3-MCPD esters in edible oils: analytical aspects

Transcription

1 French Institute for Fats and Oïl 3-MCPD esters in edible oils: analytical aspects Florent JOFFRE, Hugues GRIFFON, Bénédicte SOULET and Florence LACOSTE

2 3-MCPD esters in oils: context Analysis of 3-MCPD: focus on the DGF method Recent development in 3-MCPD diesters analysis

3 3-MCPD Free 3-MCPD was known for decades especially in hydrolyzed vegetable protein (HVP) and in soy sauces EU legislation: 0.02 mg/kg for HVP and soy sauces More recently, free 3-MCPD was detected in foods like bread, toast, noodles and smoked products. Bread and noodles could be important contributors to the total daily intake especially for their strong consumption rather than for their content in 3-MCPD. 3

4 3-MCPD esters In 2004, 3-MCPD esters were reported in thermal processed foodstuffs such as french fries, donuts, salty crackers, roasted coffee In most of these foodstuffs, bound 3-MCPD were found in very higher quantity than free 3-MCPD. In 2006, 3-MCPD esters were reported in edible oils, especially in refined oils but not in crude oils. The critical step of refining may be the deodorization. In this step mono- and di-glycerides, chloride ion and temperature led to the formation of 3-MCPD monoesters and 3-MCPD diesters. Recent data, in refined oils, showed that 3-MCPD esters were mainly diesters (90%).

5 Toxicity of free and bound 3-MCPD Free 3-MCPD is nongenotoxic but thresholded carcinogenic and has a testicular and renal toxicity in rats. In 2008 statement from the EFSA CONTAM panel concluded that: there was no toxicological and bioavailability data on 3-MCPD esters. the German BfR based its recent risk assessment on toxicological data on 3-MCPD, under the assumption that 100% of 3-MCPD was released from its esters. But Seefelder et al. (2007) on intestinal model lipase studies showed that the release of 3-MCPD from 3-MCPD monoesters was rapid but slow from 3-MCPD diesters. So more kinetic release studies with 3-MCPD esters are necessary to calculate a Tolerable Daily Intake.

6 Analysis of total 3-MCPD DGF Standard method based on the Weissharr s work Discard two times the hexane phase which contains the fatty acid esters Oil (bound 3-MCPD) + 3-MCPD-d5 Free 3-MCPD in the aqueous phase PBA (80 C-20min) Ester cleavage with NaOCH 3 (5-10 min room temp) Add 3 ml of hexane and 3 ml of NaCl solution containing acetic acid derivatization GC-MS 5% phenyl silicon 30m length, 0.25mm i.d. and 0.25µm film thickness m/z 197 (3MCPD) and 201 (3-MCPD-d 5 )

7 Quantification of 3-MCPD DGF Standard method based on the Weissharr s work Oil (bound 3-MCPD) + 3-MCPD-d5 Calibration curve 3-MCPD-d5 in solvent remove the solvent Recovery of Free 3-MCPD in the aqueous phase PBA (80 C-20min) derivatization Add increasing content of free 3-MCPD in NaCl-solution PBA (80 C-20min) derivatization GC-MS The final results were expressed as total 3-MCPD (free and bound) in mg/kg of oil GC-MS

8 Critical step of the DGF method Oil analysis Oil (bound 3-MCPD) + 3-MCPD-d5 Recovery of Free 3-MCPD in the aqueous phase Esters cleavage 3 ml of NaCl solution Calibration curve 3-MCPD-d5 in solvent Remove the solvent Add increasing concentration of free 3-MCPD in NaCl-solution Perform the calibration curve in oil Derivatization with PBA (80 C-20min) Derivatization with PBA (80 C-20min) GC-MS Replace the NaCl solution by Water NaBr Ammonium sulfate KCl GC-MS

9 % Critical step of DGF method 120,0 100,0 Maximal response of standard Titre du graphique 80,0 60,0 40,0 Effect of methylation with NaHCO3 Loss of 65% of the signal KCl is less efficient than NaCl 20,0 0,0 Substitution of NaCl Loss of 95% of the signal D0+D5 D0+D5+MeONa HOV+NaCl HOV+eau pure HOV+NaBr HOV+sulfate HOV+KCl 3,4M MCPD-d5 MCPD

10 A (3MCPD)/A(3MCPD-d5) Critical step of DGF method Calibration curve 1,0 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0,1 0,0 calibration curves realized in HOV in NaCl-solution HOV+d5+d0 methylation and derivatization y = 0,7272x R2 = 0,9985 d5+d0 only derivatization y = 0,5165x R 2 = 0,9955 Effect of methylation with NaHCO3 0 0,2 0,4 0,6 0,8 1 1,2 1,4 m (3MCPD) / m (3-MCPD d5) Realization of the calibration curve without the step of derivatization by NaHCO3 overestimated the quantity of 3-MCPD. For example, for a ratio area of 0.3, the DGF method overestimated the quantity by 30%

11 Occurrence of 3-MCPD in edible oils Impact of the method on the results Coconut oil Hydrogenated soyabean oil Hydrogenated Palm oil Refined Shea Crude Shea Refined palm oil Commercial mix of 4 refined oil Walnut oil Refined grapeseed oil Refined peanut oil Refined rapeseed oil Refined sunflower oil Cocoa butter Anhydrous milk fat Crude oil Olive Oil < 0,15 mg/kg Calibration curve in NaCl-solution Calibration curve in oil 25% between the two methods Crude oil: sunflower, rapeseed, soyabean

12 Correlation between DAG and 3-MCPD content Hydrogenated soyabean oil Hydrogenated Palm oil Refined Shea Crude Shea Refined palm oil Commercial mix of 4 refined oil Walnut oil DAG 3MCPD Refined grapeseed oil Refined peanut oil Refined rapeseed oil Refined sunflower oil No correlation between DAG and 3-MCPD was found. Lack of information concerning chloride ion content may explain these results

13 Critical step of DGF method Conclusion Sodium methoxide cleavage can decompose a high quantity of 3MCPD esters (65% in our trials). So it is essential to use a deuterated 3-MCPD and to add it before the methoxide cleavage. But if the calibration curves were realized in NaClsolution, we overestimated the quantity of 3-MCPD. It may be difficult to substitute the NaCl-solution and to keep on a good sensibility.

14 Synthesis of 3-MCPD diesters 98.3% C16 0.7% C14 0.7% C18 0.3% C15+C18:1 1g of DAG SOCl2 98,9% C8 1.1% C10+C12 Diesters chloride GCECD Purification on silica column High purity fraction of 99,2% 99,4% diesters chloride GCFID IR

15 GC-ECD of 3-MCPD diesters DB5, 30m 3-MCPD diester before reaction after reaction

16 InfraRed spectra of 3-MCPD diesters Loss of -OH Blue: before reaction Black: after purification Gain of -Cl Acknowledgement to the Lipochemical department of ITERG

17 GCFID of purified 3-MCPD diesters dic16-chloride Others MCPD-diesters 99,2% purity calculated by GCFID

18 Gas chromatogram of palm oil and mixture of our two diesters chloride TAG DAG dic8-cl FFA MAG dic16-cl Palm oil Diesters chloride

19 Recovery of dic16-chloride in HOVE calibration curve realized in HOVE spiked with dic16-chloride HOVE NaCl-solution 0.2 mg/kg 80% 102% 1 mg/kg 72% 92% 10 mg/kg 71% 90% 20 mg/kg 72% 91% Better recovery with DGF-method but results overestimated Constant recovery between 0.2 to 20 mg of 3MCPD-diesters/kg oil but lost of 30% Hypothesis: interference during the methylation step? Different yield of methylation between TAG, diesters-chloride and 3-MCPDd5? Purity of diesters synthesized?

20 Analysis of diesters chloride Background 3-MCPD diesters have a polarity close to TAG due to the substitution of OH by Cl. But 3-MCPD diesters have steric hindrance different from TAG due to the loss of a fatty acid but have steric hindrance close to DAG. Analytical challenge Elimination of TAG using size exclusion methods. Elimination of DAG using conventional chromatography methods, silica gel for example. Analysis of 3-MCPD diesters by GCMS or GCFID using dic8-chloride as internal standard.

21 Size - exclusion chromatography 4 columns (30cm, 100 Ǻ, 5µm) THF 50 C 1 ml/min Run: 30 min TAG dic16-chloride reference oil dic16 chloride mix TAG, DAG, MAG palm oil + dic16 chloride DAG MAG

22 Size-exclusion chromatography TAG dic16-chloride MAG DAG reference oil dic16 chloride mix TAG, DAG, MAG palm oil + dic16 chloride Natural DAG + spiked dic16-chloride

23 Conclusion on extraction of 3-MCPD diesters by HPSEC method Increase the chromatographic resolution between TAG and DAG by using 6 columns TAG residue may be a problem for GCMS analysis but not for GCFID analysis Increase the quantity injected by using preparative HPSEC (60cm, i.d. 20mm) or Biobeads methods Optimize the quantification using dic8-chloride or another diesters chloride (dic17 for example)

24 CONCLUSION Development of a method to quantify 3-MCPD or diesters of 3-MCPD is an analytical challenge. To our opinion it will be of interest to work together to develop a strong method instead of normalize a method which has analytical critical point. Firstly, DGF method as method of global measure of 3-MCPD have to be optimized. Especially the realization of calibration curve in oil and not in NaCl-solution and the expression of results in equivalent bound 3-MCPD have to be taken into account. Secondly, works on analysis of di-esters and mono-esters chloride have to be performed.

25 Thanks for your attention