Rancidity is associated with characteristic of flavour and odour of fats and oils A condition produced by aerial oxidation of unsaturated fat present in foods and other products, marked by unpleasant odour or flavour.

1. Rancidity
Dr.Gayathri Devi.M
Dept. Nutrition & Dietetics
SRNM College,Sattur

2. Introduction
• Rancidity is associated with characteristic of
flavour and odour of fats and oils
• A condition produced by aerial oxidation
of unsaturated fat present in foods and other
products, marked by unpleasant odour or
flavour.

3. Cont.
• When a fatty substance is exposed to air, its
unsaturated components are converted into
hydroperoxides, which break down into
volatile aldehydes, esters, alcohols, ketones,
and hydrocarbons, some of which have
disagreeable odours.

4. • Butter becomes rancid by the foregoing
process and by hydrolysis, which liberates
volatile and malodorous acids,
particularly butyric acid.
• Saturated fats such as beef tallow are resistant
to oxidation and seldom become rancid at
ordinary temperatures.

5. Rancidity
• Rancidity is the process of complete or
incomplete oxidation or hydrolysis of fats and
oils when exposed to air, light, or moisture or
by bacterial action, resulting in unpleasant
taste and odor.

6. Causes
• Temperature – Rancidity rate increases with increase in
temperature.
• Duration – For the more time you keep a thing unattended or
without using it, it has more chances to turn rancid.
• Oxygen – Oxygen promotes the decomposition of food.
• Light - In the presence of oxygen, light promotes the
decomposition of unsaturated fatty acids.
• Microorganisms and fungi (molds) – They are the most common
reason for the food to become rancid . They use their enzymes on
the food material and destroy its chemical composition.
• Moisture - Moist air helps the microbes in their activity upon the
food material.
• Trace elements – Trace elements like Fe and Zn also increase the
rate of rancidity.

7. Types
• Hydrolysis is the decomposition of fats into
free fatty acid and glycerol by enzymes in the
presence of moisture. These free fatty acids
released are responsible for the unpleasant
flavour and odour.

8. • During oxidation, oxygen is added to the
unsaturated linkage and this result in the
formation of peroxides. These
peroxides decompose to yield aldehyde and
ketones which are responsible for the
pronounced flavour.
• Rancidity may also be caused by the
absorption of odour and action of micro
organism and enzymes.

9. Preventive measures

10. Preventive measures
• Adding inert Gases Inert gas can be added to the
packet or the container like nitrogen, which does
not react with oxygen Example Chips packets are
flushed with nitrogen gas, so they don’t become
rancid.
• Adding antioxidant: are added to some foods to
slow down or eliminate oxidative deterioration.
• Refrigeration reduce the temperature and hence
don’t allow the microbes to continue their
processes.

11. Preventive measures
• Vacuum Packaging is done to keep oxygen out.
• By using oxygen scavengers or oxygen absorbers
are added to enclosed packaging to help remove
or decrease the level of oxygen in the package.
They are used to help maintain product safety
and extend shelf life.
• Keeping food in air tight containers Less air too
prevents rancidity.
• By storing food in dark place.