Preparation, characterization, and antimicrobial activity of nanoemulsions incorporating citral essential oil

Wen-Chien Lu ^a, Da-Wei Huang ^b, Chiun-C.R. Wang ^c, Ching-Hua Yeh ^d, Jen-Chieh Tsai ^d, Yu-Ting Huang ^e, Po-Hsien Li ^d,*

^a Department of Food and Beverage Management, Chung-Jen Junior College of Nursing, Health Sciences and Management, Chia-Yi City, Taiwan, ROC

^b Department of Food and Beverage Management, China University of Science and Technology, Taipei City, Taiwan, ROC

^c Department of Food and Nutrition, Providence University, Shalu, Taichung, Taiwan, ROC

^d Department of Medicinal Botanical and Health Applications, Da-Yeh University, Dacun, Changhua, Taiwan, ROC

^e Institute of Food Science and Technology, National Taiwan University, Taipei, Taiwan, ROC

Citral is a typical essential oil used in the food, cosmetic, and drug industries and has shown antimicrobial activity against microorganisms. Citral is unstable and hydrophobic under normal storage conditions, so it can easily lose its bactericide activity. Nanoemulsion technology is an excellent way to hydrophilize, microencapsulate, and protect this compound. In our studies, we used a mixed surfactant to form citral-in-water nanoemulsions, and attempted to optimize the formula for preparing nanoemulsions. Citral-in-water nanoemulsions formed at So 0.4 to 0.6 and ultrasonic power of 18 W for 120 seconds resulted in a droplet size of < 100 nm for nanoemulsions. The observed antimicrobial activities were significantly affected by the formulation of the nanoemulsions. The observed relationship between the formulation and activity can lead to the rational design of nanoemulsion-based delivery systems for essential oils, based on the desired function of antimicrobials in the food, cosmetics, and agrochemical industries.

Keywords: antimicrobial activity, citral, mixed surfactant, nanoemulsions