Level of Acrylamide Precursors Asparagine, Fructose, Glucose, and Sucrose in Potatoes Sold at Retail in Italy and in the United States

The free amino acid asparagine and the reducing sugars glucose and fructose has been reported to serve as precursors for the heat‐induced formation of potentially toxic acrylamide in a variety of plant‐based food. To contribute to our knowledge about the levels of these precursors, we used ion‐exchange chromatography to measure free asparagine and high‐performance liquid chromatography (HPLC) to measure free glucose, fructose, and sucrose in 9 potato varieties sold at retail in Italy and in 22 varieties sold in the United States. Asparagine levels (in mmol/kg of fresh wt) ranged from 1.17 for the Agata potatoes to 57.65 Russet potatoes, a 49.3‐fold variation from lowest to highest value. The corresponding levels for fructose ranged from 1.73 (Fingerling Ozette) to 33.63 (Red), a 19.4‐fold variation from the lowest to the highest value. For glucose, the concentration ranged from 1.11 (Jelli) to 34.73 (Yukon Gold B) potatoes, a 31.3‐fold variation from lowest to highest value. The corresponding values for sucrose ranged from 1.16 (Fingerling Ozette) to 40.61 (Marabel) potatoes, a 35fold variation. The American potato varieties Kennebec, White, and Fingerling Ozette and the Italian potato varieties Agria, Merit, and Marabel had very low levels of both asparagine and reducing sugars. The results may enable consumers, restaurants, and processors to select commercial potatoes with low levels of acrylamide precursors for baking or frying.     

Tuber components affecting acrylamide formation and colour in fried potato: variation by variety,year, storage temperature and storage time

Variation in asparagine and glucose contents, identified as precursors for acrylamide development in model experiments, has been studied in eight potato clones during long‐term storage at 3 and 10 °C. In addition, glutamine, fructose and sucrose contents were determined and the role of all five substances in colour formation in fried potato products was assessed. Large genotype differences were found in all characteristics, and the ranking order was almost the same for different years and storage times. Breeding for potatoes with low asparagine levels as well as low reducing sugar levels might be another way, in addition to altering processing parameters, to keep the acrylamide level low in fried products. Storage per se at low temperature did not result in higher asparagine levels. The risk that elevated reducing sugar levels during low‐temperature storage might lead to increased acrylamide levels needs further investigation. The determined tuber components accounted for only 11–60 per cent of the total variation in fry colour after storage at 3 °C. It is suggested that screening based on crisp colour in November, perhaps complemented with a few later controls on interesting clones, could be useful for sorting out clones with good crisping abilities during the rest of the low‐temperature storage season. Copyright © 2004 Society of Chemical Industry     

Compositions of phenolic compounds,amino acids and reducing sugars in commercial potato varieties and their effects on acrylamide formation

BACKGROUND: Potato is consumed as an important source of carbohydrate and other nutrients as well as a good source of phenolics. Acrylamide is a potential carcinogen formed during frying of potato products. This study investigated the compositions of phenolic compounds, amino acids and reducing sugars in 16 commercial potato varieties from eight countries and analysed the relationships between these compositions and the levels of acrylamide generated by heating (185 °C, 25 min) potato powders. RESULTS: Major phenolic compounds in the tested potato varieties were identified as hydroxycinnamoylquinic/hydroxycinnamoyl derivatives by liquid chromatography/mass spectrometry. Great variations in the contents of phenolic compounds, free reducing sugars and amino acids as well as wide variations in acrylamide concentration were found among the different potato varieties. Correlation analysis revealed that fructose (r = 0.956***), glucose (r = 0.826***) and asparagine (r = 0.842***) were positively correlated with acrylamide formation. Interestingly, it was observed that higher levels of phenolic compounds were related to lower levels of acrylamide (r = ? 0.692*). CONCLUSION: Careful selection of potato varieties with lower levels of fructose, glucose and asparagine and higher levels of phenolic compounds may mitigate acrylamide formation during thermal processing of potato products. Copyright © 2010 Society of Chemical Industry     

Important factors to consider for acrylamide mitigation in potato crisps using pulsed electric fields

This preliminary study aimed to compare the application of pulsed electric field (PEF) with a traditional blanching as pre-treatments before frying for the mitigation of acrylamide content in potato crisps.Measuring the degree of cell disintegration index (p_o) and the changes in water electrical conductivity during washing of potato slices, PEF protocol and sample preparation scheme were optimized. Peeled potato slices (thickness 1.5 ± 0.2 mm) were subjected to PEF (1.5 kV/cm, pulse duration 10 μs, total treatment time 10 ms, pulse frequency 100 Hz) and to blanching (85 °C for 3.5 min) pre-treatments and then to washing in water, evaluating the reduction of acrylamide precursors (reducing sugars and free asparagine). After frying (175 °C, 3 min), product quality, in terms of colour, texture and acrylamide content were evaluated. Results showed that PEF promoted acrylamide precursors leaching followed by a reduction of the final acrylamide content of around 30%, significantly higher if compared to the reduction obtained with blanching, with only slight modifications of the final quality of the product, in terms of colour and texture.Industrial relevanceThe Commission Regulation (EU) 2017/2158 of 20 November 2017 has introduced new benchmark levels and mitigation strategies for the reduction of the presence of acrylamide in foods, directing food businesses to the research of measures to lower the acrylamide formation in foods. The actual industrial production process of fried potato crisps involves the use of many mitigation strategies, such as a blanching of raw potatoes. However, the traditional blanching treatment presents several practical drawbacks and leads to undesirable changes of the product quality. The application of PEF as a pre-treatment could reduce the acrylamide content in deep-fat fried potato crisps. This preliminary study gives important indications regarding the possibility of combining a PEF pre-treatment on raw potato slices with subsequent industrial processing steps for the production of potato crisps with low acrylamide concentration.     

Ultrasonic-assisted leaching of glucose and fructose as an alternative mitigation technology of acrylamide and 5- hydroxymethylfurfural in potato chips

The effect of ultrasound (480 W, 40 kHz) on the leaching of reducing sugars during the water soaking of potatoes slices (60, 70 and 80 °C- 1, 8 and 15 min) was investigated to reduce the formation of acrylamide (AA) and 5-hydroxymethylfurfural (5-HMF) in potato chips.Ultrasound (US) influenced abruptly the reducing sugar leaching during the first 15 min, significantly increasing their extraction rate (glucose: 60%, fructose: 30%) at all evaluated temperatures. When potato slices were treated with US, the formation of AA (~95%) and 5-HMF (~96%) were reduced significantly after frying. Although AA content did not correlate with glucose and fructose concentrations, 5-HMF did (r²: 0.80 and 0.83, respectively), probably because reducing sugars are their main precursors. The AA and 5-HMF concentrations of potato chips presented good correlation coefficient (r²:0.76), suggesting the use of 5-hydroxymethylfurfural as an acrylamide indicator for potato chips.     

Acrylamide levels in potato crisps in Europe from 2002 to 2016

ABSTRACT

European manufacturers’ data on acrylamide in potato crisps from 2002 to 2016 were analysed. A previous study showed a 53% reduction in mean acrylamide levels from 763 ng g^?1 in 2002 to 358 ng g^?1 in 2011. Analysis of data from the longer period showed that since 2011 there has been a levelling off, with the mean level for 2016 being 412 ng g^?1 (still a 46% reduction from 2002), suggesting that the most effective acrylamide reduction measures had been devised and implemented by 2011. There were similar trends in the 90^th and 95^th quantile values, with the 90^th quantile values being below 1000 ng g^?1 (the European Commission’s current ‘Indicative Value’ for acrylamide in potato crisps) since 2010. The proportion of samples with acrylamide above 2000 ng g^?1 fell from 4.8% in 2002 to 0.6% in 2016. Acrylamide levels showed marked seasonal variability, being highest in the first half of the year when potatoes were being used from storage, and lowest from July to September when potatoes were being harvested. Acrylamide levels were higher in thicker types of crisp in the early years of the study, but this difference disappeared in the later years, suggesting that manufacturers had acted to reduce acrylamide formation in these products. Higher values for acrylamide were recorded in north and east Europe than in the south and west up to 2013. Levels in the north and east declined in recent years, but remained higher in the north than in the other regions. The manufacturers’ data were compared with a much smaller dataset provided by the European Food Safety Authority (EFSA). Levels of acrylamide in the EFSA dataset were consistently higher than in the manufacturers’ data, possibly due to uneven sampling through the year and the seasonality of acrylamide levels.     

A methodology for evaluating the formation and human exposure to acrylamide through fried potato crisps

Potato crisps are a popular snack food which have been implicated as a potential source of acrylamide. This study develops a farm-to-fork human exposure assessment model for acrylamide in fried potato crisps for Irish consumers. The model used Monte Carlo simulation techniques to model the various stages from on farm production of potatoes, storage, processing, crisp production and final human consumption of potato crisps. A baseline model is created and a number of scenarios are subsequently created to look at the impact of different model assumptions and input parameters. The baseline model found that the mean level of acrylamide in potato crisps in Ireland was 720 μg/kg. Irish consumer exposure to acrylamide in potato crisps was estimated to be 0.052 and 0.064 μg/kg bw/day for males and females, respectively. A sensitivity analysis revealed the important parameters influencing the model predictions. The initial level of reducing sugars was found to be the most important parameter (correlation coefficient 0.58 and 0.57 for glucose and fructose, respectively), highlighting the importance of selecting cultivars with low reducing sugar levels for crisp production. The cooking regime had a significant impact on model predictions, highlighting the need for further research into the impact of different time and temperature combinations. Blanching and soaking of potatoes were also identified as important risk reduction processes.     

Acrylamide content in fried chips prepared from irradiated and non-irradiated stored potatoes

The content of reducing sugars and asparagine, responsible for the formation of acrylamide, was determined in eight Indian potato varieties. Among these, Kufri chipsona-2 and Kufri lavkar showed the lowest level of reducing sugar (680.68 ± 56.50 mg/kg) and asparagine (2074.36 ± 122.27 mg/kg), respectively. The acrylamide content in potato chips prepared from Kufri chipsona-2, the variety that is used commercially in India for making potato chips was also the lowest. Irradiation of this variety of potatoes at the sprout inhibition dose of 60 Gy and subsequent storage for six months showed a 10.7% lower content of reducing sugars at both 14 and 4 °C. The acrylamide content was 8.41% and 6.95% lower in chips from irradiated potatoes stored at 14 and 4 °C than the corresponding non-irradiated controls. The colour of the chips was also better in irradiated potatoes as judged from the L∗ and a∗ values.     

Potential for acrylamide formation in potatoes: data from the 2003 harvest

Reducing sugars, free amino acids, and the potential for acrylamide formation were determined in more than 50 potato samples from the 2003 harvest in Switzerland. The reducing sugar content strongly correlated with acrylamide, whereas no correlation was found between acrylamide and free asparagine or the pool of free amino acids. The reducing sugar contents and the acrylamide potentials were higher in most of the cultivars tested than in the samples from 2002. This was probably due to the hot and dry summer of 2003. Monitoring sugars and amino acids during heating at 120 °C and 180 °C showed that glucose and fructose reacted much faster than sucrose and the amino acids. Glutamine was consumed to a larger extent than any of the other amino acids. During prolonged storage, the reducing sugars decreased considerably while only moderate changes in the free amino acids were observed. Altogether, glucose and fructose remain the critical factors for acrylamide formation in potatoes and represent the most feasible way of reducing the formation of acrylamide in potato products.     

Optimization of the blanching process to reduce acrylamide in fried potatoes

A central composite design was used to study the effect of blanching time and temperature on the extraction of reducing sugars from potato strips and slices. After frying, the impact of both factors on the acrylamide content in French fries and potato crisps was evaluated. Acrylamide could be lowered more efficiently in potato crisps compared to French fries, due to a more pronounced extraction of sugars from potato slices upon blanching. In both products, blanching temperature was the main influencing factor for sugar extraction and subsequent acrylamide mitigation. Blanching at temperatures of about 70 °C for a short period of time (about 10 min) was more efficient compared to blanching at lower temperatures, which appeared more time-consuming. However, the extraction efficiency of reducing sugars was over 10% lower when the potato cuts were blanched in water which was previously used for blanching, leading to over 10% less reduction in the final acrylamide content.     

Current issues in dietary acrylamide: formation,mitigation and risk assessment

Acrylamide (AA) is known as a neurotoxin in humans and it is classified as a probable human carcinogen by the International Agency of Research on Cancer. AA is produced as by‐product of the Maillard reaction in starchy foods processed at high temperatures (>120 °C). This review includes the investigation of AA precursors, mechanisms of AA formation and AA mitigation technologies in potato, cereal and coffee products. Additionally, most relevant issues of AA risk assessment are discussed. New technologies tested from laboratory to industrial scale face, as a major challenge, the reduction of AA content of browned food, while still maintaining its attractive organoleptic properties. Reducing sugars such as glucose and fructose are the major contributors to AA in potato‐based products. On the other hand, the limiting substrate of AA formation in cereals and coffee is the free amino acid asparagine. For some products the addition of glycine or asparaginase reduces AA formation during baking. Since, for potatoes, the limiting substrate is reducing sugars, increases in sugar content in potatoes during storage then introduce some difficulties and potentially quite large variations in the AA content of the final product. Sugars in potatoes may be reduced by blanching. Levels of AA in different foods show large variations and no general upper limit is easily applicable, since some formation will always occur. Current policy is that practical measures should be taken voluntarily to reduce AA formation in vulnerable foods since AA is considered a health risk at the concentrations found in foods. © 2013 Society of Chemical Industry     

Acrylamide concentrations in potato crisps in Europe from 2002 to 2011

A dataset of manufacturers’ measurements of acrylamide levels in 40,455 samples of fresh sliced potato crisps from 20 European countries for years 2002 to 2011 was compiled. This dataset is by far the largest ever compiled relating to acrylamide levels in potato crisps. Analysis of variance was applied to the data and showed a clear, significant downward trend for mean levels of acrylamide, from 763 ± 91.1 ng g^?1 (parts per billion) in 2002 to 358 ± 2.5 ng g^?1 in 2011; this was a decrease of 53% ± 13.5%. The yearly 95th quantile values were also subject to a clear downward trend. The effect of seasonality arising from the influence of potato storage on acrylamide levels was evident, with acrylamide in the first 6 months of the year being significantly higher than in the second 6 months. The proportion of samples containing acrylamide at a level above the indicative value of 1000 ng g^?1 for potato crisps introduced by the European Commission in 2011 fell from 23.8% in 2002 to 3.2% in 2011. Nevertheless, even in 2011, a small proportion of samples still contained high levels of acrylamide, with 0.2% exceeding 2000 ng g^?1.     

Dietary exposure to acrylamide from potato crisps to the Spanish population

Potato crisps are one of the food commodities that contribute most to overall dietary human exposure of acrylamide. This investigation has estimated the dietary exposure to acrylamide form potato crisps in the Spanish population. Sampling of potato crisps (n = 36) from 16 different producers were carried out in March 2008. An average level of 740 µg kg^?1 (ranging from 81 to 2622 µg kg^?1; minimum to maximum) and a median of 592 µg kg^?1 were obtained. Acrylamide levels in marketed potato crisps have been significantly reduced (nearly to 50%) compared with a previous sampling performed 4 years earlier. The observed signal value (90th percentile) was 1377 µg kg^?1 with 86% of the samples with acrylamide levels lower than 1000 µg kg^?1. Dietary exposure to acrylamide from potato crisp consumption in the total Spanish population was estimated to be 0.042 µg kg^?1 body weight day^?1 by using a deterministic approach based on the National consumption database. In a second study, dietary exposure (based on a 3-day food record) was determined to be 0.053 µg kg^?1 body weight day^?1 for the adult population (17–60 years) and 0.142 µg kg^?1 body weight day^?1 for children (7–12 years). The contribution of potato crisps to the estimated dietary acrylamide exposure of the Spanish population is moderate as compared with other European Member States.     

Lactic Acid Fermentation Reduces Acrylamide Formation and Other Maillard Reactions in French Fries

ABSTRACT Blanched and nonblanched potato rods (var. Beate) were fermented with Lactobacillus plantarum strain NC8 (10⁹ colony‐forming units [CFU]/mL) at 37 °C for 45 and 120 min. Potato rods were pre‐fried at 170 °C for 3 min, cooled, and subsequently deep‐fried for 2 min 15 s. Potato juice (var. Beate) was fermented with the same strain (108 CFU/mL) at 30 °C for 1 to 5 h. Lactic acid fermentation of nonblanched potato rods for 45 min reduced acrylamide level in French fries with 48%, and with 71% after 120 min. By blanching potato rods before fermentation, reductions in acrylamide after 45 min and 120 min were 79% and 94%, respectively. Blanching, and especially fermentation, reduced visually judged browning of the French fries. Fermentation of potato juice reduced pH from 5.70 to 4.05 after 3 h. Simultaneously, glucose declined from 610.8 mg/100 mL to 7.9 mg/100 mL, fructose from 457.8 mg/100 mL to 0.0 mg/100 mL, and sucrose from 132.0 mg/100 mL to 29.2 mg/100 mL. Asparagine content remained largely unaffected between 0 h (1217.5 μmol/100 mL) and 4 h (1175.6 μmol/100 mL) and increased slightly (1470.3 μmol/100 mL) after 5 h fermentation. Levels of several other amino acids involved in Maillard reactions, that is, alanine, arginine, phenylalanine, and serine, decreased during fermentation. It is concluded that acrylamide formation during production of French fries can be effectively lowered by lactic acid fermentation of potato rods before deep‐frying. The reduction is due to reduced levels of reducing sugars rather than reduction of available asparagine.     

Acrylamide in potato crisp—the effect of raw material and processing

Reducing sugars and free amino acids were analysed in slices from three potato cultivars before and after blanching (0-3 min). The potato crisps were deep fried at 185 °C for different times (3-8.5 min), and analysed for the concentration of acrylamide (AA) and moisture. Potato cultivar and the temperature during processing were important parameters for AA formation in potato crisps. The amount increased with an increase in the processing time. Blanching before deep-frying reduced the concentration of free asparagine and reducing sugar in the raw material. We found no effect of blanching as pretreatment on the concentration of AA in the potato crisps. Any relationship was not detected between the levels of asparagine in the different cultivars, before and after blanching, and the formation of AA in the crisp products. However, it was shown that the content of reducing sugars determined the level of AA after frying.     

How much reducing sugar may potatoes contain to avoid excessive acrylamide formation during roasting and baking?

For many consumers, potatoes fried or roasted in professional or private kitchens are the most important source of exposure to acrylamide. Acrylamide formation can be reduced by appropriate preparation techniques, but suitable potatoes are a prerequisite. The tendency of potato to form acrylamide can be approximated by the content of reducing sugar. Roast potatoes (hash browns, Rösti) and oven-fried potatoes (Bratkartoffeln) were prepared to optimum culinary quality regarding crispiness and then evaluated in terms of browning, roasting flavor and acrylamide content. Preparation procedures were optimized to produce a minimum of acrylamide. It is concluded that potatoes with less than 0.2 g/kg fresh weight fructose and glucose are not suitable for roasting (insufficient browning and flavor), while roasted products of minimum crispiness prepared from potatoes with more than 1 g/kg reducing sugar contain more than 500 µg/kg acrylamide. It is proposed that potatoes which may be used for roasting and frying should contain less than 1 g/kg fresh weight of reducing sugar. This can easily be fulfilled with the most important potato cultivars grown in Switzerland, but presupposes that potatoes are no longer stored at 4 °C.     

Acrylamide in home-prepared roasted potatoes

Potato is one of the world's most widely grown tuber crop, in which starch is the predominant form of carbohydrates. Potatoes can be prepared in many ways: boiled, fried or roasted. Frying and roasting potatoes at high temperatures result in an appetizing crust, but at the same time acrylamide can form. In this study, the concentrations of the acrylamide precursors, asparagine and sugars, were determined in five different Swedish-grown potato varieties, together with the acrylamide content after typical home-cooking procedures; oven-roasting of potato wedges and pan-frying of cubes of boiled potatoes. Pan-frying of boiled potato cubes resulted in higher levels of acrylamide (530-1100 microg/kg) than in the wedges (140-250 microg/kg). Blanching combined with a shorter roasting time was shown to be an efficient way of reducing the acrylamide content in roasted potato wedges, especially in the experiments performed after long-term storage, where the acrylamide content was reduced from 110-260 to 50-140 microg/kg. No correlation was found between precursor content and acrylamide content, and this finding emphasizes the need for further studies on factors affecting acrylamide formation, for example, the availability of precursors at the surface during cooking.     

In vitro availability of starch in heat‐treated potatoes as related to genotype,weight and storage time

The objective of the study was to determine the influence of potato variety, weight and storage time after lifting on the glycaemic index (GI) and resistant starch (RS) content predicted from measurement of the rate and extent of in vitro starch hydrolysis, respectively. The potatoes were either boiled, or boiled and subjected to different heat‐cycling conditions selected to promote retrogradation of amylose or amylopectin, respectively. The hydrolysis indices (HI) and predicted GIs of all 19 potato products were high and fell within narrow ranges of 122–144 and 118–138, respectively. No correlation between average weight of the potato tuber and HI was found. Furthermore, there was no difference in HI between potatoes stored for 1–3 or 8–10 months, nor between varieties of new potato and winter potato. However, the HI was significantly lowered by temperature cycling at conditions known to promote retrogradation of amylopectin (6 °C, 48 h) compared with 6 °C for 24 h followed by 70 °C for 24 h. RS content was already substantial in boiled potatoes, 4.5 g 100 g^?1 (starch basis), and could be increased further by temperature cycling, the highest yield obtained, 9.8 g 100 g^?1 (starch basis), following heat treatment at 6 °C for 24 h followed by 70 °C for 24 h; that is at conditions known to favour amylose retrogradation. Copyright © 2004 Society of Chemical Industry     

Acrylamide monitoring in Switzerland, 2007–2009: results and conclusions

Parallel to the European Union acrylamide monitoring for the years 2007–2009, Switzerland performed its own monitoring, covering the whole range of products that significantly contain acrylamide (almost 300 samples per year), but focusing on those products that may result in high exposure. As reducing sugars are critical for potato products, these were included. No significant change, particularly improvement, was noticed, especially regarding those products for which substantial potential for improvement is known. ‘Western-style’ French fries continued to contain some four times more reducing sugars than ‘traditional’ fries, with correspondingly higher acrylamide in the finished product. The supply of raw potatoes low in reducing sugars by retail shops needs improvement, but there seemed to be insufficient willingness on a voluntary basis. A foreign producer was successful in penetrating the Swiss market with special potato chips containing up to 7000 µg kg^?1 acrylamide and only harsh measures could stop this. Three of about 61 products in the group of bakery ware showed a marked improvement. But there was also a store brand cracker that competed with a leading brand which contained 15 times more acrylamide (845 µg kg^?1). Cereals contained 1080 µg kg^?1 acrylamide and even a warning did not prompt the producer to sell substantially better products one year later. It seems that only measures by the authorities will achieve improvements. The following seem promising: a limit for reducing sugars in prefabricates for French fries; the improved supply of raw potatoes low in sugars for roasting and frying; a legal limit for acrylamide content in potato chips; a general provision that products must not contain substantially more acrylamide than achievable by good manufacturing practice; and fryers with a temperature profile from an initial high to a lower final value.