NANOEMULSION OF D-LIMONENE IN WATER SYSTEM 251 visible and the droplet size correlated well with the results from droplet size analysis us- ing Nanotrac 150 light scattering instrument. In addition, the morphology of the D - limonene droplet was spherical, and the gray parts of the droplet were D -limonene precipitation incorporated in emulsion system. CONCLUSION Nanoemulsion droplet can be obtained in D -limonene in water system by ultrasonic emulsifi cation. The optimum conditions for ultrasonic emulsifi cation of D -limonene na- noemulsions were applied power of 18 W, ultrasonic time of 120 s, and So ratio of 0.6 with an HLB value below 12. Nanoemulsion droplet in D -limonene nanoemulsion system was probably a solution for solving the low bioavailability and low solubility problems of D -limonene and thus might be applied as nanoencapsulated fl avor and fragrance systems for industry. ACKNOWLEDGMENT The fi nancial support (NSC 98-2313-B-002-042-MY3) provided from the National Science Council, the Republic of China (Taiwan) is gratefully acknowledged. REFERENCES (1) C. Solans, J. Esquena, A. M. Forgiarini, N. Usón, D. Morales, P. Izquierdo, N. Azemar, and M. J Garcia- Celma, Nanoemulsions: Formation, properties and applications, J. Surf. Sci. Series, 109, 525–554 (2003). (2) L. Weirong, S. Dejun, L. Caifu, L. Qian, and X. Jian, Formation and stability of paraffi n oil-in-water nano- emulsions prepared by the emulsion inversion point method, J. Colloid Interf. Sci., 303, 557–563 (2006). (3) C. M. Pey, A. Maestro, I. Solé, C. González, C. Solans, and J. M. Gutiérrez, Optimization of nano- emulsions prepared by low-energy emulsifi cation methods at constant temperature using a factorial design study, Colloids Surf. A, 288, 144–150 (2006). Figure 4. Visual appearance and transmission electron micrographs of nanostructured droplet in D -limonene in water emulsion system. The scale bar represents a distance of 50 nm.

JOURNAL OF COSMETIC SCIENCE 252 (4) W. Lijuan, L. Xuefeng, Z. Gaoyong, D. Jinfeng, and E. Julian, Oil-in-water nanoemulsions for pesticide formulations, J. Colloid Interface. Sci., 314, 230–235 (2007). (5) O. Sonneville-Aubrun, J. T. Simonnet, and F. L. Alloret, Nanoemulsions: A new vehicle for skincare products, Adv. Colloid Interface Sci., 108–109, 145–149 (2004). (6) M. Atmane, J. Muriel, S. Joël, and D. Stéphane, Flavour encapsulation and controlled release: A review, Int. J. Food Sci. Technol., 41, 1–21 (2006). (7) H. Mirhosseini, Y. Salmah, S. A. H. Nazimah, and C. P. Tan, Solid-phase microextraction for headspace analysis of key volatile compounds in orange beverage emulsion, Food Chem., 105, 1659–1670 (2007). (8) S. M. Jafari, Y. He, and B. Bhandari, Production of sub-micron emulsions by ultrasound and microfl u- idization techniques, J. Food Eng., 82, 478–488 (2007). (9) T. Tadros, P. Izquierdo, J. Esquena, and C. Solans, Formation and stability of nano-emulsions, Adv. Col- loid Interface Sci., 108–109, 303–318 (2004). (10) S. Kentish, T. J. Wooster, M. Ashokkumar, S. Balachandran, R. Mawson, and L. Simons, The use of ultrasonics for nanoemulsion preparation, Innov. Food Sci. Emerg., 9, 170–175 (2008). (11) B. Abismaïl, J. P. Canselier, A. M. Wilhelm, H. Delmas, and C. Gourdon, Emulsifi cation by ultrasound: Drop size distribution and stability, Ultrason. Sonochem., 6, 75–83 (1999). (12) P. Izquierdo, J. Feng, J. Esquena, T. F. Tadros, J. C. Dederen, M. J. Garcia, N. Azemar, and C. Solans, The infl uence of surfactant mixing ratio on nano-emulsion formation by the pit method, J. Colloid Interf. Sci., 285, 388–394 (2005). (13) R. S. Juang and K. H. Lin, Ultrasound-assisted production of W/O emulsions in liquid surfactant mem- brane processes, Colloid Surf. A, 238, 43–49 (2004). (14) D. M. Kim, S. S. Hyun, D. Yun, C. H. Lee, and S. Y. Byun, Identifi cation of an emulsifi er and conditions for preparing stable nanoemulsions containing the antioxidant astaxantin, Int. J. Cosmet. Sci., 34, 64–73 (2012). (15) W. Liu, D. Sun, C. Li, Q. Liu, and J. Xu, Formation and stability of paraffi n oil-in-water nano-emulsions prepared by the emulsion inversion point method, J. Colloid Interf. Sci., 303, 557–563 (2006).