Vegetable oil has a
great role in day to day life; it’s been used for cooking, cosmetics and many
other industrial purposes. Quality of these oils is a big concern because oils
can be easily adulterated with other similar cheap oils. Some of these
vegetable oils like olive oil are very expensive in the market so the
fraudsters try to adulterate these oils and sell in the market. The vegetable oils
include olive oil, coconut oil, mustard oil, sesame oil, palm oil, canola oil,
sunflower oil etc. The analysis of the purity of these oils is important
because many of these oils are not pure in the market.
The adulterated oils
has great health impact in some consumers all these depends upon the adulterant
added; for instance the adulterant added in mustard oil like argemone oil has
great impact on human health .
Argemone oil is
extracted from the seeds of Argemone mexicana which
contains toxic alkaloids and appearance is similar to that of mustard oil.
Consumption of adulterated vegetable oil with Argemone oil leads to poisoning
called Epidemic dropsy. Similarly olive oil which is adulterated with hazelnut oil
has allergic effects in consumers. Many adulterated vegetable has health
impacts on the consumers. Among all adulterant Argemone oil has severe impact.
The poisoning by Argemone oil can lead to Epidemic dropsy; it is a form of
edema which leads to fever, muscle pain, cough and breathlessness, swelling of
liver, erythema, glaucoma in some case and even cardiac failure can happen.
oils like coconut oil are adulterated with cheap palm kernel oil, olive oil is
adulterated with sunflower oil or low graded olive oil. Similarity of the
appearance makes them vulnerable to adulteration. In order to analyze the
purity many analytical methods have been used like high performance liquid
chromatography, gas chromatography and electro analytical techniques but the issue
in using this methods are they have
drawbacks like it can be time consuming ,expensive ,some techniques may require additional training,
portability etc. In order to overcome this various optical spectroscopy methods
are used for analysis..
et.al reported that the purity of adulterated essential oil has been analyzed
by FT-IR and partial least square regression method. They have used partial
least square regression method for the accurate percent composition of the
essential oils. Using FT-IR spectroscopy they have observed and correlated the
change in FT-IR spectra of different oil samples with adulteration.
Kongbonga et.al had characterized vegetable oils by
fluorescence spectroscopy and studied the properties of vegetable oil using
cheap material and no sample preparation. The distinction between unrefined and
refined has studied and also the adulteration in oil sample where noted by
comparing and studying the fluorescence spectra obtained.
Jiménez-Sanchidrián et.al had analyzed vegetable oils using
Raman spectroscopy .They have showed the determination of degree of
unsaturation of oil samples and
detection of adulterants in the oil samples. Finally determination of minor
components of vegetable oils using Raman spectroscopy.
Williams et.al has
analyzed the free fatty acid present in the oil by Gas
chromatography, here gas liquid chromatography is used.It yield good amount of
free fatty acids from the oil samples. This method is highly sensitive, simple
gives quantitative results for every fatty acids and also the measure of total
free fatty acids present.
analysis of adulterated vegetable oils by optical spectroscopy.
To measure the
fluorescence signals from various brands of vegetable oils.
.To measure the chemical
composition of vegetable oil using Raman and Fourier transform infrared.
Extract and analysis the free
fatty acid content in the vegetable oils.
Statistical analysis of
results using principle component analysis.
Different vegetable oil
samples like olive oil, coconut oil, sunflower oil, mustard oil, sesame oil,
palm oil, canola oil etc. will be collected from local markets.
Raman, Fluorescence, Fourier
transform infrared, infrared spectroscopies
It is a
type of spectroscopy where it analyzes fluorescence signal in a sample. It can
be used to estimate the concentration of fluorophore in the solution. This method is quite useful for the analysis
of the purity. In this spectroscopy, a beam with wavelength varying between
280-800nm is passed through the solution which is to be analyzed. The light
emitted by the sample from an angle is measured here both excitation spectrum
and emission spectrum can be measured.
intensity of the spectrum depends on the excitation wavelength, self-absorption
of the sample and concentration of fluorophore in the sample. It depends upon
the vibrational and electronic state. In fluorescence spectroscopy the sample
is excited by absorbing a photon from the lowest energy state to various
vibrational states in the excited electronic state. The molecule drops to the
ground state by emitting a photon. The detection wavelength varies according to
the fixed excitation wavelength.
It is a
spectroscopy which is used mainly to observe rotational, vibrational and other
low frequencies. Raman spectroscopy depends on the inelastic scattering of monochromatic
light. In Raman spectroscopy by showing intensity of the exiting radiation for
each frequency spectrum is produced for different frequency of radiation. This
spectrum can correlate which frequency of radiation have absorbed by the
molecule in order rise to higher vibrational energy level.
used to get infrared spectrum of emission or absorption it is a sensitive
technique can be used for identifying organic chemicals .This can be used to
measure intensities over a narrow range of wavelength. This method has more
advantage than the dispersive spectroscopy method. The chemical characteristics
of the samples can be analyzed. In FT-IR spectroscopy it can beam light
containing many frequencies and can measure how much light is absorbed, it is
easy and fast method. The instrumentation for FT-IR contains Infrared light
source, detectors and beam splitter, attenuated total reflectance.
It is a statistical
method that helps in transforming a number of associated variables into a
number of unassociated variables known as principle component. PCA reduces
attribute space, it is basically
dimensionality reduction method or say data compression method. PCA will be used
for the analysis of the spectral data. It is used often when various
explanatory variables are present in the analysis that may correlate with one
another .PCA allows to identify the component of the dataset that has maximum
variance making a standard linear model.
method is used for the analysis of the fatty acid present in the oil samples.
It is used in splitting and analyzing samples that can be vaporized without
decomposition. Here gas liquid chromatography (GLC) is used. In GLC the
stationary phase is a low volatile liquid whereas the mobile phase is a
suitable gas. It is chemical analysis method where it separate chemicals in a
complex sample, in this method a known amount of liquid or gas analyte is administrated
into the entrance of the column and let them pass through the carrier gas.
Carrier gas. The rate of the molecule move along the column varies upon the
strength of adsorption of the sample molecules and it relies upon the sort of
molecule present in the stationary phase. Detectors are used to evaluate the
outlet of the column, the rate of flow through the column is studied.