Producing 'low acrylamide risk' potatoes

Lead Research Organisation: Rothamsted Research
Department Name: Plant Biology & Crop Science

Abstract

Acrylamide is a chemical that is considered to be probably carcinogenic (cancer causing) and which affects the nervous and reproductive systems. The discovery in 2002 that it is present in many cooked foods was, therefore, quite a shock for the science community, the food industry and regulatory authorities. The disquiet was compounded when it became clear that acrylamide is formed not as a result of the presence of an additive or a change in agricultural or food processing methods that could be readily reversed, but from naturally-occurring substances reacting at the high temperatures achieved during the basic cooking processes of frying, baking and roasting. Any complacency that had built up since that first discovery has just been swept aside by the publication of two studies linking the eating of 'high-acrylamide' foods with cancer in humans. Foods derived from potatoes have a particularly high acrylamide risk. The major route for acrylamide formation is the breakdown of an amino acid called asparagine in the presence of sugars. This is part of the Maillard reaction, which occurs during the cooking of food and is also responsible for the production of flavour and colour. This puts a constraint on what food processors can do to deal with the problem and, despite the fact that some progress has been made, the levels of acrylamide in foods such as French-fried potatoes, crisps and other potato-based snacks are still commonly several hundred parts per billion (ppb). While no limit has yet been set for food, regulatory authorities around the world have stated that they wish to see dietary intake of acrylamide reduced. Methods for lowering acrylamide in foods include reducing cooking times and temperatures and making the processing conditions more acidic. However, these methods are reaching the limit of what can be achieved. The use of asparaginase reduces acrylamide levels in certain processed foods but it is ineffective in, for example, sliced and chipped potatoes and is unsuitable for use in the home. An alternative is to produce raw materials with reduced levels of sugars and asparagine. This is the aim of this project, focusing on potato. The strategic target is to produce potatoes that retain sufficient sugars and amino acids for the generation of colour and flavour compounds but which produce less acrylamide. The project will involve researchers from Rothamsted Research, the University of Reading and Scottish Crops Research Institute, and key companies in potato production, processing and marketing. Outputs will include advanced knowledge of the mechanisms regulating asparagine and sugar accumulation in potatoes, the identification of important genes that are responsible for the differences between varieties and 'proof of concept' using genetic modification. The project will generate new tools for plant breeders to use in breeding programmes and will enable a better understanding of the effects of plant nutrition on acrylamide risk.

Technical Summary

Acrylamide, a neurotoxin and possible carcinogen, was first reported in cooked foods in 2002, causing considerable disquiet within the food industry and regulatory authorities. Concern has been heightened recently by the publication of two studies linking high dietary intake of acrylamide with cancer in humans. Foods with the highest levels of acrylamide are carbohydrate-rich and cooked at high temperatures and the thermal degradation of free asparagine in the presence of sugars during the Maillard reaction is the major route for acrylamide formation. This reaction also generates desirable flavours and colours. Methods for lowering acrylamide in foods include reducing cooking times and temperatures and lowering the pH. However, these methods are reaching the limit of what can be achieved. The use of asparaginase reduces acrylamide levels in certain processed foods but it is ineffective in sliced and chipped potatoes and unsuitable for use in the home. An alternative is to produce raw materials with reduced levels of sugars and asparagine. This is the aim of this project, focusing on potato, a major UK crop with a high acrylamide risk. The strategic target is to produce potatoes that retain sufficient sugars and amino acids for the generation of colour and flavour compounds but which produce less acrylamide. The project will involve researchers from Rothamsted Research, the University of Reading and Scottish Crops Research Institute, and key companies in potato production, processing and marketing. Outputs will be advanced knowledge of mechanisms regulating asparagine and sugar accumulation in potatoes, the identification of genes underpinning trait variation and proof of concept using transgenic approaches. The project will generate gene-specific markers and improved germplasm for breeding programmes. It will also enable a better understanding of the effects of plant nutrition on acrylamide risk.

Publications

10 25 50
publication icon
Halford N (2011) Sugars in crop plants in Annals of Applied Biology

publication icon
Elmore J (2013) Acrylamide and flavour in potato crisps. in Aspects of Applied Biology

publication icon
Powers SJ (2017) Acrylamide levels in potato crisps in Europe from 2002 to 2016. in Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment

publication icon
Powers SJ (2013) Acrylamide concentrations in potato crisps in Europe from 2002 to 2011. in Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment

publication icon
Muttucumaru N (2015) Effects of water availability on free amino acids, sugars, and acrylamide-forming potential in potato. in Journal of agricultural and food chemistry

publication icon
Halford N (2012) The acrylamide problem: a plant and agronomic science issue in Journal of Experimental Botany

 
Description The project brought together Rothamsted Research (Prof. Nigel Halford and Dr. Nira Muttucumaru), the University of Reading (Prof. Don Mottram and Dr. Steve Elmore) and the James Hutton Institute (Prof. Howard Davies, Dr. Louise Shepherd, and others), supported by a consortium of companies and organisations from throughout the potato supply chain (http://www.acrylamide-potato.org.uk/). The participation of multiple academic partners and the level of funding and involvement from such a broad-based industrial consortium are testament to how seriously the acrylamide issue is being taken. The project aimed to identify genotypes and varieties of potato that have low levels of the key acrylamide precursors, free asparagine (particularly in relation to other amino acids) and sugars. In addition, the project aimed to provide the knowledge and tools for plant breeders to reduce the levels of acrylamide precursors further and achieve the strategic aim of 'low acrylamide risk' potato varieties. It also aimed to establish optimum levels of soil sulphur (S) and nitrogen (N) for growers to be able to produce a healthy, high-yielding potato crop without exacerbating acrylamide risk with excessive S and N fertilizer. Output from the project included a study of nine varieties of potato (French fry varieties Maris Piper (from two suppliers), Pentland Dell, King Edward, Daisy, and Markies; and crisping (US chipping) varieties Lady Claire, Lady Rosetta, Saturna, and Hermes) grown in the United Kingdom in 2009. Tubers were analyzed at monthly intervals through storage from November 2009 to July 2010 and acrylamide formation was measured in heated flour and crisps fried in oil. The study showed that varietal selection could be a powerful tool in ensuring that potato products comply with the indicator levels set by the European Commission and other regulatory authorities. Crisps produced from Lady Claire and Saturna were consistently below the 1000 µg/kg acrylamide level, as were crisps from Lady Rosetta during early storage and Markies in late storage. Acrylamide formation in heated flour showed that the acrylamide-forming potential of all the varieties was considerably higher than 1000 µg/kg; however, it correlated well with acrylamide formation in crisps. The flour method is relatively easy to control and gives high levels of acrylamide formation, providing a good, consistent indication of acrylamide-forming potential in different raw materials. The study also highlighted the effect of long-term storage on acrylamide risk, and showed it to be variety-dependent, with some varieties being much more prone to fluctuations in acrylamide precursors than others. Concentrations of reducing sugars rose in most varieties in late storage, showing the importance of not using potatoes outside their prescribed storage window, but were stable in Maris Piper and actually fell in Markies, potentially making this a valuable variety for crisp production from late storage, even though it is usually considered to be a French fry variety. Storage is an important issue for the potato industry in Europe, North America and other temperate regions because potato tubers have to be stored for long periods to enable a year-round supply. The study added considerably to information about the relationship between precursor concentration and acrylamide formation in potato, and reinforced the conclusion that the relationship is a complex one. These issues have been discussed in detail in reviews arising from the project (Halford et al., 2011; 2012b). Glucose concentration was the most important factor, and there was also a significant correlation between total reducing sugars and acrylamide formation. Fructose concentration on its own, however, only showed a significant correlation with acrylamide formation in the crisping varieties, which generally had lower concentrations of both glucose and fructose than the French fry varieties. On the other hand, both total free amino acid concentration and free asparagine concentration correlated with acrylamide formation in the French fry varieties but not the crisping varieties. The effects of nitrogen (N) and sulphur (S) fertilizer were investigated in a field trial of 13 varieties in 2010 (Muttucumaru et al., 2013). The study was conducted over a single growing season, and the potential effects of different environmental conditions from one season to another should be considered when assessing the implications of the study for commercial potato cultivation. Nevertheless, some important conclusions could be drawn. The study showed that N application can affect acrylamide-forming potential in potatoes but that the effect is type (French fry versus crisping)-dependent, with French fry varieties showing an effect that is not apparent in crisping varieties. The different varieties within type also showed different responses, with most varieties showing an increase in acrylamide formation when fried in response to high N application (200 kg N per hectare) compared with no N application, but Pentland Dell and Saturna showing a large decrease, making the situation even more complicated. S application was shown to reduce glucose concentrations and mitigate the effect of high N application on the acrylamide-forming potential of some of the French fry-type potatoes. Advice on both N and S application would have to be carefully tailored for specific varieties, and with S application having no significant effect on yield it may be difficult to convince farmers that expenditure on S fertilizer represented good value for money. Subsequent field trials expanded the number of varieties and assessed the effect of location versus genotype. Field and glasshouse material was also analysed to study the effects of drought stress, with both mild and severe drought causing significant and different effects on the composition of potato tubers. Genetic modification experiments were pre-empted to some extent by publications from other research groups, notably that led by Caius Rommens at Simplot Plant Sciences, Idaho, who used RNA interference (RNAi) to reduce expression of asparagine synthetase. Another genetic approach, undertaken at James Hutton Institute, involved the analysis of a potato breeding population that showed segregation of acrylamide-forming potential. Data from the analysis of this population over successive seasons through the project has been analysed to identify QTL for the trait. The role of asparagine transport from the leaves versus synthesis in situ in determining free asparagine accumulation in tubers was studied by supplying 14CO2 to a single leaf or leaves of potato plants and tracking the transport of 14C incorporated into free amino acids from the leaf or leaves to the tuber. An important consideration for the food industry partners in the project was the link between acrylamide formation, flavour and colour. Melanoidin pigments are produced in the Maillard reaction, as are a plethora of aroma and flavour volatiles that give different fried, baked and roasted foods their character, so reducing acrylamide-forming potential could affect product quality. The effects of storage and crop nutrition on flavour volatiles was investigated, and approximately 50 compounds were quantified in the headspace extracts of potato flour heated at 180 °C for 20 min, of which over 40 were affected by the fertilization regime and/or variety. The conclusion to be taken from these studies is that acrylamide mitigation strategies that cause large changes in free amino acid and/or sugar concentration are likely to lead to significant effects on aroma and flavour. The location of cultivation was found to have a profound effect on asparagine levels, with levels in one trial so low that free asparagine concentration became limiting for acrylamide formation. This enabled a tipping point in the ratio of free asparagine to reducing sugars at which free asparagine became the limiting factor. Conclusions It is important that potato breeders are encouraged to make reduced acrylamide-forming potential a priority and that they have sufficient information on how to achieve that goal. 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.
Exploitation Route The project addressed a key issue for the food industry and its findings will help food processors to produce potato-based products that are within the indicative levels for acrylamide that have been set by the European Commission. The project has also provided new knowledge on the genetic and environmental factors that affect the acrylamide-forming potential of potato and this could be exploited by potato breeders to produce new, low acrylamide varieties. The project was a LINK and the partner companies and organisations provide the main rouite for exploitation
Sectors Agriculture, Food and Drink

URL http://www.acrylamide-potato.org.uk/
 
Description The findings have been used by crisp and French fry manufacturers to reduce the risk of acrylamide formation in their products. This has arisen in part through information on varietal differences, and also a much better understanding of the relationship between acrylamide and its precursors (Sugars such as fructose and glucose, and free asparagine). This is important in enabling manufacturers to comply with indicative levels for acrylamide in food that have been set by the European Commission. In addition, some of our data was used and reproduced by EFSA in its 2015 opinion document on the risk posed by acrylamide in food, and incorporated into the compulsory Code of Practice issued by the European Commission as part of its revised risk management measures. These measures should be in place in April 2018. Update 2019: In April 2018, the European Commission revised its risk management measures for acrylamide with Commission Regulation (EU) 2017/2158 establishing mitigation measures and benchmark levels for the reduction of the presence of acrylamide in food. The regulation included compulsory risk management measures, incorporating the findings and advice generated in this project.
First Year Of Impact 2012
Sector Agriculture, Food and Drink
Impact Types Societal,Economic,Policy & public services

 
Description Influence of results and advice on Commission Regulation (EU) 2017/2158 establishing mitigation measures and benchmark levels for the reduction of the presence of acrylamide in food
Geographic Reach Europe 
Policy Influence Type Citation in other policy documents
Impact The findings of our work had a direct influence on the compulsory mitigation measures incorporated into Commission Regulation (EU) 2017/2158 establishing mitigation measures and benchmark levels for the reduction of the presence of acrylamide in food, notably ensuring sulphur sufficiency and good phytosanitary practice in the cultivation of wheat in order to avoid the presence of high levels of acrylamide in wheat products. The regulations came into force on 11th April 2018.
URL https://eur-lex.europa.eu/eli/reg/2017/2158/oj
 
Description Potato acrylamide LINK project collaborators 
Organisation Agricultural and Horticulture Development Board
Department Potato Council
Country United Kingdom 
Sector Charity/Non Profit 
PI Contribution Project lead
Collaborator Contribution LINK project partners
Impact See project output
Start Year 2009
 
Description Potato acrylamide LINK project collaborators 
Organisation Conagra Brands Inc.
Country United States 
Sector Private 
PI Contribution Project lead
Collaborator Contribution LINK project partners
Impact See project output
Start Year 2009
 
Description Potato acrylamide LINK project collaborators 
Organisation European Snacks Association
Country Belgium 
Sector Public 
PI Contribution Project lead
Collaborator Contribution LINK project partners
Impact See project output
Start Year 2009
 
Description Potato acrylamide LINK project collaborators 
Organisation Higgins Agriculture Ltd
Country United Kingdom 
Sector Private 
PI Contribution Project lead
Collaborator Contribution LINK project partners
Impact See project output
Start Year 2009
 
Description Potato acrylamide LINK project collaborators 
Organisation Kettle Foods Ltd
Country United Kingdom 
Sector Private 
PI Contribution Project lead
Collaborator Contribution LINK project partners
Impact See project output
Start Year 2009
 
Description Potato acrylamide LINK project collaborators 
Organisation PepsiCo
Country United States 
Sector Private 
PI Contribution Project lead
Collaborator Contribution LINK project partners
Impact See project output
Start Year 2009
 
Description Potato acrylamide LINK project collaborators 
Organisation Potato Processors Association
Country United Kingdom 
Sector Private 
PI Contribution Project lead
Collaborator Contribution LINK project partners
Impact See project output
Start Year 2009
 
Description Potato acrylamide LINK project collaborators 
Organisation Scottish Crop Research Institute (SCRI)
Country United Kingdom 
Sector Academic/University 
PI Contribution Project lead
Collaborator Contribution LINK project partners
Impact See project output
Start Year 2009
 
Description Potato acrylamide LINK project collaborators 
Organisation Tesco Plc
Country United Kingdom 
Sector Private 
PI Contribution Project lead
Collaborator Contribution LINK project partners
Impact See project output
Start Year 2009
 
Description Potato acrylamide LINK project collaborators 
Organisation Tesco Plc
Country United Kingdom 
Sector Private 
PI Contribution Project lead
Collaborator Contribution LINK project partners
Impact See project output
Start Year 2009
 
Description Potato acrylamide LINK project collaborators 
Organisation United Biscuits Ltd
Country United Kingdom 
Sector Private 
PI Contribution Project lead
Collaborator Contribution LINK project partners
Impact See project output
Start Year 2009
 
Description Potato acrylamide LINK project collaborators 
Organisation University of Reading
Department Centre for Integrative Neuroscience and Neurodynamics
Country United Kingdom 
Sector Academic/University 
PI Contribution Project lead
Collaborator Contribution LINK project partners
Impact See project output
Start Year 2009
 
Description Interview with Newstalk ZB (New Zealand) on acrylamide issue, 23rd January 2017 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact I was interviewed live on Newstalk ZB, New Zealand's largest news radio station, on the FSA's 'Go for Gold' campaign
Year(s) Of Engagement Activity 2017
 
Description Interviewed by CNN on acrylamide issue 
Form Of Engagement Activity A press release, press conference or response to a media enquiry/interview
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact I was interviewed on the phone by a reporter from CNN who was doing a piece on the FRSA's 'Go for Gold' campaign. The reporter wrote an article for CNN on-line but part of the interview was also broadcast in the US (so I have been told). Quotes from the interview were used by 64 other media outlets, mostly in the US.
Year(s) Of Engagement Activity 2017
URL http://edition.cnn.com/2017/01/23/health/burnt-toast-cancer-risk-roast-potatoes-acrylamide-bn/
 
Description Invited speaker at the EAPR Post Harvest Section meeting, June 28 - 30, 2016, Wageningen, Netherlands. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Invited speaker at the EAPR Post Harvest Section meeting, June 28 - 30, 2016, Wageningen, Netherlands. Presentation title: Producing low acrylamide risk potatoes: a public/private sector collaborative project focussed on genetics, agronomy and storage.
Year(s) Of Engagement Activity 2016
 
Description Invited speaker: International Potato Processing and Storage Convention, Bucharest, June 17th - 19th 2015. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact It was a valuable update on the acrylamide issue for many delegates

Organisers of future conferences have expressed an interest in inviting me
Year(s) Of Engagement Activity 2015
 
Description Invited speaker: Meijer potato breeders and food industry conference, Middelburg, Holland, June 2014 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Presentation: Genetic and agronomic approaches to acrylamide reduction in potato

Useful contacts made with potato breeders from UK
Year(s) Of Engagement Activity 2014
 
Description Presentation to American Chemical Society Meeting, Boston, USA, 2015 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Lots of discussion on the way forward on the acrylamide issue

Plans for future collaborations, e.g. through EU funding
Year(s) Of Engagement Activity 2015