microencapsulation of spearmint (mentha spicata) oil by modified starch

introduction : flavors play an important role in consumer satisfaction and influence further consumption of foods. most available aroma compounds are produced via chemical synthesis or extraction. foodstuffs containing synthetic flavor in many cases are avoided, because the consumers suspect that these compounds are toxic or harmful to their health. recently, the market of flavors is focused in using aromatic materials arriving from natural sources to replace the use of synthetic flavors gradually (badee, et al., 2012). flavorsare indispensable ingredients of food preparations, and usually they are in liquid form that makes their handling and incorporating into food more difficult. furthemore, many flavorcomponents exhibit considerable sensitivity to oxygen, light, and heat. in response to these difficulties, dried flavors have been developed. the objective of this work was to study the influence of different wall material concentration on the emulsion and spray dried flavor powder characteristics. materials&methods;: spearmint oil was obtained by clevenger distillation method and modified starch was obtained from national starch&chemical; limited company (england). different concentration of modified starch solutions (10, 20 & 30% w/w) were prepared by dispersing the solids in deionized water and heating at 40 ⁰c over a steam bath to facilitate solubilization. thesolutions were allowed to cool to room temperature before storing at 4°c overnight. the spearmint oil (2.5 % w/w) was added to the solution and was homogenized vigorously (15000 rpm for 10 min.) with an ultra turrax homogenizer (t25, ika, germany) at ambient temperature. the emulsions were then further emulsified using ultrasounds (20khz, 1 min) (jafari, et al., 2007). the obtained emulsion was spray dried in a buchi 190 spray dryer (swiss) with an evaporation rate of 600 lit/1 hour, equipped with a pressurized nozzle operating at 4bar pressure. feed ismetered into the dryer by a peristaltic pump. powder was collected at the bottom of dryer cyclone and kept inair tight containers at -18⁰c until analyzed. the particle size of emulsion droplets and spray dried powder were determined using dynamic laser light scattering (analysette22, fritsch company, germany). encapsulation efficiency was defined as the percentage of menthol ad d-limonene thatwere entrapped inside the microcapsules to the total loaded to the emulsion. . theequations was as follows: encapsulation efficiency=(menthol or limonene in microcapsul(ppm))/(menthol or limonene in emulsion(ppm))×100% the powders were attached to sem stubs using double adhesivetape, coated with 3–5 ma gold/palladium under vacuum,and examined with a scanning electron microscope (s360 model, oxford , england). results&disscussion;: emulsion particle size were found to be in the range of 1.8 to 3.3 μm and wall material concentration had significant effect on it ( p<0.05). increasing the wall material concentration cause decrease in emulsion droplet size.microparticles size was between 1.2 to 2.5 μm. increasing the wall material concentration caused increase in powder particle size. frascareli et al., 2012 &hogan; et al., 2001 observed the same results in their studies. encapsulation efficiency was significantly increased by increasing wall material concentration.