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The Origin and Formation of 3-MCPD in Foods and Food Ingredients
Project Code: C03017
Central Science Laboratory
The principal objectives of this project were:
Determine the kinetics of 2- and 3-MCPD production and breakdown in model systems
Determine the factors affecting the formation of 3-MCPD during the roasting of cereal grains and also of other roasted foods such as coffee,
Determine the factors affecting the formation and stability of 2-and 3-MCPD in model and whole doughs during the baking process.
Determine the factors affecting the production of 3-MCPD in a number of meat products, salted fish and cheese products identified as containing detectable levels of 3-MCPD in the recent FSA funded surveillance exercise.
The following were the key findings:
- Cooked Meat Products and Roasted coffee - MCPD formation is not a major issue
- Baked Cereal Products - Precursors identified and options identified for controlling levels
- MCPD-esters - have been confirmed in a range of foods and both 2 and 3-MCPD can be released from these by some lipases and by toasting in bread
- Malts - An optimised temperature / time regime for reducing 2 and 3-MCPD levels whilst maintaining desirable colour formation
- Production of 2 and 3-MCPD in water + emulsifier + salt + lipid model systems suggested that in a low water (<15%) environment glycerol was the major precursor during high temperature processing while in higher water content models lecithin became a more significant precursor.
- Commercial emulsifiers, based on partial glycerides, acted as precursors with efficiencies similar to triglycerides / phospholipids (on a weight basis)
- 3-MCPD was unstable at neutral and alkali pH, unlike 2-MCPD, which remained as the predominant chloropropanol in neutral or alkali treated foods.
- The addition of reducing agents such as glutathione and cysteine at ~0.07 % (w/w) were effective at limiting both 2 and 3-MCPD production in water + emulsifier + salt + lipid model systems
- Adjustment of temperature/time profiles (lower temperature for longer time) was identified as a potential option for lowering 3-MCPD in dry roast malts. However, when this was investigated it was found to be unreliable in practice.
- Higher temperatures (which would increase degradation of 3-MCPD) are not commercially feasible because of the danger of fire.
- A feasible approach to control 2 and 3-MCPD concentrations in dry roast products is to limit the residence time at the highest temperatures as far as is consistent with achieving the desired colour specifications.
- Comparison of current 3-MCPD concentrations with those in similar products produced 5 years ago suggests that limited residence time at high temperature is being used successfully in commercial manufacture.
- Levels of 3-MCPD in commercial wet roast products are generally relatively low. Experimental results indicate that the temperatures already used in commercial production are likely to give the lowest levels of 3-MCPD.
- Any further manipulation of temperature/time profiles would need to take into consideration any consequential effects on acrylamide concentrations as well as effects on commercially important specifications for colour and flavour.
Baked cereal products
- Glycerol (from yeast) and added chloride are the major precursors of MCPD's in leavened dough products.
- Minor precursors in dough were monoglycerides, lysophospholipids, and phosphatidylglycerols present in wheat together with DATEM, present in flour improvers.
- Added glucose or short chain organic acids promoted the formation of 3-MCPD in an apparent 'catalytic' way
- The physical states of the matrix, i.e. glass, rubber, gel, did not affect the production of 3- MCPD in dough.
- Differences between the lipid composition of germ in wheat and barley may account for some of the observed differences in 3-MCPD production between these two cereals.
- It was shown that both 2 and 3-MPCD could be released from MCPD-esters, identified in bread crust and toasted bread, following treatment with a commercial lipase from Aspergillus oryzae.
- Oil extracted from savoury crackers was shown to contain high levels of esterified 3-MCPD (>100 times the amount of free 3-MCPD) which is a potential source of free 3-MCPD during cracker production / storage.
Meat dairy and smoked products
- Salami fat also contained significant amounts of esterified 3-MCPD although no evidence could be found to show that the action of lipases, present in the spices, bacterial culture, and endogenous to the meat were responsible for the increase in free 3-MCPD during storage.
- Obvious precursors of 3-MCPD production in processed cheese could not be identified. Migration of 3-MCPD from packaging material is a possibility for some cheeses and salami and the release of 3-MCPD from esters by endogenous lipase activity during storage cannot be ruled out.
- Detection of high levels of 3-MCPD in burgers, seen in the FSA survey, could not be repeated with new samples from the same suppliers or in-house burgers. The addition of HVP, or release of glycerol by lipase activity during storage of the uncooked burger could account for the levels observed in the FSA survey.
- Formation of 3-MCPD in smoked fish was shown to be directly proportional to both salt concentration in the flesh and smoking time.
- For salted anchovies 3-MCPD formation was predominantly seen after curing, once the fish had been filleted, suggesting that storage time may be important.
- Studies on roasted and green coffee aqueous extracts suggest that a number of both high and low molecular mass components in coffee are capable of destroying 3-MCPD in model cereal systems
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