Aqueous extraction of oil bodies from maize germ (Zea mays) and characterization of the resulting natural oil-in-water emulsion

Oil bodies in the form of an adequately dispersed suspension were extracted from maize germ by applying aqueous extraction. The effect on the yield of oil body extraction of parameters, such as pH of aqueous medium, state of germ comminution, and number of successive extraction steps applied, was evaluated, indicating that an extraction yield as high as 95% could be reached when a finely comminuted germ material is extracted 3 times under alkaline conditions. The extracted oil body suspension was coagulated by pH manipulation, and the resulting cream, consisting of intact oil bodies, was studied with respect to protein composition, particle size distribution, and oil body ζ potential. Changes in particle mean diameter resulting during oil body cream storage as well as the creaming behavior of emulsions prepared by cream dilution with water were also investigated. The findings are discussed in terms of the presence at the oil body surface of an adsorbed mixed layer made up of phospholipids, oleosins, and extraneous germ proteins that determine the physical stability of oil droplets upon long-term storage.