CHAPTER TWO
LITERATURE REVIEW
LITERATURE REVIEW
2.1 SOYBEAN OIL
The soybean (Glycine max) is a species of legume
nature to east Asia, widely grown for its edible bean which has numerous uses.
The plant is classed as an oil seed rather than a pulse by the Food and
Agricultural Organization (FAO, 2005) Oil and protein contents account for
about 60% of dry soybeans by weight, protein at 40°A and oil at 20%. The
remainder consists of 35% carbohydrate and about 5% ash. Soybean
cultivars comprise approximately 8% seed coat or hull, 90% cotyledons and
2%hypocotyls axis germ (USDA NUTRIENT DATA BASE, 2003)
Soybeans are an important global crop, that provide
oil. In the United State, the bulk of the harvest is solvent extracted with
hexane.
2.2 SOYBEAN OIL
2.2 SOYBEAN OIL
Soybean seed contain about 19% oil. To extract soybean
oil from seed, the soybeans are cracked adjusted for moisture content, rolled
into flakes and solvent extracted with commercial hexane. The oil is then
refined, blended for different applications and sometimes hydrogenated, are
exported abroad, sold as vegetable oil or end up in a wide variety of processed
foods. The remaining soybean meal is used mainly as animal feed.
Soybeans contain all three of the micro nutrients
required for good nutrition complete protein, carbohydrate and fat as well as
vitamin and minerals; include calcium, folic acid and iron. Soybeans are the
only common plant foods that contain complete protein. Soybean protein provide
all the essential amino acid in the amount needed for human health. The amino
acid profile of soybean protein is nearly equivalent in quality to meat, milk and
egg protein.
Soybean oil is 61% polyunsaturated fat and 24% monounsaturated fat which is comparable to the total unsaturated fat content of other vegetable oil (85%) like other vegetable oils, soybean oil contain no cholesterol.
Polyunsaturated vs saturated fats
Soybean oil is 61% polyunsaturated fat and 24% monounsaturated fat which is comparable to the total unsaturated fat content of other vegetable oil (85%) like other vegetable oils, soybean oil contain no cholesterol.
Polyunsaturated vs saturated fats
Excessive intake of any fat is undesirable. Nutrition
experts recommends limiting total fat consumption to 30% or less of the total
daily calories and limiting saturate fats to 10% or less saturate fatty acid
raise blood cholesterol which can thicken arterial walls and increase the risk
of heart disease. (Soybean National Research February, 2010).
Essential
Fatty Acid
Soybean oil is rich in polyunsaturated fatty acid
including the two essential fatty acids, linoleic and linolenic that are not
produced in the body. Linoleic and linolenic acid aid the body absorption of
vital nutrients and are required for human health. These two essential acids
are also precursors to hormones that regulate smooth muscle contraction blood
pressure and the growth of health cells.
Pure soybean oil is about. 50% linoleic acid and & Iinoienic acid.
Pure soybean oil is about. 50% linoleic acid and & Iinoienic acid.
2.3 HYDROGENATED SOYBEAN OIL
Hydrogenation is used to solidify soybean oil for the
manufacture of margarine. This process increase stability of oils and to raise
the melting point of soybean oil shortening hydrogenation changes the chemical
composition and physical properties of oils and effects of the nutritional
value. The degree of changes in nutritional value depends upon the amount of
hydrogenation necessary to produce the final product and the reduction of
polyunsaturation that occurs. The hydrogenation process also creates trans
fatty acids from acids unsaturates rearranging hydrogens around the double bond
in a monounsaturated or polyunsaturated fatty acid. The table below shows the
fatty acid composition of soybeans oil per 100g.
Table 1: Fatty acid composition of soybean oil
Fatty acid
|
Content
|
Saturate fat
|
16g
|
Monounsaturated fat
|
23g
|
Polyunsaturated fat
|
58g
|
Source: Soybean Natural
research February, 2012.
Table 2: The major unsaturated fatty acids in soybean
oil triglyceride are
Fatty acid
|
Content
|
Chain length
|
Alpha linolenic acid
|
7-10%
|
C-18:3
|
Linoleic acid
|
51%
|
C-18:2
|
Oleic acid
|
23%
|
C-18:1
|
SOURCE: Soybean natural
research February,2012.
It
also contains the saturated fatty acids 4% stearic acid and 10% palmitics acid.
(USDA Nutrient Data Base 2003).
SOYBEAN PREPARATION AND CLEANING
Soybeans are cleaned and dried, then
dehulled by cracking and separating the soybeans from the hulls. Magnets are
used to separate any iron from the soybeans. The soybeans are adjusted for
moisture content and heated to coagulate the soy proteins and make the oil
extraction easier.
The prepared soybeans are cut into flakes and placed
into percolation extractors and combined with a solvent. The hexane/soybean oil
mix is separated from the flakes and transferred to evaporators where the oil
and hexane are separated. The evaporated hexane is recovered and reused in
future extraction processes, while the hexane free crude soybean oil is taken
for further refining.
Refining
Soybean Oil
The crude soybean oil contains many impurities that
need to be removed oil insoluble materials are removed through filtration,
while oil soluble materials are removed through degumming, neutralizing or
bleaching. A stripping and/or deordorizing step completes the refining process.
However, these processing techniques allow us to refine oils, make them melt
more slowly or rapidly change their crystal habit, rearrange their molecular
structure, and literally take them apart and put them back together again to
suit our requirements of the moment. Processing involves a series of stages
which are outlined below.
Degumming
Washing
Drying
Crude oil
Refining
Bleaching
Deodorizing
Winterization Interesterification
Hydrogenation
RBD oil
Refining
/Neutralization
The process of refining (sometimes referred to as alkali
refining) is aimed at reducing the free fatty acid content. The acids are
removed by neutralizing the soil with a solution of caustic soda, which
converts the fatty acid into an insoluble soap. The soap is then removed by
allowing it to settle to the bottom of the neutralizing tanks. If the acid
impurity is palmitic acid for example, then insoluble sodium palmitate is
formed according to the reaction.
C15H31COOH+NaoH
→
C12H13COONa + H2O
Washing
and Drying
In other to remove the last traces of soap from the
oil, it is washed with warm water. Two layers form and lower water layer is run
off leaving the oil layer which is then dried under vacuum.
Bleaching.
The process aim at removing colour producing
substances from fats and oils. Normally, bleaching is accomplished after the
oil has been refined. The usual method of bleaching is by absorption of the
colour producing substances on an adsorbent. Acid activated bleaching earth or
clay sometimes called betonite, is the adsorbent that has been used
extensively. This substance consists primarily of hydrated aluminum silicate.
Anhydrous silica gel and activated carbon are also used as bleaching
adsorbents.
Deodorization
Deodorization is a vacuum steam distillation process
for the purpose of removing trace constituents that gives rise to undesirable
odors and flavors in oils. This process is normally accomplished after refining
and bleaching. Deodorization is simply the removal of relatively volatile
compound from fats and oils, using steam. It is carried out under vacuum to
facilitate the removal of the volatile substances and to avoid hydrolysis.
Winterization/De
Waxing/Fractionation
Winterization is the process whereby component
triglycerides of fats and oils are crystallized from a melt. The two component
fractional crystallization is a accomplished by partial solidification of
higher melting triglyceride components, followed by separation (by filtration)
of the two components.
The term winterization evolved from the observation
that refined cotton seed oil, stored in outside tanks during the winter months
physically separated into a hard and clear fraction. Decanting the clear oil
from the top of the tanks provided oil that remained liquid without clouding
for long periods at cool temperatures. The need for liquid oil with these
characteristics was created by the use of refrigerators in the home and the
requirements of the mayonnaise and salad dressing industry. A similar process
called dewaxing is used to clarify oils containing trace amounts of clouding
constituents.
Edible fats and oils are complex multicomponent
mixtures of various triglycerides with different melting points. The melting
behaviours of fats are important properties for functionality in various
prepared food products.
Fractionation:
Process separates fats and oils into fractions with
different melting points. The aim of fractionation is to provide new materials
that are more useful than the natural product.
Interesterification
The term refers to the reaction in which fatty acid
esters react with other esters or fatty acids to produce new esters by an
interchange of fatty acid groups. More simply state, interesterification can be
visualized as a break up of a specific triglyceride removal of a fatty acid at
random, shuffling it among the rest of the fatty acid pool, and replacing at
random by another fatty acid. Because of the random re-arrangement of the fatty
acids of the natural oil, the interesterification process is also commonly
referred to as randomization, rearrangement or modification.
Interesterifcation process can alter the original
order of distribution of the fatty acids in the triglyceride molecule with
melting and crystallization
characteristics
different from the original oil or fat. Unlike hydrogenation,
interesterification neither affects the degree of saturation nor cause
isornerization of the fatty acid double bond. It does not change the fatty acid
composition of the starting oil, but rearranges the fatty and on the glycerol molecule.
Hydrogenation
Hydrogenation is the conversion of oil to a fat by a
chemical method. It involves the addition of hydrogen to the double bonds of
unsaturated fatty acids of triglyceride, using nickel as catalyst. During
hydrogenation, one molecule of hydrogen is absorbed by a double bond, according
to the reaction.
-
CH = Ch- + H2 → CH2 - CH2
Hydrogenation only proceeds at a reasonably fast rate
in the presence of a catalyst, nickel being used industrially. The catalyst is
added in small quantities large closed steel vessel known as converters. The
oil is stirred and hydrogen gas is pumped in. the oil is heated to star
reaction, and after reaction the oil is cooled and filtered to remove the
nickel which can be reused. Hydrogenation is a selective process, some
triglycerides becoming saturated more rapidly than others. The most unsaturated
triglycerides are partially hydrogenated before the less unsaturated ones
react. Thus, more linolenic acid is converted into linoleic acid in a given
time than linoleic into oleic. The reactive rates of reaction of oleic,
linoleic and linolenic are in the ratio 1:20:40.
In the process of hydrogenation, hydrogen gas
chemically reacts with the double bonds in the carbon chain of an unsaturated
fatty acid converting it to a more saturated fatty acid, shifting it to a new
position, or twisting it to the trans configuration, all of which increase it
melting point.
Oil
is hydrogenated for two(2) reasons.
1. Change
naturally occurring fats and oils into physical forms with the consistency and
melting characteristics required for functionality.
2. To
increase oxidative stability.
Degumming
Crude oil having relatively high level of phosphatides
(e.g soybean is degummed prior to refining to remove the majority of those
phospholipids compounds. The process generally involves treating the crude oil
with a limited amount of water to hydrate the phosphatide and make them
separable by centrifugation. The phospholipids content of some crude vegetable
oils are shown in the table below.
Vegetable oil
|
Phosphotide
content (%)
|
Soybean
|
1.1-3.2
|
Corn
|
1-2
|
Cotton
seed
|
0.7-0.9
|
Linseed
|
0.3
|
Rape
seed
|
0.1
|
A relatively new process in the United State is
enzymatic degumming An enzyme, phospholipids present in crude oil, into
lysophospholipids that can be removed by centrifugation. Crude oil is
pre-treated with a combination of sodium hydroxide and citric acid, mixed with
water and enzyme (phospholipase) by a high share mixer which results in a
stable emulsion. The emulsion allows the transforming them into water solution
lysophospholipids. This emulsion is broken by centrifuge, separating the gums
and phospholipids from the oil. This process generates a better oil yield than
traditional degumming; however, it had not been widely commercialized.
2.5 TALLOW
2.5 TALLOW
Tallow consists mainly of triglyceride (fat) whose
major constituents are derived from stearic and oleic acids. Rendered animal
fat is fat derived from rendering meat, including bones and intended for human
consumption. Tallow is rendered animal fat from bovines origin. For the purpose
of the present opinion, tallow is defined as fats obtained by pressing or any
extraction system down from ruminant tissues which are derived directly from
discrete adipose tissue masses from mechanically recovered meat and from
rendered animal waste including bones.
General
Description of Fat
Commercial fats produced by organic processes in
plants are
palm kernel oil is an edible plant oil derived from the kernel of oil palm Elaeis guineenis) coconut oil, extracted from the kernel of the coconut, and palm oil, extraction from the pulp of the oil palm fruit.
palm kernel oil is an edible plant oil derived from the kernel of oil palm Elaeis guineenis) coconut oil, extracted from the kernel of the coconut, and palm oil, extraction from the pulp of the oil palm fruit.
Palm kernel oil, coconut oil, and palm oil
are three of the few
highly saturated vegetable fats. Palm kernel oil, which is semi-solid at room temperature, is more saturated than palm oil and comparable to coconut oil. like all egetab1e oils, these three palm derived oils, do not contain cholesterol (found in unrefined animal fats) although saturated fat intake increases both LDL and HDL cholesterol.
The approximate concentration of fatty acids (FAS) palm kernel oil is as follows.
highly saturated vegetable fats. Palm kernel oil, which is semi-solid at room temperature, is more saturated than palm oil and comparable to coconut oil. like all egetab1e oils, these three palm derived oils, do not contain cholesterol (found in unrefined animal fats) although saturated fat intake increases both LDL and HDL cholesterol.
The approximate concentration of fatty acids (FAS) palm kernel oil is as follows.
Fatty
Acid Content of Palm Kernel Oil
TYPE OF
FATTY ACID
|
PERCENTAGE
|
Lauric
saturated C12
|
48.2%
|
Myristic
saturated C14
|
16.2%
|
Palmitic
saturated C16
|
8.4%
|
Capric
saturated C10
|
3.4%
|
Caprylic
saturated C8
|
3.3%
|
Stearic
saturated C18
|
2.5%
|
Oleric
monounsaturated C18
|
15.3%
|
Linoleic
polyunsaturated C18
|
2.3%
|
Source – (USDA Nutrient data base 2003).
And other fatty acids. Tallow is a refined hard fat
extracted from fatty deposits of animals, especially from suet (fatty tissue
around the kidneys of cattle and sheep). The molecules of most natural fatty
acid have an even number of carbon chains due to the linkage together by ester
units. Analogue compounds of odd numbers carbon chain fatty acid can be made
synthetically. All fats are insoluble in water and have lighter weight than
water. Industrial fat can be sub classified as fat or oil depending on melting
point. Fat that are liquid at room temperature are referred to as oil.
Most naturally occurring fats and oils are the fatty
acid esters of glycerol. Coconut or palm oils are better source to get
saturated fatty acids than sunflower, soybean or rapeseed oils which have more
unsaturated fatty acid composition of triglyceride. Oil fatty acid is a low
cost unsaturated fatty acid (oleic acid) and is a source of low boiling point
fatty acids.
2.5.1
METHOD OF PRODUCTION
Tallow does not appear in its usable from when
separated from cattle. It first needs to be cooked and separated from cattle
residue. This separation can occur either through filtering or centrifugal
processing, using gravity. The pure tallow is then produced after the
processing and directed to its next purpose.
COMPOSITION
BEEF TALLOW NUTRITIONAL VALUE PER 100G.
|
|
Energy
|
3774KJ
(902k cal)
|
Carbohydrate
|
0g
|
Fat
|
100g
|
Saturated
|
50g
|
Monounsaturated
|
42g
|
Polyunsaturated
|
4g
|
Protein
|
0g
|
Cholesterol
|
109ng
|
Selenium
|
0.2mg
|
Source
– (USDA Nutrient data base 2003).
The
composition of the fatty acid typically as follows:
BEEF TALLOW NUTRITIONAL VALUE PER 100G.
|
|
Palmatic
acid
|
26%
|
Myristic
acid
|
14%
|
Stearic
acid
|
3%
|
MONOUNSATURATED FATTY ACID
|
|
Oleic
acid
|
47%
|
Palmitoliec
acid
|
3%
|
MONOUNSATURATED FATTY ACID
|
|
Linoleic
acid
|
3%
|
Linolenic
acid
|
1%
|
2.5.2 MELTING
POINT
This is an important property; it is about the same
for the fatty acid and for the homogenous saturate triglyceride (with the three
fatty acid). Important consideration is as follows (Brain and Cameron, 1982).
For a given
type, the melting of the fatty acid increases according to the length of the
hydrocarbon chain, for example in
the saturated acid series, the increase varies from between 6.5 and 9.5 degree
for every 2 additional carbon atoms.
Fatty acid
|
Chain length
|
Melting point (oC)
|
Lauric acid
|
C12
|
44.3
|
Myristic acid
|
C14
|
53.9
|
Palmitic acid
|
C16
|
68.1
|
Steraric acid
|
C18
|
69.6
|
Arachidic acid
|
C20
|
76.5
|
Lignoceric acid
|
C22
|
86.0
|
For a given chain length, the melting point is lowered
with increase in the number of double bonds, the reduction is greater for the
CIS form than for the trans form (rare) (Brian and Cameron 1982).
Fatty acid
|
Chain length
|
Melting point (oC)
|
Vaccenic (trans)
|
C 18: 1
|
44.0
|
Oleic (Cis)
|
C 18:1
|
13.4
|
Linoleic (Cis)
|
C 18:2
|
-15
|
Linolenic (Cis)
|
C18:3
|
-11
|
The
plasticity of fat results of from its being a mixture of a number of different
triglycerides, each triglyceride having its own melting point. When a large
proportion of the triglycerides are below their melting point the
mixture
is solid and consists of a network of minutes crystals surrounded by a smaller
quantity of liquid triglyceride. The solid network is not rigid, however, and
the crystals can slide over one another so given rise to the plastic character
of the fat. (Brain and Cameroon. 1882).
If the temperature of the fat is raised an increasing
proportion of trigylcerides melt, the solid network gradually breakdown and the
plasticity of the mixture increase until it become liquid when all the
triglycerides have melted. The melting point of fat is also affected by the
fact that many triglycerides exist in several crystalling forms that is they
are polymorphic. Each crystalline form has its own melting point and when oils
are cooled, mixture of different crystalline form, and therefore, different
melting point, ma be obtained depending upon how the cooling was carried out.
The way
in which oil is cooled therefore affects the texture and consistency of the product formed. Such considerations are important in commercial methods of fat manufacture.
in which oil is cooled therefore affects the texture and consistency of the product formed. Such considerations are important in commercial methods of fat manufacture.
Chemical
Properties
Tallow includes 70% of carbon, the remaining third is
made up of 11% hydrogen and 19% oxygen. A kilogram of tallow can produce 40,000
calories of energy. However, the temperature needs to be high enough to
actually convert the material to a usable form. Tallow burns at a heat range of
288 — 316 degree Celsius (288-3160°C). So an average cow, when slaughtered
produces between 15kg to 115kg of tallow, depending on how the meat on the cow
is cut. In consistency terms, tallow keeps a solid form a room temperature but
it does need to remain sealed. If not, the tallow eventually rots due to
oxidation, similar to other biological material.