|Jin, Qiangwei - Shanghai Jiaotong University|
|Li, Xiaobei - Shanghai Jiaotong University|
|Cai, Zhixiang - Shanghai Jiaotong University|
|Zhang, Hongbin - Shanghai Jiaotong University|
|Zhang, Fei - Shanghai Jiaotong University|
Submitted to: Food Hydrocolloids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/2/2017
Publication Date: 4/26/2017
Publication URL: http://handle.nal.usda.gov/10113/5674100
Citation: Jin, Q., Li, X., Cai, Z., Yadav, M.P., Zhang, H., Zhang, F. 2017. A comparison of corn fiber gum, hydrophobically modified starch, gum arabic and soybean soluble polysaccharide: interfacial dynamics, viscoelastic response at oil/water interfaces and emulsion stabilization mechanisms. Food Hydrocolloids. 70:329-344.
Interpretive Summary: Corn fiber gum (CFG) is isolated from a low valued by-product (corn fiber) of the corn wet milling process for producing corn starch and bioethanol. CFG has potential applications in the food industry as a thickener, stabilizer and emulsifier. However, the interfacial flow behavior in its oil in water emulsion and its effects on emulsion stability has not been well studied. Usually the flow behavior of an emulsifier at the oil and water interface is related to its structure. From the application point of view, a better understanding of how the emulsifier behaves on the interface of oil and water emulsion would be very valuable. Therefore, this comparative study of flow properties of CFG at oil water interface was undertaken to compare CFG with three commercial carbohydrate polymer emulsifiers, (a) octenyl succinate anhydride-modified starch (OSA-s), (b) gum arabic (GA) and (c) soybean soluble polysaccharides (SSPS). Our studies indicated that although all these polymers are all good emulsifiers, they differ significantly in their interfacial properties, making some of them superior to others in terms of emulsion stability. Among these carbohydrate emulsifiers, CFG shows superior slow and continuous increment of interfacial viscoelastic behavior, which makes it a better emulsifier than the other polymers. Also significant differences in the viscoelastic properties of these four emulsifiers at the oil water interface were found indicating that there are major differences in their structures and chain associations. These findings will benefit U. S. corn processors and manufacturers of CFG by providing a better understanding the interfacial flow behavior of these emulsifiers and being able to better match them to various potential applications. The generation of a 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 interfacial rheology of polysaccharide adsorption layers of corn fiber gum (CFG), octenyl succinate anhydride-modified starch (OSA-s), gum arabic (GA) and soybean soluble polysaccharides (SSPS) at the oil/water interface and their emulsifying properties in oil-in-water (O/W) emulsions were compared. All four amphiphilic polymers contain different amounts of protein and they are of high molecular weight and highly branched. Based on the detailed interfacial shear rheological information (shearing time, concentration, temperature, strain), dependency of interfacial dynamic moduli, creep or relaxation response, and steady/dynamic flow behavior of the interfacial layers, we found pronounced differences in the viscoelastic response of the four hybrid polyelectrolytes in shear flow. The adsorbed film of CFG is unique because it exhibits a predominantly viscous layer (loss modulus G’ > storage modulus G'’) showing an apparently increasing G' throughout the whole test without a saturated value, whereas OSA-s produces a viscous layer at the interface with a very low viscosity, G'<<G' and quick forming kinetics. In contrast, both GA and SSPS form more rigid, solid–like layers with G' > G'. Emulsifying properties of the four polymers were evaluated in terms of the emulsion physical properties, droplet-size distribution and optical microscopy observation. The effect of concentration and storage temperature on the interfacial viscoelastic response and the corresponding emulsion stability of each biopolymer were correlated. Models to describe the distinct interfacial dynamics and stabilizing mechanism of the four emulsifiers involving steric repulsion and electrostatic repulsion were proposed.