Date post: | 30-Oct-2014 |
Category: |
Documents |
Upload: | awilda-mike-pertiwi |
View: | 53 times |
Download: | 0 times |
ARTIKEL KIMIA ORGANIK I
Essential Oil ( Minyak Atsiri)
Oleh:
AWILDA MIKE PERTIWI
1120006
I A
KIMIA ANALISIS
AKADEMI TEKNOLOGI INDUSTRI PADANG
PADANG
2012Essential oil
An essential oil is a concentrated hydrophobic liquid containing volatile aroma compounds from plants.
Essential oils are also known as volatile oils, ethereal oils or aetherolea, or simply as the "oil of" the
plant from which they were extracted, such as oil of clove. An oil is "essential" in the sense that it
carries a distinctive scent, or essence, of the plant. Essential oils do not form a distinctive category for
any medical, pharmacological, or culinary purpose.
Essential oils are generally extracted by distillation. Other processes include expression, or solvent
extraction. They are used in perfumes, cosmetics, soaps and other products, for flavoring food and
drink, and for adding scents to incense and household cleaning products.
Various essential oils have been used medicinally at different periods in history. Medical applications
proposed by those who sell medicinal oils range from skin treatments to remedies for cancer, and often
are based solely on historical accounts of use of essential oils for these purposes. Claims for the
efficacy of medical treatments and treatment of cancers in particular, are now subject to regulation in
most countries.
As the use of essential oils has declined in evidence-based medicine, one must consult older textbooks
for much information on their use. Modern works are less inclined to generalize; rather than refer to
"essential oils" as a class at all, they prefer to discuss specific compounds, such as methyl salicylate,
rather than "oil of wintergreen".
Interest in essential oils has revived in recent decades with the popularity of aromatherapy, a branch of
alternative medicine that claims that essential oils and other aromatic compounds have curative effects.
Oils are volatilized or diluted in a carrier oil and used in massage, diffused in the air by a nebulizer,
heated over a candle flame, or burned as incense.
Characteristic of essential oil
Essential oils are volatile due to low vapor point. In addition, the arrangement of its component
compounds strongly affects the human nervous (especially in the nose) so it is often a certain
psychological effect (strong smell). Each constituent has the effect of individual compounds, and
mixtures can produce different flavors.
Chemically, essential oils are composed of a complex mixture of various compounds, but a particular
compound is usually responsible for a particular scent. Most of the Essential Oils in a class of organic
compounds including terpenes and terpenoids which are soluble in oil / lipophilic.
Production
Distillation
Today, most common essential oils, such as lavender, peppermint, and eucalyptus, are distilled. Raw
plant material, consisting of the flowers, leaves, wood, bark, roots, seeds, or peel, is put into an alembic
(distillation apparatus) over water. As the water is heated, the steam passes through the plant material,
vaporizing the volatile compounds. The vapors flow through a coil, where they condense back to liquid,
which is then collected in the receiving vessel.
Most oils are distilled in a single process. One exception is ylang-ylang (Cananga odorata), which takes
22 hours to complete through a fractional distillation.
The recondensed water is referred to as a hydrosol, hydrolat, herbal distillate or plant water essence,
which may be sold as another fragrant product. Popular hydrosols include rose water, lavender water,
lemon balm, clary sage and orange blossom water. The use of herbal distillates in cosmetics is
increasing. Some plant hydrosols have unpleasant smells and are therefore not sold.
Expression
Most citrus peel oils are expressed mechanically, or cold pressed (similar to olive oil extraction). Due to
the relatively large quantities of oil in citrus peel and low cost to grow and harvest the raw materials,
citrus-fruit oils are cheaper than most other essential oils. Lemon or sweet orange oils that are obtained
as byproducts of the citrus industry are even cheaper.
Prior to the discovery of distillation, all essential oils were extracted by pressing.
Solvent extraction
Most flowers contain too little volatile oil to undergo expression and their chemical components are too
delicate and easily denatured by the high heat used in steam distillation. Instead, a solvent such as
hexane or supercritical carbon dioxide is used to extract the oils. Extracts from hexane and other
hydrophobic solvent are called concretes, which are a mixture of essential oil, waxes, resins, and other
lipophilic (oil soluble) plant material.
Although highly fragrant, concretes contain large quantities of nonfragrant waxes and resins. Often,
another solvent, such as ethyl alcohol, which is more polar in nature, is used to extract the fragrant oil
from the concrete. The alcohol is removed by evaporation, leaving behind the absolute.
Supercritical carbon dioxide is used as a solvent in supercritical fluid extraction. This method has many
benefits including avoiding petrochemical residues in the product and the loss of some "top notes"
when steam distillation is used. It does not yield an absolute directly. The supercritical carbon dioxide
will extract both the waxes and the essential oils that make up the concrete. Subsequent processing
with liquid carbon dioxide, achieved in the same extractor by merely lowering the extraction
temperature, will separate the waxes from the essential oils. This lower temperature process prevents
the decomposition and denaturing of compounds. When the extraction is complete, the pressure is
reduced to ambient and the carbon dioxide reverts to a gas, leaving no residue. An animated
presentation describing the process is available for viewing.
Supercritical carbon dioxide is also used for making decaffeinated coffee. Although it uses the same
basic principles, it is a different process because of the difference in scale.
Usefulness of essential oils in the industry
Essential oil obtained from distillation or can be extracted by distillation. So that the extract can be used
for cosmetics, soaps, perfumes, food flavorings, add flavor to the household products and other
products. In the medical science of essential oils are used as medicine.
The main components of essential oils
Terpenes are a large and diverse class of organic compounds, produced by a variety of plants,
particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit
terpenes from their osmeteria. They are often strong smelling and thus may have had a protective
function.
They are the major components of resin, and of turpentine produced from resin. The name "terpene" is
derived from the word "turpentine". In addition to their roles as end-products in many organisms,
terpenes are major biosynthetic building blocks within nearly every living creature. Steroids, for
example, are derivatives of the triterpene squalene.
When terpenes are modified chemically, such as by oxidation or rearrangement of the carbon skeleton,
the resulting compounds are generally referred to as terpenoids. Some authors will use the term
terpene to include all terpenoids. Terpenoids are also known as isoprenoids.
Terpenes and terpenoids are the primary constituents of the essential oils of many types of plants and
flowers. Essential oils are used widely as natural flavor additives for food, as fragrances in perfumery,
and in traditional and alternative medicines such as aromatherapy. Synthetic variations and derivatives
of natural terpenes and terpenoids also greatly expand the variety of aromas used in perfumery and
flavors used in food additives. Vitamin A is an example of a terpene.
Terpenes are released by trees more actively in warmer weather, acting as a natural form of cloud
seeding. The clouds reflect sunlight, allowing the forest to regulate its temperature.
The aroma and flavor of hops, highly desirable in some beers, comes from terpenes. Of the terpenes in
hops myrcene, b-pinene, b-caryophyllene, and a-humulene are found in the largest quantities.
Types
Terpenes may be classified by the number of terpene units in the molecule; a prefix in the name
indicates the number of terpene units needed to assemble the molecule.
Hemiterpenes consist of a single isoprene unit. Isoprene itself is considered the only
hemiterpene, but oxygen-containing derivatives such as prenol and isovaleric acid are
hemiterpenoids.
Monoterpenes consist of two isoprene units and are derived from the molecular formula
C10H16. Examples of monoterpenes are: geraniol, limonene and terpineol.
Sesquiterpenes consist of three isoprene units and are derived from the molecular formula
C15H24. Examples of sesquiterpenes are: farnesenes, farnesol. (The sesqui- prefix means one
and a half.)
Diterpenes are composed of four isoprene units and have the molecular formula C20H32. They
derive from geranylgeranyl pyrophosphate. Examples of diterpenes are cafestol, kahweol,
cembrene and taxadiene (precursor of taxol). Diterpenes also form the basis for biologically
important compounds such as retinol, retinal, and phytol. They are known to be antimicrobial
and antiinflammatory.
Sesterterpenes, terpenes having 25 carbons and five isoprene units, are rare relative to the
other sizes. (The sester- prefix means half to three, i.e. two and a half.) An example of a
sesterterpene is geranylfarnesol.
Triterpenes consist of six isoprene units and are derived from the molecular formula C30H48.
The linear triterpene squalene, the major constituent of shark liver oil, is derived from the
reductive coupling of two molecules of farnesyl pyrophosphate. Squalene is then processed
biosynthetically to generate either lanosterol or cycloartenol, the structural precursors to all the
steroids.
Sesquarterpenes are composed of seven isoprene units and are derived from the molecular
formula C35H56. Sesquartepenes are typically microbial in their origin. Examples of
sesquarterpenes are ferrugicadiol and tetraprenylcurcumene.
Tetraterpenes contain eight isoprene units and are derived from the molecular formula C40H64.
Biologically important tetraterpenes include the acyclic lycopene, the monocyclic gamma-
carotene, and the bicyclic alpha- and beta-carotenes.
Polyterpenes consist of long chains of many isoprene units. Natural rubber consists of
polyisoprene in which the double bonds are cis. Some plants produce a polyisoprene with trans
double bonds, known as gutta-percha.
Kesimpulan :
Minyak Atsiri, atau dikenal juga sebagai Minyak Eteris (Aetheric Oil), Minyak Esensial, Minyak
Terbang, serta Minyak Aromatik, adalah kelompok besar minyak nabati yang berwujud cairan kental
pada suhu ruang namun mudah menguap sehingga memberikan aroma yang khas. Minyak Atsiri
merupakan bahan dasar dari wangi-wangian atau minyak gosok (untuk pengobatan) alami. Di dalam
perdagangan, sulingan Minyak Atsiri dikenal sebagai bibit minyak wangi.
Minyak Atsiri merupakan metabolit sekunder yang biasanya berperan sebagai alat pertahanan diri agar
tidak dimakan oleh hewan (hama) ataupun sebagai agen untuk bersaing dengan tumbuhan lain (lihat
alelopati) dalam mempertahankan ruang hidup. Walaupun hewan kadang-kadang juga mengeluarkan
bau-bauan (seperti kesturi dari beberapa musang atau cairan yang berbau menyengat dari beberapa
kepik), zat-zat itu tidak digolongkan sebagai Minyak Atsiri.
Minyak Atsiri merupakan suatu minyak yang mudah menguap (volatile oil) biasanya terdiri dari
senyawa organik yang bergugus alkohol, aldehid, keton dan berantai pendek. Minyak atsiri dapat
diperoleh dari penyulingan akar, batang, daun, bunga, maupun biji tumbuhan, selain itu diperoleh juga
terpen yang merupakan senyawaan hidrokarbon yang bersifat tidak larut dalam air dan tidak dapat
disabunkan. Beberapa contoh minyak atsiri yaitu minyak cengkeh, minyak sereh, minyak kayu putih,
minyak lawang dan lain-lain.
Ciri-ciri :
Minyak Atsiri bersifat mudah menguap karena titik uapnya rendah. Selain itu, susunan senyawa
komponennya kuat mempengaruhi saraf manusia (terutama di hidung) sehingga seringkali memberikan
efek psikologis tertentu (baunya yang kuat). Setiap senyawa penyusun memiliki efek tersendiri, dan
campurannya dapat menghasilkan rasa yang berbeda.
Secara kimiawi, minyak atsiri tersusun dari campuran yang rumit berbagai senyawa, namun suatu
senyawa tertentu biasanya bertanggung jawab atas suatu aroma tertentu. Sebagian besar Minyak
Atsiri termasuk dalam golongan senyawa organik terpena dan terpenoid yang bersifat larut dalam
minyak / lipofil.
Produksi Minyak Atsiri
1. Destilasi
Minyak atsiri yang berasal dari tumbuhan yang diambil bunga, biji, kulit kayu, akar dan daun yang
dimasukkan kedalam labu didih dari alat destilasi (satu set alat destilasi), kemudian ditambahkan
dengan pelarut dan dipanaskan. Setelah itu uap akan melewati bahan tanaman dan kemudian uap
menuju kondensor dan didinginkan hingga diperoleh destilat yang murni.
Destilat ini disebut juga dengan esensi tanaman yang memiliki bau yang harum, namun juga ada
yang tidak berbau enak atau busuk sehingga tidak bisa dijual.
2. Ekspresi
Sebelum adanya teknik destilasi maka untuk mendapatkan minyak atsiri dari tanaman dapat
digunakan dengan cara merendam dan menekan bahan sehingga didapatkan hasil pres-an. Namun
cara ini sepertinya tidak efektif karena akan memerlukan bahan yang banyak dan tenaga yang lebih
serta waktu yang lama. Cara ini juga tidak efektif karena hasil pres-an tidak terlalu murni.
Kedua cara inilah yang umum digunakan untuk mendapatkan minyak atsiri dari bahan-bahan yang
mengandung minyak tersebut.
Kegunaan minyak atsiri dalam industri
Minyak atsiri diperoleh dari penyulingan atau dapat diekstrak dengan cara destilasi. Sehingga hasil
ekstrak tersebut dapat digunakan untuk kosmetik, sabun, parfum, penyedap makanan, menambahkan
aroma pada produk-produk rumah tangga serta produk lainnya. Didalam ilmu medis minyak atsiri
digunakan sebagai obat
Komponen Utama Minyak atsiri
Terpena merupakan suatu golongan hidrokarbon yang banyak dihasilkan oleh tumbuhan dan terutama
terkandung pada getah dan vakuola selnya. Pada tumbuhan, senyawa-senyawa golongan terpena dan
modifikasinya, terpenoid, merupakan metabolit sekunder. Terpena dan terpenoid dihasilkan pula oleh
sejumlah hewan, terutama serangga dan beberapa hewan laut. Di samping sebagai metabolit
sekunder, terpena merupakan kerangka penyusun sejumlah senyawa penting bagi makhluk hidup.
Sebagai contoh, senyawa-senyawa steroid adalah turunan skualena, suatu triterpena; juga karoten dan
retinol. Nama "terpena" (terpene) diambil dari produk getah tusam, terpentin (turpentine).
Terpena dan terpenoid menyusun banyak minyak atsiri yang dihasilkan oleh tumbuhan. Kandungan
minyak atsiri memengaruhi penggunaan produk rempah-rempah, baik sebagai bumbu, sebagai
wewangian, serta sebagai bahan pengobatan dan kesehatan.
Tipe-tipe Terpena
Terpen-terpen adalah suatu golongan senyawa yang sebagian besar terjadi dalam dunia tumbuh-
tumbuhan. Hanya sedikit sekali terpen-terpen yang diperoleh dari sumber-sumber lain.
Monoterpen-monoterpen dan seskuiterpen adalah komponen utama dari minyak menguap atau minyak
atsiri. Minyak menguap ini diperoleh dari daun atau jaringan-jaringan tertentu dari tumbuh-tumbuhan
atau pohon-pohonan. Minyak atsiri adalah bahan yang mudah menguap, sehingga ia mudah
dipisahkan dari bahan-bahan lain yang terdapat dalam tumbuh-tumbuhan. Salah satu cara yang paling
popular untuk memisahkan minyak atsiri dari jaringan tumbuh-tumbuhan ialah penyulingan. Senyawa-
senyawa di dan triterpen tidak dapat diperoleh dengan jalan destilasi uap, tapi diperoleh dari tumbuh-
tumbuhan dan tanaman karet atau resin dengan jalan isolasi serta metoda pemisahan tertentu.
Beberapa contoh terpenoid :
Monoterpen :
Seskuiterpen :
Politerpen :
Terpenoid Tak Teratur :