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Formation of Acrylamide in Food

Formation of Acrylamide in Food. Lauren Jackson, Ph.D. U.S. Food and Drug Administration Center for Food Safety and Applied Nutrition National Center for Food Safety & Technology Summit-Argo, IL. Food Advisory Committee Contaminants and Natural Toxicants Subcommittee ACRYLAMIDE

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Formation of Acrylamide in Food

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  1. Formation of Acrylamide in Food Lauren Jackson, Ph.D. U.S. Food and Drug Administration Center for Food Safety and Applied Nutrition National Center for Food Safety & Technology Summit-Argo, IL Food Advisory Committee Contaminants and Natural Toxicants Subcommittee ACRYLAMIDE December 4-5, 2002

  2. OBJECTIVES • Summarize what is known about mechanisms, precursors and factors that affect acrylamide formation • Identify the research needs • Discuss the FDA Action Plan for Acrylamide- Formation • Understand the conditions that lead to the formation of acrylamide in food • Develop methods to prevent or reduce formation of acrylamide

  3. What is Known About Acrylamide Formation? • How is acrylamide formed in food? • Precursors • Pathways/mechanisms • What factors affect acrylamide formation? • Food composition • Processing

  4. Precursors of Acrylamide/Pathways of Formation • Acrolein • Acrylic acid • Amino acids alone • Amino acids + reducing sugars via Maillard browning/Strecker degradation

  5. H O H Acrolein c c c H H (O) H O H c c c Acrylic Acid OH H (+NH3) H O H Acrylamide c c c NH2 H Acrolein • Acrolein (2-Propenal) • Structurally similar to acrylamide • Formed in oil during frying • Also formed from thermal degradation of starches, sugars, amino acids and proteins • Disproven as the major acrylamide precursor**

  6. H O H c c c Acrylic Acid OH H (+NH3) H O H Acrylamide c c c NH2 H Acrylic Acid • Acrylic Acid • Structurally similar to acrylamide • Formed from thermal deamination of alpha- and beta-alanine • Formed from assorted di-acids (malic, tartaric) and amino acids (cysteine, serine) • Not believed to be the major acrylamide precursor**

  7. NH2 O OH H2N H2N OH O NH2 O O Asparagine Glutamine R. H O H c c c NH2 H Acrylamide Amino Acids Alone • Alanine • Asparagine • Glutamine • Methionine • Amino acids alone not believed to be a major pathway in potatoes and grains • Relevance to acrylamide formation in other foods (coffee?) needs to be verified Stadler et al. Nature Vol 419 3 Oct. 2002, p. 449

  8. Amino Acids + Reducing Sugars (Maillard Reaction and Strecker Degradation) • What are the Maillard and Strecker reactions? • Reaction of amino acids with reducing sugars (glucose, fructose, ribose etc.) or other source of carbonyls • Responsible for color and flavor formation in heated foods • Reasons for suspecting mechanism • Potatoes have a relatively high levels of free amino acids • Potatoes and grain products are rich in carbohydrates (possible sources of reducing sugars and carbonyls) • Acrylamide levels in some foods tend to increase with level of browning

  9. Which Amino Acids Form Acrylamide?Aqueous Model System Studies Conditions: 0.1 mmole amino acid: 0.1 mmole glucose in 100 microliters of 0.5 M phosphate buffer (pH 5.5); 185°C, 20 min. From: Mottram et al. (2002)

  10. Which Amino Acids Form Acrylamide?Potato Chip Model System Studies • Acrylamide Formation • Potato starch <50 ppb • Potato starch + glucose <50 ppb • Potato starch + asparagine 117 ppb • Potato starch + glucose + asparagine 9270 ppb • Other Amino Acids • Alanine <50 ppb Arginine <50 ppb • Aspartic Acid <50 ppb Cysteine <50 ppb • Lysine <50 ppb Methionine <50 ppb • Threonine <50 ppb Valine <50 ppb • Glutamine 156 ppbAsparagine 9270 ppb From: Sanders et al. (2002)

  11. 15 15 NH2 NH2 #1) C C O O CH2 CH2 NH2 CH COOH NH2 NH2 #2) C O C O CH2 CH2 15 NH2 CH COOH 15 NH2 15 NH2 #3) 13 C O 13 C O 13 CH2 13 CH2 13 13 15 NH2 CH COOH 13 Further Proof of Asparagine as Precursor of Acrylamide:Origin of Nitrogen and Carbons of Acrylamide 15N-acrylamide m/z 73 CH2 Unlabeled Acrylamide m/z 72 CH2 15N13C13C13C-acrylamide m/z 76 CH2 From: R.A. Sanders et al. (2002)

  12. Mechanisms of Formation:A. Maillard Reaction/Strecker Degradation • Formation of acrylamide after Strecker degradation of asparagine (and methionine) in the presence of dicarbonyls (Maillard browning products) • Heating asparagine with butanedione, instead of glucose, resulted in acrylamide formation From: Mottram et al. (2002)

  13. Mechanisms of Formation:B. Formation from N-Glycosides N-(D-glucos-1-yl)-L-asparagine N-(D-fructos-2-yl)-L-asparagine N-(D-glucos-1-yl)-L-glutamine N-(D-glucos-1-yl)-L-methionine From: Stadler et al. (2002)

  14. Speculated Pathway Bvia Formation of N-Glycosides Acrylamide formed (micromole per mole N-glycoside) Conditions: 180°C; 30 min; dry state From: Stadler et al. (2002)

  15. Formation of Acrylamide from Other Amino Acids + Sugars • Glutamine • Aspartic acid • Cysteine? • Methionine • believed to be the second most important precursor amino acid • May form acrylamide via N-glycoside formation as well as through Maillard/Strecker pathway May be due to impurities

  16. Foods high in asparagine/sugars tend to have greater acrylamide formation upon cooking Which Mechanism(s) Occur in Food?

  17. Which Mechanism(s) Occur in Food? • Potatoes:Asparagine/sugar; Maillard browning Strecker degradation • Use of asparaginase to treat potato (mashed) before frying decreased asparagine levels by 95% and acrylamide levels by >99% (Zyzak, 2002; personal communication) • Grain-based foods: Asparagine/sugars are believed to be precursors and Maillard browning/Strecker degradation are believed to be mechanism- Needs to be verified • Other foods: • Coffee, chocolate/cocoa, almonds- amino acid/sugar? • Meat- methionine/sugar?

  18. What Factors Affect Acrylamide Formation? • Food composition • Precursors • pH • Moisture • Other compounds • Processing conditions • Time • Temperature • Other

  19. What Factors Affect Acrylamide Formation? • Food composition • Amino acids • ASN, MET, GLN, ASP, CYS • Other amino acids- LYS • Sugars • Fructose > glucose > sucrose (Becalski et al, 2002- personal communication)- aqueous model system • No difference in yield of acrylamide from D-fructose, D-galactose, lactose or sucrose (Stadler et al., 2002) under pyrolysis conditions • pH • pH 8.0 > 5.5 > 3.0 (Becalski et al., 2002- personal communication)

  20. What Factors Affect Acrylamide Formation? • Food composition • Moisture content • Effects unclear • Others • Sulfites- no effect on acrylamide formation in model systems (Zyzak et al., 2002; Becalski et al., 2002- personal communications) • Antioxidants- Rosemary extract had no effect on acrylamide production during frying (Becalski et al., 2002) • Glutathione/cysteine • Fermentation

  21. What Factors Affect Acrylamide Formation? Processing Conditions • Temperature- Yes • Time- Yes

  22. Effect of Temperature Asparagine/glucose aqueous model system (closed) In simple model systems: • At temperatures 120-170°C, acrylamide levels increase with processing temperature • Acrylamide forms at 120-140°C • May degrade at temperatures > 170°C? From Mottram et al. (2002)

  23. Effect of Temperature Oven-cooked French fries In food: • Boiling and retorting produce little to no acrylamide • Frying and baking result in modest to high levels • Acrylamide levels increase with cooking/processing temperature Oven Temperature (°C) From: Tareke et al. (2002)

  24. 160°C; 4 min 27 ppb 170°C; 4 min 70 ppb 180°C; 4 min 326 ppb Effect of Temperature • Acrylamide levels increased with frying oil temperature

  25. 3.5min 12 ppb 180°C; 3.5 min 12 ppb 180°C; 4.0 min 46 ppb 180°C; 4.5 min 227 ppb 180°C; 5.0 min 973 ppb Effect of Time • Acrylamide levels increased with frying time

  26. Summary of Research Findings • ASN/reducing sugar are important precursors for forming acrylamide in many foods; other amino acids may be important precursors in some foods • The Maillard reaction/Strecker degradation pathway is important in many foods • The acrolein pathway is unlikely • Processing conditions (time/temperature) are critical to levels of acrylamide in food

  27. What Are the Research Gaps? • Measure the levels of free asparagine, other amino acids and reducing sugars in foods on a dry weight basis and correlate levels to acrylamide production during processing/cooking • Determine the mechanism(s) of formation of acrylamide in each food category • Determine the effects of time, temperature, pH, and moisture on acrylamide formation in various matrices • Measure the kinetics of acrylamide inhibition/destruction/scavenging under various reaction/process conditions

  28. FDA Action Plan on Acrylamide: Formation • ***Understand the food processing and cooking conditions that affect acrylamide formation, destruction, and inhibition in model systems and in food • FDA Research • CFSAN Exploratory Survey of Acrylamide Levels in U.S. Foods • FDA/NCFST work on effects of processing on acrylamide formation in food (potato products and baked grain products) and in model systems • Worldwide Research: WHO/JIFSAN clearing house

  29. CFSAN Exploratory Survey of Acrylamide Levels in U.S. Foods

  30. FDA Action Plan on Acrylamide: Formation • Determine the precursors/mechanisms resulting in acrylamide formation in foods • FDA Research • FDA/NCFST work on verifying precursors/mechanisms in grain products • Worldwide Research: WHO/JIFSAN clearing house • Understand the role of product composition on acrylamide levels in food • FDA Research • CFSAN Survey of Acrylamide Levels in Food • Worldwide Research: WHO/JIFSAN clearing house

  31. Research on Acrylamide Worldwide U.S. - FDA; Food Industry; Trade Organizations; Academia Canada - Health Canada U.K. – Food Standards Agency; Univ. of Reading/Leeds; Leatherhead; Food Industry, Trade Organizations, Academia Netherlands - Dutch Food Authority Australia France - AFSSA Germany - BLL Spain – CNCV/Univ. of Baeares/Rocasolano Institute & FIAB Norway - MATFORSK Switzerland - Government agencies; Nestle Research Centre Sweden – Swedish Food Administration; Stockholm Univ.

  32. Study effects of processing time and temperature on formation of acrylamide in a model system and in food Next Step

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