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Mitigating acrylamide in chicorea using fluorescence
1. Inès BIRLOUEZ-ARAGON Optimization of a roasting process by means of rapid monitoring of quality indicators and kinetic modelling Food Factory 2010 - Sweden
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3. Situation 8 years after discovery of acrylamide in food products Food Factory 2010 - Sweden Potato crisps, instant coffee, and substitute coffee products, such as those based on barley or chicory, all showed significantly higher levels of acrylamide in 2008 compared to 2007. EFSA survey of acrylamide in food products indicates that voluntary efforts to reduce levels of the carcinogen are working but only in a limited number of food groups: Roasted Chicory : p to 2000 µg/kg the product with highest acrylamide levels Chicory root Roasted Chicory
5. The drying process initiates reactions. Food Factory 2010 - Sweden F D F F F D D D F D F F F D D D Sugar degradation : formation of carbonyl substrates ? Asparagine formation =
6. The roasting process Food Factory 2010 - Sweden 3 burners 2 burners 1 burner Target colour Dry chicory was roasted by Chicorée du Nord according to a standard process .
8. Bell shape of acrylamide formation: importance of the cooling process Food Factory 2010 - Sweden ( µg/kg ) Acrylamide Asparagine Cooling process Complete destruction of asparagine
9. Process Modelling and optimisation regarding acrylamide 1- Development of a fluorescence prediction model to monitor acrylamide under various roasting conditions Food Factory 2010 - Sweden Prediction model : acrylamide (µg/kg) 8% error Predicted values Measured values (LC-MS) FLUORALYS The food quality parameters in one FLASH
10. 9 different roasting processes and 3 reproductions Food Factory 2010 - Sweden Acrylamide between 1000 and 2200 µg/kg depending on the roasting conditions Initial T°; heat energy; time on different heat energies error of reproducibility : 25% including raw material
11. Reaction modelling: prediction of acrylamide using apparent reaction kinetics Asparagine Acrylamide degradation products k1 1st order Food Factory 2010 - Sweden
12. Process modelling: prediction of browning using apparent reaction kinetics substrates browning k1 0 order Food Factory 2010 - Sweden
13. Simulation of the process Initial T° : 60°C Two steps T° increase : change at 70min Food Factory 2010 - Sweden Acrylamide formation Browning T° increase in the second heating step T° increase in the second heating step T° increase in the first heating step T° increase in the first heating step
14. Food Factory 2010 - Sweden Cooling once the target colour has been reached T° always lower than 160°C Optimization of the process Optimal zone
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16. Rapid Methods 2010 - The Netherlands Chicorée du Nord for the roasting experiments and samples; CSIC (Fran Morales) for conventional analysis of acrylamide and AgroParisTech (Bertrand Heyd) for process simulation and optimisation. Thanks to …
Editor's Notes
The Food industry must face new challenges regarding the safety of the processed food they produce. As I’m sure you know, certain processing contaminants were discovered recently to form during severe heat treatment. A couple of the most important are acrylamide and furan, which are mutagenic and carcinogenic. Although no regulations have been edited up to now, recommendations have been addressed for regular control of contaminant levels in targeted food products. The food industry must anticipate possible future regulations by performing analysis of their products. But conventional analytical methods are very expensive and require several days’ delay before they give results. There is an urgent need for rapid techniques making it possible for industrialists to carry out their own analyses simply and at low cost making it possible to monitor those contaminants throughout the processing as a basis for optimization.
EFSA recently reported the remaining concern regarding the increasing levels of acrylamide in roasted products, such as coffee and chicory, while the trend of significantly lower levels was confirmed in other food products, such as biscuits, bread, french fries … There is therefore an urgent and special need to control the chemical reactions leading to acrylamide during the roasting process such as chicory in order to mitigate acrylamide while maintaining the sensorial attributes, such as brown colour in the case of chicory.
Let’s describe roughly the reaction system leading to browning and acrylamide in roasted chicory: There are two main sources of reactive reducing sugars : sucrose and inuline. During the roasting process, these unreactive molecules hydrolyze and produce the substrates of acrylamide, glucose and fructose. But the same molecules are also responsible for the final browning of chicory by the intermediary product, hydroxymethylfurfural, which is formed at high temperatures and low moisture conditions. On the other hand, a mixture of free amino acids, including asparagine the precursor of acrylamide, will react with the reducing sugars in the Maillard reaction to form a complex mixture of Maillard products, including the brown melanoïdins, various odorant molecules and the undesirable acrylamide.
The roasting process is applied to dried chicory roots cut in slices. Not only the sugar and asparagine content of the roots vary depending on the geographical origin and variety, but the drying process also impacts the concentration in such compounds before the roasting process. There is a trend to sucrose and fructose degradation during drying, probably leading to reactive intermediates, substrates of acrylamide. There is also a trend to formation of asparagine, with sometimes a considerable increase in the concentration.
Once the roasting process begins, glucose and fructose are formed, mainly through sucrose hydrolysis but also due to inulin hydrolysis. At the same time, HMF is formed once a sufficiently high temperature( around 140°C) and low water content are reached . The HMF and other Maillard reaction products further polymerize to produce the brown melanoïdins which confer the typical brown colour of roasted food. The roasting process is stopped once the target browning is reached (robe de moine).
In parallel, asparagine slowly reacts with reducing sugars during the first minutes of the roasting process, before being drastically transformed into acrylamide when reducing sugars become available and the temperature reaches 110°C. After a first acute formation, a maximum is reached before a rapid drop occurs, due to acrylamide volatilization and /or polymerization. In addition, we observe that before the end of the process almost all the asparagine has reacted, explaining that no more acrylamide may be formed, thus accelerating the disappearance curve.
From these results we understand that a description of the reactions possible by the monitoring of key intermediates and final products is of great advantage to optimize the process. But such analysis are very long and expensive. An optical sensor, Fluoralys, was developed that recovers the natural fluorescence of the product and analyses automatically and simulatenously the content of various pertinent indicators of the reactions in the product throughout the roasting process. Such analysis are possible because a previous prediction model is built by calibration of the fluorescence signal with the conventional analysis of the indicator. In the figure on the right, you can see the highly satisfactory calibration model obtained for acrylamide prediction in the chicory samples. Glucose, fructose, HMF, browning, and water content were also analyzed in one flash in the chicoree samples produced by different time –temperature diagrammes, producing a wide data base for reaction modelling.
Nine different processes and three reproduction of one of them were carried out by changing some parameters of the process, namely the initial temperature, the heat energy intensity resulting from the number of « bruleur » and the time at different energy level. Consequently different final products were obtained, all with the same target browning but different acrylamide levels, from 1000 to 2200 µg/kg.
Nine different processes and three reproduction of one of them were carried out by changing some parameters of the process, namely the initial temperature, the heat energy intensity resulting from the number of « bruleur » and the time at different energy level. Consequently different final products were obtained, all with the same target browning but different acrylamide levels, from 1000 to 2200 µg/kg.
From the reaction modelling, a simulation of the impact of time temperature on acrylamide formation and browning was possible. We proposed to simulate a roasting process in two steps defined by the temperature increase rate. Initial T° was set at 60°C and the time when the second step begins was set at 170°C. The response cartography is presented here for the two parameters of interest.
From these data the optimization map can be designed which evidences the optimal zone corresponding to samples expected to have the target colour with zero acrylamide. This zone corresponds to a first rapid increase in temperature (0,9-1°C/min), followed by a second step with a much lower increase rate (0,2-0,4°C/min). This map indicates that, contrary to some assumptions, it is possible to mitigate acrylamide in chicory and very probably in any roasted material.
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