Meet Acrylamide – a Dangerous Compound found in Thermally Processed Food

Various foodstuffs that we fry or bake end up on our plates almost every day. Such food is often labelled as a guilty pleasure – we don’t really eat it every day, but it is so tasty that we allow ourselves to indulge in it from time to time as a reward. These are often french fries, toast with crispy crust or similar bites. However, hiding behind that appealing golden-brown colour  and the familiar taste is a complex chemical process – a non-enzymatic browning reaction during which acrylamide is formed. This compound forms during thermal processing of food that is rich in simple carbohydrates, especially at high temperatures, and it can have long-term consequences for our health.

Origin of Acrylamide

Acrylamide is a chemical compound which can form in certain foods during cooking at high temperatures, such as frying, baking and roasting. Before it was discovered in food it was known as an industrial chemical which primary use was as a building block in various industrial processes, in the production of plastic, adhesives and paper, as a component of tobacco smoke and in the processing of drinking and wastewater including sewage systems. Acrylamide has also been found in some consumer goods, such as food packaging and certain types of adhesives.

Food processing

Heating food enhances its properties by changing the molecules at high temperature conditions, which results in a longer shelf life and better organoleptic properties such as colour, texture and taste. This process is applied to various food products, including fried, baked, dried, pasterized, sterilized and ultra-high temperature treated food.

Heating is an effective way of extending shelf life, improving taste and food saftey because it removes enzymes and microorganisms  as well as reduces the activity of water. However, such thermal processing can cause changes in the chemical composition of food, including hydrolytic degradation, oxidation, protein denaturation, molecular-level changes, colour degradation, enzyme digestion, carbohydrate caramelisation, the formation of newly formed contaminants, as well as interactions between proteins and organic compounds which may have mutagenic, carcinogenic and cytotoxic properties. Acrylamide does not occur in raw food itself, however it is formed during the heating process when the temperature reaches 120°C or more.

Even though acrlyamide exists as long as humans baked, fried or toasted food, it was only in April 2002 that the Swedish national food administration published that long-term thermal treatment of some foods can produce significant amounts of acrylamide.

What is the Maillard Reaction?

Acrylamide in food is formed from sugars and amino acids which are naturally present in foodstuffs, through a process known as the Maillard reaction. It is a non–enzymatic browning reaction in which carbohydrates react with amino acids during heating. This reaction creates very charatheristic colours and aromas which enhance the falvour of the food but also its saftey and certain useful properties thanks to the formation of flavour–desirable Maillard reaction products. Many factors influence the Maillard reaction including the source of the proteins, temperature and the duration of heating, pH value, water activity and the type of used supstrate.

In the initial phase of Maillards reaction, known as the sugar-amine condensation, a nucleophilic condensation occurs betwen the carbonyl group of sugar and the amino group of the amino acid. This is followed by the degradation phase of amino acids which leads to a reduced nutritional value. The final stage includes the creation of advanced glycation end products (AGEs), which are responsible for various effects linked to skin aging, including the formation of coloured compounds, melanoidins and aromatic substances.

Acrylamid is formed when asparagine, naturally present amino acid, reacts with reducing sugars or their degradation products at high temperatures and low moisture content. In that reaction α-amino group of asparagine reacts with the carbonyl group of the sugar, forming the N-glycosyl-asparagine (carbinolamine) which then, by removing water molecules during heating, transforms into a Schiff base.

Toxicity of Acrylamide

Acrylamide has shown neurotoxic effects with people that are proffesionally exposed to high concentrations, with reported symptomes like ataxia, muscle weakness, weight loss and damage to nerve fibers. One case from Sweden describes peripheral neuropathies in tunnel workers exposed to injection mixtures containing acrylamide. Longterm exposure in animal experiments has been associated with tumor formation, although evidence of carcinogenicity in humans is so far inconsistent. IARC classifies acrylamide as „probably carcinogenic to humans“. Also, animal studies show possible reproductive, hepatic and immunotoxicity at higher doses, while evidence in humans is limited and insufficient for final conclusions.

How to Reduce Acrylamide Levels?

In order to reduce the production of acrylamide, its crucial to control the concentration of precursors such as fructose, glucose and asparagine, as well as to adjust cooking time. Effective strategies for reduction include enzymatic hydrolysis of asparagine using asparaginase, the addition of specific additives, lowering the pH value or reducing heat treatment. Acrylamide is a potentionally carcinogenic compound.

Should I stop Eating Fried, Baked or Roasted food?

No. The best advice of the FDA for decreasing the intake of acrilyamide with food is to eat a healthy food diet which emphasises the intake of fruits, vegetables, whole grains and low-fat dairy products. Includes lean protein sources such as meat, fish, eggs, beans and nuts, and limits saturated and trans fats, cholesterol, aslt and added suggars. Since acrylamide levels are directly linked to the browning of food, some countries are reccomending the consumers: „Do no over-brown food, let it lightly brown.“  Recommended practices also include different cooking methods and the finding a better balance, for an example boiling, steaming, stewing which could also help reduce consumers overall exposure.

Translated by: Dea Radek