Aqueous Enzymatic Extraction Method Of Maize Germ Oil Bodies And Their Physiochemical Properties

Lipids in maize appear as small spherical droplets called oil bodies. Maize germ oil bodies are coated by a layer of phospholipids and oleosin proteins. The objectives of this study are to recover the oil bodies form maize, determine their physiochemical properties and oxidation stability under high temperature (110℃). To utilize maize germ oil bodies as food ingredient in the food industry zeta potential determination and particle diameter analysis and confocal laser scanning microscopy were used in this study as indicators of the stability of maize germ oil body suspensions.The aqueous enzymatic extraction method was used to extract oil bodies from maize germ. The yield of maize germ oil bodies and the total available oil remained in the maize germ residue after recovers the oil bodies were measured. The extraction conditions of oil bodies in this study concluded that oil body yields depend on high temperature, cellulase, and blending. Heating maize germ at90℃prior to blending followed by an aqueous enzymatic extraction (cellulase) was an executable approach to improve the oil body yields. The oil body yield from extraction by using these conditions was approximately23.09%and the total oil remained in the maize germ residue was approximately18.74%.At pH3-7, the zeta potential of the oil bodies changed from around+23.3mV to around-16.4mV and the isoelectric point (IEP) ranged from4.6to4.8. The zeta potential and mean particle diameter of the oil bodies were easily affected by salt (7.05mV and d32=1.43μm at100mM NaCl) and pH (23.30,15.00,-16.43mV and d32=1.02,2.55, and0.95μm at pH3, pH4, and pH7, respectively). Results demonstrated that aggregation and instability of the oil bodies were promoted by high salt concentrations but not by heating. The association between oil bodies and surfactant properties resulted in the disruption of hydrophobic interactions among oil body surface proteins because of the smaller mean particle sizes and the reduced negative charges (-75.73mV and d32=0.46μm at pH3). Thus, the oil body aggregation behavior and stability of proteins are based on hydrophobic interactions present on the surface of oil bodies.Peroxide value and iodine value of heated oil bodies at110℃for6h were0.42mequiv. O2/kg and115.27g I2/100g oil, respectively. However, under the same conditions with the heated oil bodies both values of the heated commercial corn oil were15.57mequiv. O2/kg and90.52g I2/100g oil, respectively. Peroxide value of the hydrolyzed oil bodies prior to heating for24h was a more profound oxidation state than the hydrolyzed oil bodies prior to heating for12h, hydrolyzed oil bodies without heating, and non-heated oil bodies. The results indicated that the heat treatment had not affect the oxidation stability on intact oil bodies compared to commercial corn oil due to proteins on the surface were the most important component involved in protecting the entrapped oil of the oil bodies from interacting with pro-oxidants. Thus, maize oil bodies can be utilized as emulsifier in food industrial applications in order to avoid oxidation process.The influence of sodium stearoyllactylate (SSL) concentration (0-0.1wt%) on the stability of maize germ oil body emulsions was studied. The z-average size decreased to minimum values and the electrostatic charge of the oil bodies were decreased by the addition of SSL (0.44μm and-70.46mV at0.1%of SSL). Heat treatment had no effect on the interaction between SSL and oil bodies, as shown by the unchanged z-average size and zeta potential values. SSL demonstrated excellent stability of oil body emulsions to aggregation and may be beneficial to applications on oil body emulsions.