Glossary
Terms
Glossary
Definitions
- Antioxidants
- Antioxidants
are substances that inhibit oxidation. They are added to oils and
fats to provide greater stability and longer shelf life by delaying
the onset of oxidative rancidity.
- Bleaching
- This
is a process whereby pigments, impurities, trace metals; gums and
oxidized materials are removed from oils and fats by absorptive cleansing
using bleaching clays or activated carbon. Bleaching of edible oils
or fats is generally carried out under vacuum at 70 ºC to 120 ºC.
Blending
- Single
or straight oils and fats are often unable to satisfy the complex
technical specifications prescribed for a particular product application.
Only by blending, i.e. mixing two or more straight or modified oils
and fats, can the correct balance of properties such as melting point,
plastic range, color, texture, iodine value, etc. be obtained.
Carotenes
- Natural
constituents that give crude palm oil its bright orange-red color
and which are completely destroyed during refining. Carotenes can
also be partially destroyed by oxidation under adverse conditions
during production, storage and transport of crude palm oil. However,
upon request, palm oil can be specially processed to maintain the
carotenes.
Centrifugation
- Substances
having different densities will separate by gravity. For instance,
oil is lighter than water and easily forms a separate upper layer.
The effect of gravity can be accentuated by centrifugation, i.e. by
rotating the mixture to be separated in a container. Centrifugation
is often used in oil mills and refineries to separate impurities and
water from oils and fats and also fat crystals from a fat slurry after
addition of a surface-active agent.
Chemical Refining
- This
refers particularly to the removal of free fatty acids by alkali.
The alkalis used are usually sodium hydroxide (caustic soda) or soda
ash, either singly or in combination. One novel chemical refining
technique uses aqueous ammonia as the alkali.
Cloud Point
- This
is a test to determine the temperature at which oil begins to cloud
as a result of crystallization under controlled cooling. The cloud
point is related to the unsaturation of an oil. In general, the higher
the unsaturation of an oil, the lower its cloud point will be.
Cocoa Fat
- This
fat has a unique chemical composition, consisting mainly of the triglycerides
POS (palmito-oleo-stearin), POP (palmito-oleo-palmitin) and SOS (stearo-oleo-stearin).
lt is hard and brittle at room temperature but melts very sharply
below body temperature. It therefore gives chocolate its desirable
properties of 'snap' and 'melt-in-the-mouth', and is highly valued.
Cocoa Butter Equivalents (CBE)
- These
are fats designed to have a glyceride composition similar to that
of cocoa butter. Their properties are similar and they are compatible
with cocoa butter in mixtures for chocolate manufacture.
Cocoa Butter Substitutes (CBS)
- These
are fats usually based on laurics, i.e. on palm kernel oil or coconut
oil. They have snap and melting properties similar to cocoa butter
but a different chemical composition. They are not compatible with
cocoa butter and the presence of more than 20% cocoa butter in a mixture
with them leads to softening and / or bloom formation.
Crystallization
- Crystallization
is the three-step process of forming crystals and may take place from
a melt or from a solution. The three steps are supercooling or super
saturation; formation of crystalline nuelei; and growth of crystals.
The process is important for fats in order to produce the desired
texture in a solid product, or as a preliminary to fractionation.
Degumming
- Fats
and oils contain complex organo-phosphorus compounds referred to as
phosphatides, or more commonly as gums. They are removed during processing
by a variety of treatments collectively referred to as degumming.
The process involves treatment with water, or phosphoric acid, or
polybasic organic acids, either individually or in combination, followed
by centrifuging the precipitated material or by its absorption on
a bleaching earth or filter.
Deodorization
- This
process involves removal of those trace components, present in all
edible oils, which give rise to odors and flavors. It is accomplished
by the application of heat, steam and vacuum.
Fatty Acid Composition
- The
Triglyceride molecules that make up oils and fats are each composed
of three molecules of fatty acids and one molecule of glycerol. The
fatty acid composition of a fat or oil is expressed as the percentage
of each of the various fatty acids present in the mixture.
Fractionation
- Fractionation
is the process of separation of an oil or fat into two or more fractions.
The oil is cooled and crystallized under controlled conditions and
the solid separated from the liquid by filtration or centrifugation.
Fractionation of a fat is made possible by solubility differences
between the component triglycerides. The fractions obtained have different
physical and chemical properties from the original oil, and have wide
applications.
Hydrogenation
- This
process involves addition of hydrogen to the double bonds of unsaturated
acids in the molecules of an oil. By doing this, the properties of
the fatty acids are changed and therefore also the properties and
physical behavior of the oil. This chemical reaction is carried out
by reacting the oil with gaseous hydrogen at elevated temperature
and pressure, in the presence of a catalyst, usually nickel. Hydrogenation
of oils and fats is also known as hardening.
Interesterification
- The
fatty acids of palm oil can be rearranged in relation to their position
on the triglyceride molecules. The rearrangement, which occurs in
a random manner, is conducted in the presence of a catalyst, and is
termed interesterification. The rearrangement brings about a change
in the physical properties of the oil, which may leave the products
more useful for making margarine, vanaspati and shortening.
Iodine Value (IV)
- IV
is a measure of the total number of unsaturated double bonds present
in an oil. The determination of iodine value involves the addition
of halogen in the presence of potassium iodide and titration with
standard sodium thiosulphate using starch solution as the indicator.
Of the various procedures available, the most widely used is the Wijs
method.
Oleic Acid
- This
is the most widely distributed of all fatty acids, found in practically
every vegetable and animal fat. Rich sources are olive and peanut
oils and palm olein. Oleic acid contains 18 carbon atoms and one double
bond in the cis configuration. Palm oil contains about 40% oleic acid.
Oxidation
- When
oils or fats are oxidized, the unsaturated fatty acids react, resulting
in rancidity. The most common mechanism of oxidation is a free radical
chain reaction. This process is retarded by antioxidants such as tocopherols
and tocotrienols, and accelerated by prooxidants such as trace metals
and heat. The primary products of oxidation are hydroperoxides. These
then decompose into secondary oxidation products such as aldehyes
and ketones.
Palm Olein
- Palm
olein is the liquid, more unsaturated fraction separated from palm
oil after crystallization at a controlled temperature. The olein consists
of a more homogeneous mixture of triglycerides and has properties
and uses which are different from those of the original oil.
Palm Kernel Oil
- This
is the oil obtained from the kernel of the oil palm fruit. Its chemical
composition is quite different from that of palm oil, which is obtained
from the flesh of the palm fruit. Palm kernel oil is a lauric type,
similar to coconut oil.
Palm Stearin
- Palm
stearin is the more saturated and more solid fraction of palm oil.
Its fatty acid composition is variable depending on the process employed
to isolate it, ranging from 53% to 88% for saturates, 16% to 37% for
monounsaturates, and 3% to 10% for polyunsaturates. Palm stearin is
used in formulating products that require a higher degree of saturation,
such as margarines and shortenings.
Physical Refining
- Physical
refining may be defined as the removal of free fatty acid from an
oil by the action of high temperature, high vacuum and live steam.
lt is also referred to as steam refining. This process is normally
carried out in a single step with deodorization.
Polyunsaturated Fatty Acids (PUFA)
- These
are fatty acids having two or more double bonds in their carbon chain.
The most common polyunsaturated fatty acid is linoleic acid. Corn
oil, sunflower oil and soyabean oil are some vegetable oils that are
rich in PUFA.
Rancidity
- Rancidity
is a condition in which an off-flavor has developed in edible oils
or fats, or manufactured food products; it is caused by oxidative
deterioration. Primary oxidation products are odorless and tasteless
but certain secondary decomposition products have particularly potent
off-flavors and are detected by the palate at extremely low concentrations.
The term rancidity is sometimes also used to describe the soapy taste
resulting from the hydrolysis of lauric oils, which is due to the
short chain fatty acids formed.
Refining
- All
crude oils and fats when freshly produced contain unwanted impurities.
These consist essentially of free fatty acids, gums, trace metals,
odoriferous materials and water. The various processes used to remove
all these entities are normally known collectively as 'refining'.
Slip Melting Point
- Fats
consist of a complex mixture of glycerides and therefore do not have
sharp melting points, unlike pure chemical substances. The slip melting
point of a fat is defined as the temperature at which a column of
fat in an open capillary tube moves up the tube when it is subjected
to controlled heating in a waterbath. Because of their polymorphic
behavior, the slip point of some fats is dependent on the previous
treatment of the sample.
Splitting
- Fat
splitting is usually carried out with steam at high temperature and
pressure (e.g. 260 'C and 55 bar) to give glycerol and a mixture of
fatty acids. This process opens the gateway to the oleochemical field.
Soapstock
- In
the chemical refining of crude oils, the free fatty acids are removed
by neutralization with alkali and settle to the bottom as alkali soaps,
known as soapstock.
Stearic Acid
- Chemically,
stearic acid is an 18-carbon saturated fatty acid. Commercially, the
term is used for mixed solid acids of various compositions. Stearic
acid is used for industrial purposes in the rubber and oleochemical
industries.
Trans Fatty Acids
- Trans
fatty acids are formed during the partial hydrogenation of an oil.
Some of the unsaturated fatty acids present are changed from their
natural, bent cis shape to a straight trans shape like that of the
saturated acids. In consequence, many of the physical properties of
trans-acids, such as melting point, are nearer to those of the saturated
acids, although double bonds are still present.
Tocotrienols & Tocopherols
- These
are components of Vitamin E. In both unprocessed and processed forms,
palm oil has significant concentrations of tocopherols and tocotrienols.
Both act as powerful nutritional antioxidants, probably helping to
reduce cellular damage due to oxidative metabolism, as well as that
resulting from the action of toxic chemicals and pollutants in our
environment.
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