Emulsifying Properties of Corn Germ Proteins (1989)

Cereal Chem. 66(4):263-267 Emulsifying capacity and emulsion stability of hexane-defatted corn content; 70.39% water was retained by the emulsion. High emulsion germ protein obtained by modified and conventional extraction processes stability was obtained as the result of specific protein properties. Increasing were studied. Defatted corn germ protein obtained by the modified fat content in emulsions from 20 to 40% had a positive effect on emulsion extraction process had higher emulsifying capacity and emulsion stability stability. Because of its better functional properties, hexane-defatted corn than that obtained by the conventional process. The highest emulsion germ protein obtained by the modified process is recommended for stability was obtained with 7% defatted corn germ protein and 40% fat utilization as an additive in food products. Emulsifying capacity and emulsion stability of defatted corn germ protein can be used to define how these proteins can be added to existing foods and how they can replace more expensive proteins traditionally used. A knowledge of the emulsifying properties of defatted corn germ protein is necessary to evaluate their potential use as food additives. The stabilizing effect of proteins in emulsions results from the protective barrier they form around fat droplets, which further prevents their coalescence (Kinsella 1979). Long-term stability of emulsions depends basically on the thickness and strength of adsorbed protein films at the oil-water interface. Emulsifying capacity and emulsifying stability are important functional properties of food proteins. Many chemical and physical factors are involved in the formation, stability, and textural properties of protein-fat-water emulsions. Emulsifying capacity and emulsion stability depend on the properties of the stabilizer and vary with the type of protein, its concentration, pH, ionic strength, and viscosity of the system. Nakai (1980) reported that solubility, surface hydrophobicity, and molecular flexibility influence the emulsification behavior of globular proteins. Crenwelge et al (1974), working with soybean protein, found a direct correlation between solubility of the protein suspension and emulsifying capacity of proteins. At the same time, some investigators have suggested that solubility is not necessarily associated with emulsifying capacity and emulsion stability of vegetable proteins (Aoki et al 1980, McWatters and Holmes 1979a). McWatters and Holmes (1979b) and Ramanatham et al (1978) showed that emulsifying capacity of peanut protein cannot be predicted solely on the basis of protein solubility level. Solubility appears to contribute more to the quality of emulsions formed than to quantities of oil emulsified. Some proteins have optimal emulsifying properties at their isoelectric points (egg white, gelatin), whereas others perform best at pH values away from their isoelectric points (soybean and peanut proteins). The pH influences the emulsifying capacity of proteins indirectly by affecting their solubility. A number of studies have shown that the pH-emulsifying property profile of various proteins resembles the pH-solubility profile (Pearson et al 1965, Crenwelge et al 1974). Stabilizing effects of proteins in emulsions were established at all pH values below that of the isoelectric point of the protein and up to pH 6.5. In another study, stable emulsions were prepared at the pH range of 3- 10 (Crenwelge et al 1974). Emulsifying capacity of peanut flour was poorest at pH 4.0, a level near the isoelectric point of the predominant native peanut protein (arachin). At this point, proteins have a net electrical charge of zero and minimum solubility and reactivity (McWatters 'Contribution no. 88-427-J from the Kansas Agricultural Experiment Station,