Processing contaminants in bread from bread making ... - CiteSeerX

Processing contaminants in bread from bread making machines A continuing project under C03020

Colin Hamlet Sanal Jayaratne Carol Morrison September 2005 Issue 2: January 2006

C03020 - Contaminants in bread from bread machines

Executive summary The aim of this study was to determine whether bread produced from domestic bread machines contains significantly higher levels of process contaminants, i.e. 3-monochloropropane-1,2-diol (3-MCPD), acrylamide and ethyl carbamate, compared to retail products.

Outcome/key results obtained 1. Compared to the commercial products, levels of 3-MCPD were slightly higher while ethyl carbamate levels showed a four-fold increase in domestic white and wholemeal breads respectively. Acrylamide levels were significantly lower (three-fold) in domestic breads. 2. For a given recipe, baking performance and contaminant generation was very consistent both within and between bread machines. There was a slight trend towards higher 3-MCPD and acrylamide levels in wholemeal breads compared to white breads from each bread machine. 3. Baking performance and contaminant generation was recipe dependent: there was a trend towards higher levels of each contaminant with decreasing loaf volume; bread mixes containing added onion or tomato produced significantly more acrylamide. 4. Dough from a bread machine produced higher contaminant levels when baked in a fan oven (hotter) and the level of all contaminants increased linearly with increasing bake time. 5. With the exception of 3-MCPD, all contaminants showed losses (from spiked doughs) during baking in a bread machine. These losses were higher in oven baked breads and more so for acrylamide and ethyl carbamate. 6. Crust colour (L value) is a good indicator of contaminant levels in all white breads.

What it means and why it’s important This study has shown that higher levels of ethyl carbamate, and lower levels of acrylamide, can be formed in most bread from domestic bread machines than in 2

C03020 - Contaminants in bread from bread machines commercial products. However, the overall level of all process contaminants measured in breads remains very low.

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C03020 - Contaminants in bread from bread machines

Table of contents Executive summary ................................................................................................. 2 Outcome/key results obtained ............................................................................. 2 What it means and why it’s important................................................................. 2 1.

Introduction ..................................................................................................... 7 Background ......................................................................................................... 7 Rationale and objectives...................................................................................... 8 Approach ............................................................................................................. 9

2.

Materials and methods................................................................................... 10 2.1.

Chemicals and reagents ......................................................................... 10

2.2.

Domestic bread machines...................................................................... 10

2.3.

Bread mixes and retail breads ............................................................... 10

2.4.

Preparation of bread samples ................................................................ 11

2.5.

Analytical methods................................................................................ 13

Results and discussion........................................................................................... 16 2.6.

Variability due to bread machine .......................................................... 16

2.7.

Variability due to bread mix.................................................................. 20

2.8.

Oven baked breads from dough prepared in a bread machine .............. 22

2.9.

Contaminant losses during baking ........................................................ 25

2.10.

Comparison with commercial breads ................................................ 25

3.

Conclusions ................................................................................................... 28

4.

References ..................................................................................................... 29

Appendix A: Analytical quality control data ........................................................ 32 Appendix B: Proving and baking temperatures for each bread machine .............. 33 Appendix C: Loaf volume and height variability.................................................. 37 Appendix D: Summary of contaminant levels by bread machine......................... 38 Appendix E: Crust colour v contaminant levels for white breads......................... 40 Appendix F: Raw data summary ........................................................................... 42

Figures Figure 1. Time and temperature profiles for commercial (CBP) bread production and bread produced from a domestic bread machine............................................. 8 4

C03020 - Contaminants in bread from bread machines Figure 2. Mean baking temperatures and bake times for all bread machines. Vertical bars show maximum temperature recorded. ........................................... 16 Figure 3. Typical temperature profiles from individual measurements within a bread machine ....................................................................................................... 17 Figure 4. Contaminant variability by bread machine in approximate order of decreasing levels (dry weight basis): vertical bars show range of values from replicate bakes....................................................................................................... 18 Figure 5. Correlation between crust colour (L) and acrylamide (dry weight basis) in white breads ...................................................................................................... 19 Figure 6. Loaf volume/height variability for breads prepared from different bread mixes using a single bread machine. With the exception of M5 (white 375 g) and M8 (Ciabatta 250 g) all breads were prepared on a 500 g mix basis; the estimated repeatability was 3.5% .......................................................................................... 20 Figure 7. Contaminant variability (dry weight basis) by bread mix: vertical bars show range of values from replicate bakes ........................................................... 21 Figure 8. Typical correlation between crust colour and 3-MCPD levels (dry weight basis) generated from different white bread mixes.................................... 22 Figure 9. Effect of oven baking on contaminants (dry weight basis) from dough produced in a bread machine. Vertical bars show the range of values from replicate bakes....................................................................................................... 23 Figure 10. Effects of oven bake time on contaminant generation (dry weight basis) in white bread prepared from bread mix M1 (single bakes)................................. 24 Figure 11. Correlation between top crust colour and contaminant levels (dry weight basis) generated in all oven baked breads (white and speciality)............. 24 Figure 12. Losses of each contaminant during baking (dry weight basis, corrected for generation)....................................................................................................... 25 Figure 13. Difference between contaminant levels in bread from domestic bread machines and commercial products: means (dry weight basis) and ranges (vertical bars) for white and wholemeal products only ........................................ 26

Tables Table 1. Domestic bread machines and bake programs used in this study........... 10 Table 2. Details of bread mixes and retail breads (whole loaves) used in this study ............................................................................................................................... 11 5

C03020 - Contaminants in bread from bread machines Table 3. Summary of contaminant levels (dry weight) in commercial and domestic breadsa................................................................................................................... 27

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C03020 - Contaminants in bread from bread machines

1.

Introduction

Background It is known that low levels of toxic contaminants can be generated during the processing of cereal products, particularly at high temperature e.g. during baking. Of these, acrylamide, 3-MCPD and ethyl carbamate have received considerable attention because of toxicological concerns for human health1-5. The precursors of these contaminants can be present naturally in the cereal grains6-8 and other raw materials used, e.g. fruit and vegetables9; they may also be added directly and/or formed during processing, e.g. ethanol10, glycerol6 and sugars11 from the proving of leavened bread dough. Researchers have discovered that acrylamide is linked to the Maillard reaction12,13, a series of important and complex chemical reactions that provide the desirable colours, tastes, and odours in cooked foods. The Maillard reaction describes the cascade of chemical reactions that occur when amino (e.g. amino acids) and carbonyl compounds (e.g. reducing sugars) react together in heated foods. Studies involving amino acids and simple sugars12-15 have established that the amino acid asparagine is a key precursor of acrylamide and it is the reaction of this compound with carbonyl sources, e.g. simple reducing sugars, that is believed to be the key acrylamide forming reaction in cooked foods. Although acrylamide levels found in commercial bread products are typically low16 (