Submitted to: Food Hydrocolloids Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/7/2011
Publication Date: 9/13/2011
Citation: Yadav, M.P., Strahan, G.D., Mukhopadhyay, S., Hotchkiss, A.T., Hicks, K.B. 2011. Fomation of corn fiber gum-milk protein conjugates and their molecular characterization. Food Hydrocolloids Journal. 26:326-333. Interpretive Summary: Corn bran/fiber, obtained from corn dry/wet milling industries, is a low value material mostly used for animal feed. Corn bran produced by the corn dry milling process comes mostly from the pericarp portion of corn kernel and contains very little protein. For adding value to corn bran, we have isolated corn fiber gum (CFG) from it and studied flavor stabilizing capacity of obtained CFG. Our study has indicated that CFG derived from corn bran is deficient in protein and so it is an inferior flavor stabilizer. This finding has prompted us to attach protein to CFG for changing it into a better flavor stabilizer and characterize the product to confirm protein attachment. For this purpose whey protein (a low value by-product of cheese processing) has been linked to CFG by a natural, non-toxic dry heating reaction, which increases its oil flavor binding capacity. The formation of CFG and protein conjugate is fully confirmed by microscopic, nuclear magnetic resonance and molecular mass (size) studies. This process is a simple and economical food grade heating technique to introduce protein onto CFG for converting it into a better flavor stabilizer for a soft drink system. These findings will benefit U. S. corn and cheese processors by adding value and creating additional market for their by-products. It will also benefit U. S. manufacturers of CFG who will be able to produce a constant supply of improved quality corn fiber gum emulsifiers at reasonable prices. The generation and recovery of additional valuable product from corn dry milling by-products will also indirectly help to reduce overall cost of fuel ethanol produced from corn kernels.
Technical Abstract: Corn fiber arabinoxylan is hemicellulose B isolated from the fibrous portions (pericarp, tip cap, and endosperm cell wall fractions) of corn kernels and is commonly referred to as corn fiber gum (CFG). Our previous studies showed that CFG isolated from corn bran (a byproduct of corn dry milling) contains very little protein and is an inferior emulsifier for oil-in-water emulsion systems as compared to corn fiber gum isolated from corn fiber derived from the corn wet-milling process. The protein deficient CFG isolated from corn bran was covalently conjugated with byproducts of cheese processing, Beta-lactoglobulin (Beta-LG) and whey protein isolate (WPI) using an economical food-grade Maillard-type heating reaction for the purpose of increasing their commercialization potential as a superior food emulsifier and soluble nutritional additive in beverages as reported in our recent publication (Yadav et. al., 2010b). The molecular characterization of CFG-protein conjugates was performed by high-performance size-exclusion chromatography (HPSEC) coupled to on line multi-angle laser light-scattering and viscometric detection systems. The analysis by HPSEC revealed that CFG-protein conjugates have higher weight-average molar mass (Mw, 340-359 kDa) and polydispersity (Mw/Mn, 1.74) than the corresponding unconjugated CFG (Mw, 290 kDa and Mw/Mn, 1.35). The z-average root-mean-square radius of gyration (Rgz) of CFG-protein conjugates is slightly higher (30.5-33.5 nm) in comparison to CFG (29.5 nm) but their weight average-intrinsic viscosities ('w) remain unchanged to about 1.32 dL/g. The Mark-Houwink exponent “a” of conjugates (0.40) is lower than the unconjugated CFG (0.53) indicating the formation of a more compact structure after conjugation with protein. The commercial availability of a high quality beverage emulsifier made from the low value byproducts of corn dry milling and cheese processing would benefit the beverage industry as well as corn- and dairy-processing industries.