C03020: An investigation into the formation of processing contaminants in bread from bread making machines.

Study Duration: September 2005

Contractor: RHM Technology

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-monochloropropane-1, 2-diol (3-MCPD) and ethyl carbamate have received considerable attention because of toxicological concerns for human health.

Bread produced from bread machines can vary significantly from a quality perspective, i.e. in terms of loaf height, volume, colour, texture and taste/flavour, compared to commercial products. Consequently, the parameters controlling this variability, i.e. proof time, heat transfer processes and recipes, could also have a significant impact on the generation of process contaminants such as 3-MCPD, acrylamide and ethyl carbamate.

The project will aim to determine whether bread produced from domestic bread machines contains significantly higher levels of process contaminants, i.e. 3-MCPD, acrylamide and ethyl carbamate, compared to commercial products.

Bread machines representing different manufacturers, price ranges, and specifications together with a range of bread mixes, will be investigated.

The study will investigate:

• Variability between bread machines: The effects on contaminant levels (acrylamide, ethyl carbamate and 3-MPCD) are to be determined both within and between bread machines, under controlled conditions (fixed recipes).
• Recipe contributions: The effects on contaminant levels from different recipes will be assessed using a single bread machine.
• The effect of oven baking: Dough prepared in a domestic bread machine will be baked in a fan oven and contaminant levels compared.
• Contaminant losses during baking: (bread machine and fan oven).
• Comparison with commercial practice

Where possible, the baking performance characteristics of loaf height, volume, temperature and crust colour will also be measured.

Compared to the commercial products, levels of 3-monochloropropane-1, 2-diol (3-MCPD) were found to be slightly higher in bread made in bread makers. While the levels of ethyl carbamate were four-fold higher in wholemeal breads made using a domestic bread machine. Acrylamide levels were significantly lower (three fold) in domestically produced breads.

For a given recipe, levels of each contaminant showed only minor variation, both within and between each bread machine. These observations were consistent with similar baking performance (height, volume, temperature, time) obtained from each bread machine.

There was a slight trend towards higher 3-MCPD and acrylamide levels in wholemeal breads, compared to white breads, from each bread machine.

The effect of different bread mix recipes was most significant for acrylamide generation: highest levels were found in products containing added tomato or onion, which may be a source of additional asparagine.

Dough from a bread machine produced higher contaminant levels when baked in a fan oven than a conventional oven. The effect was most significant for 3-MCPD and acrylamide, and the level of all contaminants increased linearly with increasing cooking time in a fan oven.

With the exception of 3-MCPD, all contaminants showed losses (from spiked doughs) during baking in a bread machine. These were higher in oven baked breads and more so for acrylamide and ethyl carbamate.

Crust colour (L value) is a good indicator of contaminant levels in some plain white breads.

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 commercial products. However, the overall level of all process contaminants measured in breads remains very low.

The final report is available from the Agency's Information Centre.

To obtain a copy, please contact the Enquiry Desk, Information Services, Food Standards Agency (tel: 020 7276 8181/8182 or email: infocentre@foodstandards.gsi.gov.uk)