microencapsulation
Micro-encapsulation is a process in which tiny particles or droplets are surrounded by a coating to give small capsules of many useful properties. In general, it is used to incorporate food ingredients, enzymes, cells or other materials on a micro metric scale. Microencapsulation can also be used to enclose solids, liquids, or gases inside a micrometric wall made of hard or soft soluble film, in order to reduce dosing frequency and prevent the degradation of pharmaceuticals . In a relatively simple form, a microcapsule is a small sphere with a uniform wall around it. The material inside the microcapsule is referred to as the core, internal phase, or fill, whereas the wall is sometimes called a shell, coating, or membrane. Some materials like lipids and polymers, such as alginate, may be used as a mixture to trap the material of interest inside. Most microcapsules have pores with diameters between a few micrometers and a few millimeters. The coating materials generally used for coating are:- 1. Ethyl cellulose 2.Poly vinyl alcohol 3. Gelatin 4.sodium alginate
The definition has been expanded, and includes most foods, where the encapsulation of flavos is the most common. The technique of microencapsulation depends on the physical and chemical properties of the material to be encapsulated.
Many microcapsules however bear little resemblance to these simple spheres. The core may be a crystal, a jagged adsorbent particle, an emulsion, a Pickering emulsion, a suspension of solids, or a suspension of smaller microcapsules. The microcapsule even may have multiple walls.
Essential 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, 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 contains the "essence of" the plant's fragrance--the characteristic fragrance of the plant from which it is derived. Essential oils do not form a distinctive category for any medical, pharmacological, or culinary purpose. They are not essential for health.
Essential oils are generally extracted by distillation, often by using steam. 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.
Essential oils have been used medicinally 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.
The earliest recorded mention of the techniques and methods used to produce essential oils is believed to be that of Ibn al-Baitar (1188–1248), an Andalusian physician, pharmacist and chemist.
THE WHITEFLY, Trialeurodesvaporariorum Westwood,
was accidentally introduced into South Korea from Saudi Arabia and Japan in 1977 (Han 1998). This insect is now well established in the greenhouse ecosystem and is an economically important pest of various greenhouse vegetables, particularly tomatoes, cherry tomatoes, and cucumbers, as well as ornamentals. Control of T. vaporariorum populations worldwide is primarily dependent on repeated applications of conventional insecticides, such as organophosphates, carbamates, and pyrethroids. Although effective, their repeated use for decades has disrupted natural biological control systems and led to resurgence of this insect (Dittrich et al. 1990), sometimes resulted in the
development of resistance (Dittrich et al. 1990, Omeret al. 1993), had undesirable effects on nontar get organisms, and fostered environmental and human
health concerns (Hayes and Laws 1991). Furthermore, T. vaporariorum dwells on the undersurface of plant foliage, not easily reached by conventional spraying equipment (Dittrich et al. 1990). These problems have highlighted the need for the development of selective T. vaporariorum control alternatives with fumigant action but without phytotoxicity in greenhouses, where ventilation can be controlled. Plant essential oils may be an alternative source for
T. vaporariorumcontrol because they constitute a rich source of bioactive chemicals and are commonly used as fragrances and ßavoring agents in foods and beverages. Because of this, much effort has been focused on plant essential oils or phytochemicals as potential sources of commercial insect control agents. Little work has been done in relation to the control of T.vaporariorum, although insecticidal activity of plant essential oils has been well described by Isman (2000).
This paper describes a laboratory study aimed at assessing the potential of plant essential oils for use as commercial insecticides. Insecticidal activity of 53 essential oils was assessed against each developmental stage (eggs, nymphs, and adults) of T. vaporariorum. The insecticidal route of action of the test plant oils is also discussed.