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R425 Producing Low-Acrylamide Risk Potatoes

Publication Date: 
23 August 2011
Author/Contact :
Author/Contact: 
Nigel Halford

Contractor :
Contractor: 
Rothamsted Research

Full Research Project Title: Producing low-acrylamide risk potatoes
Duration: April 2009 - March 2012

Aim: To generate new knowledge and understanding of the genes and processes that control acrylamide forming potential.

Industry Challenge

Acrylamide was discovered in a range of foods in 2002. It is classified by the World Health Organisation and the International Agency for Research on Cancer as 'probably carcinogenic to humans and has neurological and reproductive effects at high doses. Acrylamide forms in food through the Maillard reaction, a complex series of reactions between amino groups and sugars, such as glucose and fructose. The Maillard reaction gives rise to lots of products, many of which impart colour, aroma and flavour; acrylamide only forms when an amino acid called asparagine participates in the final stages of the reaction. Asparagine, glucose and fructose can therefore be regarded as the precursors for acrylamide formation. Foods with the highest levels of acrylamide are carbohydrate-rich and cooked at high temperatures (frying, roasting or baking). Potatoes have a high acrylamide potential. The challenge is whether potatoes can be produced with modified levels of the acrylamide precursors (sugars and asparagine) either by agronomic or genetic means.

Collaboration

Advanced Technologies Cambridge Ltd, Conagra Foods, European Snacks Association, Higgins Agriculture, Kettle Foods, Potato Processors Association, Rothamsted Research, James Hutton Institute, Tesco Stores, United Biscuits, University Of Reading.

Approach

The main aim is to be achieved primarily by understanding key components of amino acid and sugar metabolism in potato, how they interact with each other and how they are affected by environmental factors. It should also increase the understanding of colour and flavour development, how these key parameters are affected by amino acid and sugar levels and how they relate to acrylamide risk.

Objectives

a) To identify potato germplasm/varieties with ‘high’ and ‘low’ acrylamide-producing potential.

b) To identify key genes and quantitative trait loci (QTL) controlling asparagine levels in potato tubers..

c) To determine the effect of stress on asparagine and sugar accumulation.

d) To compare the relative importance of import and synthesis in situ for asparagine accumulation in potato tubers.

e) To confirm the importance of candidate genes by genetic modification (hypothesis testing).

f) To determine the extent of allelic variation in candidate genes involved in asparagine metabolism.

g) To determine the optimum soil nitrogen and sulphur levels for minimum acrylamide-forming potential.

h) To understand the relationship between colour and flavour formation and acrylamide risk.

Key Findings

  • A simplified method for acrylamide analysis (using LC-MS-MS) was developed specifically for potato crisps, fries and other potato products, but is also applicable to acrylamide in most foods and related model systems.
  • Initially, 9 commercial potato varieties were studied (French fry varieties Maris Piper, Pentland Dell, King Edward, Daisy, and Markies; and crisping varieties Lady Claire, Lady Rosetta, Saturna, and Hermes); subsequently this was extended to 20 varieties in controlled field trials. Crisps produced from Lady Claire and Saturna were consistently below the 1000μg/kg acrylamide level, as were crisps from Lady Rosetta during early storage and Markies in late storage. These studies showed the potential of variety selection for reducing acrylamide formation in potato products, and the importance of using potatoes within their normal storage window.
  • The results also increased the understanding of the complex relationship between asparagine and sugar concentration and acrylamide risk in potatoes. Glucose concentration was the most important factor, and there was also a significant correlation between total reducing sugars and acrylamide formation. Both total free amino acid concentration and free asparagine concentration correlated with acrylamide formation in the French fry varieties but not the crisping varieties.
  • It was shown that glutamine and glutamate, and not asparagine, were the major transported amino acids in potato; the asparagine that accumulates in potato tubers must therefore be made there.
  • Nitrogen increased acrylamide-forming potential in some varieties, while sulphur mitigated the effect of high nitrogen application but again only in some varieties. It was concluded that advice to growers on fertiliser application would have to be tailored for each variety.

To conclude, the project has shown that improving the storage characteristics of potatoes, reducing the concentrations of both free asparagine and reducing sugars and making the concentrations of these metabolites less responsive to environmental factors should all be targets. However, reducing acrylamide formation while not affecting the qualities of a product that are demanded by consumers is likely to be difficult and it is important that breeders take this into account. Further details can be found in the reports below.

Reports

A summary of the findings from the project can be found in this Assciation of Applied Biologists (AAB) report.

J.S. Elmore, A.T. Dodson, N. Muttucumaru, N.G. Halford, M.A.J. Parry, D.S. Mottram, 2010. Effects of sulphur nutrition during potato cultivation on the formation of acrylamide and aroma compounds during cooking, Food Chemistry, Volume 122, Issue 3, pages 753-760.

N.G. Halford, N. Muttucumaru, S.J. Powers, P.N. Gillatt, L. Hartley, J. S. Elmore, and D.S. Mottram, 2012. Concentrations of Free Amino Acids and Sugars in Nine Potato Varieties: Effects of Storage and Relationship with Acrylamide Formation, J. Agric. Food Chem., 60 (48), pages 12044–12055.

S.J. Powers, D.S. Mottram, A. Curtis and N.G. Halford, 2013. Acrylamide concentrations in potato crisps in Europe from 2002 to 2011. Food Additives & Contaminants: Part A, Volume 30, Issue 9, 2013, pages 1493-1500.

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