Effect of natural extracts on the formation of acrylamide in fried potatoes

LWT - Food Science and Technology xxx (2014) 1e7

Contents lists available at ScienceDirect

LWT - Food Science and Technology journal homepage: www.elsevier.com/locate/lwt

Effect of natural extracts on the formation of acrylamide in fried potatoes Gema Morales a, Maribel Jimenez a, *, Oscar Garcia b, María Remedios Mendoza b, Cesar Ignacio Beristain a a b

Instituto de Ciencias Básicas, Universidad Veracruzana, Apdo. Postal 575, CP 91192, Xalapa, Veracruz, Mexico Unidad de Servicios de Apoyo en Resolución Analítica, Universidad Veracruzana, Xalapa, Veracruz, Mexico

a r t i c l e i n f o

a b s t r a c t

Article history: Received 12 April 2013 Received in revised form 21 February 2014 Accepted 23 March 2014 Available online xxx

The objective of the present work was to evaluate the effect of natural extracts on the formation of acrylamide in fried potatoes. The aqueous extracts used were obtained from wild oregano (Origanum vulgare), thyme (Thymus vulgaris), cinnamon (Cinnamomum verum), bougainvillea (Bougainvillea spp) and green tea (Camellia sinensis), which presented a high percentage of free radical inhibition (DPPH) (48 e99%) and content of total phenolic compounds (205e547 mg EAG/mg of d.w.). Potatoes were submerged in the antioxidant extracts at a concentration of 1 g/L for 1 min, before being fried and their acrylamide concentration quantified by GCeMS. The extracts from green tea, cinnamon and oregano reduced the acrylamide level by 62%, 39% and 17%, respectively. The potatoes submerged in cinnamon and bougainvillea extracts showed differences in the color parameters compared to the control potatoes (P < 0.05); however, no significant differences (P > 0.05) were found in the texture and the peroxide values. The sensorial evaluation showed that the acceptance of the potatoes was not affected by the treatment applied. Thus, we can conclude that pre-treating potatoes with antioxidants before frying produces beneficial effects such as a reduction in acrylamide content, without any significant changes in their physicochemical, sensorial and textural properties. Ó 2014 Elsevier Ltd. All rights reserved.

Keywords: Acrylamide Fried potatoes Natural antioxidant Texture

1. Introduction Acrylamide is a substance commonly used in various industries and is considered a genotoxin, neurotoxin and probable carcinogen in humans (Bong-Kyung, 2006; Tareke, Rydberg, Karlsson, Eriksson, & Törnqvist, 2002). Recently, researchers at the National Food Administration of Sweden (NFA) and the University of Stockholm reported that foods rich in carbohydrates generate significant amounts of acrylamide when subjected to high temperatures lu, 2008; Masson et al., 2007). Since this sub(Gökmen & Palazog stance is harmful to health, having been classified in group 2A as “a probable human carcinogen” by the International Agency for Research on Cancer (IARC, 1994), its presence in foods is a cause for great concern. Acrylamide is produced naturally in foods with a high carbohydrate content and a low protein composition that, when subjected to processes such as frying, baking or toasting, generate this toxin mainly through the Maillard reaction (Mottram,

* Corresponding author. Tel.: þ52 (228) 8 41 89 00; fax: þ52 (228) 8 41 89 32. E-mail addresses: [email protected], [email protected] (M. Jimenez).

Wedzicha, & Dodson, 2002; Stadler et al., 2002; Taeymans & Wood, 2004; Taubert, Harlfinger, Henkes, Berkels, & Schömig, 2004). The concentration of acrylamide can vary enormously in any one food item, depending on factors such as temperature, cooking time, and the amount of reducing sugars and free amino acids like asparagine (Cheong, Hwang, & Hyong, 2005). Among the food types that may present significant amounts of acrylamide are products derived from cereals (cookies, bread and tostadas), coffee and, mainly, fried potatoes (Granda, Moreira, & Tichy, 2004; Moreno, Armendáriz, Gutiérrez, Fernández, & Torre, 2007; Takatsuki, Nemoto, Sasaki, & Maitani, 2003). Up to 12, 000 mg/kg of acrylamide has been quantified in fried potatoes (Friedman, 2003). The accepted levels of acrylamide should not be higher than 0.5 mg/L in processes such as water treatment (WHO, 2003) and not over 10 mg/kg in plastics (European Commission, 1992). Most of the research on this aspect is focused mainly on the reduction of acrylamide in fried potatoes, since they are widely consumed all over the world. The techniques currently applied to achieve said reduction are based on the modification of frying conditions (Granda et al., 2004), as well as the addition of other compounds such as amino acids (Cheong et al., 2005), acids (Jung,

http://dx.doi.org/10.1016/j.lwt.2014.03.034 0023-6438/Ó 2014 Elsevier Ltd. All rights reserved.

Please cite this article in press as: Morales, G., et al., Effect of natural extracts on the formation of acrylamide in fried potatoes, LWT - Food Science and Technology (2014), http://dx.doi.org/10.1016/j.lwt.2014.03.034

2

G. Morales et al. / LWT - Food Science and Technology xxx (2014) 1e7

Choi, & Ju, 2003; Kita, Brathen, Knutsen, & Wicklund, 2004), ions (Mestdagh, De Wilde, Delporte, Van, & De Menulenaer, 2008) and enzymes (Taeymans & Wood, 2004; Zyzak et al., 2003). However, many of these methods affect their color, taste and texture. Recent studies have reported a reduction of acrylamide levels through the addition of plant extracts to food products. Becalski, Lau, Lewis, and Seaman (2002) could decrease the amount of the toxin by adding rosemary (Rosmarinus officinalis) to the oil used for frying potatoes. Zhang, Chen, Zhang, Wu, and Zhang (2007) evaluated the effect of an antioxidant extract from bamboo leaves on the formation of acrylamide, achieving a decrease of 74% of the neurotoxin in fried potatoes, whereas Zhang and Zhang (2007) obtained an 83% reduction of acrylamide in bread by combining the extract from bamboo leaves with green tea. Plant extracts mainly contain phenolic compounds (Manzocco, Anese, & Nicoli, 1998) such as flavonoids, cinnamic acids, coumarins, phenolic acids, lignans and tannins, which all have antioxidant activity and are probably responsible for decreasing toxin levels. Many reports indicate that marjoram, thyme, cinnamon and bougainvillea contain total phenolic compounds that confer antioxidant activity (Shibamoto & Moon, 2009). Flowers of bougainvillea exhibited the highest DPPH radical scavenging activity and the major flavonoid found in flowers was quercetin and apigenin (Kaisoon, Siramornpun, Weerapreeyakul, & Meeso, 2011). Therefore, the objective of this study was to evaluate the reduction of acrylamide in fried potatoes through their immersion in extracts from diverse plants such as wild oregano, thyme, cinnamon, bougainvillea and green tea.

spectrophotometer (Cary 100, Varian, Palo Alto, CA, USA). These determinations were performed in duplicate. 2.4.2. Determination of total phenolic compounds The quantification of total phenolic compounds with the Foline Ciocalteau colorimetric reaction employed the method of Spanos and Wrolstad (1990). To 50 mL of the sample (1 mg/mL dissolved in distilled water), 2.5 mL of the FolineCiocalteu reagent (diluted 1/ 10) and 2 mL of Na2CO3 (75% p/v) were added and the mixture incubated at 45  C for 15 min. Absorbance was measured at 765 nm with a UVeVIS spectrophotometer (Cary 100, Varian, Palo Alto, CA, USA), the final results being expressed as equivalent micrograms of gallic acid per microgram of dry weight (mg EAG/mg dw) by interpolation from the calibration curve with a range of 20e1000 mg/mL of gallic acid (y ¼ 0.0011x þ 0.0688, R2 ¼ 0.9835).

2. Material and methods

2.4.3. Percentage of reducing power The determination of the reducing power percentage was made according to the method of Oyaizu (1986). To 0.125 mL of the sample at a concentration of 1 mg/mL, 1.25 mL of phosphate buffer (200 mM, pH 6.6) and 1.25 mL of potassium ferricyanide (1%) were added. The mixture was incubated at 50  C for 20 min. Then, 1.25 mL of 10% trichloracetic acid was added to the mixture, which was centrifuged at 650 g for 10 min. An aliquot of 2.5 mL was taken, 2.5 mL of distilled water and 0.5 mL of ferric chloride were added, and the absorbance measured at 700 nm with a UVeVIS spectrophotometer (Cary 100, Varian, Palo Alto, CA, USA). The results were reported as the percentage of reducing power. Absorbance of ascorbic acid at a concentration of 1 mg/mL was considered 100% for reference.

2.1. Reagents

2.5. Preparation and analysis of potatoes

1,1-diphenyl-2-picrilhydrazil (DPPH), FolineCiocalteu reagent, acrylamide (99%), L- ascorbic acid (>99.8%), gallic acid and L-glucose were acquired from SigmaeAldrich (Mexico). All reagents and solvents were of analytic grade.

2.5.1. Preparation of potatoes In the experiment were used 10 kg of potato Solanum tuberosum L. var. Atlantic obtained from the local market. The potatoes were washed and disinfected. The bare was carried out with a peeler friction and was removed black or green spots. Potatoes were cut into slices approximately 1.5  0.2 mm thick, with a manual cutter. After, samples were subjected to immersion treatment in antioxidant extracts, then were fried and immediately after the antioxidant and peroxide value were analyzed.

2.2. Raw material The dried plants used, wild oregano (Origanum vulgare), thyme (Thymus vulgaris), cinnamon (Cinnamomum verum), bougainvillea (Bougainvillea spp) and green tea (Camellia sinensis) belonging to the trademarks CatarinosÒ and La MercedÒ, were purchased in a local supermarket.

2.4. Analysis of antioxidant extracts

2.5.2. Quantification of total reducing sugars and pH in potatoes The quantification of total reducing sugars was made through the colorimetric method proposed by Somogyi and Norton (1952). To quantify the reducing sugars in the extracts, their clarification was first carried out. This was done by adding 1.0 mL of the extract (1 g/L) to 0.9 mL of sub-acetate of lead, 1.5 m/L of saturated sodium sulfate solution, 0.15 mL of glacial acetic acid, and 0.12 mL of zinc acetate and potassium ferrocyanide. This mixture was centrifuged for 5 min, and the reducing sugar content in the supernatant determined by interpolation from the calibration curve of L-glucose (10e100 mg/mL) (y ¼ 0.0082x þ 0.0649, R2 ¼ 0.9979). The pH measurements were performed using a potentiometer according to the method 943.02 (AOAC, 1998).

2.4.1. 1,1-Diphenyl-2-picrilhydrazil (DPPH) The capacity for capturing free radicals was determined using the radical 1,1-diphenyl-2-picrilhydrazil (DPPH) (Brand-Williams, Cuvelier, & Berset, 1995). To 0.1 mL of a concentration of 1 mg/L from the sample in methanol, 2.9 mL of the methanol solution of DPPH (36 mg/mL) were added and the mixture was shaken vigorously. The vials remained at ambient temperature for 30 min, before measuring absorbance at 517 nm with a UVeVIS

2.5.3. Extraction, identification and quantification of acrylamide The extraction was performed with the technique proposed by Biedermann et al. (2002). From the extract obtained, 2.0 ml of each sample were injected in duplicate. A gas chromatograph (trademark Hewlett-Packard, model 1800B, GCD System, Santa Clara, CA, USA), equipped with a column CP-WAX 52CB (VARIAN) (60 m  0.25 mm  0.25 mm), was used for the analysis. The initial temperature of 80  C was maintained for 5 min and subsequently

2.3. Preparation of extracts Fifty grams of the each dry plant were homogenized using an orbital shaker (MaxQÔ, Thermo Scientific, USA) at 200 rpm with 200 mL of distilled water at 60  C during 24 h then were filtered with Whatman No.1 filter paper. The extracts were frozen with liquid nitrogen and lyophilized, (being obtained, 1e2 g of powder) (lyophilizer Labconco 4.5 L, Kansas, USA) for subsequent analysis.

Please cite this article in press as: Morales, G., et al., Effect of natural extracts on the formation of acrylamide in fried potatoes, LWT - Food Science and Technology (2014), http://dx.doi.org/10.1016/j.lwt.2014.03.034

G. Morales et al. / LWT - Food Science and Technology xxx (2014) 1e7

increased to 250  C using a heating ramp of 30  C/min. This temperature was then maintained for15 min. Helium was used as the carrier gas at a flow of 1 mL/min; the injector temperature was 250  C, with split less injection and a purging time of 1 min. The mass spectra were obtained through ionization by electronic impact (EI) at 70 eV. Data acquisition was accomplished in the SIM mode, the monitored ions being m/z 71 and 44. Once the chromatograms were obtained, identification was performed by comparing the mass spectra obtained with the database HP Chemstation-NIST 05 Mass Spectral search program, version 2.0d. They were also compared with a standard for acrylamide analyzed under the same conditions. For quantification, a calibration curve with a range of 0.010e50 mg/mL (y ¼ 38465x þ 2751.4, R2 ¼ 0.9977) was developed. 2.6. Determination of the concentration and the immersion time of the potatoes in the antioxidant extract The evaluated concentrations of ascorbic acid were 0.1 g/L, 1 g/L and 10 g/L, the potatoes being submerged in each ascorbic acid solution for 1, 5 and 10 min. After these immersion times, the samples were dried with absorbent paper and fried at 150  5  C for 3 min in canola oil brand Canoil (AGYDSA, México) using a T-Fal fryer (GSEB, México). The concentration of acrylamide in the fried potatoes treated with ascorbic acid and the control potatoes submerged in distilled water was quantified. Of the times and concentrations evaluated, we selected the ones producing the largest reduction of acrylamide concentration. Using these conditions, the effect of the antioxidant extracts was evaluated. The proportion of the extract evaluated in regard to the weight of the potato was 1:3.8 (w:w). 2.7. Color evaluation Color analysis of the fried potatoes was performed with the colorimeter ColorFlex V1.72 SN#CX115 Hunter Lab (Sunset Hills Road, Reston, USA) to evaluate parameters L*, a* and b*. Starting from these, the shade of the color was calculated with the formula tan1(b*/a*) and the value of Chroma with (a*2 þ b*2)1/2. 2.8. Texture analysis The texture of the fried potatoes was evaluated with a texture analyzer TA.XT2i (Stable Micro Systems, Ltd., UK), provided with the software “Texture expert” to determine their hardness by measuring the force needed for compression. The evaluation was carried out with the following equipment and conditions: probe, 6.35 mm sphere; compression, up to complete fracture; distance, 2.5 mm; pre-test velocity, 0.5 mm/s; test velocity, 0.01 mm/s; posttest velocity, 0.01 mm/s; charging cell, 5 kg; and temperature, 25  C.

3

answers were converted to numeric values, “I like it extremely well” being designated number 1 and “I dislike it extremely” number 9. The average grade was obtained from the reported data. 2.11. Statistical analysis Data analysis was performed using the program Statistica 7.0 by StatSoft, Inc. (2004), the analysis of variance (ANOVA) and the Tukey test (P  0.05). The experimental data are presented as the mean  standard deviation (SD). 3. Results and discussion 3.1. Analysis of antioxidant activity in the extracts Fig. 1 presents the inhibition percentage of DPPH in the extracts evaluated. The highest percentage was obtained with the cinnamon extract (98%), followed by the thyme extract (76% of radical inhibition). The extracts from green tea and bougainvillea showed an inhibition percentage of 75% and 72%, respectively, and the wild oregano extract a percentage of only 48%. However, the highest concentration of phenolic compounds was found in this extract and in the one from cinnamon, with 547 and 293 mg EAG/mg. d.w., respectively (Fig. 2A). The extract with the lowest content of phenolic compounds was that of bougainvillea with 205 mg EAG/mg d.w. As regarding reducing power, the extracts exhibited a lower percentage (25e44%) than that obtained with ascorbic acid, which was used as control (Fig. 2B); however, it should be noted that ascorbic acid was used as a pure substance, whereas the antioxidant extracts were composed of complex mixtures of compounds. The results obtained in this part of the study are similar to those reported by some authors. For example, Castañeda, Ramos, and Ibáñez (2008), who evaluated the antioxidant activity of various plants, reported 97.2% of DPPH inhibition for the aqueous extract of cinnamon at 10% due to its high content of phenolic compounds. Satoh, Tohyama, and Nishimura (2005) determined a DPPH inhibition of 70% for the aqueous extract of green tea (30 mg/mL). Rice and Miller (1996) mentioned that this effect of green tea was mainly attributable to catechins, phenolic compounds with major antioxidant activity. Milos, Dragovic-uzelac, and Kulisic (2006) reported that the Lamiaceae family, which includes marjoram and thyme plant species, has high antioxidant activity, with a DPPH

2.9. Determination of peroxide index The peroxide value was examined according to the 965.33 method (AOAC, 1998). Five grams of the potatoes after frying were weighed, the fat was extracted with chloroform and the residue from the extraction was taken as the weight of the sample. 2.10. Sensorial evaluation The sensorial evaluation of all the treated fried potatoes was carried out using a hedonic scale of nine points. This scale included two extreme evaluations: “I like it extremely well” and “I dislike it extremely.” The test was conducted with 65 untrained panelists (32 men and 33 women) whose ages ranged from 10 to 50 years. The

Fig. 1. Percentage of DPPH radical inhibition demonstrated by the extracts. The results are presented as the average  SD (n ¼ 2).

Please cite this article in press as: Morales, G., et al., Effect of natural extracts on the formation of acrylamide in fried potatoes, LWT - Food Science and Technology (2014), http://dx.doi.org/10.1016/j.lwt.2014.03.034

4

G. Morales et al. / LWT - Food Science and Technology xxx (2014) 1e7

from bougainvillea the highest pH (6.4). One of the strategies employed to diminish acrylamide concentrations in potatoes is to immerse them in acids or solutions with a low pH, since under these conditions the amino group of asparagine acquires protons, thus preventing its union with reducing sugars and thereby preventing the Maillard reaction from occurring. Mestdagh et al. (2008) achieved a 100% reduction of acrylamide in fried potatoes by immersing them in citric acid solutions (0.1, 0.05 and 0.025 mol L1). Although the lowest pH was obtained with the cinnamon extract (5.1), this was not sufficient to achieve a significant reduction of acrylamide levels, since this requires a pH < 5, according to a report by Jung et al. (2003). 3.2. Determination of concentration and immersion time of potatoes in the antioxidative extract Fig. 3 shows the acrylamide concentration in fried potatoes treated with different concentrations and immersion times in ascorbic acid compared to the control group. The acrylamide contents in the potatoes immersed for 1 min at different concentrations of ascorbic acid were lower than those obtained at five and at 10 min. At 1 min, ascorbic acid concentrations of 1 g/L and 10 g/L generated significantly different acrylamide levels (P < 0.05) from those obtained in the control group. The acrylamide contents quantified at these concentrations (1 g/L and 10 g/L) were 120 and 176 mg/kg, respectively. Thus, reduction percentages of 60% and 42% were achieved compared to control. Upon failing to find significant differences between the two concentrations (1 g/L and 10 g/L) of ascorbic acid affecting the formation of acrylamide (P > 0.05) and considering the efficiency in reducing the toxic substance obtained with a concentration of 1 g/L for 1 min (60%), we decided to use these conditions to evaluate the effect of natural antioxidants on the formation of acrylamide. The results obtained agree with those reported by Zhang et al. (2007), who achieved the greatest decrease in acrylamide levels (74%) in fried potatoes by immersing them in an extract of bamboo leaves at a concentration of 1 g/L for 1 min. Fig. 2. (A) Total phenolic compounds and (B) percentage of reducing power for the extracts evaluated. The results are presented as the average  SD (n ¼ 2).

inhibition percentage of 69% and 85% for each of the two species just mentioned. In these plants, compounds such as apigenin, luteonin, thymol, carvacrol and eugenol have been identified, which can stabilize free radicals (Shibamoto & Moon, 2009). The pH and reducing sugar content of the extracts are provided in Table 1. The extract with the highest reducing sugar content was that from bougainvillea (2.8 g/100 g dry solids), followed by the green tea extract (1.0 g/100 g dry solids). The quantification of this parameter made it possible to establish a reason for why acrylamide levels were not reduced by some extracts. Reducing sugars play an important role in the generation of acrylamide through the Maillard reaction (Mottram et al., 2002). Of the extracts evaluated, the one from cinnamon presented the lowest pH (5.7) and that

3.3. Effect of natural antioxidants on the formation of acrylamide Fig. 4 shows the concentration of acrylamide in fried potatoes with the applied treatment, as well as the reduction percentage of

Table 1 Content of reducing sugars and pH of antioxidant extracts. Antioxidant extracts (g/L)

Reducing sugars (g/100 g d.w.)

pH

Green tea Bougainvillea Thyme Cinnamon Wild oregano

1.0 2.8 0.6 0.6 0.4

0.15a 0.38b 0.02a 0.02a 0.07a

6.1 6.4 6.3 5.7 6.1

    

    

0.0a 0.2a 0.0a 0.1b 0.1a

Data are expressed as means  SD (n ¼ 3). Different letters within the same column indicate significant difference (P < 0.05).

Fig. 3. Formation of acrylamide in fried potatoes treated with different concentrations of and immersion times in ascorbic acid. The results are presented as the average SD (n ¼ 4). Control group, 0.1 g/L; 1 g/L; 10 g/L; *P < 0.05.

Please cite this article in press as: Morales, G., et al., Effect of natural extracts on the formation of acrylamide in fried potatoes, LWT - Food Science and Technology (2014), http://dx.doi.org/10.1016/j.lwt.2014.03.034

G. Morales et al. / LWT - Food Science and Technology xxx (2014) 1e7

5

capacity, thereby preventing the sugar from uniting with the asparagine (Ciesarová et al., 2008; Schieberle, Kohler, & Granvogl, 2005). In the oxidation of lipids, during the degradation of these macro-molecules, acrolein is formed, which reacts by generating acrylic acid or an intermediary acrylic radical through oxidation (Becalski, Lau, Lewis, & Seaman, 2003). Both these intermediaries finally generate acrylamide by interacting with nitrogen sources. The antioxidants may block the oxidation of acrolein, thereby reducing the formation of acrylamide (Ciesarová et al., 2008; Zhang et al., 2007). 3.4. Analysis of color in fried potatoes treated with antioxidant extracts

Fig. 4. Content and percentage of acrylamide reduction in fried potatoes treated with different natural antioxidant extracts. The results are presented as the average  SD (n ¼ 4). *P < 0.05.

the neurotoxic substance compared with the control potatoes and those treated with ascorbic acid. The fried potatoes treated with the green tea extract presented the lowest concentration of acrylamide (116 mg/kg), indicating a reduction of 62%, which was significantly different from that in the control potatoes (P < 0.05), as was the concentration obtained with the potatoes treated with ascorbic acid (120 mg/kg), which showed a reduction of 61%. These results are encouraging, since there are currently no reports on the use of green tea extract to decrease acrylamide in fried potatoes. However, some publications have already mentioned the effect of green tea on the formation of the toxin. For example, Zhang and Zhang (2007) studied the reduction of acrylamide in bread by adding the aqueous extract of green tea at different concentrations, achieving a reduction of 72.5% with a concentration of 0.1 g/kg of the tea. On the other hand, Hedegaard, Granby, Frandsen, Thygesen, and Skibsted (2007) published the effect of the flavonoids of green tea (epicatechin and epigalocatechin galata) on the decrease in acrylamide amounts in a glucose-asparagine model system. In potatoes submerged in the extracts of cinnamon and oregano, 186 and 253 mg/kg of acrylamide was quantified, thus achieving an inhibition of 39% and 17%, respectively. However, these values were not significantly different from those found in the control potatoes (P > 0.05). Regarding oregano, Ciesarová, Suhaj, and Horváthová (2008) evaluated the effect of the methanolewater extract (4:1) of this plant (O. vulgare) on the formation of acrylamide in a model system (asparagine/glucose/potato starch), obtaining a reduction of 50% of the toxin. Unfortunately, with the aqueous extract used for this work, the reduction of the toxin was lower (17%). In potatoes treated with the extracts of bougainvillea and thyme, no decrease in the toxin was observed. The bougainvillea extract presented a higher content of reducing sugars (2.8 g/100 g dry solids), and it may be that this greater quantity of sugars favored the Maillard reaction and, consequently, the formation of acrylamide. At present, little is known about the mechanism of antioxidant action on the decrease of acrylamide. It has been published that natural antioxidants can interact with the precursors of acrylamide in two of the most important reactions that lead to their formation, the Maillard reaction and lipid oxidation (Ciesarová et al., 2008; Taeymans & Wood, 2004; Zhang et al., 2007). In the Maillard reaction, it is proposed that a fragment of the reducing sugar reacts with the conjugated system of polyphenols with the antioxidative

Table 2 shows the values of the color parameters evaluated in the fried potatoes. These presented positive values in parameter b* (yelloweblue) from 11.5 to 15.2, that is, they presented the yellow color characteristic of the food. For parameter a* (redegreen), the values were negative (from 1.5 to 2.6). The appearance of positive values would indicate an overcooking of the potatoes, as described by Granda et al. (2004).The color of the potatoes submerged in the cinnamon and bougainvillea extracts was significantly different from that of the control potatoes (P < 0.05), specifically for parameters L*, a*, b* and Chroma. No significant differences were found in the hue. In most cases, the bleaching of potatoes in substances like acids and amino acids leads to changes in the color parameters (Mestdagh et al., 2008). In the potatoes submerged in green tea extract, however, in which the highest percentage of acrylamide inhibition was obtained, no differences in the color parameters were found in comparison with the control potatoes (P > 0.05). 3.5. Analysis of texture in the fried potatoes The results regarding the hardness of the treated potatoes are shown in Fig. 5 and were compared with commercial brands (MC1 and MC2). The hardest potatoes were those treated with bougainvillea extract (5.1 m kg s2); by contrast, the least hard potatoes were those submerged in ascorbic acid (2.9 m kg s2). No significant differences (P < 0.05) in hardness were observed when comparing the commercial potatoes MC1 and MC2 with the treated potatoes; therefore, the antioxidant treatment applied to the fried potatoes did not affect this property. The average hardness determined in the fried potatoes agreed with those reported by Granda et al. (2004), who analyzed this parameter in potatoes of the Atlantic variety under traditional frying conditions, obtaining compression force values of 3e4 m kg s2. 3.6. Quantification of the peroxide index The fat content before frying was 1 g/100 g d.w and the fried potatoes showed a content of fat of 30 g/100 g d.w. The quantified peroxide index of the fried potatoes submerged in antioxidant Table 2 Color parameters evaluated in fried potatoes treated with antioxidant extracts. Treatment Control Ascorbic acid Green tea Bougainvillea Thyme Cinnamon Wild marjoram

L* 54.6 61.3 60.7 52.3 55.5 43.5 55.9

a*       

a

3.8 5.6a 1.1a 7.0a 3.1a 2.9b 4.4a

2.4 2.1 2.6 1.5 1.7 1.5 2.5

b*       

a

0.0 0.4a 0.0a 0.3b 0.4a 0.2b 0.2a

15.0 12.96 14.29 11.48 14.37 11.99 14.25

Chroma       

a

1.3 1.2a 1.6a 1.1b 0.9a 1.2b 0.8a

15.2 13.1 14.5 11.5 14.4 12.0 14.4

      

Hue a

1.2 1.3a 1.6a 1.1b 1.0a 1.2b 0.9a

80.6 80.6 79.3 82.2 83.0 82.8 79.9

      

0.8a 0.9a 1.1a 1.3a 1.6a 0.7a 0.5a

Results are presented as average  SD (n ¼ 3). The means in each one of the columns with a different letter are significantly different (P < 0.05).

Please cite this article in press as: Morales, G., et al., Effect of natural extracts on the formation of acrylamide in fried potatoes, LWT - Food Science and Technology (2014), http://dx.doi.org/10.1016/j.lwt.2014.03.034

6

G. Morales et al. / LWT - Food Science and Technology xxx (2014) 1e7

Fig. 5. Force (mKgs2) of two commercial fried potatoes (MC1 and MC2) and of potatoes treated with antioxidant extracts. The results are presented as the average  SD (n ¼ 5).

extracts and control potatoes is shown in Fig. 6. The samples treated with bougainvillea, cinnamon and wild oregano extract showed peroxides value of 9.5, 8.5 and 6.7 meq/kg, respectively. By the other hand, samples treated with green tea and thyme extract presented peroxides value (16.3 and 15.9 meq/kg) numerically greater than that obtained for the control potatoes (11.9 meq/kg). However, no statistically significant differences (P < 0.05) were seen between the peroxide indices of the treated potatoes and the control potatoes, indicating the same protection against the oxidation of oil. The peroxide index quantifies the hydro-peroxide formed as the initial product of lipid oxidation. This parameter was determined because the antioxidative treatment applied to fried potatoes cannot only contribute to lowering the concentration of acrylamide, but can also prevent the oxidation of lipids that produces a disagreeable rancid odor in some foods. Kochhar (2000) mentioned that antioxidants retarded oxidation reactions and inhibited the formation of free radicals by donating hydrogen atoms. It is important to point out that the concentration of the antioxidants present may influence their behavior. Nogala-Kalucka, Korczak, Elmadfa, and Wagner (2005) found that at high concentrations, tocopherol may act as a pro-oxidant by diminishing the stability of fats or oils and that this may also be the effect of green tea and thyme extracts. Moreover, Manzocco et al. (1998) stated that the

Fig. 7. Mean Hedonic ratings of control potato and samples treated with antioxidant extracts. The results are presented as the average  SD (n ¼ 65).

use of antioxidants in frying processes has the inconvenience of creating low stability in most of them at high temperatures. 3.7. Sensorial evaluation No significant difference in the acceptance level was found between fries submerged in different antioxidant extracts and untreated (P > 0.05). Although, tested extracts are strong spices. The range of the values obtained for the fried potatoes treatment and untreated with the extracts was in the categories of “I like it slightly” (6 points) and “I like it moderately” (7 points) on the hedonic scale, indicating that the fried potatoes impregnated with the different natural extracts (green tea, bougainvillea, thyme, cinnamon and oregano) were similar accepted compared to control (Fig. 7). It is possibly due to the short time of immersion in the antioxidant extracts. 4. Conclusions The lowest concentration of acrylamide was obtained by submerging the potatoes in green tea extract before frying, achieving a 62% reduction of the toxin. The results obtained in this study demonstrate that it is possible to diminish the acrylamide formed in fried potatoes without affecting sensorial acceptance and physicochemical characteristics (color and texture), using a simple and economical process that can be applied in homes as well as at the industrial level, since it does not require any specialized equipment and involves neither a significant increase in preparation time nor elevated costs. References

Fig. 6. Peroxide indices in fried potatoes treated with antioxidant extracts. The results are presented as the average  SD (n ¼ 3).

AOAC Official Methods of Analysis. (1998). Association of Official Analytical Chemist Inter. Arlington, Virginia, U.S.A. Biedermann, M., Biedermann-Brem, S., Noti, A., Grob, K., Egli, P., & Mandli, H. (2002). Two GCeMS methods for the analysis of acrylamide in foodstuffs. Mitteilungen aus Lebensmitteluntersuchung und Hygiene, 93, 638e652. Becalski, A., Lau, B. P., Lewis, D., & Seaman, S. (2002). Acrylamide in foods: occurrence and sources. In Association of Official Analytical Chemists (AOAC) Annual Meeting, The Angeles, CA. September 22e26.. Becalski, A., Lau, B., Lewis, D., & Seaman, S. (2003). Acrylamide in foods: occurrence, sources, and modeling. Journal of Agricultural and Food Chemistry, 51, 802e808. Bong-Kyung, K. (2006). Determination of acrylamide content of food products in Korea. Journal of the Science of Food and Agriculture, 86, 2587e2591.

Please cite this article in press as: Morales, G., et al., Effect of natural extracts on the formation of acrylamide in fried potatoes, LWT - Food Science and Technology (2014), http://dx.doi.org/10.1016/j.lwt.2014.03.034

G. Morales et al. / LWT - Food Science and Technology xxx (2014) 1e7 Brand-Williams, W., Cuvelier, M., & Berset, C. (1995). Use of the free radical method to evaluate antioxidant activity. Lebensmittel-Wissenschaft und Technologie, 20, 5e30. Castañeda, B., Ramos, E., & Ibáñez, L. (2008). Evaluación de la capacidad antioxidante de plantas medicinales peruanas nativas e introducidas. Revista Peruana de Medicina Experimental y Salud Pública, 15, 1. Cheong, T. K., Hwang, E., & Hyong, L. (2005). Reducing acrylamide in fried snack products by adding amino acids. Journal of Food Science, 70, 354e357. Ciesarová, Z., Suhaj, M., & Horváthová, J. (2008). Correlation between acrylamide contents and antioxidant capacities of spice exracts in a model potato matrix. Journal of Food and Nutrition Research, 47, 1e5. European Commission. (1992). Directive 92/39/EEC, amending Directive 90/128/ EEC relating to plastic materials and articles intended to come in contact with foodstuffs. Official Journal of the European Communities, L168, 21e29. Friedman, M. (2003). Chemistry, biochemistry and safety of acrylamide. A review. Journal of Agricultural and Food Chemistry, 51, 4504e4526. lu, T. (2008). Acrylamide formation in foods during thermal Gökmen, V., & Palazog processing with a focus on frying. Food Bioprocess Technology, 1, 35e42. Granda, C., Moreira, R. G., & Tichy, S. E. (2004). Reduction of acrylamide formation in potato chips by low-temperature vacuum frying. Journal of Food Science, 69, 405e411. Hedegaard, R. V., Granby, K., Frandsen, H., Thygesen, J., & Skibsted, L. (2007). Acrylamide in bread. Effect of prooxidants and antioxidants. European Food Research and Technology, 227, 519e525. IARC. Intl. Agency for Research on Cancer. (1994). Monographs on the valuation of carcinogen risk to humans: Some industrial chemicals. Nr 60. Lyon: IARC. Jung, M. Y., Choi, D. S., & Ju, J. W. (2003). A novel technique for limitation of acrylamide formation in fried and baked corn chips and in French fries. Journal of Food Science, 68, 1287e1290. Kaisoon, O., Siramornpun, S., Weerapreeyakul, N., & Meeso, N. (2011). Phenolic compounds and antioxidant activities of edible flowers from Thailand. Journal of Functional Foods, 3, 88e99. Kita, A., Brathen, E., Knutsen, S. H., & Wicklund, T. (2004). Effective ways of decreasing acrylamide content in potato crisps during processing. Journal of Agricultural and Food Chemistry, 52, 7011e7016. Kochhar, S. P. (2000). Stabilization of frying oils with natural antioxidative components. European Journal of Lipid Science and Technology, 102, 552e559. Manzocco, L., Anese, M., & Nicoli, M. C. (1998). Antioxidant properties of tea extracts as affected by processing. Lebensmittel-Wissenschaft und Technologie, 31, 694e 698. Masson, L., Muñoz, R. J., Romero, N., Camilo, C., Encina, C., Hernández, L., et al. (2007). Acrilamida en patatas fritas: Revisión actualizada. Grasas y Aceites, 58, 185e193. Mestdagh, F., De Wilde, T., Delporte, K., Van, C., & De Menulenaer, B. (2008). Impact of chemical pre-treatments on the acrylamide formation and sensorial quality of potato crisps. Food Chemistry, 106, 914e922. Milos, M., Dragovic-uzelac, V., & Kulisic, T. (2006). Antioxidant activity of aqueous tea infusions prepared from oregano, thyme and wild thyme. Food Technology Biotechnology, 44, 485e492. Moreno, N. M., Armendáriz, R., Gutiérrez, F., Fernández, C., & Torre, H. (2007). La acrilamida, contaminante químico de procesado: Revisión. Revista Toxicológica, 24, 1e9.

7

Mottram, D. S., Wedzicha, B. L., & Dodson, A. T. (2002). Acrylamide is formed in the Maillard reaction. Nature, 419, 448e449. Nogala-Kalucka, M., Korczak, J., Elmadfa, I., & Wagner, K. H. (2005). Effect of a- and d-tocopherol on the oxidative stability of a mixed hydrogenated fat under frying conditions. European Food Research and Technology, 221, 291e297. Oyaizu, M. (1986). Studies on products of browning reaction prepared from glucoseamine. Journal of Nutrition, 44, 307e314. Rice, C., & Miller, N. (1996). Antioxidant activities of flavonoids as bioactive components of foods. Biochemical Society Transactions, 20, 790e795. Satoh, E., Tohyama, N., & Nishimura, M. (2005). Comparison of the antioxidant activity of roasted tea with green, oolong and blacks teas. International Journal of Food Sciences and Nutrition, 56, 551e559. Shibamoto, T., & Moon, J. K. (2009). Antioxidant assays for plant and food components. Journal of Agricultural and Food Chemistry, 57, 1655e1666. Schieberle, P., Kohler, P., & Granvogl, M. (2005). New aspects on the formation and analysis of acrylamide. In M. Friedman, & D. Mottram (Eds.), Chemistry and safety of acrylamide in food (Vol. 561); (pp. 205e222). New York: Springer. Somogyi, M., & Norton, N. (1952). A photometric adaptation of the Somogyi method for the determination of glucose. Journal of Biological Chemistry, 200e245. Spanos, G., & Wrolstad, R. (1990). Influence of processing and storage on the phenolic composition of Thompson seedless grape juice. Journal of Agricultural and Food Chemistry, 38, 1565e1571. StatSoft, Inc. (2004). STATISTICA (data analysis software system), version 7. www. statsoft.com. Stadler, R. H., Blanck, I., Varga, N., Robert, F., Hau, J., Guy, P. A., et al. (2002). Acrylamide from Maillard reaction products. Nature, 419, 449e450. Taeymans, D., & Wood, J. (2004). A review of acrylamide: an industry perspective on research, analysis, formation, and control. Critical Reviews in Food Science and Nutrition, 44, 323e347. Takatsuki, S., Nemoto, S., Sasaki, K., & Maitani, T. (2003). Determination of acrylamide in processed foods by LC/MS using column switching. Shokuhin Eiseigaku Zasshi, 44, 89e95. Tareke, E., Rydberg, P., Karlsson, P., Eriksson, S., & Törnqvist, M. (2002). Analysis of acrylamide, a carcinogen formed in heated foodstuffs. Journal of Agricultural and Food Chemistry, 50, 4998e5006. Taubert, D., Harlfinger, S., Henkes, L., Berkels, R., & Schömig, E. (2004). Influence of processing parameters on acrylamide formation during frying of potatoes. Journal of Agricultural and Food Chemistry, 52, 2735e2739. WHO. (2003). Acrylamide in drinking-water. Guidelines of drinking-water quality. Health criteria and other supporting information. Geneva, Switzerland: WHO/ SDE/WSH/03.04/71. Zhang, Y., & Zhang, Y. (2007). Study on reduction of acrylamide in fried bread sticks by addition of antioxidant of bamboo leaves and extract of green tea. Asia Pacific Journal of Clinical Nutrition, 1, 131e136. Zhang, Y., Chen, J., Zhang, X., Wu, X., & Zhang, Y. (2007). Addition of antioxidant of bamboo leaves (AOB) effectively reduces acrylamide formation in potato crisps and French fries. Journal of Agricultural and Food Chemistry, 55, 523e528. Zyzak, D. V., Sanders, R. A., Stojanovic, M., Tallmadge, D. H., Eberhart, B. L., Ewald, D. K., et al. (2003). Acrylamide formation mechanism in heated foods. Journal of Agricultural and Food Chemistry, 51, 4782e4787.

Please cite this article in press as: Morales, G., et al., Effect of natural extracts on the formation of acrylamide in fried potatoes, LWT - Food Science and Technology (2014), http://dx.doi.org/10.1016/j.lwt.2014.03.034