Submitted to: Food Hydrocolloids Journal
Publication Type: Review Article
Publication Acceptance Date: 8/11/2008
Publication Date: 2/28/2009
Citation: Yadav, M.P., Johnston, D., Hicks, K.B. 2009. Corn fiber gum: New structure/function relationships for this potential beverage flavor stabilizer. Food Hydrocolloids Journal. 23:1488-1493. Interpretive Summary: The United States' beverage industry uses hundreds of tons of high quality emulsifiers each year for stabilizing flavors in soft drinks. 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 inexpensive byproducts of corn processing called "corn fiber." We have now analyzed the chemical structure of CFG and found it to be primarily a "polysaccharide," which is a type of complex carbohydrate made up of simple sugars that are connected together in a long chain. CFG is composed of the simple sugars arabinose and xylose, and is therefore referred to as an "arabinoxylan." Polysaccharides, like starch and cellulose, are not known for their ability to act as emulsifiers. However, our studies on CFG show it to be an excellent emulsifier, equal to or better than gum arabic. We therefore did additional studies to determine how CFG could exhibit this unusual and commercially useful property. First we prepared CFGs from corn fiber produced from different corn milling processes. We then tested their ability to emulsify citrus oil in water and also analyzed their molecular and chemical composition. In this current study we found for the first time that in addition to arabinoxylan, purified CFG also contains three other components including protein, phenolic acids and lipids, which contribute to its emulsifying properties. CFG with a higher protein and lipid content was a better flavor stabilizer than CFG with a lower protein and lipid content. We also found for the first time that CFG fractions which are bigger in size and more compact are better flavor stabilizers than those which are smaller in size and less compact. These results will benefit corn farmers because new uses for corn byproducts will ultimately improve market for corn. It will also benefit U.S. consumer and the U. S. economy since home grown corn fiber gum can substitute for imported gum Arabic for flavor stabilization.
Technical Abstract: Corn fiber arabinoxylan is a hemicellulose B isolated from the fibrous portions (pericarp, tip cap, and endosperm cell wall fractions) of corn kernels by alkaline solution, often in the presence of hydrogen peroxide and is commonly referred to as “Corn fiber gum” (CFG). The unique polysaccharide, CFG with its low solution viscosity has been proposed as a good stabilizer for oil-in-water emulsions and we have verified that in some model systems, it can out-perform the "gold standard" emulsifier, gum arabic. But the precise mechanism for the stabilization of oil-in-water emulsion is not well understood due to its structural and molecular complexity. It is unclear and even puzzling how a water-soluble, hydrophilic arabinoxylan could function as an emulsifier, since most emulsifiers have hydrophobic as well as hydrophilic surfaces and regions on the molecule. To understand the structural properties of CFG that may be responsible for its emulsifying properties, we have prepared a number of purified and modified CFG samples from different sources of corn fiber. We then studied their detailed structures and measured their ability to stabilize oil-in-water emulsions. The results show that "pure" CFG fractions often contain minor, but perhaps functionally important amounts of associated lipids and proteins. Understanding the critical structural elements required for optimal emulsification properties will allow future commercial producers of CFG to provide consistent quality and functionality in their products.