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Acrylamide: Mechanism of Formation in Heated Foods

Acrylamide: Mechanism of Formation in Heated Foods. David Zyzak, Ph.D. Procter & Gamble Snacks and Beverage Analytical and Microbiology Cincinnati, Ohio. ACRYLAMIDE SHOCK Press Release April 24, 2002.

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Acrylamide: Mechanism of Formation in Heated Foods

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  1. Acrylamide: Mechanism of Formation in Heated Foods David Zyzak, Ph.D. Procter & Gamble Snacks and Beverage Analytical and Microbiology Cincinnati, Ohio

  2. ACRYLAMIDE SHOCK Press Release April 24, 2002 Stockholm University/Swedish NFA revealed acrylamide presence in variety of cooked foods.

  3. Food Product Acrylamide (ppb) Toasted English Muffin, 5 min 50 Tortilla Chips 97 Baby Food Potatoes 101 Banana Chips 125 Roasted Asparagus 143 Pretzels 196 Hearty Rye Crispbread 242 Baked Potato Chips 317 Corn Chips 331 Cooked Taco Shell 559 Blue Potato Chips 736 Kettle Potato Chips 3400 Sample Survey Results

  4. Acrylamide What is Acrylamide? • high boiling point • very hydrophilic – water loving

  5. Initial Thoughts on the Mechanism of Acrylamide Formation Acrolein Acrylic Acid X X carbonyl Asparagine Acrylamide

  6. Effectiveness of Amino Acids and Dextrose to Form Acrylamide Model System Amino acid Reducing sugar Variety of ingredients fry + Measure Acrylamide Potato Starch + Water • Acrylamide Formation • Potato starch <50 ppb • Potato starch + dextrose <50 ppb • Potato starch + asparagine 117 ppb • Potato starch + dextrose + asparagine 9270 ppb • Other Amino Acids • Alanine <50 ppb Arginine <50 ppb • Aspartic A. <50 ppb Cysteine <50 ppb • Lysine <50 ppb Methionine <50 ppb • Threonine <50 ppb Valine <50 ppb • Glutamine 156 ppbAsparagine 9270 ppb

  7. Amino Acid Composition in Potatoes Approximately 50% of amino acids are in the free state (not incorporated into protein). Asparagine is roughly half of the free amino acid content.

  8. Free vs. Bound Asparagine + dextrose Acrylamide? N-acetyl asparagine Asparagine occurring as component of protein does not have an accessible primary amine group for Schiff base formation, and would not be expected to participate in the production of acrylamide. Blocking the amine group in asparagine, N-acetyl asparagine, is an effective analogue to test. Result: No acrylamide formation observed

  9. Dose/Response: Dextrose Asparagine at 1.25%

  10. GLYOXAL GLYCERALDEHYDE 2-DEOXYGLUCOSE Other Carbonyl Sources Which Produce Acrylamide Also: ribose All of these carbonyl sources produce significant acrylamide in the model system with asparagine.

  11. Acrylamide carbonyl Asparagine Use of Isotopes to Understand the Mechanism of Acrylamide Formation from the Reaction of Asparagine and Dextrose

  12. Label Expt #1: Amide15N-Labeled Asparagine Mono-labeled Acrylamide + dextrose m/z 73 97+ % of Total Acrylamide Response m/z 72 Unlabeled Acrylamide m/z 73

  13. Label Expt #2: Amine 15N-Labeled Asparagine m/z 73 + dextrose Unlabeled Acrylamide m/z 72 m/z 72

  14. Label Expt #3: Uniformly Labeled Asparagine Tetra-labeled Acrylamide m/z 76 + dextrose m/z 75 m/z 74 m/z 73 m/z 72 m/z 76

  15. Acrylamide Formation Mechanism

  16. Monitoring Intermediates in Acrylamide Formation A B

  17. Understanding Acrylamide Formation in Food Products • Is asparagine the only precursor to acrylamide in heated foods? • What about other potential sources of acrylamide? • methionine, glutamine, cysteine, acrolein, etc… • Selective removal of asparagine with asparaginase to address these questions.

  18. Asparaginase: Mode of Action

  19. Asparaginase Experiment on Potato Product Washed Russet Burbank Potatoes Boil for 1 hour Blend flesh 1:3 with distilled water Asparaginase-treated Control 45 min @ RT Microwave @ 2 min intervals for total of 10 min. Highly Cooked to Maximize Acrylamide Formation (both control and asparaginase-treated products were dry and brown)

  20. Asparagine Analysis of Enzyme-Treated Potato Product Control Asparatic acid Asparagine Unreacted FMOC ISTD Asparaginase treated Asparagine

  21. Asparaginase Reduces Acrylamide in Cooked Potato Products Potato Product Microwaved snack Acrylamide (ppb) Control Asparaginase 20,500 164 % Reduction1 >99 1Calculated as (control – asparaginase treated)/control x 100.

  22. Acrylamide Precursors – Where to Intervene Asparagine Reducing Sugars - Glucose - Fructose - Sucrose hydrolysis? • Factors affecting asparagine and reducing sugars • - Variety of potato • - Storage conditions

  23. Conclusions • Asparagine is the major source of acrylamide formation in foods. • Carbonyl source (reducing sugars) is required in the reaction. • Oil oxidation products and starch do not appear to be significant factors in acrylamide formation.

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