Rancidity refers to the deterioration of food products due to oxidation reactions which affect quality and shelf life, making the food unfit for consumption. Rancidity occurs when food is exposed to heat, light, oxygen, or moisture and can be caused by oxidative reactions between unsaturated fatty acids and oxygen, hydrolysis of fats catalyzed by enzymes, or microbial breakdown of fats. The three main types of rancidity are oxidative, hydrolytic, and microbial. Oxidative rancidity involves lipid oxidation in initiation, propagation, and termination steps leading to formation of aldehydes and ketones. Hydrolytic and microbial rancidity involve enzymatic breakdown of fats and oils. Proper storage,

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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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