Biology Assignment 代写 :Microparticles Of Menthol Palmitic Acid
Menthol is a monocyclic, saturated, secondary terpene alcohol is found in high concentrations in oils of peppermint, corn mint, occurs widely in nature and can also be made synthetically[1, 3]. Whiles d-menthol has an undesirable taste, l-Menthol has a characteristic peppermint flavor and refreshing coolness. Due to its flavor and refreshing coolness, l-menthol is widely used in foods (such as candy, beverages etc), peppermint oil, toothpaste, cigarettes, over-the-counter medications, local anesthetics, and cosmetic products [2, 3].
Menthol is unique because it is the only cigarette additive that tobacco companies actively market to consumers . Secondly, it is the only aspect of cigarette design that is unambiguously marketed due to its physiological effects, as an anti-irritant and a cooling agent . It is also the only cigarette additive about which consumers consciously choose to buy . Menthol flavoring provide cooling, Subjective effects of smoothness and also mask the undesirable taste of tobacco cigarettes [4-5]. The coolness sensation is experienced because of the ability of menthol to chemically trigger the cold-sensitive TRPM8 receptors in the skin which is responsible for the well known cooling sensation that it provokes when inhaled, eaten, or applied to the skin  with the resulting sensation of coolness perceived not only in the mouth and pharynx, but also in the lungs [7-8]. This has the tendency to lure smokers to opt for menthol cigarettes . Menthol levels in cigarette can also be manipulated to attract first-time smokers .
Most of the cigarettes available on the market contain inconspicuous amounts of menthol (approximately 0.03% of cigarettes’ tobacco weight), but most tobacco cigarette companies advertise individual brands as mentholated. These specific brands, contain between 0.1% and 1.0% of their tobacco weight as menthol, and therefore exert an appreciable cooling sensation and mint like flavor when inhaled.
Fig.1.1: Tobacco Cigarette
Fig. 1.1 is a diagram showing that cigarette is made composed of the following parts : 1. Filter made of 95% cellulose acetate; 2. Tipping paper to cover the filter; 3. Rolling paper to cover the tobacco; 4. Tobacco blend. Menthol is often applied to tobacco to form the tobacco blend by spraying the tobacco with a dilute menthol solution. This method, however, does not produce a uniform product, since the spray is in the form of discrete droplets which do not contact all of the tobacco. Also, part of the menthol may be lost, using this method, in the course of processing the tobacco.  Another method of applying menthol to tobacco is given by U.S. Pat. No. 3,548,838. This method subject the tobacco to an alcohol-menthol vapor as the tobacco is blown through a conduit. A disadvantage of this method is that alcohol is an extra cost. Secondly, there is the fear that the alcohol vapors might reach explosive concentrations 
Recent modifications to these methods involve the addition of finely dry particles produced by spray drying, RESS, PGSS and other methods. The particles which consist of the flavor encapsulated in a wall material is then blown onto the tobacco and further processed to get the perfect tobacco flavor mix.  The method and apparatus for addition of menthol flavor to tobacco cigarette should be such that 
Cleaning of apparatus
exposing personnel to irritating vapors
use of other solvents which adds to cost of production should be minimized.
These particles should meet some specific specification before it can be successfully blended with the tobacco or incorporated into a filter.
Therefore, there is an increasing interest and utmost need to developing new technologies, particularly in the case of the Tobacco industry , that allow the production of microparticles with specific particle-size distribution and morphology to be produced under mild, non-polluting operating conditions [12-13]. These microparticles should have an inner core which could be either a liquid droplet, solid particle, or gas cell with a continuous thin protective layer or wall material [15-16].
There are a host of wall materials available for microencapsulation but the choice should suit specific purposes, including optimum concentration of the active ingredient, preservation of the properties and activity of the active substance, ease to process with the selected precipitation technique, good mechanism of release, final particle size, compatibility, lack of toxicity, final physical form, and cost  [17-18].
Palmitic acid is one of the most common saturated fatty acids found in animals and plants .
It is a saturated fatty acid used. Like all fatty acids the hydrocarbon tail is lipophilic or hydrophobic and the carboxylic acid head is lipophobic or hydrophilic.
Fig 1. 2. Chemical structure of Palmitic acid
Palmitic acid has a hydrocarbon hydrophobic or lipophilic tail and a carboxylic acid hydrophilic or lipophobic head and properties of a surface active organic substance (Seidl, 2000). Ellison et al.,1999, reported that there has been the suggestion that palmitic acid could form a reverse micelle around a salt core. Indeed, field studies conducted have found palmitic acid favorably on the surface of aerosols (Tervahattu et al., 2002; Peterson and Tyler, 2003) [23,24,52]. This two unique findings and a host of others proofs that palmitic acid can be used as a wall material. To buttress this claims, palmitic acid has a low melting point, therefore the heat from cigarette can be used as a trigger to release the encapsulated menthol. Last but not the least and smell good when it burns. The encapsulation of menthol in palmitic acid will not only provide coolness and refreshing taste from menthol but will also ensure controlled release of menthol. This will improve the effectiveness, broaden the time range of menthol flavor and ensure optimal dosage . With carefully fine-tuned controlled release properties, microencapsulation of menthol in palmitic acid will not just be an added value, but is also a source of a totally new approach with matchless properties .
Various encapsulation techniques are available for improving the efficiency of aroma chemicals in fragranced consumer products like cigarette. Encapsulation methods are still being optimized in terms of fragrance performance, scaling up and cost . Conventionally, various techniques such as milling, grinding, spray drying, spray chilling or spray cooling, Centrifugal extrusion , fluidized bed coating, liposome entrapment, coacervation, inclusion complexation, air suspension coating, extrusion, Centrifugal suspension-separation and rotational suspension separation can be employed to form the microcapsules [1,27]. However, mechanical treatment most as times results in damage of products or performance degradation as a result of particle distress, frictional heat or wide particle size distribution (PSD) . Spray drying or chemical precipitation can eliminate some of the problems with mechanical treatment methods but once again, it is difficult to obtain particles with the desired particle size and distribution due to limitations in reaction rate that is controlled by mass transfer or droplet sizes formed during spraying . The use of supercritical fluids is one method to overcome some of these inherent limitations of conventional methods . For example Carbon dioxide becomes a supercritical fluid when both the temperature and pressure equal or exceed the critical point of 31Â°C and 7.3MPa (see Fig 1.3 ) . In its supercritical state, CO2 has both gas-like and liquid-like qualities, and it is this dual characteristic of supercritical fluids that provides the ideal conditions for production of fine particles in a short period of time.