Rancidity & its type

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2. RANCIDITY
 Deterioration of food products.
 Due to oxidation reaction.
 Effects the quality and shelf life.
 Unfit for consumption.
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3. Rancidity
 Rancidity occurs when food is exposed
to:
Heat
Light
Oxygen
Moisture
Microbes
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4. Rancidity
 Rancidity leads to the development of:
Off-Flavor Off-Odor
Unpleasant
Color
Harmful
compounds
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5. Types of Rancidity
 There three types of rancidity.
Rancidity
Oxidative
Microbial
Hydrolytic
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6. Oxidative Rancidity
 Occurs due to oxidation of fats.
 Unsaturated fatty acids react with
oxygen and lead to formation of free
radicals.
 Free radicals further react with oxygen
to form aldehydes and ketons.
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7. Oxidative Rancidity
Unsaturated
Fatty Acid Oxygen Free Radical
Heat, Light,
Trace Metals
Free Radical Oxygen
Peroxides
Aldehydes
Ketons
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8. Oxidative Rancidity
 Lipid oxidation takes place in three steps.
Initiation Propagation Termination
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9. Oxidative Rancidity
 Initiation:
 Free radical formation require high
activation energy.
 It is usually initiated in the presence of
light and metal ions.
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10. Oxidative Rancidity
 Propagation:
 Free radicals react with oxygen to form
per-oxide radicals.
 Per-oxide free radicals abstract
hydrogen from another unsaturated
molecule to yield new free radical.
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11. Oxidative Rancidity
 Termination:
 This step involves stopping of reaction.
 Free radicals generated during chain
reaction are eliminated.
 Factors
 Antioxidants
 Oxygen depletion
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12. Oxidative Rancidity
 Factors that affect rate of oxidation.
Amount of
Oxygen
Degree of
Unsaturation
Presence of
Antioxidants
Presence of
Prooxidants
Light
Temperature
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13. Hydrolytic Rancidity
 Occurs due to hydrolysis of fats.
 Process is catalyzed by enzymes i.e.
lipases.
 Enzymes break down ester bonds.
 Leads to the formation of free fatty
acids.
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14. Hydrolytic Rancidity
Fats/Oils Water
Free Fatty
Acids
lipases
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15. Microbial Rancidity
 Occurs when microorganisms
breakdown fats.
 Reaction is catalyzed by enzymes,
temperature, humidity.
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16. Prevention
Prevention
Proper
Storage
Use of
Antioxidants
Use of
Chelating
Agents
Hydrogenation
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17. References
 Lipids by John W. Finley and John M.
deMan
 Osman, M. A., & Al-Nadabi, H. (2014).
Rancidity in foods. Advances in Food
Science and Engineering, 1(1), 13-19.
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