Properties of soybean oil bodies and oleosin proteins as edible films and coatings
Abstract
Oleosins are major proteins associated with oil storage vesicles known as oil bodies in many plant seeds. These oil bodies and oleosins have recently gained attention, due to potential applications in foods, cosmetics, and pharmaceuticals. The oleosin proteins coat the oil bodies making them very stable. This work studied the characterization and properties of oleosins with respect to aqueous solubility, oil body separation processing, and edible films and coatings for food products. The effects of salts, solvents, surfactants, denaturants, temperature, and pH on oleosin electrical charge, physical structure, and aqueous solubility were measured along with their effects on oil body suspension stability and oil body integrity. An aqueous separation method for oil bodies was developed based on the observation of rapid oil body coagulation induced by low levels of cationic salts. This non-solvent oil extraction procedure is a promising alternative to current edible oil solvent extraction methods. As highly protective natural barrier proteins for seed oil, oleosin-based edible films were developed to serve as moisture barriers to improve food quality. Oil body films contain both oleosin membranes and oils making them very hydrophobic. The water vapor permeability (WVP) of oil body films was 3.3-times lower than that of soy protein isolate counterparts but 67% higher than that of zein films. Mechanical properties of oil body films were effectively modified by plasticizing with Tris-HCl, Ca2+/Mg2+ cross-linking, or adding carboxymethyl cellulose. The resulting films had a wide range of tensile strength and elongation properties, varying from 0.2 MPa and 60% to 5.1 MPa and 6%, and could be engineered for specific packaging applications. More importantly, oil body film-forming mechanisms were illustrated. Oleosins are predominately β-sheet proteins associated through hydrophobic, electrostatic, and Van der Waals interactions to form films. The film-forming process and film-modifying treatments were found to affect the structure of oleosins. Specific secondary structural changes were correlated to changes in the thickness, tensile strength, elasticity, and WVP of the films. Additionally, film storage stability and coating applications to food systems were examined.
Degree
Ph.D.
Advisors
Tao, Purdue University.
Subject Area
Food science
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