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Extraction And Characterization Of Vegetable Oil Using Bread Fruit Seed
CHAPTER ONE -- [Total Page(s) 5]
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1.4 Negative health effects
Hydrogenated oils have been shown to
cause what is commonly termed the "double deadly effect", raising the
level of low density lipoproteins (LDLs) and decreasing the level of
high density lipoproteins (HDLs) in the blood, increasing the risk of
blood clotting inside blood vessels.
A high consumption of omega-6
polyunsaturated fatty acids (PUFAs), which are found in most types of
vegetable oil (e.g. soyabean oil, corn oil– the most consumed in USA,
sunflower oil, etc.) may increase the likelihood that postmenopausal
women will develop breast cancer. A similar effect was observed on
prostate cancer in mice. Plant based oils high in monounsaturated fatty
acids, such as olive oil, peanut oil, and canola oil are relatively low
in omega-6 PUFAs and can be used in place of high-polyunsaturated oils.
1.5 Uses/Importance of Vegetable oils
1.5.1 Margarine
Margarine
originated with the discovery by French chemist Michel Eugene Chereul
in 1813 of margaric acid (itself named after the pearly deposits of the
fatty acid from Greek (margaritēs / márgaron), meaning pearl-oyster or
pearl, or (margarÃs), meaning palm-tree, hence the relevance to palmitic
acid). Scientists at the time regarded margaric acid, like oleic acid
and stearic acid, as one of the three fatty acids which, in combination,
formed most animal fats. In 1853, the German structural chemist Wihelm
Heinrich Heintz analyzed margaric acid as simply a combination of
stearic acid and of the previously unknown palmitic acid.
Emperor
Louis Napoleon III of France offered a prize to anyone who could make a
satisfactory substitute for butter, suitable for use by the armed forces
and the lower classes. French chemist Hippolyte Mege-Mouries invented a
substance he called oleomargarine, the name of which became shortened
to the trade name "margarine". Mège-Mouriès patented the concept in 1869
and expanded his initial manufacturing operation from France but had
little commercial success. In 1871, he sold the patent to the Dutch
company Jurgens, now part of Unilever. In the same year the German
pharmacist Benedict Klein from Cologne founded the first margarine
factory "Benedict Klein Margarinewerke", producing the brands Overstolz
and Botteram.
Margarine is a semi-solid emulsion composed mainly of
vegetable fats and water. While butter is derived from milk fat,
margarine is mainly derived from plant oils and fats and may contain
some skimmed milk. In some locales it is colloquially referred to as
oleo, short for oleomargarine. Margarine, like butter, consists of a
water-in-fat emulsion, with tiny droplets of water dispersed uniformly
throughout a fat phase which is in a stable crystalline form. Margarine
has a minimum fat content of 80%, the same as butter, but unlike butter
reduced-fat varieties of margarine can also be labelled as margarine.
Margarine can be used both for spreading or for baking and cooking. It
is also commonly used as an ingredient in other food products, such as
pastries and cookies, for its wide range of functionalities.
1.5.1.2 Manufacture of Margarine
The
basic method of making margarine today consists of emulsifying a blend
of hydrogenated vegetable oils with skimmed milk, chilling the mixture
to solidify it and working it to improve the texture. Vegetable and
animal fats are similar compounds with different melting points. Those
fats that are liquid at room temperature are generally known as oils.
The melting points are related to the presence of carbon-carbon double
bonds in the fatty acids components. Higher number of double bonds give
lower melting points.
Partial hydrogenation of a typical plant oil to
a typical component of margarine, makes most of the C=C double bonds be
removed in this process, which elevates the melting point of the
product. Commonly, the natural oils are hydrogenated by passing hydrogen
through the oil in the presence of a nickel catalyst, under controlled
conditions. The addition of hydrogen to the unsaturated bonds (alkenic
double C=C bonds) results in saturated C-C bonds, effectively increasing
the melting point of the oil and thus "hardening" it. This is due to
the increase in van der Waals' forces between the saturated molecules
compared with the unsaturated molecules. However, as there are possible
health benefits in limiting the amount of saturated fats in the human
diet, the process is controlled so that only enough of the bonds are
hydrogenated to give the required texture. Margarines manufactured in
this way are said to contain hydrogenated fat. This method is used today
for some margarines although the process has been developed and
sometimes other metal catalysts are used such as palladium. If
hydrogenation is incomplete (partial hardening), the relatively high
temperatures used in the hydrogenation process tend to flip some of the
carbon-carbon double bonds into the "trans" form. If these particular
bonds aren't hydrogenated during the process, they will still be present
in the final margarine in molecules of trans fats, the consumption of
which has been shown to be a risk factor for cardiovascular disease. For
this reason, partially hardened fats are used less and less in the
margarine industry. Some tropical oils, such as palm oil and coconut
oil, are naturally semi solid and do not require hydrogenation.
Three types of margarine are common:
•
Soft vegetable fat spreads, high in mono- or polyunsaturated fats,
which are made from safflower, sunflower, soybean, cottonseed, rapeseed
or olive oil.
• Margarines in bottle to cook or top dishes
• Hard, generally uncolored margarine for cooking or baking.
1.5.2 Soap
In
chemistry, soap is a salt of a fatty acid. Soaps are mainly used as
surfactants for washing, bathing, cleaning, in textile spinning and are
important components of lubricants. Soaps for cleansing are obtained by
treating vegetable or animal oils and fats with a strongly alkaline
solution. Fats and oils are composed of triglycerides; three molecules
of fatty acids are attached to a single molecule of glycerol. The
alkaline solution, which is often called lye, (although the term "lye
soap" refers almost exclusively to soaps made with sodium hydroxide)
brings about a chemical reaction known as saponification. In
saponification, the fats are first hydrolyzed into free fatty acids,
which then combine with the alkali to form crude soap. Glycerol
(glycerin) is liberated and is either left in or washed out and
recovered as a useful byproduct, depending on the process employed.
When
used for cleaning, soap allows otherwise insoluble particles to become
soluble in water and then be rinsed away. For example: oil/fat is
insoluble in water, but when a couple drops of dish soap are added to
the mixture the oil/fat apparently disappears. The insoluble oil/fat
molecules become associated inside micelles, tiny spheres formed from
soap molecules with polar hydrophilic (water-loving) groups on the
outside and encasing a lipophilic (fat-loving) pocket, which shielded
the oil/fat molecules from the water making it soluble. Anything that is
soluble will be washed away with the water. Synthetic detergents
operate by similar mechanisms to soap.
The type of alkali metal used
determines the kind of soap produced. Sodium soaps, prepared from
sodium hydroxide, are firm, whereas potassium soaps, derived from
potassium hydroxide, are softer or often liquid. Historically, potassium
hydroxide was extracted from the ashes of bracken or other plants.
Lithium soaps also tend to be hard these are used exclusively in
greases.
Typical vegetable oils used in soap making are palm oil,
coconut oil, olive oil, and laurel oil. Each species offers quite
different fatty acid content and, hence, results in soaps of distinct
feel. The seed oils give softer but milder soaps. Soap made from pure
olive oil is sometimes called Castile/Marseille soap, and is reputed for
being extra mild. The term "Castile" is also sometimes applied to soaps
from a mixture of oils, but a high percentage of olive oil.
1.5.2.1 Purification and finishing
In
the fully boiled process on factory scale, the soap is further purified
to remove any excess sodium hydroxide, glycerol, and other impurities,
colour compounds, etc. These components are removed by boiling the crude
soap curds in water and then precipitating the soap with salt. At this
stage, the soap still contains too much water, which has to be removed.
This was traditionally done on chill rolls, which produced the soap
flakes commonly used in the 1940s and 1950s. This process was superseded
by spray dryers and then by vacuum dryers. The dry soap (about 6–12%
moisture) is then compacted into small pellets or noodles. These pellets
or noodles are then ready for soap finishing, the process of converting
raw soap pellets into a saleable product, usually bars.
Soap
pellets are combined with fragrances and other materials and blended to
homogeneity in an amalgamator (mixer). The mass is then discharged from
the mixer into a refiner, which, by means of an auger, forces the soap
through a fine wire screen. From the refiner, the soap passes over a
roller mill (French milling or hard milling) in a manner similar to
calendering paper or plastic or to making chocolate liquor. The soap is
then passed through one or more additional refiners to further
plasticize the soap mass. Immediately before extrusion, the mass is
passed through a vacuum chamber to remove any trapped air. It is then
extruded into a long log or blank, cut to convenient lengths, passed
through a metal detector, and then stamped into shape in refrigerated
tools. The pressed bars are packaged in many ways.
Sand or pumice
may be added to produce a scouring soap. The scouring agents serve to
remove dead cells from the skin surface being cleaned. This process is
called exfoliation. Many newer materials that are effective, yet do not
have the sharp edges and poor particle size distribution of pumice, are
used for exfoliating soaps.
Nanoscopic metals are commonly added to
certain soaps specifically for both colouration and antibacterial
properties. Titanium dioxide powder is commonly used in extreme "white"
soaps for these purposes; nickel, aluminium and silver compounds are
less commonly used. These metals exhibit an electron-robbing behaviour
when in contact with bacteria, stripping electrons from the organism's
surface, thereby disrupting their functioning and killing them. Since
some of the metal is left behind on the skin and in the pores, the
benefit can also extend beyond the actual time of washing, helping
reduce bacterial contamination and reducing potential odours from
bacteria on the skin surface.
1.5.3 Biodiesel production
Biodiesel
production is the process of producing the biofuel/biodiesel, through
the chemical reactions: transesterification and esterification. This
involves vegetable or animal fats and oils being reacted with
short-chain alcohols (typically methanol or ethanol). The major steps
required to synthesize biodiesel are as follows:
1. Feedstock
pretreatment: Common feedstock used in biodiesel production include
yellow grease (recycled vegetable oil), "virgin" vegetable oil, and
tallow. Recycled oil is processed to remove impurities from cooking,
storage, and handling, such as dirt, charred food, and water. Virgin
oils are refined, but not to a food-grade level. De-gumming to remove
phospholipids and other plant matter is common, though refinement
processes vary. Regardless of the feedstock, water is removed as its
presence during base-catalyzed transesterification causes the
triglycerides to hydrolyse, giving salts of the fatty acids (soaps)
instead of producing biodiesel.
2. Determination and treatment of
free fatty acids: A sample of the cleaned feedstock oil is titrated with
a standardized base solution in order to determine the concentration of
free fatty acids (carboxylic acids) present in the vegetable oil
sample. These acids are then either esterified into biodiesel,
esterified into glycerides, or removed, typically through
neutralization.
3. Reactions: Base-catalyzed transesterification
reacts lipids (fats and oils) with alcohol (typically methanol or
ethanol) to produce biodiesel and an impure co-product, glycerol. If the
feedstock oil is used or has a high acid content, acid-catalyzed
esterification can be used to react fatty acids with alcohol to produce
biodiesel. Other methods, such as fixed-bed reactors, supercritical
reactors, and ultrasonic reactors, forgo or decrease the use of chemical
catalysts.
4. Product purification: Products of the reaction
include not only biodiesel, but also byproducts, soap, glycerol, excess
alcohol, and trace amounts of water. All of these byproducts must be
removed to meet the standards, but the order of removal is
process-dependent. The density of glycerol is greater than that of
biodiesel, and this property difference is exploited to separate the
bulk of the glycerol co-product. Residual methanol is typically
recovered by distillation and reused. Soaps can be removed or converted
into acids. Residual water is also removed from the fuel.
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