Carcinogens in Carcinogens in Cooked MeatCooked Meat

Chemistry of CookingSpring 2011

Griffin KennedyDaniel Cohen

Ruoxi WangTomomi Okajima

Mutagens and Carcinogens

Mutagens cause mutations in the genome Different than naturally occurring mutation

Carcinogens are compounds that cause cancer in an organism Can be due to mutation or impact on cellular

metabolic pathways

Carcinogenesis

Series of mutations are involved in inactivating the tumor suppressing and DNA repairing genes in cells in the body

Heterocyclic Aromatic Amines Compounds containing at least one

heterocyclic ring and one amine group Many of these compounds are beneficial, e.g.

niacin Some have been found to be some of the

most highly mutagenic substances Mutagenic varieties are created when

cooking meats

Formation

Form regardless of proportion of constituents Precursors:

Phenylalanine Threonine Alanine Creatine Sugars

Structures of Precursors

Phenylalanine

Alanine

Threonine

Creatine

CH3

OOH

NH2

OOH

NH2OH

CH3

OOH

NH2

Products

Common features: Imidazole ring (from creatine?), fused rings (probably through radical chemistry)

Mechanisms: undergoes crazy, unpredictable chemistry at high temperatures—Maillard reaction

Products formed at high temperatures

Structure of Products

N

N

N

NNH2

CH3CH3

N

N

N

NH2

CH3

N

NN

N

NH2

CH3

CH3

CH3

Formation at High Temperature Pyrolysis: heat-based d

ecomposition High temperature, long

cooking timemore HAA

High activation energy Radical reactions

mostly for polycyclic hydrocarbons, but also for HA’s

takes place more at higher temperature

Influencing Factors in Formation Degree of cooking, type of meat thought to

have effect, but not so much Key variables:

Temperature Exposure to direct flame Cooking time

Cooking method Frying, broiling, grilling creates most HAA

Prevention of Carcinogenesis

Antioxidants prevent radical reactions that form nitrogen heterocyclic compounds in the Maillard reaction

Mechanism: inactivate intermediate radicals like pyrazinium cation radicals and pyridinium cation radicals → reduce HA formation

Common antioxidative constituents in spices: Rosmanol --Carnosic acid Rosmadial --Epirosmanol Carnosol --methyl camosate

Spices as Antioxidants

Experiment: add spice powder on surface of beef 24 hours prior to frying up to 180 degrees

Spices used: Rosemary Sage Thyme Garlic Brine (contains sodium nitrite)

All spices show antioxidative properties and reduced HA formation

Sources

Pariza, M.W., Ashoor, S.H., Chu, F.S., and Lund, D.B. (1979) Cancer Letters 7, 63-69.

Dolara, P., Commoner, B., Vithayathil, A., Cuca, G., Tuley, E., Madyastha, P., Nair, S., and Kriebel, D. (1979) Mutation Research 60, 231-237.

Murkovic, M., Steinberger, D., and Pfannhauser, W. (1998) Springer Verlag 207, 477-480.

Jackson, L.S., Knize, M.G., and Morgan, J.N., 1999, Impact of Processing on Food Safety, Kluwer Academic/Plenum Publishers, Chapter 12.