Acrylamide and the Maillard reaction: mechanism, risk and mitigation

A crisp manufacturer in India buys potatoes from cold stores for most of the year, because fresh harvest supply lasts only a few months. Every season the laboratory sees the same pattern: acrylamide results climb as the stored crop ages, and the crisps fry darker at the same oil temperature. The cause is chemistry, not chance. The acrylamide Maillard reaction pathway needs two precursors the factory can measure and control. This article explains how acrylamide forms, how its risk is assessed and which mitigation measures work on a real production line.

What is acrylamide and why is it a concern?

Acrylamide (C₃H₅NO) is a small, water-soluble organic compound that forms in many starchy foods when they are fried, baked, roasted or toasted. Swedish researchers reported it in heated foods in 2002, and it has since been measured in crisps, chips, bread crust, biscuits, breakfast cereals and roasted coffee.

The International Agency for Research on Cancer (IARC) classifies acrylamide in Group 2A, probably carcinogenic to humans, largely on animal evidence and its mode of action. In the body it is converted to glycidamide, a metabolite that binds to DNA. The Joint FAO/WHO Expert Committee on Food Additives (JECFA) evaluated acrylamide in 2005 and 2010, and the European Food Safety Authority (EFSA) in 2015; both concluded that dietary exposure indicates a health concern for cancer. Studies of cancer in people have given inconsistent results, so risk managers apply ALARA, the principle that a contaminant should be kept as low as reasonably achievable.

How does the acrylamide Maillard reaction pathway work?

The Maillard reaction is the network of reactions between reducing sugars and amino groups that produces browning, roasted flavour and aroma when food is heated. Acrylamide is one of its side products, and labelling studies show that its carbon and nitrogen backbone comes from the amino acid asparagine.

1. Condensation. The carbonyl group of a reducing sugar, or another reactive carbonyl, reacts with the amino group of free asparagine and loses water to form a Schiff base, a compound with a carbon-nitrogen double bond.
2. Decarboxylation. With heat and low moisture, the Schiff base loses carbon dioxide through a cyclic intermediate (an oxazolidin-5-one) and forms an azomethine ylide.
3. Release. The ylide can release acrylamide directly, or hydrolyse to 3-aminopropionamide, which loses ammonia on further heating to give acrylamide.
4. Elimination. With long or intense heating, acrylamide also reacts further, so the level in the finished food is a balance between formation and loss.

Three conditions matter most. Formation is usually significant only above about 120 °C, which is why boiled and steamed foods contain little. It concentrates in the drying surface and crust, where water is lost and temperature climbs above 100 °C. And free asparagine and a reducing sugar must both be present: whichever is in shorter supply limits how much acrylamide forms. The Codex code notes that fructose tends to give more acrylamide than glucose.

The same pathway also creates the qualities consumers buy. Strecker degradation, the reaction of amino acids with dicarbonyl intermediates, yields many roasted and malty aroma compounds, and melanoidins, the brown nitrogen-containing polymers formed late in the reaction, give colour. The Advanced Food Science course follows the whole sequence, from the Amadori product to melanoidins and process contaminants.

Which foods and conditions produce the most acrylamide?

Fried and baked potato products, cereal products baked to low moisture, and roasted coffee are the main dietary sources. The limiting precursor and the main process drivers differ between them, which is why mitigation differs too.

Potato storage deserves particular attention. Tubers held below about 6 to 8 °C undergo cold-induced sweetening, in which starch breakdown and sucrose hydrolysis raise glucose and fructose, and acrylamide follows. The Codex code identifies storage above 6 °C as good practice for long storage, and recommends reconditioning cold-stored potatoes for a few weeks at about 12 to 15 °C before processing.

How is the risk from dietary acrylamide assessed?

Because acrylamide is genotoxic and carcinogenic in animals, risk assessors do not set a tolerable daily intake. They calculate a margin of exposure (MOE): the ratio between a dose that causes a small but measurable effect in animals and the estimated human intake. For genotoxic carcinogens, EFSA regards an MOE of 10,000 or more as of low concern for public health.

The reference dose is usually the BMDL10, the lower confidence limit of the dose estimated to cause a 10% increase in tumour incidence in animal studies.

For a manufacturer, no level is declared harmless, so the task is to apply every reasonable mitigation step and show with data that results are falling or holding low.

How can manufacturers reduce acrylamide?

Mitigation works by lowering the limiting precursor, lowering the heat load in the final low-moisture stage, or both. The Codex Code of Practice for the Reduction of Acrylamide in Foods (CXC 67-2009) sets out options across raw materials, formulation and processing:

• Raw materials. Choose potato varieties low in reducing sugars and test sugars or fry colour at intake. For cereals, low-asparagine varieties help, and wheat grown on sulphur-deficient soil accumulates more free asparagine, so adequate sulphur fertilisation matters.
• Pre-treatment. Washing and blanching cut potatoes leach out sugars and asparagine. Asparaginase, an enzyme that converts asparagine to aspartic acid and ammonia, can be added to doughs and applied to potato products.
• Process. Reduce the heat load at the end of cooking, when the product is driest. For French fries, the Codex code suggests an initial oil temperature of no more than 170 to 175 °C and cooking to a golden-yellow rather than golden-brown colour. In bakery, lower final baking temperatures and control of final moisture reduce formation.
• Formulation. Replace ammonium bicarbonate raising agents, which promote acrylamide in biscuits, and reduce reducing sugars, especially fructose-rich syrups. Calcium salts and lower pH have reduced formation in some products but may affect taste and texture.
• Sorting. In-line optical colour sorting removes dark crisps, which tend to carry the most acrylamide.

Most levers cost something in colour, flavour or texture, because Maillard chemistry also creates the product’s appeal. Asparaginase is the main exception: it removes a precursor without removing the sugars. Run sensory checks alongside every mitigation trial.

How do you verify that mitigation is working?

Verification combines periodic laboratory analysis of acrylamide with fast, on-line indicators such as product colour and intake sugar tests, trended over time and linked to every process change. Laboratory methods use liquid or gas chromatography with mass spectrometry (LC-MS/MS or GC-MS) and quantify acrylamide at microgram per kilogram levels. Colour is a useful day-to-day control once it is linked to acrylamide:

1. Collect paired samples across the normal colour range of the product, including deliberately light and dark ones, over several raw material lots.
2. Measure colour with a calibrated method and acrylamide with a validated method in a competent laboratory.
3. Plot acrylamide against colour, fit the relationship and note the scatter, since sugar and asparagine levels also vary.
4. Choose an internal acrylamide target from your risk assessment and customer or legal requirements, then set the colour limit where the upper prediction band, not the average line, meets that target.
5. Build the colour limit into operational controls with adjust or reject actions, and re-check the relationship after any change of variety, supplier, storage regime, oil, recipe or line.

Acrylamide is usually managed through prerequisite programmes and operational controls rather than a single critical control point, because no one step removes it. The Food Science for Industry Professionals course places it alongside mycotoxins and other process contaminants in a HACCP context.

What do Codex and regulators expect?

Internationally, the reference text is the Codex Code of Practice for the Reduction of Acrylamide in Foods (CXC 67-2009). It describes mitigation options for potato and cereal products, noted that commercial options for coffee were not available when it was adopted, and rests on ALARA: apply the measures that are feasible for your product and show their effect.

National rules vary. The European Union, through Commission Regulation (EU) 2017/2158, requires food businesses to apply specified mitigation measures and uses benchmark levels as performance indicators to check that mitigation is working, not as safe limits. Other countries use guidance values, monitoring programmes or no specific rules. Check your national legislation and customer specifications, and keep mitigation records ready for customer and certification audits.

Frequently asked questions

Does boiling or steaming food produce acrylamide?

Very little. Acrylamide forms mainly above about 120 °C in low-moisture conditions, while boiling and steaming hold food near 100 °C with plenty of water. That is why boiled potatoes contain far less acrylamide than chips or crisps made from the same tubers. Formation starts when a surface dries out and its temperature climbs, as in frying, baking, roasting and toasting.

Why does acrylamide rise when potatoes are stored cold?

Cold storage causes cold-induced sweetening. Below about 6 to 8 °C, potatoes break down starch and split sucrose into glucose and fructose, the reducing sugars that drive acrylamide formation in potato products. Because reducing sugars are usually the limiting precursor in potatoes, acrylamide rises with them. Store processing potatoes above about 6 °C, recondition cold-stored lots at warmer temperatures and test sugars or fry colour at intake.

Does asparaginase affect taste or colour?

Usually very little, which is its main advantage. Asparaginase converts free asparagine to aspartic acid and ammonia, removing an acrylamide precursor while leaving the sugars and other amino acids that create browning and flavour. It needs water, time, and a suitable temperature and pH to act, so it works best in doughs and on cut potato surfaces. Confirm the effect on your own product with trials and sensory tests.

Is darker roasted coffee higher in acrylamide?

Generally not. In coffee, acrylamide forms early in roasting, peaks and then declines as roasting continues, so very dark roasts tend to contain less than lighter ones. Coffea canephora beans generally give more acrylamide than Coffea arabica because they contain more free asparagine. Practical options for reducing acrylamide in coffee remain limited compared with potato and cereal products.

Is acrylamide a critical control point in HACCP?

Usually not. A critical control point (CCP) is a step at which a control measure essential to control a significant hazard is applied, with a validated critical limit. Acrylamide cannot be eliminated, has no safe threshold and forms across several steps, so it is normally managed through supplier specifications, operational controls such as frying temperature and colour limits, and verification testing.

Are there legal limits for acrylamide in food?

It depends on the country. Codex addresses acrylamide through a code of practice (CXC 67-2009) based on the ALARA principle. The European Union requires food businesses to apply mitigation measures and uses benchmark levels as performance indicators rather than safe limits. Other countries take different approaches, so check your national legislation and the specifications of the markets and customers you supply.

Next step. Advanced Food Science follows the Maillard reaction from the Amadori product and Strecker degradation to melanoidins and process contaminants such as acrylamide, and applies kinetic models to quality and contaminant formation. It ends with a proctored final assessment and an ASC certificate. To compare levels and topics, see all eleven food science and technology courses.

Sources. Codex Alimentarius Commission, Code of Practice for the Reduction of Acrylamide in Foods, CXC 67-2009 (FAO/WHO); IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 60: Some Industrial Chemicals (IARC, WHO, 1994); EFSA Panel on Contaminants in the Food Chain, Scientific Opinion on acrylamide in food, EFSA Journal 13(6):4104 (2015); Joint FAO/WHO Expert Committee on Food Additives (JECFA), evaluations of acrylamide at its 64th (2005) and 72nd (2010) meetings; S. Damodaran and K. L. Parkin (eds), Fennema’s Food Chemistry, 5th edn (CRC Press, 2017).

This article is general guidance and is not a substitute for the applicable standard, your national legislation or the advice of a qualified food safety professional.