Indirect methods for the Analysis of MCPD and Glycidyl Esters: A Critical Overview

Transcription

1 Indirect methods for the Analysis of MCPD and Glycidyl Esters: A Critical Overview Karel Hrncirik Unilever, The Netherlands ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS 9-10 November 2011 Brussels, Belgium ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS (9-10 November 2011) 1

2 Background: 3-MCPD/glycidyl 3 ester analytics food industry issue: very dynamic field analytics important for the progress (mechanism, mitigation, toxicity, ) new (modified) methods presented (+) analytical methodology diversified (-) quality of results: sometimes doubtful which methods are correct? ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS (9-10 November 2011) 2

3 Analytical methods basic approaches Direct methods individual species determined directly without any chemical transformation Indirect methods Indirect methods individual compounds converted into a single analyte which is quantified ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS (9-10 November 2011) 3

4 MCPD & glycidyl - structural diversity 3-MCPD 2-MCPD Glycidyl Mono di mono di O COR OH O COR 1 O COR O COR 1 Cl O COR 2 Cl Cl OH Cl OH O COR 2 COR O O Cl COR Exercise: - fatty acids, n=7 (C12:0, C14:0, C16:0, C18:0, C18:1, C18:2, C18:3) - number of individual? ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS (9-10 November 2011) 4

5 Indirect methods 3-MCPD 2-MCPD Glycidyl Mono di mono di O COR OH O COR 1 O COR O COR 1 Cl O COR 2 Cl Cl OH Cl OH O COR 2 COR O O COR Cl OH OH OH OH Cl Cl OH O individual converted to a single substance: 3-MCPD, 2-MCPD or glycidol (these are quantified and expressed as a sum bound form ) ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS (9-10 November 2011) 5

6 Indirect methods Advantages avoids synthesis of a series of standards good sensitivity (LOD <0.1 ppm) easy to perform (instrumentation) Points of concern Points of concern just a sum (total content) sample preparation involves chemical transformations (uncertainty) ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS (9-10 November 2011) 6

7 3-MCPD analysis (indirect methods) Basic analytical protocol: Oil sample + I.S. Transesterification (methanolysis) The most common variations: Internal standard: freeform: 3-MCPD-d5 esterified form: e.g. dipalmitoyl-3-mcpd-d5 Transesterification: acid: H 2 SO 4 /MeOH (16 h, 40 C) alkaline: NaO 3 /MeOH (1-10 min, RT) fast alkaline: NaOH/MeOH (16 h, -20 C) slow Neutralisation & salting out Derivatisation Salting out: NaCl (non-specific! - reaction with glycidol additional 3-MCPD) SO 4 2- NaBr Derivatisating agents: phenylboronic acid (PBA) heptafluorobutyrylimidazole (HFBI) GC/MS analysis ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS (9-10 November 2011) 7

8 Indirect methods Indirect methods Direct methods Acid transesterification Alkaline transesterification ( fast ) Alkaline transesterification ( slow ) Non-specific (NaCl) Specific (Cl-free) ICT BfR 008 Nestlé Unilever DGF CIII-18 (09) DGF C-VI 18 (10) A BfR 009 DGF C-VI 18(10) B SGS ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS (9-10 November 2011) 8

9 Indirect methods results quality Variability of the results is possibly given by: different performance of individual indirect methods (and their modifications) different specificity of individual methods ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS (9-10 November 2011) 9

10 Indirect methods - evaluation Acid Alkaline fast Alkaline slow Transesterification time 16 h 1-10 min (variable) 16 h Recovery [%] 1,2 ~ Chemistry (interference) no significant side reactions 3 complex 2 side reactions suppressed 4 Robustness ok +/-? References: 1. Kuhlmann, AOCS Congress, Cincinnati (2011) 2. Hrncirik et al., Eur. J. Lipid Sci. Technol. 113, (2011) 3. Ermacora & Hrncirik, J. Am. Oil. Chem. Soc. (2011) 4. Kuhlmann, Eur. J. Lipid Sci. Technol. 113, (2011) transesterification is critical optimizing its conditions is essential! ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS (9-10 November 2011) 10

11 Indirect methods results quality Variability of the results is possibly given by: different performance of individual indirect methods (and their modifications) certain modifications to be avoided can be improved by precise execution (strict following the protocol) specificity of individual methods what do we measure? ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS (9-10 November 2011) 11

12 Indirect methods available Methods 2-MCPD 3-MCPD Glycidyl Acidic Alkaline fast should be possible Alkaline fast (non-specific)? Alkaline slow Direct separation of 2- and 3-MCPD? ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS (9-10 November 2011) 12

13 Indirect methods results quality Variability of the results is possibly given by: variable performance of individual indirect methods (and their modifications) certain modifications to be avoided can be improved by precise execution specificity of individual methods what do we measure? results of several methods not comparable (required communication: results + method used) but does everyone know? ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS (9-10 November 2011) 13

14 JRC: Proficiency test on the determination of 3-MCPD 3 in edible oil ( ) 2010) Refined palm oil sample (assigned value 8.8 mg/kg) 34 data sets in total, of which Range (mg/kg) Compliance ( z 2, i.e. range mg/kg) 5 datasets obtained by acid methods mg/kg 5/5 27 datasets obtained by alkaline methods 15 specific methods 9 unspecific methods ( Weisshaar ) 3 methods with details unknown mg/kg 11/15 0/9 0/3 56 % poor performance of alkaline methods partly caused by usage of unspecific methods ( interference with glycidyl ) 9 labs were not aware of the scope of the method they used! ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS (9-10 November 2011) 14

15 FAPAS Proficiency Test: 3-MCPD 3 in refined palm oil (2011) Refined palm oil sample (assigned value 4.7 mg/kg) Range (mg/kg) Compliance ( z 2) 26 datasets in total, of which 16 obtained by specific methods (acid/alkaline) 7 obtained by unspecific methods ( Weisshaar ) 3 failed from unknown reasons mg/kg mg/kg 16/16 0/7 0/3 16/26 (62 %) 2 years later the same story ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS (9-10 November 2011) 15

16 Choice of the method further factors to consider Method 2-MCPD 3-MCPD Glycidyl Acidic Reliable, robust, suitable for routine work Alkaline fast should be Quick, reproducibility? ( critical points), for routine work possible Alkaline fast (non-specific) Quick, but limited value (due to low specificity: MCPD-E & GE), rough GE estimation (high uncertainty), for rapid (semi-quantitative) screening Alkaline slow Simultaneous determination of MCPD-E & GE, performance to be tested Direct Comprehensive separation of info, 2- and but 3-MCPD several derivatives? challenges (to be discussed in the presentation of dr. Wenzel) ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS (9-10 November 2011) 16

17 Concluding remarks Current status enormous progress in analytics, better understanding (+) nevertheless, a lot of methods available, persisting confusion (-) harmonization of current analytical methodology for MCPD/glycidyl desirable; results should be independent of the method used (the same language) Way forward review the methodology and identify methods that are fit for purpose ; more comparative studies needed selected methods to be ring-tested (e.g. AOCS initiative), validated, and adopted as official methods ILSI EUROPE WORKSHOP ON MCPD AND GLYCIDYL ESTERS IN FOOD PRODUCTS (9-10 November 2011) 17