A study by the European Commission and Nestlé Product Technology reports that efforts to reduce the acrylamide content of coffee also negatively affect flavour and nutritional benefits.
The results, published in the journal LWT - Food Science and Technology, sets up an interesting "risk-benefit" conundrum for ingredients such as coffee, with debate likely to focus on whether benefits outweigh the risks or vice versa.
Coffee is one of the world's largest traded commodities and is produced in over 60 countries, generating more than $70bn in retail sales annually.
"Increasing the roasting degree led to a decrease in acrylamide concentration as well as radical scavenging capacity," wrote lead author Carmelina Summa from the EC's Institute for Reference Materials and Measurements.
"The results of this work indicate that any mitigation efforts must also take into account the potential loss of desired food constituents and consequently changes to the risk/benefit characteristics of foods."
Acrylamide is a carcinogen that is created when starchy foods are baked, roasted, fried or toasted. It first hit the headlines in 2002, when scientists at the Swedish Food Administration first reported unexpectedly high levels of acrylamide, found to cause cancer in laboratory rats, in carbohydrate-rich foods.
Since the Swedish discovery a global effort has been underway to amass data about this chemical. More than 200 research projects have been initiated around the world, and their findings co-ordinated by national governments, the EU and the United Nations.
According to background information by Summa and co-workers, coffee contributes about 40 per cent of the total acrylamide exposure in Sweden and about 33 per cent of that in Switzerland, making it a significant contributor from dietary sources. The suspected carcinogen is formed during the Maillard reaction that is initiated during roasting.
However, the Maillard reaction also leads to the production of melanoidins, compounds with potent antioxidant activity. Coffee is said to contribute 64 per cent of an average Norwegian's antioxidant intake, and has been linked to a reduced risk of certain disease, especially liver disease and diabetes.
The researchers ran a series of experiments and determined acrylamide production and in vitro radical scavenging capacity (a measure of antioxidant activity) of Robusta and Arabica coffee samples after roasting at 236 degrees Celsius over varying times to obtain very light, light, medium and dark roasted coffee.
Summa reports that more intense roasting to obtain darker coloured beans reduced acrylamide levels, but also negatively affected the ability to scavenge free radicals, as measured with electroparamagnetic resonance (EPR).
"More intense roasting, i.e. greater thermal load, of coffee beans has been considered as a way to decrease the concentration of acrylamide in coffee, albeit with a major impact on the organoleptic properties and consequently acceptability of the product," said Summa.
"The results obtained in this study show that a reduction in the concentration of acrylamide with darker degrees of roasting is accompanied by a reduction of the radical scavenging capacity of coffee (within the same coffee species)," she said.
Reducing the acrylamide content of foods has become a major target for the food industry, but this research suggests that removing a major source of antioxidants, as well as reducing flavour and therefore acceptability of the product must also be considered.
Source: LWT - Food Science and Technology
Published on-line ahead of print, doi: 10.1016/j.lwt.2006.11.016
"Impact of the roasting degree of coffee on the in vitro radical scavenging capacity and content of acrylamide"
Authors: C.A. Summa, B. de la Calle, M. Brohee, R.H. Stadler, E. Anklam