Since the Swedish National Food Administration and Stockholm University discovered acrylamide in a variety of fried and oven-baked foods on April 24, 2002, a broad range of activities have been initiated to address the potential health hazards associated with this chemical compound.

In June 2002, in the wake of the Swedish studies, a special consultation was convened in Geneva by the World Health Organization (WHO) and the Food and Agriculture Organization (FAO) to review available data and make recommendations on further study.  This consultation spawned an international effort to characterize the risk/extent of public exposure, identify a mechanism of formation, develop methods of detection, and educate consumers throughout the assessment process.

What is Acrylamide?

Acrylamide (2-propenamide, C3H5NO) is a white odorless crystalline solid that is soluble in most polar solvents such as water, methanol and acetone, but is insoluble in non-poplar solvents such as benzene and n-heptane.  It can be synthesized by the hydration of acrylonitirile (C3H3N) with sulfuric acid monohydrate at 90 to100oC.  From the resulting sulfate solution, acrylamide is extracted by neutralization with ammonia and subsequent cooling to isolate the crystalline monomer.

The largest use for acrylamide is as a chemical intermediate in the production of polyacrylamides for the treatment of municipal drinking water and waste water.  Large quantities of polyacrylamide gel are also produced for use as a grouting agent in the construction of dam foundations, tunnels, and sewers.

It was only by accident that acrylamide’s presence in food was discovered.  Swedish scientists made the discovery during a study of Swedish tunnel workers exposed in 1997 to large amounts of acrylamide from a water sealant.  The control group in the study had not been exposed to acrylamide at work, however an unexpected presence of acrylamide was found in their systems.  Eventually, it was learned that acrylamide was present in these workers’ diets of overcooked foods.

Toxicology

To date, epidemiologic studies of workers exposed to acrylamide have failed to demonstrate any relation between exposure, and either, overall incidence of malignancy or incidence of specific cancers.  However, exposure to test rats of both sexes has shown statistically significant increases in the incidences of several tumor types by both the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Health and Human Service’s National Toxicology Program (NTP).  The EPA’s Integrated Risk Information System indicates in its Carcinogenicity Assessment for Lifetime Exposure that studies have produced tumors of the central nervous system, mammary/thyroid glands, uterus, and oral cavity for administered doses of 500µg/kg-day (Human equivalent dose = 76µg/kg-day) and above.

In addition, acrylamide is a potent human neurotoxin that affects both the central and peripheral nervous systems.  Acute exposure causes behavioral disturbance, auditory/visual hallucinations, a depressed level of consciousness, seizures, hypotension, adult respiratory distress syndrome, and/or delayed peripheral neuropathy.  Chronic occupational exposure causes contact dermatitis, excessive sweating, fatigue, weight loss with normal appetite and/or neurobehavioral changes.

Only the acrylamide monomer is toxic.  Acrylamide polymers are non-toxic.  It is unclear whether acrylamide causes cancer at the much lower levels found in food.

Mechanism of Formation

On November 17, 2003 in Brussels, Belgium, 60 participants from 16 countries, including the U.S. and Canada, attended the European Food Safety Authority (EFSA) workshop on acrylamide formation in food.  This workshop was specifically aimed at stimulating a technical level discussion on research being conducted, with an emphasis on understanding the mechanism of formation of acrylamide in food.  Several mechanisms have been proposed, yet the precise mechanism is still to be determined.  However, most experts agree that the most likely pathway is via the Maillard reaction of the natural food components asparagine (a common amino acid) and a carbonyl source (typically fructose or glucose) at temperatures greater than 125oC.

In the Maillard reaction, the carbonyl group of the sugar reacts with the amino acid, producing N-substituted glycosylamine and water.  This unstable Schiff base can undergo Amadori rearrangement to generate ketosamines which after subsequent loss of the amine group and dehydration form various dicarbonyl compounds.  Asparagine and a dicarbonyl compound can then react to form, via classical Strecker degredation, the Strecker aldehyde of asparagine. A clear path from this aldehyde to asparagine has yet to be determined.  Other thermolytic pathways under investigation include formation of acrylamide directly from the Schiff intermediate via amino acid initiated 1,2-elimination or beta-elimination of the decarboxylated Amadori products.  Research is still underway.

Typically, foods with the highest concentrations of acrylamides include: fried, baked, and microwaved (not boiled) foods with high surface areas, foods with high levels of carbohydrates, and foods with low water activity that are major sources of free asparagines, such as potato chips, French fries, cereals, toast, coffee and chocolate.

Methods of Detection

Several methods have been developed for the extraction and quantitation of acrylamide in cooked foods.

For the extraction of acrylamide, the most widely accepted and utilized methods involve the addition of an internal isotope standard (typically 13C3-acrylamide), defatting with hexane or petroleum ether, extraction with water, and cleanup with a strong cation exchange solid phase extraction (SPE) cartridge.  There is some evidence that high pH, low extraction temperature, and short extraction time can cause incomplete extraction.  Also, for assessing the long term health risks, bio-availability of the compound may need to be defined and incorporated as part of the extraction procedure.

For quantitation, either gas chromatography coupled with mass spectroscopy (GC/MS) after bromination or liquid chromatography with mass spectroscopy (LC/MS) is typically employed to obtain the necessary detection limits.  Other promising methods that have been confirmed by MS utilize LC with pulsed electrochemical detection or GC with electron capture detection.  Detection limits are in the range of 0.1 µg/kg to 10.0 µg/kg.

In 2002, the FDA published a draft method for the detection and quantitation of acrylamide in foods.  The method involves extraction with water, clean up on a solid phase extraction cartridge, and analysis by HPLC/MS/MS.  This method allows accurate measurement even at levels below 50 parts per billion (ppb).

Exposure

In May 2006, the U.S. Food and Drug Administration (FDA) released its third Exposure Assessment, and in July 2006 it released Survey Data for Individual Food Products and Total Dietary Study Results.  The current FDA database has values for acrylamide levels in food for approximately 2500 samples, representing 66 food categories including ethnic and regional foods.  In all three assessments, the average acrylamide intake for persons 2 years and older was found to be ~0.4 µg/kg-bw-day (bw=body weight).  As suspected, the foods with the highest levels of acrylamides were those processed at high temperatures, usually fried or baked.

Conclusion

Although acrylamide is of concern because it is a potential human carcinogen, it is a natural product of the cooking process and one hundred percent of the population consumes acrylamide as part of its diet.  To reduce the risk of exposure, the FDA continues to advise consumers to eat a balanced diet, choosing a variety of foods that are low in trans fat and saturated fat, and rich in high-fiber grains, fruits, and vegetables.

For more information, please contact: microbac_info@microbac.com.