Article pubs.acs.org/JAFC
Formation of Monochloropropane-1,2-diol and Its Esters in Biscuits during Baking Burçe Ataç Mogol,† Céline Pye,‡ Warwick Anderson,‡ Colin Crews,‡ and Vural Gökmen*,† †
Department of Food Engineering, Hacettepe University, Beytepe, 06800 Ankara, Turkey The Food and Environment Research Agency (FERA), Sand Hutton, York YO41 1LZ, U.K.
‡
ABSTRACT: The formation of free monochloropropane-1,2-diol (3-MCPD and 2-MCPD) and its esters (bound-MCPD) was investigated in biscuits baked with various time and temperature combinations. The effect of salt as a source of chloride on the formation of these processing contaminants was also determined. Kinetic examination of the data indicated that an increasing baking temperature led to an increase in the reaction rate constants for 3-MCPD, 2-MCPD, and bound-MCPD. The activation energies of formation of 3-MCPD and 2-MCPD were found to be 29 kJ mol−1. Eliminating salt from the recipe decreased 3MCPD and 2-MCPD formation rate constants in biscuits by 57.5 and 85.4%, respectively. In addition, there was no formation of bound-MCPD in biscuits during baking without salt. Therefore, lowering the thermal load or limiting the chloride concentration should be considered a means of reducing or eliminating the formation of these contaminants in biscuits. Different refined oils were also used in the recipe to test their effect on the occurrence of free MCPD and its esters in biscuits. Besides the baking process, the results also confirmed the role of refined oil in the final concentration of these contaminants in biscuits. KEYWORDS: 3-MCPD, 2-MCPD, bound-MCPD, biscuits, baking
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INTRODUCTION Chloropropanols and their fatty acid esters (chloroesters) are contaminants that are formed during the processing and manufacture of certain foods and ingredients.1 3-Monochloropropane-1,2-diol (3-MCPD), 1,3-dichloro-2-propanol (1,3DCP), and their isomers 2-MCPD and 2,3-DCP are the major known components of a group of chloropropanols. 3-MCPD was first found in acid-hydrolyzed vegetable protein (acidHVP) as a reaction product of either acylglycerols or glycerol with hydrochloric acid.2 It has raised concern, as free 3-MCPD is known to exhibit carcinogenic effects.3 Because of the toxicity of 3-MCPD, a tolerable daily intake of 2 μg/kg of body mass4 and a maximal limit of 20 μg/kg in acid-HVP and soy sauce (40% dry matter) has been set by the European Commission.5 Esterified forms of 3-MCPD could also be formed during hightemperature processing of fat-containing foods and are known as food-borne contaminants. It was reported that 3-MCPD esters are readily hydrolyzed in vivo, releasing the free form.6,7 3-MCPD has also been shown to be present in foods that have not been subjected to treatment with hydrochloric acid.8 Researchers conducted surveys in local markets and found that a wide range of foods other than acid-HVP and soy sauce can contain 3-MCPD. These foods include noodles, meat, cakes, and breads and biscuits, which are common foods and eaten in large quantities.9 3-MCPD is formed in these foods by the action of the naturally present or added sodium chloride with acylglycerols during manufacturing and thermal processes such as baking.10−13 3-MCPD was found in the crust of breads at high levels (up to 0.40 mg kg−1), whereas no contaminant was detected in the breadcrumbs.14,15 In other research, 3-MCPD was determined to be present in leavened dough at levels consistently greater than those of in unleavened dough because of the formation of glycerol during the fermentation.16,17 The following other cereal products have reported decreasing mean © 2014 American Chemical Society
levels of 3-MCPD: savory biscuits > doughnuts > sweet biscuits (that contained 98%) was purchased from Alfa Aesar England. 3-Chloro-1,2-propanediol (3-MCPD), sodium methoxide, filter papers (Whatman No. 4), and potassium bromide were purchased from Sigma-Aldrich (Gillingham, U.K.). MCPD-d5 and 3MCPD-palmitate-d5 were obtained from CDN isotopes and Toronto Research Chemicals, respectively. Refined wheat flour (standard T55/W150) was kindly supplied by Kraft Foods (Glattpark, Switzerland). Sucrose powder, sodium bicarbonate, ammonium bicarbonate, and sodium chloride were kindly supplied by Eti (Eskişehir, Turkey) and refined corn, canola, hazelnut, olive, and peanut oils by Zade (Konya, Turkey). Preparation of Biscuits. The biscuits were prepared according to the American Association of Cereal Chemists Method 10-54 with some modifications.22 The recipe contained 80.0 g of wheat flour, 35.0 g of sucrose powder, 20.0 g of corn oil, 1.0 g of sodium chloride, 0.4 g of ammonium bicarbonate, 0.8 g of sodium bicarbonate, and 17.6 mL of water. All ingredients were thoroughly mixed in accordance with the AACC Method 10-54 procedure using an Artisan Kitchen Aid 5KSM150 dough mixer. The dough was rolled to a 3 mm thickness and cut into three discs 5 cm in diameter and baked in a conventional oven (Memmert, UNE 400). Two different recipes were prepared with corn oil, namely, a basic recipe and a basic recipe without sodium chloride. Biscuits having the basic recipe were baked at 180, 200, and 220 °C for different times for up to 19 min. The recipe without salt was baked at 220 °C for 7−11 min. Additionally, different refined oils, namely, canola, hazelnut, olive, and peanut, were also used to determine the effect of oil type on MCPD formation by replacing corn oil in the recipe. These sets of biscuits were baked at 220 °C for 10 min. All baking experiments were performed in duplicate. Regardless of the baking condition, all biscuits prepared contained 0.05). 7299
dx.doi.org/10.1021/jf502211s | J. Agric. Food Chem. 2014, 62, 7297−7301
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Article
Figure 3. Effect of oil type on the formation of 3-MCPD (a), 2-MCPD (b), and bound-MCPD (c) (milligrams per kilogram of biscuit) in biscuits baked at 220 °C for 10 min. Values having the same letter are not significantly different (p > 0.05).
Figure 2. Effect of salt on the formation of (a) 3-MCPD, (b) 2MCPD, and (c) bound-MCPD (milligrams per kilogram of biscuit) in biscuits during baking at 220 °C.
oil were found to be the highest, i.e., 0.075 and 0.717 mg kg−1, respectively. Zelinková also reported that the bound-MCPD concentration with refined olive oil was higher than that with other refined edible oils, namely, soybean, sunflower, maize, and rapeseed.27 In conclusion, removal of chloride from biscuit formulations controlled the formation of 3-MCPD, 2-MCPD, and boundMCPD, which could be an effective mitigation strategy in which there are no adverse effects on the biscuit flavor. Careful selection of the type of vegetable oil or shortening and testing for MCPD ester content prior to their use in baking could also reduce the content of these processing contaminants in bakery products.
concentration of bound-MCPD in biscuits baked for 7 min was found to be 0.085 ± 0.003 mg (kg of biscuit)−1. There was no significant increase in the bound-MCPD concentration during baking (p < 0.05). However, the presence of salt as a source of chloride caused an increase in the rate of formation of boundMCPD in biscuits during baking. The mechanism behind this formation might be a possible reaction between di- and monoacylglycerols of oil and sodium chloride present in the biscuit recipe. In addition, it was reported that sodium chloride acts as a Lewis acid accelerating the hydrolysis of sucrose during heating.26 In a similar way, it might break the ester bond of acylglycerols, giving available sites to chloride to bind. Effect of Oil Type on the Formation of 3-MCPD, 2MCPD, and Bound-MCPD in Biscuits. A range of different vegetable oils, namely, corn oil, canola, nut, olive, and peanut, were used in the biscuit formulation to determine their effect on the formation of 3-MCPD, 2-MCPD, and bound-MCPD (Figure 3a−c). The 3-MCPD content of all biscuits prepared with different oils was found to be ∼0.06 mg kg−1. Statistical analysis showed that there was no significant difference between the 3-MCPD contents of these biscuits (p < 0.05). Among the refined oils used in this study, 2-MCPD and boundMCPD concentrations of the biscuit prepared with refined olive
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AUTHOR INFORMATION
Corresponding Author
*Phone: +90 312 2977108. Fax: +90 312 2992123. E-mail:
[email protected]. Funding
This work was conducted within the framework of the PROMETHEUS project (PROcess contaminants: Mitigation and Elimination Techniques for High food quality and their Evaluation Using Sensors & Simulation) funded by the European Commission. Notes
The authors declare no competing financial interest. 7300
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ABBREVIATIONS USED 3-MCPD, 3-chloropropane-1,2-diol; 2-MCPD, 2-chloropropane-1,3-diol; 1,3-DCP, 1,3-dichloro-2-propanol; 2,3-DCP, 2,3-dichloro-1-propanol
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REFERENCES
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