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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.