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Food Safety Focus (161st Issue, December 2019) – Food Safety Platform

Benzo[a]pyrene in Edible Fats and Oils

Reported by Dr. Lily SUEN, Scientific Officer,
Risk Assessment Section, Centre for Food Safety

Fats and oils are frequently used in our culinary practices, for example, for stir-frying, deep-frying and baking, as well as for salad dressing and bread dips.  A number of food safety hazards may be present in fats and oils, including one of the potential contaminants, benzo[a]pyrene (B[a]P).  In this article, let’s take a look at what B[a]P is, and how we can reduce its occurrence in edible fats and oils and our dietary exposure to B[a]P.

The refining process of edible fats and oils.

The refining process of edible fats and oils.

What is B[a]P and its health effects in humans?

B[a]P is a kind of polycyclic aromatic hydrocarbons (PAHs), which are ubiquitous in the environment as contaminants, being present in air, soil, water and food.  PAHs may be formed during incomplete combustion or pyrolysis (i.e. chemical decomposition by heating in the absence of oxygen) of organic matters during industrial processes and food processing.

Of note, the formation of PAHs is only significant at higher temperatures, generally over 350-400°C; below this temperature the formation of B[a]P in food is minimal.  Certain methods of food preparation, including drying (e.g. drying food through direct contact of combustion gases), roasting, smoking and barbecuing, are recognised as important sources of food contamination with B[a]P.

B[a]P is toxic to human genes and is classified as a Group 1 agent (i.e. carcinogenic to humans) by the International Agency for Research on Cancer (IARC) of the World Health Organization.  Due to the genotoxic and carcinogenic nature of B[a]P, no safety reference value for B[a]P can be determined; efforts should be focused on minimising its exposure as far as practicable so as to reduce the health risks it associated.

What are the sources of dietary exposure of B[a]P?

The Joint FAO/WHO Expert Committee on Food Additives (JECFA) has concluded that one of the major contributors to intakes of PAHs is vegetable fats and oils owing to their higher concentrations of PAHs.  Even though smoked and barbecued foods usually contain higher concentrations of PAHs in general, they do not contribute significantly to the dietary intake of PAHs as they constitute small components of the diet.

Why are edible fats and oils contaminated with B[a]P?

B[a]P present in the environment may contaminate foods including cereals and plants used for the production of vegetable oils.  In addition, vegetable oils can also be contaminated during smoking and drying processes, where combustion products may come into contact with the food, for drying oil seeds prior to oil extraction.

What are the ways to reduce B[a]P in edible fats and oils?

Codex has established a “Code of Practice for the Reduction of Contamination of Food with Polycyclic Aromatic Hydrocarbons (PAH) from Smoking and Direct Drying Processes”, which provides guidance to prevent and reduce contamination of foods with PAHs in commercial smoking and direct drying processes.  Among other things, it highlights that direct contact of oil seeds or cereals with combustion products during drying processes can result in contamination with PAHs and should therefore be avoided; contact of food with combustion gases should also be minimised.

Where a system with a burner is being used in the drying process, the temperature of the burner should be sufficient to allow complete combustion of the fuel, as incomplete combustion can lead to formation of PAHs in the drying gases.  Furthermore, the drying time should be as short as possible to decrease the exposure of the processed food to the potentially contaminating gases as much as possible. 

Last but not least, the level of B[a]P in oils can be reduced during the refining processes, including the bleaching (e.g. addition of activated carbon) and deodourisation steps, while the final level of B[a]P depends on the refining conditions adopted (see Figure). 

How can we reduce B[a]P exposure from our diet?

We should maintain a balanced and varied diet, which comprises a wide variety of fruits and vegetables; avoid overindulgence in barbecued meat, particularly charcoal grilled meat and smoked meat/fish; and remove charred parts of food.  Although fats and oils are essential in the absorption of fat-soluble vitamins, we should eat fats and oils sparingly with reference to the food pyramid.  Always choose healthier oils and fats, i.e. oils rich in monounsaturated fatty acids (e.g. canola oil and olive oil) and polyunsaturated fatty acids (e.g. corn oil and soybean oil), whenever possible.