Dr Hector Perera       London

Just not the food but the process of making food by frying or grilling are unhealthy than cooking food by the method of boiling. Research has revealed that exposure to cooking oil used to fry chips can increase the risk of health more than cooking things by boiling such as cooking rice and curries. Scientists say potentially harmful particles are released into the air when oil is heated to the temperatures needed to cook chips or stir-fries.

 Occasional frying

Repeated exposure that is people who are employed to fry things such as chips, fish and chicken and then stir frying. The processes of stir frying and cooking chips give out some aromatic chemicals and these chemicals can increase the chance of diseases such as to lungs, breasts and bladder. It must be noted that an occasional small scale frying or stir frying might not be dangerous as professional cooking.

Cooking oils

Researchers say all cooking oils produce the particles but vegetable oil is the most dangerous. Corn oil and olive oil also pose a risk, deep-frying chips, in particular, produces large amounts of the complicated chemicals such as polycyclic aromatic hydrocarbons. An aromatic molecule has a six sided ring and a polycyclic aromatic hydrocarbon has a few of them joined together.

High temperature is not safe

It also produces the compound acrylamide, another unhealthy chemical. Acrylamide is a chemical produced naturally in food as a result of cooking starch rich food at high temperatures, such as when baking or frying.

Burnt toast also contains small amounts of polycylic aromatic hydrocarbons (PAHs), better known as a class of air pollutant. “Some of those chemicals are proven carcinogens says Brent. Brent’s advice is to toast bread to the lowest acceptable level. And if you want to be really cautious, cut off the crusts as these usually contain more acrylamide from when the bread was baked.

“I’ve seen people scrape it off when they’ve burned it, but you’re better off throwing it away,” Brent advises.

Acrylamide tends to form when foods that are high in carbohydrates and/or an amino acid called asparagine are cooked at high temperatures. Cooking methods that tend to require high temperatures – like frying, roasting, and baking – are more likely to cause acrylamide formation in food. Non-cooked and boiled foods almost never contain detectable levels of acrylamide.

Prop-2-enamide is acrylamide

Acrylamide forms from sugars and an amino acid (asparagine — a building block of protein) found naturally in foods that are fried, roasted or baked. This chemical is more likely to increase the longer foods are cooked with these methods, and the higher the temperature. Boiling or steaming of the same foods do not typically result in acrylamide formation so cooking by boiling is safe.

Acrylamide was discovered accidentally in foods in April 2002 by scientists in Sweden when they found the chemical in starchy foods, such as potato chips (potato crisps), French fries, and bread that had been heated higher than 120 °C (248 °F) (production of acrylamide in the heating process was shown to be temperature-dependent).It was not found in food that had been boiledor in foods that were not heated.

Cooking is a chemical reaction

I always thought cooking is a synthetic organic chemical reaction because organic chemicals in food are reacted either in cooking or frying. In the synthesis of organic chemicals we add a few chemicals and react in a liquid media [not water] such as an alcohol for about an hour. The resulting product is analysed to prove the chemical structure or the nature of the chemical because unlike in cooking they cannot be tasted to see if it’s cooked. Those dangerous chemicals are also likely to be produced by grilling and roasting food. Research indicates that acrylamide does not occur in foods processed by boiling or microwaving. It has been found in a wide range of home cooked and processed foods including potato crisps, chips, bread and crisp breads and even in coffee.

Cooking fumes are unhealthy

The study, published by the Royal Society of Chemistry, estimates that someone regularly exposed to high levels of these chemicals would have a one in 100 chance of developing respiratory and other related problems.

The researchers advised cooks to make sure kitchens are properly ventilated and to try to boil and steam foods instead of frying.

They said: “It is highly possible for cooks to be exposed to harmful particles even while cooking at home. It is advantageous to carry out cooking activities in well-ventilated kitchens, either mechanically or naturally ventilated. Exposure could be minimised by installing an effective fume-extractor over a gas stove. In places like Sri Lanka kitchen windows and the doors are always kept wide open due natural hot weather conditions so no problems of natural ventilation. Mechanical ventilation or extractor fan ventilation is required in cold weather countries.

Water based cooking is much safer

“Water-based cooking methods, such as steaming and boiling, rather than cooking with oil, could further improve air quality, especially in confined environments.”

The team from the University of Singapore compared methods of Malaysian, Chinese and Indian cooking.

Their study, published in the Journal of Environmental Monitoring, analysed the quality of the air in the kitchens of three food stalls.

According to scientists, the deep-frying done by the Malaysian chefs released more polycyclic aromatic hydrocarbons than the stir-frying in the Chinese kitchens.

At the Indian food stall, much of the food was simmered or boiled, which cut down on the hydrocarbons.

The chemicals, also found in tobacco smoke and exhaust fumes, are released when oil is heated to high temperatures.

Researcher Dr Rajasekhar Balasubramanian said: “A comparison of the different cooking methods implies that deep-frying generates more polycyclic aromatic hydrocarbons than any other cooking method, which could be due to the higher temperature maintained during cooking and the larger amount of oil used in deep-frying.”

“The Malay stall fried mostly starchy foods,” he said. “It is highly likely that the deep-frying of chips will also produce large amounts of hydrocarbons, just like the Malay food stall.”

Cancer charities advised people to cut down on fried food.

Josephine Querido, of Cancer Research UK, said: “Heating cooking oil to very high temperatures can release chemicals into the air.

Small scale frying is safe

“But the level of chemicals in the fumes caused by cooking in the home is very small and there is no evidence to show this could increase health risk. That shows frying some fish, dry fish and papa dams at home would be safe because they are done only in small scale at domestic kitchens.

“The best way to reduce health risk food is to eat a balanced diet including plenty of fruit and vegetables and avoid too much red and processed meats. Poaching or grilling rather than frying food helps to cut down on fats.”

The British Nutrition Foundation said there were numerous reasons to eat less fried food.

Nutrition scientist Rebecca Foster said: “A high-fat diet increases the risk of high cholesterol which, in turn, can increase the risk of coronary heart disease.

“Fat also has a high calorie content, which can increase the risk of gaining weight and increase the risk of heart disease, diabetes and other problems.”

The research follows a warning last year that giving children chips could dramatically increase the chance of breast cancer.

A team from Harvard Medical School said giving under-fives one portion of chips a week increases their risk by 27 per cent. Comments are welcomed perera6@hotmail.co.uk