Role of metal ions in food oxidation
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Role of Metal Ions in Food Oxidation. Food Chemistry April 10, 2014. Neera Munjal. LIPID OXIDATION . Deteriorative Lipid oxidation during storage of fats and oils, muscle based foods. Lead to rancidity, off flavors, color changes, rheological changes, formation of toxic compounds.

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Role of Metal Ions in Food Oxidation

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Role of Metal Ions in Food Oxidation

Food Chemistry

April 10, 2014

NeeraMunjal


LIPID OXIDATION

  • Deteriorative Lipid oxidation during storage of fats and oils, muscle based foods.

  • Lead to rancidity, off flavors, color changes, rheological changes, formation of toxic compounds.

  • Mechanism of Lipid Peroxidation: Unsaturated fatty acids react with molecular oxygen via free radical chain reaction.


FACTORS ENHANCING

LIPID OXIDATION

  • Metals/Heme Compounds in food enzymes

    • pH

    • Water Activity

    • Form of Metal

    • Temperature

  • Processing, Storage

  • Fat Composition


MECHANISM OF METAL

OXIDATION IN FOOD

  • Oxygen Activation by Metal ions

    • React with triplet oxygen to form reactive oxygen species

  • Heme-protein Initiated


HEME INITIATED

LIPID OXIDATION

  • Transition metal ions (Fen+, Cun+, etc) catalyze oxidative changes in tissues.

  • Muscle pigment (heme) initiated lipid

    oxidation in muscle based foods.

    • Myoglobin in beef, pork, broilers

    • Hemoglobin in broilers, fish

  • Other sources: Water, Salt

  • Iron initiates lipid oxidation by

    generating free radicals.


MYOGLOBIN IN

MUSCLE TISSUE

PERFERRYL

OXY

MET

DEOXY

FERRYL


MET-IRON (III) MYOGLOBIN

INDUCED LIPID OXIDATION

pH dependent

  • Acidic pH

  • Pro-oxidant

  • Lipid Hydroperoxide formed while conversion of muscle to meat

  • Physiological pH

  • Anti-oxidative: Due to formation of non catalytic hemichromepigment (exposure of heme iron to unusual ligands).

  • Pro-oxidative: High Lipophilic environment result in heme release and exposure of heme to lipids resulting in oxidation (Hematin induced)

  • Potential pro oxidant at pH found in fresh meat


OXY IRON (II) MYOGLOBIN

INDUCED LIPID OXIDATION

  • Anti-oxidative: Due to formation

    of non catalytic hemochromes.

  • Pro-oxidative at high lipid

    concentration (Hematin induced)

  • MbFe(II)O2 can promote

    oxidative modification of LDL

  • Slaughtering, Low pH in muscle

    based foods accelerate autoxidation.

  • Mechanism unclear


IRON (IV) MYOGLOBIN

INDUCED LIPID OXIDATION

Perferryl

  • Activation of Met form by H2O2

  • It generates unstable hypervalent

    perferryform.

  • No oxidation at conditions found in fresh

    meat.

  • Can transfer its radicals to other proteins

    to initiate lipid oxidation.

    Effect pro oxidant : Ferryl can initiate lipid oxidation at all pH


PREVENTION OF

LIPID OXIDATION

  • Chelating agents such as Citrate anion, EDTA

  • Nitric Oxide

  • Control of oxygen by specific processing like deaeration.


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