Physicochemical characterization and rheological behavior of hemicelluloses isolated from sorghum bran, sorghum bagasse and sorghum biomass

Authors: QIU, SHUANG - China Agricultural University; Yadav, Madhav; Chau, Hoa - Rose; YIN, LIJUN - China Agricultural University

Submitted to: Food Hydrocolloids
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/2019
Publication Date: 9/14/2019
Citation: Qiu, S., Yadav, M.P., Chau, H.K., Yin, L. 2019. Physicochemical characterization and rheological behavior of hemicelluloses isolated from sorghum bran, sorghum bagasse and sorghum biomass. Food Hydrocolloids. https://doi.org/10.1016/j.foodhyd.2019.105382.
DOI: https://doi.org/10.1016/j.foodhyd.2019.105382

Interpretive Summary: Previous studies in our lab have reported a method to produce a potentially useful food additive called Corn Fiber Gum (CFG). It is a food ingredient composed of complex carbohydrates that can serve as an emulsifier of oil-in-water. The U. S. beverage industry uses hundreds of tons of high-quality emulsifiers each year for stabilizing citrus oil in soft drinks and for preventing the separation of oil and water in salad dressings plus hundreds of other applications. 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 an abundant and inexpensive byproduct of corn processing called “corn fiber.” Similar bio-based fiber gums can be prepared from other agricultural products and byproducts such as bran from grain sorghum, sorghum bagasse (the fibrous material remaining after squeezing the juice out of sweet sorghum) and biomass sorghum ( a type of sorghum that is bred to yield large plants with abundant biomass). We found for the first time that bio-based fiber gums from all three sorghum sources were as good as CFG for stabilizing flavor in oil-in-water emulsion system. These results prompted us to study their molecular characterization. By measuring their molecular weight, we found that bio-based fiber gum obtained from sorghum grain and sorghum bagasse had higher mass than the bio-based fiber gum obtained from sorghum biomass. Bio-based fiber gum obtained from all three sorghum sources were equally good flavor stabilizers in oil-in-water emulsion systems. Thus, these results indicated that the flavor stabilizing capacity of these bio-based fiber gum was not just dependent on their mass. These results will benefit U.S. sorghum processors and sorghum farmers by identifying new applications for low value high fiber fractions of sorghum.

Technical Abstract: The molecular characterization and rheological properties of hemicellulose B (Hemi. B) fractions isolated from sorghum bran (SBR), sorghum bagasse (SBA) and sorghum biomass (SBI) were undertaken. The monosaccharide analysis results confirmed that these polysaccharides had a typical arabinoxylan structure. High performance size exclusion chromatography study showed that Hemi. B from SBR and SBA had a higher weight average molar mass (Mw) (383-397 kDa), radius of gyration (Rgz) (34.7-34.9 nm), intrinsic viscosities ('w) (1.25-1.29 dL/g) and lower polydispersity index (Mw/Mn) (2.76-2.79) than Hemi. B from SBI. The Mw, Rgz, 'w and Mw/Mn of the Hemi. B from SBI were 261 kDa, 31.6, 0.931 and 6.01 respectively. The Hemi. B from SBR and SBA had a similar random coil shape, while the Hemi. B from SBI was more like a compact sphere in shape. The Hemi. B isolated from SBR showed a typical shear thinning behavior at all concentrations. But the Hemi. B from other two sources (SBA and SBI) exhibited a shear shinning behavior at high concentration, showing Newtonian behavior at lower concentration. The critical concentration was also calculated to evaluate the molecular properties. The lower Mw of Hemi. B shows a highest value of critical concentration (c*), which was in coordinate with the negative correlation between c* values and Mw of different arabinoxylan varieties.