Crisps and coffee highest acrylamide levels, warns UN
fries, potato crisps and coffee recording the highest contamination
levels of the carcinogen acrylamide, warns UN committee, but
confirm that recent studies by food industry show processing
methods could significantly reduce the levels, writes Lindsey
Partos.
Scientists from 15 countries meeting under the aegis of JECFA, the UN's committee on food additives, caution that the harmful contaminant acrylamide, in certain foods, may be of public heath concern since it has been shown to cause cancer in animals.
In April 2002, acrylamide came to the attention of the food industry when scientists at the Swedish Food Administration first reported unexpectedly high levels in fried, baked, grilled, toasted or microwaved carbohydrate-rich foods, for example chips, roast potatoes, crisps and bread.
Since then, an international effort of more than 200 research projects has been initiated around the world with their findings co-ordinated by national governments, the European Union and the United Nations.
In the absence of any health-based guidance values (tolerable intake levels) for acrylamide, and a bid to construe a way forward to slicing this potential carcinogen out of the food chain, scientists meeting in Rome last month assessed national dietary intake data for 17 countries.
"The major contributing foods to total exposure for most countries were potato chips (16-30 per cent), potato crisps (6-46 per cent), coffee (13-39 per cent), pastry and sweet biscuits (10-20 per cent) and bread and rolls/toasts (10-30 per cent). Others foods items contributed less than 10 per cent of the total exposure," the committee reports.
Tackling this figure, the UN group urged national food safety authorities to work towards improving food preparation technologies that "lower significantly the acrylamide content in critical foods."
Acrylamide appears to form when dietary items, typically plant commodities high in carbohydrates and low in protein, are subjected to high temperatures during cooking or other thermal processing.
Scientists now know that the most important precursor is the free amino acid asparagine which reacts with reducing sugars in the Maillard reactions that also form colour and flavour.
Since 2002 research has shown that although trace amounts of acrylamide can be formed by boiling, significant formation generally requires a processing temperature of 120 oC or higher.
Most acrylamide is accumulated during the final stages of baking, grilling or frying processes as the moisture content of the food falls and the surface temperature rises, with the exception of coffee where levels fall considerably at later stages of the roasting process.
Acrylamide seems to be stable in the large majority of the affected foods, again with the exception of ground coffee for which levels can decline during storage over months.Since formation is dependent on the exact conditions of time and temperature used to cook or heat-process a food, there can be large variations between brands of the same product and between batches of the same brand. Large variations are also to be expected during cooking although this aspect has been less well documented.
The composition of the food also has an influence, crucially the content of free asparagine and reducing sugars. Varietal, storage and seasonal variations can occur. Within ranges of natural variation, the limiting precursor in cereals is asparagine while fructose and glucose are more important in potatoes. Other important factors are pH and water content.
In a review submitted to the UN group by Europe's €600 billion food and drink industry (CIAA) apparently recent investigations have achieved a 30 to 40 per cent reduction in acrylamide levels of potato crisps by introducing several adjustments in the existing production procedures.
But the UN committee states: "The detailed data behind this calculation were not reported and it is not known to what extent it has been applied by crisp producers."
Significant reduction was also reported from process-optimisation for non-fermented crispbread, while little progress was obtained so far in reducing levels in various other important intake sources, for example, roasted coffee and breakfast cereals.
According to findings from the additive group the most efficient reduction has been achieved by using the enzyme asparaginase to selectively removeasparagine prior to heating.
"Although tested both in cereal and potato models, the use is probablylimited to specific food products manufactured from liquidised or slurried materials," says the group.
Several other means of lowering the precursor levels can be applied at various stages of the food chain, for instance, byvariety selection and plant breeding, controlling growth and storage factors affecting sugar concentrations in potatoes, pre-treatment of potato pieces by soaking or blanching, and prolonged yeast fermentation time in breadmaking.
Other mitigation possibilities include alteration of the product composition: addition of competing amino acids or acidic compounds, and alteration ofprocess conditions - lowering the frying temperature.
But a key obstacle to this progress is the fact that the feasibility of adapting these methods to large-scale food processing has not been "completely studied" in most cases.
Furthermore, any major changes would need to be checked for consumer acceptability, nutritional quality, and the possible increased formation of other undesirable substances.
In its final recommendations, the committee urged: continued efforts to cut acrylamide concentrations in food; and continued work on using PBPK modelling to better link human biomarker data with exposure assessments and toxicological effects in experimental animals.
In addition, the committee highlighted the need for more occurrence data on acrylamide in foods consumed developing countries.
