This document discusses rancidity and corrosion. It defines rancidity as the spoilage of food, particularly oils and fats, due to oxidation. Factors that cause rancidity include temperature, oxygen, light, microorganisms, and moisture. Some foods prone to rancidity are vegetable oils, ghee, butter, fish, bread, and pickles. Preventive measures include adding inert gases, antioxidants, refrigeration, vacuum packaging, and storing in airtight containers in dark places. Corrosion is the oxidation of metals in the presence of air and moisture. It can occur uniformly or localized in pits. Corrosion causes economic losses and safety issues through reduced strength and equipment downtime.

1. Rancidity And corrosion
Made By-
Pranav Ahlawat, class X-A, 4540/RH
Chemistry Holiday Assignment

2. Contents
 What is rancidity and how it occurs?
 Factors causing rancidity.
 Some food items that are likely to turn rancid.
 Preventive measures.
 Harmful effects of consuming rancid food.
 What is corrosion and how it occurs?
 Ill-effects of corrosion.
 Corrosion of different metals and alloys.
 Preventive measures.

3. What is Rancidity and how it occurs?
Rancidity is a very general term and in its most general
meaning, it refers to the spoilage of a food in such a way
that it becomes undesirable (and usually unsafe) for
consumption.
It is characterized by an unpleasant smell and taste.
The term “rancid” particularly applies to oils and fats. When
food scientists talk about rancidity, they are
often talking about a specific type of rancidity
Involving oxygen damage to foods, and this
type of rancidity is called "oxidative rancidity.”
Oxidation of fats (rancidity) is caused by a
biochemical reaction between fats and oxygen.
In this process the long-chain fatty acids are
degraded and short-chain compounds are formed.
One of the reaction products is butyric acid,
which causes the typical rancid taste.

4. Factors causing Rancidity
1. Temperature – Rancidity rate increases with increase in
temperature.
2. Duration – For the more time you keep a thing
unattended or without using it, it has more
chances to turn rancid.
3. Oxygen – Oxygen promotes the decomposition
of food.
4. Light - In the presence of oxygen, light
promotes the decomposition of unsaturated fatty acids.
5. 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.
6. Moisture - Moist air helps the microbes in
their activity upon the food material.
7. Trace elements – Trace elements like Fe
and Zn also increase the rate of rancidity.

5. Some food items that are likely to turn
rancid
1.
2.
3.
- Various Vegetable oils.
- Clarified butter (Ghee).
- Butter

6. Some food items that are likely to turn
rancid
4.
5.
6.
- Fishes and crustaceans.
- Bread.
- Pickle

7. Some food items that are likely to turn
rancid
7.
8.
9.
- Baked Potato.
- Shell eggs.
- Meat

8. Preventive measures
1. 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.
2. Adding antioxidants- Antioxidants are added to some foods to
slow down or eliminate oxidative deterioration. Examples-
* BHA – Butylated Hydroxy Anisole.
* BHT – Butylated Hydroxy Toluene.
3. Refrigeration – Refrigerators reduce the temperature and hence
don’t allow the microbes to continue their processes.
4. Vacuum packaging – Vacuum packaging is done to keep oxygen out.
5. By using oxygen scavengers- 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.
6. Keeping food in air tight containers – Less air too prevents
rancidity.
7. By storing food in dark place.

9. Preventive measures
Ways to
prevent
rancidity
Using inert
gases in
packaging
Using oxygen
scavengers
Refrigeration
Storing in a
dark place
Using air-
tight
containers
Vacuum
packaging
Using anti-
oxidants
(BHA, BHT)

10. Harmful effects of consuming rancid food
Consuming rancid food products is unlikely to cause immediate
illness or harm. Rancidification can reduce the nutritional value
of food, and some vitamins are highly sensitive to degradation.
In addition, rancidification can produce potentially toxic
compounds associated with long-term harmful health effects
concerning advanced aging and neurological disorders. Rancid
fats have also been implicated in increased rates of heart
disease, atherosclerosis and are carcinogenic (cancer causing).
Rancid food can cause cancer Rancid food can cause heart diseases

11. What is Corrosion and how it occurs?
Corrosion is the oxidization of metals in the presence of air(oxygen)
and moisture to form compounds of the metals. Corrosion converts
refined metal to their more stable oxide. It is the gradual destruction
of materials (usually metals) by chemical reaction with their
environment.
Corrosion can occur in two general ways:
Generalized Corrosion: Typically never
Happens , aside from in acidic conditions. This
uniform corrosion over the entire surface of
the metal is rare and leads to overall thinning
which has little effect outside of fatigue and
stress conditions.
Localized Corrosion: The most common, and most detrimental, form of
localized corrosion is pitting. Pitting is when the attack happens in one
single location on the surface and creates a pit, or small cavity, in the
metal. This type of corrosion attack is hard to prevent, engineer
against, and often times difficult to detect before structural failure is
met due to cracking. Pipes are often compromised due to pitting.

12. Ill-effects of Corrosion
Losses are economic and safety:
• Reduced Strength
• Downtime of equipment
• Decrease in weight
• Lost surface properties
• Reduced value of goods
The consequences of corrosion are many and varied and
the effects of these on the safe, reliable and efficient
operation of equipment or structures are often more
serious than the simple loss of a mass of metal. Failures
of various kinds and the need for expensive replacements
may occur even though the amount of metal destroyed is
quite small.

13. Corrosion of different metals and alloys
1.
2.
3.
- Iron (Fe) (Rusting)
- Copper (Cu)
- Silver (Ag)

14. Corrosion of different metals and alloys
4.
5.
6.
- Lead (Pb)
- Gold (Au)
- Platinum (Pt)

15. Corrosion of different metals and alloys
7.
8.
9.
- Steel
- Brass
- Zinc (Zn)

16. Preventive measures
1. Painting - Paints can protect metals from the degrading
effect of environmental gases.
2. Galvanization – It is the process of applying a
protective zinc coating to steel or iron, to prevent rusting.
The most common method is hot-dip galvanization, in which
parts are submerged in a bath of molten zinc.
3. Electroplating – This helps in avoiding the metal to have a
direct contact with the environment.
4. Alloying - Corrosion can also be prevented by making
alloys.
5. Anodization – It is a surface treatment which prevents
corrosion.
6. Cathodic protection (CP) - It is a technique to control
the corrosion of a metal surface by making that surface
the cathode of an electrochemical cell.
7. Enameling – It too helps in preventing corrosion.

17. Preventive measures
Ways to
prevent
corrosion
Painting
Galvanization
Alloying
ElectroplatingAnodization
Cathodic
Protection
(CP)
Enameling