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1. Oil, Fats and waxes
Dr. ABM Nazmul Islam
Sr. Lecturer, Dept. of TE, DIU

2. Fats and Oil
Natural fats and oils are the triesters of glycerol with long-chain carboxylic acids (12
to 20 carbons). These are known as triglycerides.

3. Distinction between fats and oils
The distinction between fats and oils is primarily based upon the difference in
melting points. Fats are composed of solid triesters of glycerol, while oils are
composed of liquid triesters of glycerol at room temperature. However, the
distinction is not well founded as the physical state depends on climate and weather.
The same glyceride may be solid at a hill station and liquid in plains.

4. Drying, semidrying and non drying oil
A drying oil is an oil that hardens to a tough, solid film after a period of exposure
to air. The oil hardens through a chemical reaction in which the components
crosslink (and hence, polymerize) by the action of oxygen (not through the
evaporation of water or other solvents). Some commonly used drying oils
include linseed oil, tung oil, poppy seed oil, perilla oil, and walnut oil.
A semi-drying oil is an oil which partially hardens when it is exposed to air.
Cottonseed oil, corn oil etc are examples of semi drying oil.
A non-drying oil is an oil which does not harden when it is exposed to air.
Coconut oil, olive oil, peanut oil etc are non drying.
In terms of Iodine value, oils with an iodine number greater than 130 are
considered drying, those with an iodine number of 115–130 are semi-drying, and
those with an iodine number of less than 115 are non-drying.

5. Edible oils have high nutritional value and less industrial demand and are beneficial for
human consumption. Such oils also require less processing to make it safe and hygienic
for health. Majority of vegetable oils come under edible oil; however not all. There are
few vegetable oils and all petroleum oils which are not suitable for eating and have
industrial demand. Such oils are grouped as non-edible oils.
Edible oil and non edible oil

6. Waxes
Waxes are organic in nature, contain long alkyl chain, lipophilic,
hydrophobic, malleable solids near ambient temperatures.
Beewax: This is probably the best known wax. It is made from honeycombs
by solvent extraction, expression, or boiling in water. A major component of
the beeswax used in constructing honeycombs is the ester myricyl palmitate
which is an ester of triacontanol and palmitic.
Spermaceti: The oil removed from the head cavity, and parts of the blubber
of the sperm whale is in reality a wax because of its chemical composition.
Spermaceti is important for lubrication. The head oil, upon chilling and
setting, is a solid wax. This constitutes about 11% of the original oil and is
largely cetyl palmitate. It is melted, treated with a hot, dilute caustic soda
solution, washed with water, and run into molds to solidify. It is translucent,
odorless, and tasteless and is used chiefly as a base for ointments.

7. Carnauba wax: The most important plant wax is Carnauba wax, a hard wax
obtained from the Brazilian palm. Containing the ester myricyl cerotate, it
has many applications, such as confectionery and other food coatings, car
and furniture polish, floss coating, and other uses.

8. Rancidity
Vegetable oils contain a mix of saturated, monounsaturated, and polyunsaturated
fatty acids. The mono- and polyunsaturated fatty acids have double bonds, all in
the normal “cis” formation. These bonds can easily be broken down by oxygen.
This produces compounds that make the oil rancid which produces off-flavors in
foods. To control this, food manufacturers use hydrogenated vegetable oils.

9. Hydrogenation
• Hydrogenation or hardening, as applied to fats and oils, may be
defined as the conversion of various unsaturated radicals of fatty
glycerides into more highly or completely saturated glycerides by the
addition of hydrogen in the presence of a catalyst.
• Various fats and oils, such as soyabean, cottonseed, fish, whale, and
peanut, are converted by partial hydrogenation into fats of a
composition more suitable for shortenings, margarine, and other
edible purposes, as well as for soap-making and numerous other
industrial uses.
• The object of the hydrogenation is not only to raise the melting point
but to greatly improve the keeping qualities, taste, and odor for many
oils