Impact of the characteristics of fresh potatoes available in-retail on exposure to acrylamide: Case study for French fries

Food Control xxx (2016) 1e8

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Impact of the characteristics of fresh potatoes available in-retail on exposure to acrylamide: Case study for French fries
rquez-Ruiz, F.J. Morales M. Mesías*, F. Holgado, G. Ma Institute of Food Science, Technology and Nutrition, ICTAN-CSIC, Jos
e Antonio Novais 10, 28040 Madrid, Spain

a r t i c l e i n f o

a b s t r a c t

Article history: Received 6 July 2016 Received in revised form 26 September 2016 Accepted 2 November 2016 Available online xxx

Different batches of stored potatoes identified as “special for frying” at the point of purchase were investigated for the formation of acrylamide under controlled handling and frying conditions. Samples were randomly obtained from February to April from six food retailers with the aim of evaluating how the characteristics of fresh potatoes available by consumers in retail impacted on end-user exposure to acrylamide. Frying processes were characterised by moisture loss, colour and oil absorption. A significant correlation between sugars and acrylamide formation was found. Depending on the point of purchase the exposure to acrylamide varied from 7.0 to 153 mg/person/day. Consequently, the commercial label “special for frying” is not adequate to guide consumers. Additional efforts in the food distribution chain are necessary to provide the consumers with potato tubers with the necessary characteristics to help mitigate the formation of acrylamide in the domestic environment. © 2016 Elsevier Ltd. All rights reserved.

Keywords: French fries Potatoes Deep-frying Acrylamide Exposure Consumers

1. Introduction Although it has not been demonstrated that current levels of dietary exposure to acrylamide are associated with carcinogenic effects in humans, the margins of exposure (MOEs) indicate a concern for neoplastic effects based on animal evidences. In this sense, the European Food Safety Agency (EFSA) has recently reconfirmed that acrylamide in food potentially increases the risk of developing certain types of cancer in all age groups (EFSA, 2015). Since acrylamide is present in a wide range of foods, the exposure to this process contaminant is a public health concern and a priority for the National Food Safety Authorities. According to the EFSA, the most important food groups contributing to acrylamide exposure are fried potato products, coffee and cereal based food (EFSA, 2014). Acrylamide forms from reducing sugars and asparagine as a consequence of the Maillard reaction when foods are subjected to high temperatures, such as during frying, roasting or baking and in low moisture conditions (Capuano & Fogliano, 2011). Basically, acrylamide is generated in fried potato products due to the presence of large concentrations of its precursors in the tuber and to the processing conditions applied (Williams, 2005). Reducing sugars are the main limiting factor for acrylamide formation in fried potato

* Corresponding author. E-mail address: [email protected] (M. Mesías).

products, and depend on the potato variety but also on other factors such as the storage conditions that influence the senescence of the tuber (Biedermann-Brem et al., 2003; Williams, 2005). Regarding the frying conditions, it is known that both temperature and time of frying determine the kinetics of acrylamide formation (Knol et al., 2009). This formation starts at temperatures above 120
C and the maximum rate takes place at temperatures higher than 170e180
C. The relationship between frying time, temperature conditions and acrylamide formation has been described by several €us, Haase, authors (Granda, Moreira, & Castell-Perez, 2005; Mattha & Vosmann, 2004; Romani, Bacchiocca, Rocculi, & Dalla Rosa, 2009; Williams, 2005). Regarding the part played by the type of frying oil used in acrylamide formation, no conclusions have been reached since various controversial effects have been described by various authors. This matter is still under discussion (Capuano, Oliviero, €kmen, & Fogliano, 2010; Napolitano, Morales, Sacchi, & Açar, Go Fogliano, 2008; Zhang, Zhang, Cheng, Wang, & Qian, 2015). The European Food Industries have made an effort to implement successful strategies to mitigate acrylamide formation as described in the Toolbox compiled by FoodDrinkEurope (FDE, 2013). However, there are many stages in the food chain from retailer to consumption that cannot be legally regulated and depend directly on consumer practices in the retail and domestic environment. Together with potato tuber composition and frying conditions, food handling practices also contribute to acrylamide formation in fried

http://dx.doi.org/10.1016/j.foodcont.2016.11.005 0956-7135/© 2016 Elsevier Ltd. All rights reserved.

Please cite this article in press as: Mesías, M., et al., Impact of the characteristics of fresh potatoes available in-retail on exposure to acrylamide: Case study for French fries, Food Control (2016), http://dx.doi.org/10.1016/j.foodcont.2016.11.005

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M. Mesías et al. / Food Control xxx (2016) 1e8

potatoes (Sanny, Jinap, Bakker, van Boekel, & Luning, 2012). As there are several critical points where consumer practices directly influence acrylamide formation, thus determining exposure to this contaminant, risk communicators have offered advice to consumers on food handling, storage and frying conditions in the domestic environment. However, the acquisition of fresh potatoes by the consumers largely depends on retail product availability as well as issues of convenience. Retailers usually sell tubers in bags, and there are few possibilities of purchasing potatoes in bulk except through a greengrocer. In the present study, levels of acrylamide in fried potatoes prepared from potatoes acquired in different Spanish markets between February and April were evaluated. French fries were used as a model for studying acrylamide formation. All the potatoes were handled and fried under the same conditions and, therefore, variations in the acrylamide content could only be linked to the characteristics of the fresh products. Our aim was to demonstrate the impact of the characteristics of the potatoes available by the consumer at the point of purchase on the levels of exposure to acrylamide. 2. Material and methods 2.1. Reagents and chemicals Acrylamide standard (99%), potassium hexacyanoferrate (II) trihydrate (98%) (Carrez-I) and zinc acetate dehydrate (99.5e101%) (Carrez-II) were purchased from Sigma (St. Louis, MO, USA). [13C3]acrylamide (isotopic purity 99%) was from Cambridge Isotope Labs (Andover, MA, USA). Formic acid (98%), D(þ)-Glucose and methanol (99.5%) were from Panreac (Barcelona, Spain). Milli-Q water used was produced using an Elix3 Millipore water purification system coupled to a Milli-Q module (model Advantage10) (Millipore, Molsheim, France). All other chemicals, solvents and reagents were of analytical grade. 2.2. Potato samples Eighteen batches of fresh potatoes with the label of “special for frying” were purchased in six food retailers (R) during three consecutive months: February, March and April 2015. All the tubers were stored potatoes belonging to category 1, and correctly characterised at the point of purchase. In the first month, six different batches were acquired. Five of them were washed potatoes sold in bags (approx. 3 kg/bag) randomly purchased in five of the major Spanish food distribution chains (R1, R2, R3, R4, R5) whereas the sixth one was unwashed loose potatoes supplied by a local greengrocer (R6). Loose potatoes, which are specially recommended for frying, were not found in the distribution chains. In the second and third months, the same six batches of potatoes were again purchased in the same food establishments. Potatoes were classified according to the variety (Agria, Caesar, Milva, and Monalisa), date of purchase and packaging company. Samples were stored at 16e18
C for 2 days after purchase. Firstly a visual inspection was carried out in order to discard damaged tubers. Samples were weighed and characterised by length and diameter in triplicate with a caliper Etalon 125 (Rolle, Switzerland). 2.3. Preparation of French fries Potato tubers were brought to room temperature at least three hours in advance. For each frying trial, three similar tubers were peeled, washed and cut into pieces for a standard French potato shape (0.8  0.8  6 cm). Strips were mixed and 30 pieces were selected; 8 strips were kept for analysis and the remaining 22

(approx. 110 g) were deep fried in 5 L of sunflower oil using a domestic fryer (Jemi, Barcelona, Spain, 5L capacity, 2200 w). Frying was carried out under controlled conditions (size, oil:potato rate, energy input rate, temperature and time) to minimize the influence of consumer practices on acrylamide formation (handling, storage, preparation and cooking steps). Temperature of the frying oil was reproducible with variations lower than 2% in the inter-day assay. Deep frying was performed following the draft of the Spanish norm for French fries production (unpublished data), which includes two steps: 150
C for 4 min (step I) and 180
C for 2 min (step II). After frying, the basket was shaken and potatoes were briefly drained on absorbent kitchen paper. Final weight was around 59 g, which involved weight losses of ~46%. A second scenario was also assayed with the samples purchased in the first month, where the potatoes were fried at only 150
C for 4 min (step I). A calibrated K-type thermocouple data logger (Delta Ohm, Caselle di Selvazzano, Italy) was used to monitor the temperature of the frying oil and externally regulate the fryer in order to reduce the temperature shift from trial-to-trial. Frying started 10 min after the oil temperature reached the target value and stabilised. Raw samples were analysed for colour, moisture and reducing sugar content. Fried samples were analysed for colour, moisture, oil absorption and acrylamide content. The oil absorption was determined in fried samples after lyophilisation using a Virtis Benchtop freeze-drying instrument (Virtis, Gardenier, NY, USA). 2.4. Determination of moisture content Moisture was determined gravimetrically to constant weight in an oven at 105
C for 24 h in both fresh and fried potatoes according to the Association of Official Analytical Chemists (AOAC) method 950.46 (AOAC, 1995). Analysis was done in duplicate. 2.5. Determination of colour The measurements were made at room temperature using a HunterLab Spectrophotometer CM-3500D colorimeter (Hunter Associates laboratory, Stamford, Connecticut, USA). Three independent measurements of a*(redness), b*(yellowness) and L*(lightness) parameters were carried out on different areas of both fresh and fried potatoes. E index was calculated according to the following equation: E ¼ (L2 þ a2 þ b2)1/2, which allows evaluating the colour changes in the samples. Analysis was done in triplicate. 2.6. Determination of reducing sugars The reducing sugar content in the fresh samples was determined by Miller (1959). Results were expressed as mg glucose equivalents/g of sample. Limit of quantification was set at 0.7 mg glucose equivalents/g sample. Analysis was done in duplicate. 2.7. Determination of oil absorption by Soxhlet extraction Four grams of lyophilised fried potato samples were weighed and total fat content was determined by Soxhlet extraction (Soxtec €gana €s, Sweden) according to the AOAC System HT6, Tecator AB, Ho method 991.36 (AOAC, 1995), using petroleum ether. Analysis was performed in duplicate. The results were expressed as g of lipid/ 100 g of product. Analysis was done in duplicate. 2.8. Direct determination of polar compounds in oil Total polar compounds were measured in heated oil after each frying cycle by a hand-held device Testo 270 (Testo INC, New Jersey, USA). Results were expressed as percentage of total polar material.

Please cite this article in press as: Mesías, M., et al., Impact of the characteristics of fresh potatoes available in-retail on exposure to acrylamide: Case study for French fries, Food Control (2016), http://dx.doi.org/10.1016/j.foodcont.2016.11.005

M. Mesías et al. / Food Control xxx (2016) 1e8

Analysis was done in triplicate. 2.9. LC-ESI-MS-MS determination of acrylamide Acrylamide was determined in fried samples as described by Mesías and Morales (2015). The recovery rate of acrylamide spiked to the samples was usually between 90 and 106%. The relative standard deviations (RSD) for the precision, repeatability and reproducibility of the analysis were calculated as 2.8%, 1.2% and 2.5%, respectively. The limit of the quantitation was set at 20 mg/kg. The accuracy of the results were recently demonstrated for potato crisps in an interlaboratory comparison study launched by the Food Analysis Performance Assessment Scheme (FAPAS) program (2016), yielding a z-score of 0.2. Results were expressed as mg/kg of product. Analysis was done in triplicate. 2.10. Statistical analysis Statistical analyses were performed using Statgraphics Centurion XV (Herndon, VA, USA). Data were expressed as mean ± standard deviation (SD). Analysis of variance (ANOVA) and the least significant difference (LSD) test were applied to determine differences between means. Differences were considered to be significant at p < 0.05. Relationships between the different parameters analysed were evaluated by computing Pearson linear correlation coefficients at the p < 0.05 confidence level.

3

weight by a local greengrocer (R6). Moisture was similar among samples, although the lowest content was for Agria (78.2%) and the highest for Monalisa (84.5%). After frying, moisture was reduced by a range of between 27.9 and 35.7% and the final moisture values ranged from 51.2% (Milva) to 58.5% (Caesar). Sugar content varied significantly among the four potato varieties. Caesar, Monalisa and Milva showed values ranging from 11.4 to 27.6 mg/g whereas levels up to 0.9 mg/g were found for the Agria variety. Flesh colour was pale-yellow but differences were found in the lightness (L*) and b* parameters. During frying, L* was reduced and a* (linked with the colour in the red zone) was increased. Overall, the E index decreased in the French fries compared to the raw tuber. Regarding the percentages of oil absorption, similar values were observed for Caesar, Monalisa and Milva (13.4e14.2%) whereas absorption in Agria was significantly higher (15.6%). In a first assay, two different scenarios were performed with the aim of evaluating the influence of frying conditions on acrylamide formation In the first one deep frying was carried out in two steps: 150
C for 4 min (step I) and 180
C for 2 min (step II) In the second scenario potatoes were fried at only 150
C for 4 min (step I). A median temperature of 148.6 ± 1.4
C for step I, and 177.4 ± 0.3
C for step II was recorded. Fig. 1 describes the levels of acrylamide for the four varieties under investigation after the different frying scenarios. Levels ranged from less than the limit of quantitation (20 mg/kg) to 839 mg/kg for French fries prepared at 150
C (first step) and significantly increased to a range between 24.7 and 2532 mg/kg at the end of the process (steps I þ II).

3. Results 3.2. Influence of the date of purchase 3.1. Influence of the potato variety and frying conditions Potato tubers with the label of “special for frying” obtained in February were of four different varieties: Caesar, Monalisa, Milva and Agria. Consumers have almost no choice in the selection of the potato variety at the point of purchase since it has already been decided by the retailer. Therefore consumer decision is limited by the availability of the potatoes on sale. Potatoes were roughly characterised as summarised in Table 1. As expected, dimensions of the different varieties varied significantly among the fresh tubers. Monalisa and Milva varieties were smaller compared to Agria. Caesar, Monalisa, and Milva were from retailers R1, R2 and R5, respectively. Agria was sold loosely by

In a second assay, three different batches of the same variety of fresh potatoes (Caesar) from three different retailers (R1, R3 and R4) were purchased in two consecutive months (February and March). In this case, the aim was to evaluate the influence of the date of purchase on acrylamide formation. All the samples were washed potatoes commercialised in bags and of the same origin. Dimensions of the tubers showed significant differences both in length, diameter and weight among the same samples, except for the Caesar-1 sample (Table 2). Tubers had similar moisture (80.4e85.1%) and decreased in a range of 23.0e31.8% after frying. Reducing sugar content was different among the three samples, increasing from the first month to the second in Caesar-1 samples

Table 1 Characteristics of fresh and fried potatoes of different varieties after frying (150
C for 4 min þ 180
C for 2 min).

Food retailers Commercialization Appearance Fresh potatoes Length (mm) Diameter (mm) Weight (g) Moisture (%) Reducing sugars (mg/g) a* b* L* E index Fried potatoes Oil absorption (%) Moisture (%) a* b* L* E index

Caesar

Monalisa

Milva

Agria

R1 Bag Washed

R2 Bag Washed

R5 Bag Washed

R6 Loose Unwashed

105.7 ± 5.2b 81.1 ± 13.4b 256.7 ± 22.4b 81.0 ± 1.6ab 11.4 ± 0.3b 1.1 ± 0.1b 14.5 ± 0.6a 59.0 ± 1.6a 60.8 ± 1.6a

89.0 ± 3.6a 65.8 ± 3.3a 167.6 ± 12.5a 84.5 ± 0.5b 27.6 ± 0.1d 1.4 ± 0.2a 20.1 ± 0.4b 61.4 ± 1.6a 64.6 ± 1.6b

82.9 ± 2.4a 62.4 ± 2.6a 161.8 ± 5.9a 79.7 ± 1.0ab 17.6 ± 0.3c 1.0 ± 0.1b 22.6 ± 1.4c 64.8 ± 2.6b 68.6 ± 2.8c

116.0 ± 11.1b 82.0 ± 1.9b 394.1 ± 3.9c 78.2 ± 3.7a 0.9 ± 0.1a 0.4 ± 0.1c 24.1 ± 0.6c 66.8 ± 1.0b 71.0 ± 0.7c

13.4 ± 0.3a 58.5 ± 3.3b 6.2 ± 0.9b 16.6 ± 0.6c 50.1 ± 2.5b 53.2 ± 2.4b

13.8 ± 0.6a 56.0 ± 0.3b 8.2 ± 0.6c 13.6 ± 0.4b 43.7 ± 0.2a 46.6 ± 0.4a

14.2 ± 0.3ab 51.2 ± 0.5a 7.4 ± 0.7c 11.8 ± 1.2a 43.4 ± 0.7a 45.6 ± 1.0a

15.6 ± 1.0b 54.9 ± 0.2ab 3.0 ± 0.2a 23.0 ± 1.0d 64.9 ± 2.2c 68.9 ± 2.0c

Values are mean ± SD. Different letters mean significant differences among varieties (p < 0.05).

Please cite this article in press as: Mesías, M., et al., Impact of the characteristics of fresh potatoes available in-retail on exposure to acrylamide: Case study for French fries, Food Control (2016), http://dx.doi.org/10.1016/j.foodcont.2016.11.005

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M. Mesías et al. / Food Control xxx (2016) 1e8

150ºC 4 min

150ºC 4 min + 180ºC 2 min

3000

Acrylamide (μg/kg)

Bc

Bc

2500 2000 Bb 1500 1000

Ad Ac

500

Ab

Aa

0 Caesar

Monalisa

Milva

Ba

Agria

Variety Fig. 1. Acrylamide content of French fries prepared by frying different varieties of potatoes (Caesar, Monalisa, Milva, and Agria) under different frying conditions. Values are mean ± SD (n ¼ 3). aed: Means with different small letters are significant (p < 0.05) in different varieties at the same frying conditions. AeB: Means with different capital letters are significant (p < 0.05) in different frying conditions at same variety.

(from 11.4 to 14.5 mg/g) and Caesar-2 (from 16.5 to 17.3 mg/g), but decreasing in Caesar-3 (from 19.5 to 12.0 mg/g). Oil absorption ranged from 11.3 to 16.9% and only the Caesar-1 sample showed significant differences between the potatoes purchased in the first month compared with those purchased in the second month (Table 2). Potatoes were fried following the two steps procedure. The levels of acrylamide in the French fries ranged from 1513 to 2116 mg/ kg (Fig. 2). Results for the potatoes purchased in the first month were lower (1513e1847 mg/kg) than those of the potatoes purchased in the second month (1932e2116 mg/kg) with significant differences for Caesar-1 and Caesar-2. 3.3. Influence of the tuber characteristics acquired from different places of purchase The third assay is more complex and compares the overall

eighteen different batches purchased in six different retailers during three consecutive months (February, March, and April). Varieties of the tubers identified as “special for frying” and available in the retailers were Caesar, Monalisa, Milva and Agria. Agria potatoes were unwashed loose potatoes whereas all the others were washed potatoes commercialised in bags. High variations were shown in the reducing sugar content, where Caesar, Monalisa and Milva exhibited values ranging from 7.5 to 27.6 mg/g and much lower values were observed in the Agria potatoes (0.9e2.1 mg/g) (data not shown). The data were organised according to the place of purchase and described as R1 to R6. Fig. 3 depicts the formation of acrylamide under controlled frying conditions according to the place of purchase. French fries displayed levels of acrylamide ranging from 25 to 2787 mg/kg. It is noticeable that there are no statistical differences in the formation of acrylamide from tubers obtained in retailers R1, R2, R3 and R4 between February, March and April. The

Table 2 Characteristics of fresh and fried potatoes of a same variety purchased in February (month-1) and March (month-2) (150
C for 4 min þ 180
C for 2 min). Caesar_1

Food retailers Commercialization Appearance Fresh potatoes Length (mm) Diameter (mm) Weight (g) Moisture (%) Reducing sugar (mg/g) a* b* L* E index Fried potatoes Oil absorption (%) Moisture (%) a* b* L* E index

Caesar_2

Caesar_3

Month-1

Month-2

Month-1

Month-2

Month-1

Month-2

R1 Bag Washed

R1 Bag Washed

R3 Bag Washed

R3 Bag Washed

R4 Bag Washed

R4 Bag Washed

105.7 ± 5.2Ab 81.1 ± 13.4Ab 256.7 ± 22.4Ab 81.0 ± 1.6Aa 11.4 ± 0.3Aa 1.1 ± 0.1Aa 14.5 ± 0.6Aa 59.0 ± 1.6Aa 60.8 ± 1.6Aa

107.3 ± 5.5Ab 74.6 ± 4.0Aab 260.1 ± 13.9Aa 85.1 ± 1.3Aa 14.5 ± 0.2Bb 0.9 ± 0.1Bb 23.1 ± 1.2Bb 64.9 ± 1.1Bb 68.9 ± 1.2Bb

83.9 ± 5.0Aa 61.3 ± 2.2Aa 159.6 ± 19.4Aa 84.1 ± 0.2Aa 16.5 ± 0.2Ab 1.3 ± 0.1Ba 18.7 ± 0.8Ab 62.3 ± 2.5Aab 65.1 ± 1.4Ab

96.0 ± 3.4Ba 70.8 ± 3.5Ba 235.7 ± 25.3Ba 81.4 ± 1.9Aa 17.3 ± 1.9Ac 1.6 ± 0.1Aa 25.3 ± 0.5Bc 67.1 ± 1.3Bb 71.7 ± 1.4Bb

120.2 ± 3.3Ac 70.7 ± 1.0Aab 284.4 ± 5.1Ab 80.4 ± 2.0Aa 19.5 ± 0.3Bc 0.9 ± 0.2Ab 19.4 ± 1.3Bb 64.3 ± 2.5Ab 67.2 ± 2.7Ab

124.7 ± 3.7Ac 80.3 ± 2.5Bb 347.4 ± 35.5Bb 82.4 ± 0.3Aa 12.0 ± 0.3Aa 1.0 ± 0.1Ab 16.2 ± 0.7Aa 60.3 ± 2.4Aa 62.4 ± 2.4Aa

13.4 ± 0.3Ba 58.5 ± 3.3Ab 6.2 ± 0.9Aab 16.6 ± 0.6Ac 50.1 ± 2.5Ac 53.2 ± 2.4Ac

11.3 ± 0.5Ab 58.0 ± 2.4Aa 7.2 ± 2.4Aa 18.9 ± 0.3Aa 52.7 ± 3.0Aab 56.5 ± 2.6Aab

14.0 ± 0.9Aa 60.5 ± 0.0Ab 5.2 ± 0.5Aa 7.4 ± 0.4Aa 37.3 ± 0.3Aa 38.4 ± 0.3Aa

12.2 ± 0.0Aa 62.7 ± 0.1Ba 8.1 ± 0.5Ba 17.5 ± 2.0Ba 49.8 ± 2.2Ba 53.4 ± 2.6Ba

16.9 ± 1.2Ab 51.9 ± 0.2Aa 7.3 ± 0.8Ab 12.7 ± 1.1Ab 44.0 ± 0.8Ab 46.3 ± 0.6Ab

11.4 ± 0.1Ab 62.0 ± 1.4Ba 6.8 ± 0.8Aa 16.6 ± 0.9Ba 51.6 ± 0.5Bb 54.6 ± 0.5Bb

Values are mean ± SD. AeB: Means with different capital letters are significant (p < 0.05) in the same sample purchased in different months. aeb: Means with different small letters are significant (p < 0.05) in different samples purchased in the same months.

Please cite this article in press as: Mesías, M., et al., Impact of the characteristics of fresh potatoes available in-retail on exposure to acrylamide: Case study for French fries, Food Control (2016), http://dx.doi.org/10.1016/j.foodcont.2016.11.005

M. Mesías et al. / Food Control xxx (2016) 1e8

Month-1

5

Month-2

3000

Acrylamide (μg/kg)

2500

Ba

Ba

Aa

Ab

2000

Ab

Aa

1500 1000 500 0 Caesar-1

Caesar-2

Caesar-3

Samples Fig. 2. Acrylamide content in French fries prepared from the Caesar variety purchased in three different retailers (R1: Caesar-1, R3: Caesar-2, R4: Caesar-3) in February (month 1) and March (month 2). Values are mean ± SD (n ¼ 3). aeb: Means with different small letters are significant (p < 0.05) in different samples purchased in the same months. AeB: Means with different capital letters are significant (p < 0.05) in the same sample purchased in different months.

Month-1

Month-2

Month-3

3000

Bd Cd

2500

Acrylamide (μg/kg)

Bd Cc

Ac 2000 Ab

Bc

Bb Ab

1500

Ad

Bc

Bc

Ac

Ab

Ab

1000 500

Ba Aa

Aa

0 R1

R2

R3

R4

R5

R6

Samples Fig. 3. Acrylamide levels of French fries prepared from potato tubers purchased in six different retailers (R1, R2, R3, R4, R5, R6) during February (month-1), March (month-2), and April (month-3). Values are mean ± SD (n ¼ 3). aed: Means with different small letters are significant (p < 0.05) in different samples purchased in the same months. AeC: Means with different capital letters are significant (p < 0.05) in the same sample purchased in different months.

lowest values were found in Agria samples from R6, whereas the rest of the varieties showed higher concentrations in a wider range. A positive correlation between sugar content in the eighteen fresh potatoes and acrylamide levels after frying was observed (r ¼ 0.732, p ¼ 0.0025) (Fig. 4). Table 3 summarises the mean acrylamide content in French fries during the three consecutive months after purchasing from the same retailer. The content of acrylamide per serving (estimated as 70 g) (FDA, 1993) was calculated as around 120 mg for retailers R1, R2, R3 and R4; 170 mg for R5 and 7.8 mg for R6. Considering that the mean consumption of fresh potatoes in the Spanish population is 62.8 g/person/day (calculated from 22.92 kg/person/year) (MAGRAMA, 2015) and assuming that potatoes lose an average of 46% of weight during frying, then the average consumption of French fries, if all fresh potatoes were consumed as French fries, can be supposed to be around 34 g/day. These estimations would involve an exposure to acrylamide ranging from 95.8 to 110 mg/

person/day for samples R1-R4, increasing up to 153 mg/person/day for R5 and dropping down to 7.0 mg/person/day for R6. Assuming a default value of 70 kg of body weight (bw) for an adult according to the EFSA Scientific Committee (EFSA SC, 2012), the acrylamide intake from French fries would range from 0.10 mg/kg bw/day (R6) to 2.18 mg/kg bw/day (R5). 4. Discussion It is known that around 50% of overall acrylamide intake is from is food cooked at home, catering services, and restaurants. However, there is a lack of information of quantitative results on exposure contribution (Dybing et al., 2005). French fries are widely consumed by the population and therefore they are a predominant source of dietary intake of acrylamide (EFSA, 2015; Fiselier & Grob, 2005). Several strategies have been developed to mitigate acrylamide formation in French fries that include surface to volume ratio

Please cite this article in press as: Mesías, M., et al., Impact of the characteristics of fresh potatoes available in-retail on exposure to acrylamide: Case study for French fries, Food Control (2016), http://dx.doi.org/10.1016/j.foodcont.2016.11.005

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M. Mesías et al. / Food Control xxx (2016) 1e8

r = 0.732

p = 0.0025

Fig. 4. Relationship between acrylamide content (mg/kg) and reducing sugar (RS) content (mg/g) for French potatoes made from different potato varieties purchased in different months. Error bars represent standard deviation of the mean (n ¼ 2 for reducing sugars determination; n ¼ 3 for acrylamide determination).

of the potato strips, blanching and soaking in water containing various additives or processing aids (Medeiros Vinci, Mestdagh, & De Meulenaer, 2012). French fries, which are consumed in the domestic environment, are purchased as a frozen par-fried product or directly prepared from potato tubers. In the present study acrylamide levels in French fries prepared from potato tubers in the laboratory under controlled conditions to avoid post-retail variations were evaluated. Eighteen batches of potato tubers, labeled as “special for frying”, were purchased in Spanish food retailers during three different months. Variations in the acrylamide content were thus, presumably linked to the initial characteristics of the fresh product and, in turn, to the availability by the consumer at the point of purchase. In this sense, the point of purchase could have a direct influence on acrylamide exposure regardless of the frying conditions applied. In parallel, other factors involved in the formation of acrylamide were investigated in different frying assays. The objective of the first assay was to evaluate the extent of acrylamide formation during frying according to the potato variety. Variations, therefore, would probably be associated with the characteristic of the fresh potato related to harvest time and storage conditions. This investigation does not include concepts related to agronomical aspects, supply chain management and logistics of harvesting, storage and transport of raw potatoes, since consumers have no impact on these factors. In addition, different frying conditions were assessed. It is well known that frying time and temperature directly affect acrylamide formation. Lower amounts of acrylamide are formed in French fries € kmen & Senyuva, 2006) followed by an when fried at 150
C (Go € kmen & Senyuva, exponential increase between 150 and 190
C (Go

2006; Matth€ aus et al., 2004). In this sense, Haase, Matthaeus, and Vosmann (2003) described that a 50% reduction in acrylamide content of potato chips was achieved by lowering the oil temperature from 185 to 165
C. The observations of the present assay are in agreement with the results from these authors. Acrylamide levels for French fries prepared at 150
C significantly increased by 1.8 (Caesar), 7.4 (Monalisa) and up to 27 times (Milva) in fried potatoes when a second frying step at 180
C was included. The Agria variety, however, increased only slightly after the second step, which coincides with the results of Yang, Achaerandio, and Pujol (2016). These authors indicated that acrylamide content in fried potatoes was significantly higher when the frying temperature increased from 150 to 170 and then to 190
C with the exception of the Agria cultivar, which only showed a slight increase. Therefore, it is suggested that although acrylamide formation is higher when frying temperature increases, the extent of the formation depends on the raw product variety involved, linked to precursors composition and moisture (Table 1). Several studies have indicated that levels of reducing sugars (glucose and fructose) in the tubers strongly correlate with those of €us et al., acrylamide in fried potatoes (Amrein et al., 2003; Mattha 2004; Sanny et al., 2012; Williams, 2005), the content of reducing sugars being the limiting factor for acrylamide formation in French fries (Williams, 2005). Therefore, the different levels of sugars observed in the fresh tubers in the present study could be involved in acrylamide formation variations during frying. In the first assay, the Agria variety, with the lowest reducing sugar content, showed the lowest acrylamide content after frying (Fig. 1); however no significant correlations were found between these two parameters in the groups of all the tested potatoes. In the second assay, although the variety of tested samples was the same, significant differences were observed in the acrylamide content of the French fries (Fig. 2). Acrylamide levels in the potatoes purchased in the first month were lower than those of potatoes purchased in the second month. These higher levels could be associated with the reducing sugar content in the raw samples since it could be supposed that the potatoes belonging to the same batch were stored for one month more, promoting an increase in the levels of the sugars. However, sugar content in the second month only increased in Caesar-1 and Caesar-2 samples, decreasing in the Caesar-3 sample (Table 2). Sugar content in fresh potatoes did not correlate with acrylamide levels in the French fries of the second assay thus suggesting that reducing sugars were not the only reason for the higher formation of acrylamide and that other factors might have been involved. The absence of correlation between sugar content and acrylamide formation in both assays 1 and 2 probably could be due to the number of the samples employed in these assays were not enough to observe this relationship. In contrast, a significant correlation was found between these parameters in the French fries samples of the third assay (r ¼ 0.732, p ¼ 0.0025) (Fig. 4), which reveals the importance of sugar content in the development of

Table 3 Acrylamide content (mean, standard deviation, minimum, maximum) in French fries prepared from fresh potatoes purchased at different food retailers (R1, R2, R3, R4, R5 and R6) in three consecutive months. Estimation of acrylamide intake based on Spanish consumption data. Acrylamide (mg/kg)

R1 R2 R3 R4 R5 R6

Serving (mg)*

Intake (mg/person/day)

Intake (mg/kg bw/day)

Mean ± SD

Min

Max

Mean ± SD

Min

Max

Mean ± SD

Min

Max

Mean ± SD

Min

Max

1722 ± 182b 1751 ± 501b 1727 ± 377b 1715 ± 245b 2432 ± 339c 112 ± 91a

1514 1281 1216 1372 1975 25

1957 2444 2116 1932 2787 237

120 ± 12.7b 122 ± 35.0b 121 ± 26.4b 120 ± 17.2b 170 ± 23.7c 7.8 ± 6.3a

106 89.7 85.1 96.0 138 1.7

137 171 148 135 195 16.6

108 ± 11.4b 110 ± 31.4b 95.8 ± 16.2b 108 ± 15.4b 153 ± 21.3c 7.0 ± 5.7a

95.1 80.5 76.4 86.2 124 1.6

123 154 116 121 175 14.9

1.54 1.57 1.37 1.54 2.18 0.10

± ± ± ± ± ±

1.36 1.15 1.09 1.23 1.77 0.02

1.76 2.19 1.66 1.73 2.50 0.21

0.16bc 0.45b 0.23b 0.22b 0.30c 0.08a

Values are mean ± SD (n ¼ 3). Different letters mean significant differences among samples (p < 0.05). *Serving is estimated in 70 g, according to the Food and Drug Administration (FDA, 1993). bw: body weight.

Please cite this article in press as: Mesías, M., et al., Impact of the characteristics of fresh potatoes available in-retail on exposure to acrylamide: Case study for French fries, Food Control (2016), http://dx.doi.org/10.1016/j.foodcont.2016.11.005

M. Mesías et al. / Food Control xxx (2016) 1e8

acrylamide in French fries. Sugar levels are associated not only with the variety of potato, the use of fertilisers, the climate and the time of harvesting, but also with storage conditions before processing (Amrein et al., 2003; Biedermann, Noti, Biedermann Brem, Mozzetti, & Grob, 2002; Haase et al., 2003). Due to the harvest season, it is very common for potatoes to be stored in cold conditions during winter. As previously explained, the storage of potatoes at temperatures lower than 8e10
C increases sugar levels in the tuber with a resulting increase in the formation of acrylamide during frying too (Amrein et al., 2003). According to the acrylamide toolbox reported by FoodDrinkEurope for the production of fried potato products, the use of potatoes with a reducing sugar content of less than 3 mg/g is recommended (CIAA, 2009). In the present study only the Agria variety conformed with this recommendation, while the rest of the batches contained higher sugar levels, which could be associated not only with the variety but also with storage conditions. Potatoes purchased in the food retailers R1, R2, R3, R4 and R5 were probably stored at colder temperature during a prolonged period of time as compared with those acquired in R6, promoting higher levels of reducing sugars and, consequently, the greater formation of acrylamide in the French fries. Although moisture content in fresh samples and oil absorption after frying can also be linked to acrylamide levels in French fries (Yang et al., 2016), no correlations were observed in the French fries analysed in the different assays. Furthermore, though it is suggested that oil is absorbed when more water is removed from the potato during frying (Ziaiifar, Achir, Courtois, Trezzani, & Trystram, 2008); neither oil absorption nor moisture content were interrelated in the present samples. As observed in Tables 1 and 2, the E index decreased in French fries. Caesar, Monalisa and Milva varieties exhibited important variations, while there was only a slight change of colour between fresh and fried samples in the Agria variety (Table 1), as previously reported by Yang et al., 2016. All the colour parameters presented significant correlations with the acrylamide levels in French fries analysed in assay 1. Negative correlations were observed between acrylamide levels and b* (r ¼ 0.993, p ¼ 0.007), L* (r ¼ 0.995, p ¼ 0.005) and E index (r ¼ 0.996, p ¼ 0.004), while a* values were positively correlated with acrylamide formation (r ¼ 0.962, p ¼ 0.038). These findings are in line with those reported by other authors (Elmore et al., 2015). However, to the contrary, results of the second assay did not show any significant correlations between levels of acrylamide and colour parameters. Although colour parameters can also be related to the oil uptake in fried potatoes (Yang et al., 2016), no correlations were observed in our experiments. Levels of acrylamide in the eighteen different French fries samples evaluated in the third assay ranged from 25 mg/kg to a maximum value of 2787 mg/kg (Fig. 3), most of the samples exceeding the indicative value of 600 mg/kg for fried ready-to-eat potatoes according to the recommendations of the European Commission (EC, 2013). An overview of the acrylamide levels which the Spanish population is exposed to through the consumption of French fries is summarised in Table 3. From this Table it can be deduced that, following the same procedure with regards to manipulation and frying, the selection of the fresh potato plays a key role in the control of acrylamide formation in French fries. In agreement with Sanny, Luning, Marcelis, Jinap, and van Boekel (2010) and Sanny et al. (2012), an inadequate control of the factors affecting acrylamide formation could lead to large variations and high acrylamide concentrations in French fries. In the eighteen samples of potatoes commercialised in retailers during the months from February to April, the acrylamide content per serving of fried potatoes varied from 1.7 to 138 mg depending of the point of purchase. Similarly, the exposure to acrylamide through French fries

7

can vary from 7.0 to 153 mg/person/day, with a factor of around 22 between the lowest (R6) and the highest (R5) values. This estimation has been carried out by considering a portion size of 70 g as the standard serving of French fries (FDA, 1993) and a mean consumption of 34 g/day (MAGRAMA, 2015), as explained before. The range of exposure includes the value of 84 mg/day, calculated as the daily exposure to acrylamide from French fries in Switzerland (Biedermann et al., 2010), being higher than the results indicated for the Swedish population (4.9 mg/day) (Svensson et al., 2003). On the other hand, assuming a default value of 70 kg of body weight (bw) for an adult according to the EFSA Scientific Committee (EFSA SC, 2012), the exposure to acrylamide from French fries would range from 0.10 to 2.18 mg/kg bw/day. Similar data have been reported by Matthys et al. (2005) for Belgian adolescents (median value: 0.15 mg kg bw/day), by Normandin et al. (2013) for adolescents in Canada (0.29 mg/kg bw/day) and by Sirot, Hommet, Tard, and Leblanc (2012) for adults (0.19 mg/kg bw/day) and children (0.42 mg/kg bw/day) in France. In contrast, lower exposures have been assessed by Zaja˛ c et al. (2013) for an adult population from Poland (13e60 years old), where acrylamide exposure from French fries ranged from 0.02 to 0.05 mg/kg bw/day. Taking into account that the no-observed-adverse-effect levels (NOAEL) for adverse effects on male reproductive parameters are stablished in a value of approximately 2 mg/kg bw/day and of 1.0 mg/kg bw/day for developmental toxicity (EFSA, 2015), the maximum exposure to acrylamide from French fries estimated in our study should not involve a risk for the population. However, due to the wide food groups contributing to the total acrylamide exposure, it is important to minimize its intake. Due to the high variability observed depending on the fresh potato acquired, the higher or lower exposure to this contaminant will be directly conditioned by the selection of the fresh products. Consequently, it is the responsibility of the distribution chain to provide the consumers with products with the adequate characteristics to help mitigate the formation of acrylamide in the domestic environment. 5. Conclusions This study concludes that different fresh potatoes, purchased in different Spanish food establishments, handled and deep fried under the same conditions resulted in French fries with very different levels of acrylamide. The composition of the fresh tuber largely impacts on the formation of the contaminant during the deep frying process. Particularly high reducing sugar content promotes a higher formation of acrylamide under the same frying conditions. Therefore, the commercial label “special for frying” is not adequate guide to help the consumers reduce acrylamide exposure. These findings demonstrate the relevance of the characteristics of potatoes available by consumers at the point of purchase to reduce exposure levels to this contaminant through consumption of French fries. Additional efforts in the food distribution chain are necessary to provide the consumers with potato tubers with adequate characteristics to help mitigate the formation of acrylamide in the domestic environment. The present results provide new data about acrylamide exposure contribution from French fries prepared at home. Conflict of interest The authors declare that they have no conflict of interest. Acknowledgements This work was supported by the Comunidad Autonoma of Madrid and FEDER program [projects S2013/ABI-3028-

Please cite this article in press as: Mesías, M., et al., Impact of the characteristics of fresh potatoes available in-retail on exposure to acrylamide: Case study for French fries, Food Control (2016), http://dx.doi.org/10.1016/j.foodcont.2016.11.005

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M. Mesías et al. / Food Control xxx (2016) 1e8

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Please cite this article in press as: Mesías, M., et al., Impact of the characteristics of fresh potatoes available in-retail on exposure to acrylamide: Case study for French fries, Food Control (2016), http://dx.doi.org/10.1016/j.foodcont.2016.11.005