Effects of Water Availability on Free Amino Acids, Sugars, and Acrylamide-Forming Potential in Potatoby Nira Muttucumaru, Stephen J. Powers, J. Stephen Elmore, Donald S. Mottram, Nigel G. Halford

J. Agric. Food Chem.


Chemistry (all) / Agricultural and Biological Sciences (all)


Effect of Raw Potato Composition on Acrylamide Formation in Potato Chips

Claudia Granda, Rosana G. Moreira, Elena Castell-Perez

Availability of aluminum from glass and an Al form ion exchanger in the presence of complexing agents and amino acids

Denise Bohrer, Paulo Cı́cero do Nascimento, Patrı́cia Martins, Regina Binotto


Effects of Water Availability on Free Amino Acids, Sugars, and

Acrylamide-Forming Potential in Potato

Nira Muttucumaru,† Stephen J. Powers,‡ J. Stephen Elmore,§ Donald S. Mottram,§ and Nigel G. Halford*,† †Plant Biology and Crop Science Department and ‡Computational and Systems Biology Department, Rothamsted Research,

Harpenden, Hertfordshire AL5 2JQ, United Kingdom §Department of Food and Nutritional Sciences, University of Reading, Whiteknights, Reading RG6 6AP, United Kingdom *S Supporting Information

ABSTRACT: Irrigation is used frequently in potato cultivation to maximize yield, but water availability may also affect the composition of the crop, with implications for processing properties and food safety. Five varieties of potatoes, including drought-tolerant and -sensitive types, which had been grown with and without irrigation, were analyzed to show the effect of water supply on concentrations of free asparagine, other free amino acids, and sugars and on the acrylamide-forming potential of the tubers. Two varieties were also analyzed under more severe drought stress in a glasshouse. Water availability had profound effects on tuber free amino acid and sugar concentrations, and it was concluded that potato farmers should irrigate only if necessary to maintain the health and yield of the crop, because irrigation may increase the acrylamide-forming potential of potatoes. Even mild drought stress caused significant changes in composition, but these differed from those caused by more extreme drought stress. Free proline concentration, for example, increased in the field-grown potatoes of one variety from 7.02 mmol/kg with irrigation to 104.58 mmol/kg without irrigation, whereas free asparagine concentration was not affected significantly in the field but almost doubled from 132.03 to 242.26 mmol/kg in response to more severe drought stress in the glasshouse. Furthermore, the different genotypes were affected in dissimilar fashion by the same treatment, indicating that there is no single, unifying potato tuber drought stress response.

KEYWORDS: acrylamide, asparagine, drought, free amino acids, potato, sugars, processing contaminants, food safety ■ INTRODUCTION

The ability of crops to tolerate abiotic stresses such as an inadequate supply of water is an important aspect of crop yield resilience and food security and has long been a target for plant breeders. It is now becoming clear, however, that the impact of water availability and other stresses on crop composition is just as important as its effect on yield. The composition of a crop product affects its processing properties and the nutritional value of the food that is produced from it. Crucially, in some cases it also affects food safety and regulatory compliance, with the potential for formation of undesirable processing contaminants being determined by the composition of the raw crop product.1,2

The most important processing contaminant for potato (Solanum tuberosum) is acrylamide, which forms within the

Maillard reaction, a series of nonenzymic reactions between reducing sugars and amino groups during high-temperature cooking (frying, baking, and roasting) and processing.3−5 It results in the formation of a plethora of products, many of which impart color, aroma, and flavor, but acrylamide forms when asparagine participates in the reaction.6−8 Free asparagine and reducing sugars can therefore be regarded as the precursors for acrylamide, but it should be noted that, whereas this appears to be the major route for acrylamide formation, others have been proposed, for example, with 3-aminopropionamide as a possible transient intermediate9,10 or, in cereals, through pyrolysis of gluten.11

Acrylamide has been classified as a group 2A, “probably carcinogenic to humans”, chemical by the International Agency for Research on Cancer12 because of the carcinogenicity it has shown in rodent toxicology studies,13,14 and the latest report on dietary acrylamide from the European Food Safety Authority (EFSA)’s Expert Panel on Contaminants in the Food Chain (CONTAM) described it as potentially increasing the risk of developing cancer for consumers in all age groups.15 The Food and Agriculture Organization of the United Nations and the

World Health Organization (FAO/WHO) Joint Expert

Committee of Food Additives (JECFA) has also concluded that the presence of acrylamide in the human diet is a concern.16 In addition to its carcinogenic properties, acrylamide has neurological, reproductive, and developmental effects at high doses, but CONTAM considered these not to be a concern at current levels of dietary exposure.15

In Europe, the contribution of potato products for adults (18−64 years) ranges from 18.3% of the total in France to 67.1% in the United Kingdom (UK).17 Most of this intake comes from French fries, with the rest from chips (UK crisps) and oven-cooked potatoes.17 These products are among those

Received: December 16, 2014

Revised: February 16, 2015

Accepted: February 21, 2015

Published: February 21, 2015

Article pubs.acs.org/JAFC © 2015 American Chemical Society 2566 DOI: 10.1021/jf506031w

J. Agric. Food Chem. 2015, 63, 2566−2575

This is an open access article published under a Creative Commons Attribution (CC-BY)

License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited. for which the European Commission has issued “indicative” levels for the presence of acrylamide.18

The European food industry has devised many strategies for reducing acrylamide formation by modifying food processing.

These have been compiled in a “Toolbox” produced by Food

Drink Europe.19 Analysis of manufacturers’ data on acrylamide levels in potato chips in Europe showed a clear, statistically significant downward trend for mean levels of acrylamide from 763 (±91.1) μg/kg (parts per billion) in 2002 to 358 (±2.5) μg/kg in 2011, a decrease of 53% (±13.5), which was taken as evidence of the effectiveness of the “Toolbox”.20 However, the effect of seasonality arising from the influence of potato storage on acrylamide levels was evident in the study, and this was consistent with the results of a study that had analyzed samples of commercial potatoes in the United Kingdom from harvest through 9 months of storage,21 showing the difficulty of processing a variable raw material to give a consistently low acrylamide level in the product. In the United States, the Food and Drug Administration has developed an “action plan” with a number of goals, including identifying means to reduce exposure. A North American perspective on the issue and the response to it has been given by Bethke and Bussan.22