Top Editors ... Acrylamide Management in Potato Crisp Manufacturing

Title: Acrylamide Management in Potato Crisp Manufacturing
Date: 01/08/2006
Autor: By Dr Ronald Schroedter

Since 2002, when the Swedish authorities published the presence of the probable
Cancerogenic substance acrylamide in food, industry has conducted many investigations to find the right adjustments in their processes to reduce the level of this food-borne intoxicant

From mechanistic studies it was discovered that the amino acid asparagine and reducing sugars play the mayor role in acrylamide formation. Formally, acrylamide is builT from the amino acid under loss of carbon dioxide and ammonia at low moisture conditions in non-enzymatic browning. Pursuing the goal of acrylamide reduction, three mayor routes have to be taken into consideration: influencing the content of asparagine, reducing sugars, and reducing heat during processing.
To reduce the original reactant levels in base products like potatoes or cereal flours it is necessary to select cultivars with low asparagine contents wherever possible. Unfortunately asparagine acts in many plants, especially within the
solanaceous herb group - with its prominent representative potato – as an inner-plant nitrogen carrier and nitrogen reservoir. Based on its functionality, asparagine is the dominating free amino-acid with concentrations at 50%. An entire reduction of this particular amino acid is therefore not possible without changing the plant’s metabolism
completely. Even classical technology in developing new cultivars will take a long time: ten years is the minimum
for checking varieties on their robustness against plant diseases and their desired new functionality.

Enzyme technology

Another hopeful approach has been developed for a group of special products made from potato doughs (staple chips). Industrial patents have been published, which suggests using the enzyme asparaginase to convert asparagine into aspartic acid, which is no longer able to react in high yields to acrylamide.
Unfortunately the use of these enzymes are at the moment too expensive for a broader application in
commodities. Controlling reducing sugars is the second approach that can be used to minimise the formation of acrylamide in food, as they are the necessary reaction partner within the Maillard reaction pathway. Again by selecting low sugar cultivars, preventative measurements could be taken to minimise one necessary component
in the Maillard reaction.
The reducing sugar level plays an even more important role during the different stages of harvesting and storage. Usually potatoes are harvested with a low sugar level, which increases during the storage period by metabolic activity of the tuber. An adapted fertilising and harvesting regime will guarantee a low sugar level in the initial stage by using good agricultural practises. The use of fresh potatoes for a longer time is one of the ideas that has been suggested to extend the time during which low sugar tubers are available for processing. With flexible sourcing from early varieties in South Europe to late cultivars in Central Europe, demand for fresh potatoes could be met.
During the storage stage, the use of sprouting suppressors will reduce the metabolic activity in potatoes and sugar formation; as well as constant cooling down to between 10 and 6°C under dry and dark conditions.
Regular sugar testing is a must to detect the first signs of activity within the stocks. A clear prediction of the
behaviour of potatoes is still not possible, however, due to the influence of climate conditions at the growing period of
potatoes. Generally warm and sunny summers have a very positive effect on the shelf life of stored tubers.

Processing solutions

During the processing stage, blanching procedures (a hot water treatment) are able to reduce sugars via a leaching process. This effect may be ensured by adding salts and acids to lower the pH. Unfortunately blanching has a negative effect on texture and sensorial behaviour of many products and will influence consumer acceptance directly.
The frying process has two different stages: in the first stage water is evaporated, resulting in moisture levels below 8% at the end of the process, with almost no acrylamide formation. Beginning from this point, and located at the surface, the Maillard reaction starts rapidly, resulting in colour and acrylamide formation. The temperature steering in combination with the resulting moisture content is the most important tool to control acrylamide formation. It is necessary to find a compromise between product shelf life, sensorial behaviour (crispiness) and colour. Optical sorting machines may help to divide the over-roasted crisps from the desired coloured ones.
To manage the food-borne intoxicant acrylamide effectively, many efforts are being made to reduce the reactants in the used raw material. Although it is not possible to reduce the amino acid asparagine completely, the reducing sugar
content could be managed, using good agricultural and storage practices. Finally, careful process management will help to minimise the development of acrylamide.