بررسی تاثیر روش پخت و زمان تخمیر بر مقدار اکریل آمید در نان‏های سنتی (تافتون، سنگک، لواش و بربری)

Introduction: Bread is the main part of the diet all over the world and especially in Iran. The baking process during the preparation of bread improve the color, taste, and texture of the bread to a great extent. At temperatures higher than 120°C, acrylamide has been found as a carcinogenic byproduct in high carbohydrate products (Lingnert, 2006). Acrylamide compounds are generally found in fried, roasted or overheated foods that are of carbohydrate origin. Heat causes the reaction of decarboxylation and deamination of asparagine, which is the main basis for the formation of acrylamide, and the presence of reducing sugars is necessary for this reaction (Keramat et al 2011). The formation of acrylamide in this route is based on the main stages of the Maillard reaction. Acrylamide is one of the major concerns for human health due to causing mutations in genes and causing cancer. No safety limit to prevent cancer has been determined for acrylamide (Tareke, 2002). During the baking process, there is a possibility of forming acrylamide as a side product therefore bread is one of the important sources of food for humans to receive high amounts of acrylamide. Considering that the most Iranian breads are still cooked in traditional ways and mostly using direct heat, therefore, in this research, the effect of the type of oven and the time of fermentation process on the amount of acrylamide formation in traditional types of bread was investigated.
Materials and methods: Sampling of Barbari, Lavash, Tufton, and Sangak breads was done from bakeries with a direct flame heat oven (traditional oven) and bakeries with an indirect flame heat oven (rotary oven) and in each bakery in two stages of incomplete and complete fermentation of the dough. The bread samples were completely dried in the shade. The amount of acrylamide was measured by GC-MS method based on the extraction of acrylamide from the sample with the help of sodium chloride and derivatization by bromine. To draw the standard curve, different concentrations of acrylamide standard were used and the calibration curve was drawn.
Results and discussion: The way of baking bread and in better words the type of oven used has a significant effect on the amount of acrylamide formation in bread, which can be due to the difference in the amount and type of heat applied, direct flame (traditional ovens) or indirect flame (rotary) and also, the cooking time which is different depending on the amount of heat applied. In Barbari and Sangak breads, the use of indirect flame heat (rotary oven) had a significant effect on reducing the amount of acrylamide in the breads. So that regardless of the fermentation time, the amount of acrylamide in Berbari breads cooked with indirect flame heat compared to the traditional oven was reduced by 49.14%, which is a very significant amount. In the case of Sangak breads, the average amounts of acrylamide were 163.95 ppb and 93.88 ppb in bakeries with traditional and rotary ovens respectively, which regardless of the fermentation time reduced 42.74% is observed in the amount of acrylamide. In Tufton breads, the difference in cooking method, the use of direct or indirect flame heat, did not significantly changes in the amounts of acrylamide. According to the obtained results, the amount of acrylamide formed in Sangak bread prepared from flour with higher ash content is higher. In fact, more ash in flour indicates a higher degree of flour extraction, and with an increase in the degree of extraction, the amount of protein, especially asparagine, which is the key factor in the reaction of acrylamide formation, will be higher. For this reason, the amount of acrylamide in breads made with wholemeal flour is higher than breads made with light flour. In all flat breads studied, regardless of the cooking method, the amount of acrylamide decreased significantly with the lengthening of the fermentation time. So that the average percentage of reduction during fermentation was 14.21% in lavash breads, 23.04% in Barbari breads, 29.39% in Sangak breads prepared from whole wheat flour, 31.77% in Tufton breads and 40.99% in Sangak breads prepared from bright flour.
Conclusion: The type of oven used has a significant effect on the amount of acrylamide formation in bread due to the difference in the amount, the type of heat applied and the cooking time, and the use of rotary ovens might be a suitable alternative to traditional ovens to reduce the formation of acrylamide in breads. In all studied breads, with the lengthening of the fermentation time, the amount of acrylamide decreased on average from 14.21% in lavash bread to 40.99% in Sangak (bright flour) bread. In the general classification of types of bread regardless of fermentation time and cooking method, there were Sangak, Tufton, Barbari and Lavash breads respectively. The amounts obtained in the examined types of bread are not dangerous for health and are much lower than the maximum amount (300 ppb) determined by the European Union Commission. It is worth mentioning that the variety of flat breads produced in the country has also been seen in people's diet, so despite the high consumption of bread in the country, the average intake of acrylamide is much lower than the set limits and is within the range of standards that have been developed so far.