Ingredients Used for Preparing Nanoemulsions
O/W or W/O nanoemulsions have an oil or a water phase, dispersed in a continuous phase of water or oil accordingly. Double nanoemulsions (also duplex or multiple emulsions) are emulsions of emulsions such as an oil-inwater-in-oil (O1/W/O2) emulsion or a water-in-oil-in-water (W1/O/W2) emulsion. In the latter case, water droplets (Wj) are dispersed in a larger oil droplet (O) which in turn is dispersed in a continuous aqueous phase (W2) (Mohammadi, Jafari, Esfanjani, & Akhavan, 2016; Mohammadi, Jafari, Assadpour, & Esfanjani, 2016). Such structure has been called emulsion in emulsion or primary emulsion in a secondary emulsion (Dickinson, 2011).
A brief review of the major components that can be used to formulate nanoemulsions is presented in the current section.
When an O/W or W/O nanoemulsion is to be prepared, the oil phase is quite important as its attributes influence the stability and qualitative properties of the final emulsion, including the emulsion sensory characteristics upon the final application (Aboalnaja, Yaghmoor, Kumosani, & McClements, 2016). Triacylglycerols, free fatty acids, essential oils, mineral oils, fat substitutes, waxes, or combination of them can be used. Some oils that are often found in the food industry include corn, olive, soybean, sunflower, coconut, canola, peanut, cottonseed, fish, and flaxseed or algae oils. Oils containing longchain triglycerides are mostly used, nevertheless medium-chain triglycerides, and in certain cases short-chain triglycerides oils are also applied (Ozturk, Argin, Ozilgen, & McClements, 2014).