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Code and Title of the Paper: F03FP Food Preservation
Code and title of the Module: F03FP09 Essential Oil Antioxidant ad antimicrobial agents in
Food Preservation
Name of the Content Writer: Mrs. R. Sinthiya
F03FP10 - ESSENTIAL OIL, ANTIOXIDANTS AND ANTI MICROBIAL AGENTS IN FOOD
PRESERVATION
INTRODUCTION:
Essential oils are valuable natural products used as raw materials in many fields such as
perfumes, cosmetics, aromatherapy, spices and nutrition. There is an increasing worldwide attempt to
screen plants for studying the biological activities of their oils from chemical and pharmacological
investigations to therapeutic aspects. Although, there are some synthetic antioxidant compounds, such
as butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA) and ascorbic acid, which are
commonly used in processed foods, it has been showed that these compounds have some side effects.
Therefore, research on the identification of the natural sources of antioxidants and antioxidant
potentials of plants is important.
Objectives
After going through this session you will be able to
1. Importance of essential oils in food preservation, Antimicrobial activity of essential oil
2. Effect of essential oil on bacterial wall, Role of antioxidants in food preservation
10.1ESSENTIAL OIL:
Essential oils (EOs) are liquid mixtures of volatile compounds obtained from aromatic plants.
Many EOs have antioxidant properties, and the use of EOs as natural antioxidants is a field of growing
interest because some synthetic antioxidants such as BHA and BHT are now suspected to be
potentially harmful to human health. Addition of EOs to edible products, either by direct mixing or in
active packaging and edible coatings, may therefore represent a valid alternative to prevent
autoxidation and prolong shelf life.
10.2 Sources of natural essential oil
Essential oils are normally obtained from one or more plant parts, such as flowers (e.g. rose, jasmine,
carnation, clove, mimosa, rosemary, lavander), leaves (e.g. mint, Ocimum spp.,lemongrass, jamrosa),
leaves and stems (e.g. geranium, patchouli, petitgrain, verbena, cinnamon), bark (e.g. cinnamon, cassia,
canella), wood (e.g. cedar, sandal, pine), roots (e.g. angelica, sassafras, vetiver, saussurea, valerian),
Code and Title of the Paper: F03FP Food Preservation
Code and title of the Module: F03FP09 Essential Oil Antioxidant ad antimicrobial agents in
Food Preservation
Name of the Content Writer: Mrs. R. Sinthiya
seeds (e.g fennel, coriander, caraway, dill,nutmeg), fruits (bergamot, orange, lemon, juniper), rhizomes
(e.g. ginger, calamus, curcuma, orris) and gums or oleoresin exudations (e.g. balsam of Peru, Myroxylon
balsamum, storax, myrrh, benzoin).
10.3 COMPOSITION OF ESSENTIAL OILS:
Essentials oils are mostly derived from spices and herbs but can also be isolated from fruits,
roots and stems of plants. Some oils and isolated plant compounds are used in food as flavoring
agents. Derived from their functionality in plants, these compounds show a wide range of interesting
biological activities. The antimicrobial activities of extract obtained from spices, herbs and other
aromatic plants or parts thereof using organic solvents or steam distillation have been used since
antiquity in folk medicine and food preservation, providing a range of compounds possessing
pharmacological activities. Most commonly, the active antimicrobial compounds are found in the
essential oil fraction. With many herbs and spices, these compounds contribute to the characteristic
aroma and flavor. Essential oils are mostly soluble in alcohol and to a limited extent in water. They
consist of mixtures of esters, aldehydes, ketones and terpenes. Essential oil components with a wide
spectrum of antimicrobial effect include thymol from thyme and oregano, cinnamaldehyde from
cinnamon, and eugenol from clove.
10.4 ESSENTIAL OILS IN FOOD PRESERVATION:
Food-borne diseases are a rising issue worldwide. It is expected that each year in the United
States, 31 species of pathogens cause 9.4 million cases of food-borne illness. Successful control of
food-borne pathogens requires the use of multiple preservation techniques in the manufacturing and
storage of food products. A recent consumer trend toward preference for products with lower salt and
sugar content presents an increased need for efficient food preservatives, as lowering the salt and
sugar content would otherwise compromise the product’s shelf-life. A wide range of preservatives are
used to extend the shelf-life of a product by inhibiting microbial growth. However, an ever more
unconstructive consumer view of synthetic food additives has encourage an interest in finding natural
option to the traditional solutions. The antimicrobial activity of essential oils makes them an choice for
replacement of synthetic preservatives.
In total, twenty-three compounds were identified in the essential oils, including ten terpenes,
(Fig-1) six alcohols, two ketones and five other compounds. Generally, three essential oils showed
Code and Title of the Paper: F03FP Food Preservation
Code and title of the Module: F03FP09 Essential Oil Antioxidant ad antimicrobial agents in
Food Preservation
Name of the Content Writer: Mrs. R. Sinthiya
similar profiles in chemical composition but different contents. The major compounds in the essential
oils were curcumol (35.77%) and 1,8-cineole (12.22%) for C. aromatica, ar-turmerone (49.04%),
humulene oxide (16.59%) and -selinene (10.18%) for C. longa, and ar-turmerone (43.52%), -selinene
(13.36%) and -cadinene (13.22%) for C. sichuanensis. Terpenes accounted for 16.06 - 35.78% of the
three essential oils. Alcohols (51.58%) were predominantly present in the essential oil of C. aromatica
whereas ketones were relatively higher in the essential oils of C. longa and C. sichuanensis (49.13 and
43.60%, respectively).
10.5 Methods of obtaining volatile oils
The method of obtaining volatile oils depends upon the condition of plant materials.
Oil production can be divided into three major ways
i. Distillation
ii. Solvent extraction
iii. Mechanical expression
Specialized methods are:
i. Ecuelle Method
ii. Enfleurage
iii. Destructive distillation
i) Distillation
Three types of distillation are used
a. Water distillation
b. Water and steam distillation
c. Direct steam distillation
a. Water distillation
It is applied to plant material that is dried and is not destroyed by boiling. Turpentine oil is obtained by
this method. The crude turpentine oleoresin is introduced into the distilling chamber. It is subjected to
heat until all volatile matter, both oil and water, is condensed in the condensing chamber. Turpentine oil
is not affected by this amount of heat.
Code and Title of the Paper: F03FP Food Preservation
Code and title of the Module: F03FP09 Essential Oil Antioxidant ad antimicrobial agents in
Food Preservation
Name of the Content Writer: Mrs. R. Sinthiya
b. Water and steam distillation
It is applied to plant material that may be dried or fresh and can be destroyed by boiling. In case of dried
material e.g. cinnamon or clove, the drug is ground. It is then covered with a layer of water. Steam is
passed through the macerated mixture. As the oil can be damaged by direct boiling; therefore, steam is
generated elsewhere and is conveyed into the container that keeps the drug. Oily layer of condensed
distillate is separated from the aqueous layer. The oil is then marketed with or without further
processing.
c. Direct steam distillation
It is applied to plant material that is fresh e.g. peppermint or spearmint. The plant is cut and is placed
directly into a metal distilling tank on a truck bed. The truck is moved to a distilling shed, where steam
lines are attached to the bottom of the distilling tank. The plant material is still green and contains
natural moisture; therefore, maceration is not needed. Steam is passed through the fresh herb and
carries the oil droplets through a vapor pipe that is attached to condensing chamber. During steam
distillation, some components of a volatile oil are hydrolyzed while the other are decomposed due to
high temperatures.
ii) Solvent extraction
Solvent extraction is either carried out by using various solvents or fats. It can be classified into three types.
a. Absolute Solvent extraction
b. Supercritical fluid extraction
a. Absolute Solvent extraction
It is usually carried out for the extraction of volatile oil from rose flowers etc.The flowers are agitated in a
vat with a solvent such as hexane.This solvents takes out the aromatic compounds as well as other soluble
substances.The extract is then exposed to vacuum processing which removes the solvent for re-use.The
remaining waxy mass is known as concrete.The concrete is then mixed with alcohol which dissolves the
aromatic constituents and leaves behind the other substances.The alcohol is evaporated leaving behind the
absolute.The absolute may be further processed to remove any impurity left.
b. Supercritical fluid extraction
It is the process of separating one component (the extractant) from another (matrix) using supercritical fluids as
the extracting solvents. The system must contain a pump for CO2, a pressure cell that contains the sample, a
mean of maintaining pressure in the system and a collecting vessel.The liquid is pumped to heated zone,
where it is heated to supercritical conditions. It is then passed into extraction vessel. Here it diffuses into the
solid matrix and dissolves the material to be extracted.The dissolved material is taken out from extraction
vessel into a separator at low pressure.The extracted material then settles out.
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