Acrylamide forms in burnt areas of food, particularly starchy foods like potatoes, when cooked with high heat, above 120 °C (248 °F).[7] Despite health scares following its discovery in 2002, and its classification as a probable carcinogen, acrylamide from diet is thought unlikely to cause cancer in humans; Cancer Research UK categorized the idea that eating burnt food causes cancer as a "myth".[8][9]
Production
Acrylamide can be prepared by the hydration of acrylonitrile, which is catalyzed enzymatically:[6]
CH2=CHCN + H2O → CH2=CHC(O)NH2
This reaction also is catalyzed by sulfuric acid as well as various metal salts. Treatment of acrylonitrile with sulfuric acid gives acrylamide sulfate, CH=CHC(O)NH2·H2SO4. This salt can be converted to acrylamide with a base or to methyl acrylate with methanol.
Uses
The majority of acrylamide is used to manufacture various polymers, especially polyacrylamide. This water-soluble polymer, which has very low toxicity, is widely used as thickener and flocculating agent. These functions are valuable in the purification of drinking water, corrosion inhibition, mineral extraction, and paper making. Polyacrylamide gels are routinely used in medicine and biochemistry for purification and assays.[6]
Toxicity and carcinogenicity
Acrylamide can arise in some cooked foods via a series of steps by the reaction of the amino acid asparagine and glucose. This condensation, one of the Maillard reactions, followed by dehydrogenation produces N-(D-glucos-1-yl)-L-asparagine, which upon pyrolysis generates some acrylamide.
The discovery in 2002 that some cooked foods contain acrylamide attracted significant attention to its possible biological effects.[11]IARC, NTP, and the EPA have classified it as a probable carcinogen, although epidemiological studies (as of 2019) suggest that dietary acrylamide consumption does not significantly increase people's risk of developing cancer.[8]
Europe
According to the EFSA, the main toxicity risks of acrylamide are "Neurotoxicity, adverse effects on male reproduction, developmental toxicity and carcinogenicity".[9][12] However, according to their research, there is no concern on non-neoplastic effects. Furthermore, while the relation between consumption of acrylamide and cancer in rats and mice has been shown, it is still unclear whether acrylamide consumption has an effect on the risk of developing cancer in humans, and existing epidemiological studies in humans are very limited and do not show any relation between acrylamide and cancer in humans.[9][13] Food industry workers exposed to twice the average level of acrylamide do not exhibit higher cancer rates.[9]
Baking, grilling or broiling food causes significant concentrations of acrylamide. This discovery in 2002 led to international health concerns. Subsequent research has however found that it is not likely that the acrylamides in burnt or well-cooked food cause cancer in humans; Cancer Research UK categorizes the idea that burnt food causes cancer as a "myth".[9]
Laboratory research has found that some phytochemicals may have the potential to be developed into drugs which could alleviate the toxicity of acrylamide.[16]
Mechanism of action
Acrylamide is metabolized to the genotoxic derivative glycidamide. On the other hand, acrylamide and glycidamide can be detoxified via conjugation with glutathione.[17][18]
Occurrence in food
Acrylamide was discovered in foods, mainly in starchy foods, such as potato chips (UK: potato crisps), French fries (UK: chips), 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 boiled,[19] or in foods that were not heated.[20]
Acrylamide has been found in roasted barley tea, called mugicha in Japanese. The barley is roasted so it is dark brown prior to being steeped in hot water. The roasting process produced 200–600 micrograms/kg of acrylamide in mugicha.[21] This is less than the >1000 micrograms/kg found in potato crisps and other fried whole potato snack foods cited in the same study and it is unclear how much of this enters the drink to be ingested. Rice cracker and sweet potato levels were lower than in potatoes. Potatoes cooked whole were found to have significantly lower acrylamide levels than the others, suggesting a link between food preparation method and acrylamide levels.[21]
Acrylamide levels appear to rise as food is heated for longer periods of time. Although researchers are still unsure of the precise mechanisms by which acrylamide forms in foods,[22] many believe it is a byproduct of the Maillard reaction. In fried or baked goods, acrylamide may be produced by the reaction between asparagine and reducing sugars (fructose, glucose, etc.) or reactive carbonyls at temperatures above 120 °C (248 °F).[23][24]
The US FDA has analyzed a variety of U.S. food products for levels of acrylamide since 2002.[30]
Occurrence in cigarettes
Cigarette smoking is a major acrylamide source.[31][32] It has been shown in one study to cause an increase in blood acrylamide levels three-fold greater than any dietary factor.[33]
See also
Acrydite: research on this compound casts light on acrylamide
^Mendel Friedman (2003). "Chemistry, Biochemistry, and Safety of Acrylamide. A Review". J. Agric. Food Chem. 51 (16): 4504–4526. doi:10.1021/jf030204+. PMID14705871.
^Friedman, Mendel (2003). "Chemistry, Biochemistry, and Safety of Acrylamide. A Review". Journal of Agricultural and Food Chemistry. 51 (16): 4504–4526. doi:10.1021/jf030204+. PMID14705871.
^Tareke, Eden; Rydberg, Per; Karlsson, Patrik; Eriksson, Sune; Törnqvist, Margareta (August 2002). "Analysis of Acrylamide, a Carcinogen Formed in Heated Foodstuffs". Journal of Agricultural and Food Chemistry. 50 (17): 4998–5006. doi:10.1021/jf020302f. PMID12166997.
^ abOno, H.; Chuda, Y.; Ohnishi-Kameyama, M.; Yada, H.; Ishizaka, M.; Kobayashi, H.; Yoshida, M. (March 2003). "Analysis of acrylamide by LC-MS/MS and GC-MS in processed Japanese foods". Food Additives and Contaminants. 20 (3): 215–220. doi:10.1080/0265203021000060887. PMID12623644. S2CID9380981.
^Jung, MY; Choi, DS; Ju, JW (2003). "A Novel Technique for Limitation of Acrylamide Formation in Fried and Baked Corn Chips and in French Fries". Journal of Food Science. 68 (4): 1287–1290. doi:10.1111/j.1365-2621.2003.tb09641.x.
^Mottram D.S.; Wedzicha B.L.; Dodson A.T. (2002). "Acrylamide is formed in the Maillard reaction". Nature. 419 (6906): 448–449. doi:10.1038/419448a. PMID12368844. S2CID4360610.