Title: Adhesive performance of sorghum protein extracted from sorghum DDGS and flour Authors
|Li, Ningbo -|
|Wang, Ying -|
|Wu, Xiaorong -|
|Sun, Xiuzhi (Susan) -|
|Wang, Donghai -|
Submitted to: Journal of Environment and Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2011
Publication Date: June 1, 2011
Citation: Li, N., Wang, Y., Tilley, M., Bean, S., Wu, X., Sun, X., Wang, D. 2011. Adhesive performance of sorghum protein extracted from sorghum DDGS and flour. Journal of Environment and Polymers. 19:755-765. Interpretive Summary: About 20 billion pounds of adhesives and resins are used annually in the United States in plywood, particleboard, lamination, and various composites for construction, packaging, furniture, etc. These adhesives are derived mostly from petroleum-based chemicals, however, due to finite petroleum resources, non-uniform distribution of these resources, volatile prices and environmental concerns, the adhesive industry is increasingly interested in bio-based adhesives. We therefore investigated the use of sorghum proteins extracted from distillers dried grains with solubles (DDGS), which is the main co-product from grain-based ethanol production. Our results showed that sorghum proteins extracted from DDGS using acetic acid had the best adhesion performance. Furthermore, the wet strength of adhesives made from these sorghum proteins was better than that of unmodified soy proteins. These results indicated that sorghum protein has huge potential as an alternative to petroleum-based adhesives.
Technical Abstract: Distillers dried grains with solubles (DDGS) is the main co-product from grain-based ethanol production. The objective of this research was to compare the adhesive performance of three types of sorghum proteins: acetic acid-extracted sorghum protein from DDGS (PI), aqueous ethanol-extracted sorghum protein from DDGS (PII) and acetic acid-extracted sorghum protein from sorghum flour (PF). Physicochemical properties including amino acid composition, and rheological, thermal and morphological properties also were characterized. Results showed that PI had the best adhesion performance in terms of dry, wet and soak adhesion strength, followed by PF and PII. The wet strength of PI at a concentration of 12% protein assembled at 150 °C was 3.15 MPa, compared to 2.17 MPa and 2.59 MPa for PII and PF, respectively. DSC thermograms indicated that the PF protein isolates contained higher levels of carbohydrates than PI and PII; such non-protein contaminants in the PF isolate could be the reason for its lower adhesion strength than PI. In addition, PI might have more hydrophobic amino acids aligned at the protein-wood interface than PII, which could explain the better water resistance of PI. The optimum sorghum protein concentration and pressing temperature for maximum adhesion strength was 12% and 150 °C. PI had a significantly higher wet strength (3.15 MPa) than unmodified soy protein (1.63 MPa for soy protein). The high percentage of hydrophobic amino acids in PI (57%) was likely a key factor in the increased water resistance of PI compared with soy protein (36% hydrophobic amino acids). These results indicated that sorghum protein has huge potential as an alternative to petroleum-based adhesives.