Elsevier

Food Control

Volume 38, April 2014, Pages 221-226
Food Control

Acrylamide formation in traditional Czech leavened wheat-rye breads and wheat rolls

https://doi.org/10.1016/j.foodcont.2013.10.022Get rights and content

Highlights

  • Acrylamide content in breads was lower than reported for similar products in EU.

  • Due to lower pH, breads leavened by natural rye sourdough have less acrylamide.

  • Changes of rye/wheat ratio in dough do not influence acrylamide content in bread.

  • Smaller loaves with higher crust–crumb ratio have more acrylamide per weight unit.

  • No influence of varying content of added yeast/vital gluten in rolls was observed.

Abstract

The main aim of our study was to collect the data on the acrylamide content in typical Czech leavened wheat-rye breads and wheat rolls, and to demonstrate the influence of various technological factors on its contents. We analysed several sets of industrially and laboratory baked breads to better understand the acrylamide formation. Following factors were tested: (i) the content of rye in respective bread formulae and (ii) the character of leavening procedure. We were, as well, monitoring for ten days the variability of acrylamide levels in bread baked by one bakery and, afterwards, we analysed the same type of bread baked in 12 bakeries. In the case of rolls, the influence of yeasts and vital gluten content in the dough were subjects of an assessment. The levels of acrylamide in a common type of the Czech bread baked in various bakeries were relatively low, ranging from 7 to 22 μg kg−1. The content of acrylamide was rather higher in breads prepared using a commercial starter (Lactobacilli) and yeasts than in bread prepared using natural rye sourdough only. A varying content of rye flour did not seem to have any impact on acrylamide levels. The ‘size dilution effect’ was observed when comparing the same type of bread with different weight. Since acrylamide is exclusively located in the bread crust, smaller loaves contained higher acrylamide content per kg. The contents of acrylamide in standard wheat bakery goods were very low, bellow 10 μg kg−1. No influence of varying content of added yeast or vital gluten was observed.

Introduction

Acrylamide (prop-2-enamide) has been classified as a probable human carcinogen 2A (IARC, 1994) and is known as neurotoxin (WHO, 2002). This compound is formed during the Maillard reaction, especially in heat-processed starch-rich foods such as potato and bakery products. High acrylamide contents can be found in coffee and coffee surrogates, as well (EFSA, 2011).

Currently, acrylamide is monitored in the European Union member's states according to the European Commission Recommendation (2010/307/EU). Indicative acrylamide values based on the EFSA (European Food Safety Authority) monitoring data from 2007 to 2008 were established within the European Commission recommendation released on January 10, 2011 (“on investigations into the levels of acrylamide in food”) (EC, 2011). The indicative values are not safety thresholds, but, if exceeded, subsequent investigation of the reasons should be conducted. Cereal products are there divided into 5 categories with relevant indicative values: Soft bread (150 μg kg−1); Breakfast cereals excl. muesli and porridge (400 μg kg−1); Biscuits, crackers, wafers, crisp bread and similar, excl. ginger bread (500 μg kg−1); Biscuits and rusks for infants and young children (250 μg kg−1); Processed cereal based foods for infants and young children, excl. biscuits and rusks (100 μg kg−1) (EC, 2011). For other commodities such as potato products or coffee indicative values are available as well (EC, 2011).

The latest exposure estimates in Europe evaluated by European Food Safety Authority (EFSA) were reported within the EFSA scientific report in 2011 (EFSA, 2011). Besides of potato products and coffee, bakery products, including soft bread and biscuits, have been identified as significant contributors to the overall acrylamide exposure through all groups of population (EFSA, 2011). The found mean acrylamide contents in soft breads ranged between 30 and 75 μg kg−1 within the years 2007–2010 (EFSA, 2012). Despite the fact that acrylamide contents found in EU countries in soft breads are reasonably low, it is an important acrylamide source in European diets (EFSA, 2011). The results obtained within the EFSA report demonstrate that the contribution to the acrylamide dietary intake from soft bread in EU countries is approximately 20% among children and adolescents and up to 30% among adults (EFSA, 2011). These percentages are influenced by many factors such as age or gender of the respondents or the consumer's habits. In the Czech Republic, the contribution of bakery products to consumers' exposure to acrylamide is important due to their relatively high daily consumption. The contribution of soft bread to the total acrylamide dietary exposure in the Czech Republic is 13% for adults and 9–10% for children and adolescents (EFSA, 2011).

The results of several studies confirmed asparagine as a key precursor of acrylamide formation in cereal based heat-treated food (Hamlet et al., 2008, Taeymans et al., 2004). According to the results of 5 years monitoring study (2006–2010), the mean asparagine content in wheat flours in the Czech Republic was found in the range from 36 to 309 mg kg−1 (National project NPV II results). These values found in crop grown in the Czech Republic were comparable with those reported in other countries (69–443 mg kg−1) (Konings, Ashby, Hamlet, & Thompson, 2007). It should be noted that not only the asparagine content in flour but also the glucose/fructose ratio and other ingredients added to the dough play an important role (Hamlet et al., 2008). Several studies were concerned with a detailed monitoring of factors influencing acrylamide formation in bakery products with the aim to find the conditions enabling reduction of acrylamide. The current state of the art is summarized in the ‘Toolbox’, the document published by Food Drink Europe in 2011(FDE, 2011).

For instance the addition of Ca2+ salts into flours was shown to have a potential for significant acrylamide reduction. The fortification of flour by 0.3% of Ca2+ salts is required by the U.K. law for nutritional reasons and results in up to 30% decrease according to some authors (Hamlet et al., 2005, Sadd et al., 2008). The addition of glycine may lead to acrylamide reduction in yeast leavened bread. Nevertheless, the addition of high amounts of this amino acid may have a negative impact on yeast fermentation (Brathen et al., 2005, Fink et al., 2006).

Size dilution in bread seems to be another important factor influencing the acrylamide content expressed on the whole product. The acrylamide formation is typical for the bread crust, where the temperature reaches much higher values than in the bread crumb, where the temperatures do not exceed 100 °C (Surdyk, Rosén, Andersson, & Aman, 2004). Production of a larger bread loaf can reduce the average acrylamide content in a loaf due to the dilution caused by decreasing the ratio surface area to the volume ratio (Amrein et al., 2007, Surdyk et al., 2004).

Another possible way for reduction of the acrylamide amount is prolonged yeast fermentation during which asparagine is assimilated by yeasts (Fredriksson, Tallving, Rosén, & Aman, 2004). Some studies have shown an acrylamide reduction of about 50% after 1 h of fermentation (Hamlet et al., 2005, Sadd et al., 2008). Nevertheless, the reduction was not so successful in industrially prepared breads.

During dough baking, the time and temperature are the crucial factors responsible for the extent of thermal input and, consequently, of acrylamide formation (FDE, 2011).

The type of baking technology may have an impact on acrylamide contents. Infrared heating, as an alternative technology, seems to be an effective tool in acrylamide minimization, nevertheless, this approach is not fully acceptable for a production of traditional bread loaf for Czech consumers. (Ahrne et al., 2007, HEATOX, 2007).

Within our study we studied several technological factors influencing the acrylamide formation during bread and rolls baking. We compared the products obtained from industrial bakeries and the experimental products baked in the laboratory. The objective of our study was first to obtain more information about variability of acrylamide contents in commercial products (bread and rolls), prepared from locally grown cereals according to traditional recipes and baked under common industrial conditions. Second, based on the obtained data and considering current knowledge on acrylamide formation, we attempted to evaluate the factors that might contribute to the reduction of the acrylamide content in bakery products. We tested breads recipes with a varying content of rye and the use of different type of bread fermentation.

Section snippets

Chemicals

Acrylamide (CAS 79-06-1, purity 99.5%) and magnesium sulphate (p.a. purity ≥ 98%) were from Sigma–Aldrich/Fluka (Switzerland). 13C3-Acrylamide (isotopic purity ≥ 99%) was purchased from Cambridge Isotope Laboratories (USA). Sodium chloride was from Penta (Czech Republic). Aluminium oxide (basic) was from Merck (Germany). Acetonitrile and n-hexane were of HPLC grade quality and were supplied by Sigma–Aldrich (Germany) and Merck (Germany), respectively. Deionized water was obtained from a

Experiment A: ten days monitoring of acrylamide contents in fermented bread from one Czech bakery

As outlined in the Introduction, there are many factors that may influence acrylamide contents at producer's site. Not only the changes in raw materials composition as regards acrylamide precursors content, but also (even small) fluctuation of technological process parameters are related to acrylamide formation (FDE, 2011). To learn more about the variability of acrylamide content in typical Czech fermented soft breads, we organized, in cooperation with one of high capacity bakeries, a small

Conclusions

The current study concerned both with the monitoring of the acrylamide occurrence in several types of commercial breads available at the Czech market and prepared by experimental baking aimed at the assessment of various factors related to acrylamide formation. The main outcomes can be summarized as follows:

  • The contents of acrylamide found in traditional Czech soft breads available at the market (16 μg kg−1 mean/17 μg kg−1 median) were lower compared to values reported by EFSA (EFSA, 2012) for

Acknowledgement

This study was carried out with the support from the following projects financed by the Ministry of Education, Youth and Sports of the Czech Republic: (i) the NPV II. project 2B06168; (ii) project MEB 080882 and (iii) Specific University Research (MSMT No. 20/2013).

References (22)

  • L. Ahrne et al.

    Effect of crust temperature and water content on acrylamide formation during baking of white bread: steam and falling temperature baking

    LWT - Food Science and Technology

    (2007)
  • A. Claus et al.

    Impact of formulation and technological factors on the acrylamide content of wheat bread and bread rolls

    Journal of Cereal Science

    (2008)
  • T. Amrein et al.

    Occurrence of acrylamide in selected foods and mitigation options

    Food Additives and Contaminants

    (2007)
  • E. Brathen et al.

    Addition of glycine reduces the content of acrylamide in cereal and potato products

    Journal of Agricultural and Food Chemistry

    (2005)
  • EC. (2011). Commission recommendation on investigations into the levels of acrylamide in food Document C(2010) 9681...
  • EFSA

    European Food Safety Authority. Results on acrylamide levels in food from monitoring years 2007–2009 and exposure assessment, Scientific report of EFSA, Parma, Italy

    EFSA Journal

    (2011)
  • EFSA

    European Food Safety Authority. Update on acrylamide levels in food from monitoring years 2007 to 2010, Scientific report of EFSA, Parma, Italy

    EFSA Journal

    (2012)
  • European Commission Recommendation from the 2nd of June 2010 (on the monitoring of acrylamide levels in food;...
  • FDE

    FoodDrinkEurope acrylamide Toolbox

    (2011)
  • M. Fink et al.

    Effect of added asparagine and glycine on acrylamide content in yeast-leavened bread

    Cereal Chemistry

    (2006)
  • H. Fredriksson et al.

    Fermentation reduces free asparagine in dough and acrylamide content in bread

    Cereal Chemistry

    (2004)
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