Oil of oil. Keywords: edible oil, extraction methods,

Oil was
extracted from plant source using conventional extraction methods like soxhlet
extraction, reflux extraction and non-conventional extraction methods like
ultrasound-assisted extraction (UAE), microwave-assisted extraction (MAE),
supercritical fluid extraction (SFE).
The conventional methods were compared with novel extraction methods based on numerous
parameters such as extraction times, consumption of organic solvents, and
extraction yield. The non-conventional methods were superior to conventional
methods because they need less time, consume less solvent, and produce more
yield. Many methods can be used to measure thermal as well as the oxidative
stability of plant oil. The oxidative stability of plant oil was studied using
classic methods such as active oxygen method (AOM), oxygen stability index
(OSI), rancimat method based on conductometric measurements and
thermoanalytical methods like differential scanning calorimetry (DSC) and
thermogravimetry (TG). The onset temperature Tonset DSC and Tonset
TG can be measured from dynamic DSC and TG curves, respectively. Rancimat
technique is used to assess the influence of synthetic as well as natural
antioxidants in the oxidative stability. Schaal test can be  used to evaluate the thermal stability of oil.

 

Keywords: edible
oil, extraction methods, oxidative analysis, thermal analysis.

 

INTRODUCTION

Plant
oil is a prime source of raw materials like fat, carbohydrate, protein with
possible application in nutraceuticals as well as functional foods. Essential
fatty acids (EFAs) are macronutrients that are essential for the human body as
it can’t be produced and hence must be acquired from dietary source and
nutritional supplements. It is of two types: ?-3 series and ?-6 series. Omega-3
fatty acids are polyunsaturated fatty acids (PUFAs) with a double bond (C=C) at
the third carbon atom from the end of the carbon chain. Omega-3 fatty acids
which are involved in human physiology are of three types: ?-linolenic acid
(ALA) is widely distributed in plant oils, eicosapentaenoic acid (EPA), and
docohexaenoic acid (DHA) both generally found in marine oils. One of the most
important ?-3 fatty acids is ?-linolenic acid (ALA). ALA is one of the essential
fatty acids and is found in seeds (chia, flaxseed, hemp), nuts and many
vegetable oils. Omega-3 fatty acids (ALA) have been reported to show a
protective effect and even maximize the effect in the treatment of various
diseases. Due to their anti-carcinogenic, glucose metabolism controlling effect
and anti-hypercolesterolemic, this component help prevents or minimize the risk
of a variety of diseases including diabetes, lupus nephritis, hormone-dependent
type of cancer, cardiovascular diseases, eczema, and Sjogren’s syndrome. Thus
it is crucial for maintaining the overall body’s health. Intake of sufficient
amount of ALA is important in daily life (2.22g/day). 19

Fatty
acid of oils obtained from plants is usually classified as saturated and
unsaturated fatty acid. Unsaturated fatty acid includes oleic, linoleic acid,
EPA, DHA and their content is always high as compared to saturated fatty acids.
In Sunflower oil, unsaturated
fatty acid content is >90%. 2, poppy and safflower oil have a high content
of linoleic acid (omega-6) 74.5% and 70.5% respectively 14.  A Major component of flax oil and
camelina oil is ALA containing 45-58.3% and 35-36% of total fatty acid,
respectively.3,14

 

Oils
are extracted from plant source in a variety of ways: ultrasound-assisted
extraction, microwave-assisted extraction, supercritical fluid extraction, and
conventional extraction (maceration, solvent extraction, reflux extraction, press
extraction).

FOOD OILS

SERVING SIZE

KCALS

OMEGA-3

Canola oil

1 tbsp.

124

1302

Perilla oil

1 tbsp.

120

8960

Flaxseed oil

1 tbsp.

120

7980

Mustard oil

1 tbsp.

124

826

Walnut oil

1 tbsp.

120

1414

Soybean oil

1 tbsp.

120

925

Sunflower oil

1 tbsp.

124

27

Peanut oil

1 tbsp.

119

0

Coconut oil

1 tbsp.

117

0

Grapeseed oil

1 tbsp.

120

14

Cottonseed oil

1 tbsp.

120

27

Olive oil

1 tbsp.

119

81

 

Edible oils can
undergo lipid oxidation leading to the rancidity of the products. It is a
severe problem in the food industry. Plant oil that have a high concentration
of ALA is highly susceptible to oxidation,
leading to rapid deterioration of quality. It must be stored in an amber
colored bottle. According to ICH, Stability
testing is to provide indication on how the quality of a substance or a product
varies with time under the influence of a variety of environmental factors such
as temperature, humidity, light, and storage etc., set to establish a retest
period and to promote their shelf life, to optimize the product storage
conditions stability indicating study is a promising tool. Historically, classic
methods for determining oxidative stability of oils in the edible oil industry
are active oxygen method (AOM) or swift method and Schaal test. The stability
of oils and fats can be assessed by various accelerated stability tests.
Maximum of the accelerated tests are aimed to accelerate the oxidation process
by exposing the oil samples to high temperature in the presence of surplus
quantity of air or oxygen. Presently, oxidative stability of oils and fats can
be measured by rancimat and oxidative stability instrument (OSI). A method for determining the thermal
stability of oil is differential scanning calorimeter (DSC). Currently, thermoanalytical
methods are used for the characterization of fats and oils along with the
investigation of their thermal auto-oxidation process. DSC provides unique
profile information which specifically measures the temperatures and heat flows
associated with material transitions as a function of time and temperature.

Isolation
and purification methods are used to acquire fractions which are rich in
unsaturated fatty acid from plant seed oil. It generally depends on the
difference in polarity and/or geometrical configuration of fatty acids present
in the extract. These differences are usually correlated with the number of
double bonds in the carbon chain. Fatty acids can be separated on the basis of the
degree of unsaturation.

Precise
determination and quantification of ALA can be achieved by using several
analytical techniques in which most are based on gas chromatography (GC) and
few on high performances liquid chromatography (HPLC). HPLC can be coupled with
numerous detection methods such as refractive index (RI), fluorescence (FD),
mass spectroscopy (MS), flame ionization detector (FID), evaporative light
scattering (ELSD), electrochemical detection and UV being most frequently used.