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

Role of Metal Ions in Food Oxidation

Food Chemistry

April 10, 2014

NeeraMunjal


Lipid oxidation

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.


Role of metal ions in food oxidation

FACTORS ENHANCING

LIPID OXIDATION

  • Metals/Heme Compounds in food enzymes

    • pH

    • Water Activity

    • Form of Metal

    • Temperature

  • Processing, Storage

  • Fat Composition


Role of metal ions in food oxidation

MECHANISM OF METAL

OXIDATION IN FOOD

  • Oxygen Activation by Metal ions

    • React with triplet oxygen to form reactive oxygen species

  • Heme-protein Initiated


Role of metal ions in food oxidation

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.


Role of metal ions in food oxidation

MYOGLOBIN IN

MUSCLE TISSUE

PERFERRYL

OXY

MET

DEOXY

FERRYL


Role of metal ions in food oxidation

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


Role of metal ions in food oxidation

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


Role of metal ions in food oxidation

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


Role of metal ions in food oxidation

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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