to evaluate the formation of trans fat following the heating/frying process of various oils/fats.
No need for high-end industrial gadgets to create trans fats after all.
About Trans Fats
Trans fats are the villain of the bunch, causing more damage to the body than saturated fats. They are known to cut down the good cholesterol and elevate the bad cholesterol in our body. Some studies suggest a possible link between the consumption of trans fats and the development of insulin resistance and type 2 diabetes.
The formation of trans fats depends on two major cooking factors: the temperature of the oil and the number of time it is reused. Longer cooking time, multiple usages, and higher temperature generate more trans fat. Some European guidelines recommend keeping the frying oil below 180°C to limit the formation of trans fat.
The researchers selected six fats/oils that are commonly used in Indian cuisine to conduct their experiment: refined soybean oil, refined groundnut oil, refined olive oil, refined rapeseed oil, clarified butter (ghee), and partially hydrogenated oil. Oils and fats underwent two cooking temperature: 180°C and 220°C. Frying and heating were repeated four times each and sample of oils were collected for analysis.
Both cooking temperature led to an increase of trans fats, saturated fats, and a reduction of cis-unsaturated fatty acids.
“Although there were significant variations in the amount of TFA [trans fatty acids] formation depending upon the fat/oil (p < 0.001), the overall trend indicated an increase in formation of TFA on subsequent heating/frying,” reported the authors.
The absolute net change in trans fat content reaches nearly 4 g/100 g, with no significant difference between frying and heating.
Bottom line: Reusing oil, cooking at high temperature, and long cooking time appear to be a winning combination for the formation of trans fats.