C03037: Examination of the effect of domestic cooking on acrylamide levels in food

Study Duration: March 2004 to May 2005

Contractor: Leatherhead Food International

Acrylamide is a process contaminant that is formed in starch-rich foods, which have undergone cooking or processing at a high temperature. These foods include crisps, chips, bread and crispbread. Acrylamide is known to cause cancer in animals and its presence in some foods may harm people's health.

Acrylamide has been classified as a potential genotoxic carcinogen and so levels of acrylamide in food should be as low as reasonably achievable.

The study will enable a better understanding of domestic cooking conditions responsible for acrylamide formation in food prepared at home. This may provide information on how domestic cooking and preparation of foods could be altered to reduce levels of acrylamide in food.

The study will investigate the effects of various cooking methods with a view to reducing acrylamide formation. Cooking methods that lead to reduction will be identified and, as a result, sensory and consumer trials will be undertaken to verify that a reduction in acrylamide levels do not impair quality or consumer acceptance of domestically cooked food.

The objectives of the project are to:

• compile a list of foods relevant to home cooking that are high in asparagine, taking into account levels of consumption
• investigate the relationship between different types of ingredients used before cooking and acrylamide formation
• examine the effects of cooking on acrylamide levels of less complex foods (i.e. vegetables) as well as complex foods (cereal and flour-based)

This study was carried out to investigate the effects of domestic cooking methods on the level of acrylamide in food particularly in potatoes. Onions were also studied to a lesser extent. The research was done as part of the international effort to determine the mechanism by which acrylamide is formed in food with a view to developing reduction measures.

The following were the key findings:

• Acrylamide was formed in potatoes cooked at the high temperatures typically used in domestic cooking. Acrylamide was formed in roast, sautéed, chipped and baked potatoes. No acrylamide was detected in the raw, boiled or microwaved potatoes. Similar results were found for onions.
• Acrylamide was found in fried onions and baked onions cooked from frozen.
• Acrylamide levels in commercially-produced chips sold frozen for cooking at home, showed that in all cases the chips “as sold” contained acrylamide, resulting from the partial cooking process they had undergone already.
• Further increases in acrylamide were minimised when the commercially-produced chips were cooked according to cooking instructions on the packaging.
• Chips made from fresh potatoes cooked to a lighter colour were found to have lower acrylamide levels than chips cooked to a darker colour but care must be taken as not all chips were edible at the lighter colour. The same results were found with fried and roast onions.
• Soaking chips made from fresh potatoes in water for 30 minutes before cooking also led to lower levels of acrylamide.
• Potatoes which were refrigerated prior to chipping showed an increase in acrylamide level due to an increase in the sugar content of the potatoes, confirming the link between the formation of acrylamide and sugar content in potatoes. Storing potatoes in a fridge causes an increase in their sugar content which may lead to higher acrylamide levels when cooked.
• Potato varieties recommended as ‘general purpose’ were found to have higher levels of acrylamide when cooked (roast or chips) compared to other varieties analysed.
• A range of commercial potato varieties with contrasting characteristics were selected and stored conventionally according to typical current practices for the pre-pack industry in order to investigate the effect of storage. In all cases stored potatoes were higher in acrylamide and this correlated with an increase in acrylamide on cooking.
• Repeated use of oil for frying chips showed that for most of the oils there was no effect on acrylamide levels when the oils were re-used.

The final report is available from the Agency’s Information Centre.
To obtain a copy, please contact the Enquiry Desk, Information Services, Food Standards Agency (tel: 020 7276 8181/8182 or email: infocentre@foodstandards.gsi.gov.uk)