|Jin, Q - Shanghai Jiaotong University|
|Cai, Z - Shanghai Jiaotong University|
|Li, X - Shanghai Jiaotong University|
|Zhang, H - Shanghai Jiaotong University|
Submitted to: Food Hydrocolloids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/2/2016
Publication Date: 1/1/2017
Citation: Jin, Q., Cai, Z., Li, X., Yadav, M.P., Zhang, H. 2017. Comparative viscoelasticity studies: Corn fiber gum versus commercial polysaccharide emulsifiers in bulk and at air/liquid interfaces. Food Hydrocolloids. 64:85-98.
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 but the flow behavior of its solution in water has not been well studied. The flow behavior of a food ingredient in solution is related to its structure. From the application point of view, to know how a solution of any food ingredient behaves on mixing is important. So a comparative study of flow properties of CFG has been done and compared 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 indicate that though all these polymers dissolve in water to make a clear solution and they are good emulsifiers, they differ significantly in their flow properties, when a force is applied to mix them. The viscosity (thickness) of CFG and OSA-s does not change when their solution is mixed by applying some kind of force. But the solution of GA and SSPS becomes thin (less viscous) on mixing under applied force. Also the solution of CFG and OSA is more viscous (thick) and less elastic (flexible) than the solution of GA and SSPS. These significant differences in flow, viscosity and flexibility of these four emulsifiers in solution indicate that there are major differences in their structures. These findings will benefit U. S. corn processors and manufacturers of CFG by providing a better understanding the flow behaviors of these emulsifiers and being able to better match them to various potential applications. The generation of valuable products from corn milling by-products will also indirectly help to reduce overall cost of fuel ethanol produced from corn kernels.
Technical Abstract: A comparative study of both the bulk and air/liquid interfacial rheological responses was carried out by using four kinds of high molecular weight and highly branched polysaccharide emulsifiers, (a) corn fiber gum (CFG), (b) octenyl succinate anhydride-modified starch (OSA-s), (c) gum arabic (GA) and (d) soybean soluble polysaccharides (SSPS), spanning the concentration range of 1-15 wt%. We found that the bulk and interfacial rheological properties of their aqueous solutions were significantly different. While both CFG and OSA-s showed Newtonian flow behavior even at 15 wt% concentration, both GA and SSPS exhibited obvious shear thinning behavior or thixotropy even at a low concentration of 1 wt%. The time-dependent flow behavior for CFG, GA and SSPS suggested microstructural breakdown and rebuilding in solutions under shear, and also suggested that their proteinaceous portion was strongly bound to their polysaccharide part. This phenomenon was not observed for the almost protein-free OSA-s. The interfacial rheology responses showed that the layers formed by CFG and OSA-s were more viscous with faster formation kinetics, while the layers formed by GA and SSPS were more elastic with slower formation kinetics. Interfacial viscoelastic responses of CFG and OSA-s were weaker than those of GA and SSPS. By comparison, the interfacial layer for OSA-s showed pure viscous responses whereas SSPS showed the highest elastic responses. These significant disparities in bulk and interfacial viscoelasticity of the four polysaccharide emulsifiers reflect the influence of different fine chain structures on the dissimilarity in the intermolecular associations and the architectures of the interfacial layers.