Enzymatically catalyzed corn fiber gum-bovine serum albumin conjugates: their interfacial adsorption behaviors in oil-in-water emulsions

Authors: LIU, YAN - China Agricultural University; Yadav, Madhav; YIN, LIJUN - China Agricultural University

Submitted to: Food Hydrocolloids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/27/2017
Publication Date: 12/8/2017
Citation: Liu, Y., Yadav, M.P., Yin, L. 2017. Enzymatically catalyzed corn fiber gum-bovine serum albumin conjugates: their interfacial adsorption behaviors in oil-in-water emulsions. Food Hydrocolloids. 77:986-994. https://doi.org/10.1016/j.foodhyd.2017.11.048.
DOI: https://doi.org/10.1016/j.foodhyd.2017.11.048

Interpretive Summary: Corn bran/fiber is obtained from corn dry or wet milling industries. It is an abundant low value material used for animal feed. We have found that corn fiber gum (CFG), deficient in protein, is an inferior flavor stabilizer in comparison to protein rich CFG. To increase the flavor stabilizing capacity of protein deficient CFG, a commercial protein was attached to it by using an enzyme. Bovine serum albumin (BSA), a readily available commercial protein, has the appropriate structure to bind with CFG. So this protein was reacted with CFG in the presence of an enzyme (horseradish peroxidase) to form a conjugate. The CFG and BSA conjugate showed an increase in its oil binding capacity in comparison to CFG or BSA alone. This process is a simple and economical food grade green technique to attach protein onto CFG to convert it into a better flavor stabilizer for a soft drink system. In the current study we have studied the interfacial behaviors of the horse radish peroxidase catalyzed conjugate of CFG and BSA. CFG-BSA conjugate stabilized emulsion remained stable with low flocculation and coalescence during storage, in comparison to the emulsion by BSA or CFG alone. This indicated a higher amount of adsorbed CFG-BSA conjugate than individual CFG or BSA on the oil droplets. These findings will benefit U. S. corn processors by adding value and creating an 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 milling by-products will also indirectly help to reduce overall cost of fuel ethanol produced from corn kernels.

Technical Abstract: The purpose of the present study was to investigate the interfacial properties of the peroxidase-catalyzed intermolecular conjugates of corn fiber gum (CFG) and bovine serum albumin (BSA) at a gum to protein ratio of 4:1, w/w. The CFG-BSA conjugate stabilized emulsion remained stable with low flocculation and coalescence degree during storage in comparison to single BSA or CFG stabilized emulsion, which can be attributed to its higher amount of adsorbed protein and polysaccharide. As shown by SDS-sulfate polyacrylamide gel electrophoresis, the adsorbed protein at the surface of oil droplets stabilized by CFG-BSA conjugate was partly cross-linked with CFG, forming an intertwined emulsion network with increased apparent viscosity. Adsorbed CFG-BSA conjugates were loosely distributed around the droplet interfaces as revealed by images of confocal laser scanning microscopy. Their interfacial layer thickness was estimated to be 85.1 nm using a mono-disperse polystyrene latex particle model, which was not only larger than the adsorbed layer thickness of only CFG (71 nm) or BSA (6.9 nm) but also their combined layer thickness. To the best of our knowledge, this is the first report on the interfacial properties of enzymatically-cross-linked polysaccharide and protein conjugate prepared by enzymatic treatment.