Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/18/2009
Publication Date: 3/3/2010
Citation: Yadav, M.P., Cooke, P.H., Johnston, D., Hicks, K.B. 2010. Importance of protein rich components in the emulsifying properties of corn fiber gum. Cereal Chemistry. 87(2):89-94.
Interpretive Summary: For stabilizing citrus oil flavor in soft drinks, the U. S. beverage industry uses hundreds of tons of high quality emulsifiers each year. The most commonly used emulsifier, “gum arabic” is an imported gum that is expensive and is often in short supply due to political and environmental issues in the African countries of origin. To solve this problem, we previously extracted and purified a new type of “gum” called “corn fiber gum (CFG)” from an abundant and inexpensive byproduct of corn processing called “corn fiber”. We have now analyzed the chemical structure of CFG and found it to be primarily a polysaccharide. Polysaccharides, like starch and cellulose, are not known for their ability to act as emulsifiers. We then tested the ability of different types of CFG samples to emulsify citrus oil in water and also analyzed their chemical composition. We found that CFG with higher protein content was a better flavor stabilizer than CFG with lower protein content. So to totally understand the importance of proteinaceous component in the emulsification process, we separated protein rich components by chemical treatment and studied its effect. We found that after removing protein rich components from CFG its emulsifying properties decreased slightly but not completely. Also the separated protein-rich component was not a good emulsifier by itself but the original unseparated CFG was a superior emulsifier. This finding proves that the combination of protein and carbohydrate is important to be a good emulsifier. These results will benefit new U.S. soft drink industries to prepare high quality emulsifiers for stabilizing flavor in beverages. U.S. corn processors will also benefit by having new markets for their low-valued byproducts.
Technical Abstract: Purified corn fiber gum (CFG-F) isolated from "fine" (kernel endosperm-derived) corn fiber that contained about 2% residual protein was extracted with 70% aqueous ethanol. The aqueous ethanol extract (AEE), which contained 19.5% of the total CFG, contained a high percentage of the proteinaceous material present in the original gum sample. The AEE gum contained 6.81% protein by weight. The residue (R) which constituted 66% of the total CFG-F contained only 0.55% of protein. The emulsifying properties of R and AEE in a model oil-in-water emulsification system were studied by measuring turbidity after 1, 2, and 3 weeks, particle size after 4 weeks and by confocal laser scanning microscopy after 3 months storage at room temperature. These gums were compared with the standard well-known emulsifiers native acacia gum (NAG) and modified acacia gum (MAG). The results indicate that although AEE contains protein-rich components, it is not as good an emulsifier as the residue which contains only 0.55% of protein. However, emulsions prepared with the whole (un-fractionated) CFG-F under similar conditions were more stable showing higher turbidity and smaller particles size than the one prepared with either R or AEE.